Payday loans
Home Publications Journal Publications

Journal Publications

This section contains all refereed journal publications that have some connection either with the Mace Head Research Station or with members, both present and past, of the Atmospheric Physics Research Cluster at NUI, Galway.

Click on the "Search Document" icon above to find a publication based on the search criteria you create.

 


Documents

Order by : Name | Date | Hits | [ Ascendant ]

Light backscattering and scattering by non-spherical sea-salt aerosols Light backscattering and scattering by non-spherical sea-salt aerosols

Date added: 08/01/2003
Date modified: 07/24/2009
Filesize: 483.03 kB

Chamaillard K., Jennings S.J., Kleefeld C., Ceburnis D. and Yoon Y.J. Light backscattering and scattering by non-spherical sea-salt aerosols. J. of Quantitative Spectroscopy & Radiative Transfer, Vol. 79-80, 577-597, 2003.


Abstract


The scattering coefficient, single-scatter albedo, and up-scatter fraction are key parameters in direct climate forcing by aerosols. Usually the contribution of sea-salt is estimated using Mie theory, assuming that these particles are spherical. The optical properties of particles are known to strongly depend on the shape of the particles. The question of the applicability of using Mie theory in recent studies is mainly devoted to nonspherical dust-like tropospheric aerosols. In this study, we attempt to quantify the relative contribution of nonspherical sea-salt to measured scattering and backscattering coefficients. The shape of nonspherical sea-salt is assumed to be cubic. The discrete dipole approximation model is applied to estimate the optical properties of the nonspherical particles. Measurements are then compared to Mie theory calculations and to DDA cubic calculations. The results are presented for two wavelengths: λ=0.55 μm and 0.7 μm, It is found that the size of particles responsible for scattering is larger than 0.3 μm. The backscattering coefficient, unlike the scattering coefficient, is very sensitive to particle shape. Cubic particles give better agreement to the measurements. Compared to spherical particles, the cubic approach underestimates the backscattering coefficient in contrast to prolate spheroidal calculations.

Direct Measurements of New-Particle Fluxes in the Coastal Environment Direct Measurements of New-Particle Fluxes in the Coastal Environment

Date added: 08/06/2005
Date modified: 07/27/2009
Filesize: 228.88 kB

Flanagan, Robert J., Michael Geever, and Colin D. O'Dowd (2005), Direct Measurements of New-Particle Fluxes in the Coastal Environment, Enviro Chem, 2(4), 256, doi:10.1071/EN05069.


Abstract


Measurements of the flux of new secondary aerosol particles during nucleation events in the coastal environment using an eddy-correlation technique are reported for the first time. Events are divided into two types based on the prevailing wind direction. During tidal-related nucleation events, new-particle upward fluxes are typically of the order of 109–1010 particles m-2 s-1. A close correlation (r2 = 0.86) was found between total particle concentration and total (positive) flux when air masses were not affected by multiple sources. This would suggest that continuous measurements of particle number concentration at Mace Head can be translated into a flux using the resulting parameterization. It is expected that parameterizations obtained from similar data and analysis would be equally feasible at other coastal locations.

Hygroscopic and CCN properties of aerosol particles in boreal forests Hygroscopic and CCN properties of aerosol particles in boreal forests

Date added: 07/31/2001
Date modified: 07/02/2009
Filesize: 498.17 kB
Hämeri, K. J.M. Mäkelä, L. Pirjola, M. Väkevä, P. Aalto, P. Miikkulainen, and C.D. O'Dowd, Hygroscopic properties of boreal forest aerosol during nucleation events. Tellus B, 53, 359-378, 2001

Abstract


The measurements of the hygroscopic and cloud condensation nuclei (CCN) properties of submicrometer atmospheric aerosol particles were performed with two tandem differential mobility analysers (TDMA) and a CCN counter at the Hyytia¨ la¨ forest field station in south-central Finland during the BIOFOR campaign. The TDMAs were used to measure hygroscopic diameter growth factors of individual aerosol particles in the dry particle diameter range 10–365 nm when taken from the dry state (relative humidity RH<5%) to RH=90%. The CCN counter was used to study the activation of aerosol particles when exposed to supersaturated conditions. The measurements show clear diurnal pattern of particle solubility. The pattern was strongest for particles in nucleation and Aitken modes. The lowest growth factor (soluble fraction) values were detected during late evening and early morning and the maximum was observed during noon–afternoon. The highest soluble fractions were determined for nucleation mode particles. The response of hygroscopic growth to changes of relative humidity suggests that the soluble compounds are either fully soluble or deliquescent well before 70% RH. The hygroscopic growth was investigated additionally by a detailed model using the size-resolved composition from the impactor samples. The comparison between different instruments shows good consistency. We found good agreement for the 20 nm growth factors measured with two TDMAs, not only on average but also regarding the temporal variation. The similar conclusion was drawn for comparison of TDMA with CCNC for Aitken mode particles with dry sizes 50 and 73 nm. Differences between wet and dry spectra measured using APS and CSASP spectrometer probes were used to derive growth factors for coarse mode particles. Growth factors for coarse mode particles (Dp ca. 2 mm) ranged between 1.0 and 1.6. Agreement between the evolution of growth factors with time for both accumulation and coarse modes was observed regularly. However, similar portions of the data set also indicated clear differences and consequently different chemical compositions between both modes. When the differences between both modes were observed, the coarse mode always behaved in a less hygroscopic manner, with growth factors near one.

Globally significant oceanic source of organic carbon aerosol Globally significant oceanic source of organic carbon aerosol

Date added: 08/06/2008
Date modified: 07/24/2009
Filesize: 1.07 MB

Spracklen, D. V., S. R. Arnold, J. Sciare, K. S. Carslaw, and C. Pio (2008), Globally significant oceanic source of organic carbon aerosol, Geophys. Res. Lett., 35, L12811, doi:10.1029/2008GL033359.


Abstract


Significant concentrations of organic carbon (OC) aerosol are observed at three oceanic surface sites (Amsterdam Island, Azores and Mace Head). Two global chemical transport models (CTMs) underpredict OC concentrations at these sites (normalised mean bias of −67% and −58%). During periods of high biological activity monthly mean concentrations are underpredicted by a factor of 5–20. At Amsterdam Island and Mace Head, observed OC correlates well (R2 = 0.61–0.77) with back-trajectory weighted chlorophyll-a, suggesting an oceanic OC source driven by biological activity. We use a combination of remote sensed chlorophyll-a, back trajectories and observed OC to derive an empirical relation between chlorophyll-a and the total oceanic OC emission flux. Using the GEOS-chem CTM we show a global oceanic OC emission, from primary and secondary sources, of ∼8 Tg/year matches observations. This emission is comparable in magnitude to the fossil fuel OC source and increases the simulated global OC burden by 20%.

 

Light scattering enhancement factors in the marine boundary layer (Mace Head, Ireland) Light scattering enhancement factors in the marine boundary layer (Mace Head, Ireland)

Date added: 02/15/2011
Date modified: 02/15/2011
Filesize: 1.01 MB

Fierz-Schmidhauser, R., P. Zieger, A. Vaishya, C. Monahan, J. Bialek, C. D. O'Dowd, S. G. Jennings, U. Baltensperger, and E. Weingartner (2010), Light scattering enhancement factors in the marine boundary layer (Mace Head, Ireland), J. Geophys. Res., 115, D20204, doi:10.1029/2009JD013755.


Direct climate aerosol radiative forcing is influenced by the light scattering of atmospheric aerosols. The chemical composition, the size distribution, and the ambient relative humidity (RH) determine the amount of visible light scattered by aerosols. We measured the aerosol light scattering coefficients at RH varying from 30% to 90% of the marine atmosphere at the Mace Head Atmospheric Research Station on the west coast of Ireland. At this site, two major air mass types can be distinguished: clean marine and polluted air. In this paper, we present measurements of light scattering enhancement factors f(RH) = σsp(RH)/σsp(dry) from a 1 month field campaign (January–February 2009). At this site in winter, the mean f(RH = 85%) (standard deviation) for marine air masses at the wavelength of 550 nm was 2.22 (±0.17) and 1.77 (±0.31) for polluted air. Measured σsp(RH) and f(RH) agreed well with calculations from Mie theory using measurements of the size distribution and hygroscopic diameter growth factors as input. In addition, we investigated the RH influence on additional intensive optical properties: the backscatter fraction and the single scattering albedo. The backscatter fraction decreased by about 20%, and the single scattering albedo increased on average by 1%–5% at 85% RH compared to dry conditions.

Applicability of condensation particle counters to measure atmospheric clusters Applicability of condensation particle counters to measure atmospheric clusters

Date added: 09/12/2008
Date modified: 07/10/2009
Filesize: 617.3 kB

Sipilä, M., Lehtipalo, K., Kulmala, M., Petäjä, T., Junninen, H., Aalto, P. P., Manninen, H. E., Kyrö, E.-M., Asmi, E., Riipinen, I., Curtius, J., Kürten, A., Borrmann, S., and O'Dowd, C. D.: Applicability of condensation particle counters to measure atmospheric clusters, Atmos. Chem. Phys., 8, 4049-4060, 2008


Abstract


This study presents an evaluation of a pulse height condensation particle counter (PH-CPC) and an expansion
condensation particle counter (E-CPC) in terms of measuring ambient and laboratory-generated molecular and ion clusters. Ambient molecular cluster concentrations were measured with both instruments as they were deployed in conjunction with an ion spectrometer and other aerosol instruments in Hyyti¨al¨a, Finland at the SMEAR II station between 1 March and 30 June 2007. The observed cluster concentrations varied and ranged from some thousands to 100 000 cm−3. Both instruments showed similar (within a factor of 5) concentrations. An average size of the detected clusters was approximately 1.8 nm. As the atmospheric measurement of sub 2-nm particles and molecular clusters is a challenging task, we conclude that most likely we were unable to detect the smallest clusters. Nevertheless, the reported concentrations are the best estimates to date for minimum cluster concentrations in a boreal forest environment.

On the production of Aitken nuclei by sunlight in st. Moritz  On the production of Aitken nuclei by sunlight in st. Moritz

Date added: 08/07/1962
Date modified: 07/15/2009
Filesize: 4.41 MB
C. Mc Greevy & TC O Connor, On the production of Aitken nuclei by sunlight in st. Moritz, (1962) Geofisica E Meteorologia

Abstract

 

It has been found by VERZAR & al. that the concentration of Aitken nuclei in atmospheric air increased from sunrise until  mid-day and decreased again in the afternoon. This effect occurred over the ordinary ground, in a city and also over snow. A similar effect had been reported by MCLAUGHLIN in Paris in 1926 '). It seemed likely that irradiation by the sun caused the increase in the numher of condensation nuclei. In order to study this ii suneffect ), V E R ~&~ RKU NZa nd VERZAR& EVANS  investigated nucleus-free atmospheric air stored in a polyethylene balloon and showed that the same effict took place when the air in the balloon was exposed to direct and scattered sunlight ("5). As a result of their researches and from the findings of other investigators (C.'.'") it was considered a reasonable hypothesis that trace gases in the air were partly responsible for nucleus prduction when irradiation by the sun took place. It was suggested that the production of nuclei by sunrays was due to a photochemical reaction of some impurity in the air. Suspected impurities were SO,, H,S, NH, and ozone. The amount of these contaminants in ordinary atmospheric air has
been discussed by JUNGE( 9.In support of the above hypothesis it was found that when traces of SO, or H,S or NH, were added to nucleus-free atmospheric air in such polyethylene hallons a striking increase in the number of nuclei
produced by sun irradiation occurred over the nnmher produced by irradiation when no traces were added (9. The sun-effect also took place when industrial oxygen or nitrogen replaced the nucleus-free air in the balloons. This also could he due to impurities present in the oxygen or nitrogen. In order to show quite definitely that traces of impurity
gases were partly the cause of nucleus-production in atmospheric air we decided to eliminate the suspected trace gases by filling the balloons with atmospheric air through chemicals which would absorb these trace gases or at least reduce their concentration. In this way it was hoped to he able to discover what trace gases were partly responsible for nucleus production in the sun-effect.


Regional-scale Ozone Deposition to North-East Atlantic Waters Regional-scale Ozone Deposition to North-East Atlantic Waters

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 4.87 MB

Coleman, L., S. Varghese, O.P. Tripathi, S G. Jennings, C.D. O’Dowd, Regional-scale Ozone Deposition to North-East Atlantic Waters, Adv. in Meteorol., Volume 2010, Article ID 243701, doi:10.1155/2010/243701 2010.


A regional climate model is used to evaluate dry deposition of ozone over the North East Atlantic. Results are presented for a deposition scheme accounting for turbulent and chemical enhancement of oceanic ozone deposition and a second non-chemical, parameterised gaseous dry deposition scheme. The first deposition scheme was constrained to account for sea-surface ozone-iodide reactions and the sensitivity of modelled ozone concentrations to oceanic iodide concentration was investigated. Simulations were also performed using nominal reaction rate derived from i

n-situ ozone deposition measurements and using a preliminary representation of organic chemistry. Results show insensitivity of ambient ozone concentrations modelled by the chemicalenhanced scheme to oceanic iodide concentrations, and iodide reactions alone cannot account for observed deposition velocities. Consequently, we suggest a missing chemical sink due to reactions of ozone with organic matter at the air-sea interface. Ozone loss rates are estimated to be in the range of 0.5–6 ppb per day. A potentially significant ozone-driven flux of iodine to the atmosphere is estimated to be in the range of 2.5–500Mmolec cm2 s1, leading to amixing-layer enhancement of organo-iodine concentrations of 0.1–22.0 ppt, with an average increase in the N.E. Atlantic of around 4 ppt per day.

International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland

Date added: 07/31/1999
Date modified: 07/24/2009
Filesize: 195.51 kB

Ebinghaus, R., Jennings, S.G., Schroeder, W.H., Berg, T., Donaghy., Guentzel, J., Kenny, C., Kock, H.H., Kvietkus, K., Landing, W., Munthe, J., Prestbo, E.M., Schneeberger, D., Slemr, F., Sommar, J., Urba, A., Wallschlager, D. & Xiao, Z. 1999. International field intercomparison measurements of atmospheric mercury species at Mace Head, Ireland. Atmos. Environ., 33, 3063-3073.


Abstract


Eleven laboratories from North America and Europe met at Mace Head, Ireland for the period 11-15 September 1995 for the first international field intercomparison of measurement techniques for atmospheric mercury species in ambient air and precipitation at a marine background location. Different manual methods for the sampling and analysis of total gaseous mercury (TGM) on gold and silver traps were compared with each other and with new automated analyzers. Additionally, particulate-phase mercury (Hgpart) in ambient air, total mercury, reactive mercury and methylmercury in precipitation were analyzed by some of the participating laboratories. Whereas measured concentrations of TGM and of total mercury in precipitation show good agreement between the participating laboratories, results for airborne particulate-phase mercury show much higher differences. Two laboratories measured inorganic oxidized gaseous mercury species (IOGM), and obtained levels in the low picogram m-3 range.

Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 1014.54 kB

Sellegri, K., Y. J. Yoon, S. G. Jennings, C. D. O’Dowd, L. Pirjola, S. Cautenet, H. Chen, T. Hoffmann, Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign. Environ. Chem. 2, 260. doi:10.1071/EN05074, 2005.


Abstract


Secondary processes leading to the production of ultra-fine particles by nucleation are still poorly understood. A fraction of new particles formed can grow into radiatively active sizes, where they can directly scatter incoming  solar radiation and, if partly water soluble, contribute to the cloud condensation nuclei population. New particle formation events have been frequently observed at the Mace Head Atmospheric Research Station (western Ireland), under low tide and sunny conditions, leading to the hypothesis that new particles are formed from iodo-species emitted from macroalgae.

Ground-based Retrieval of Continental and Marine Warm Cloud Microphysics Ground-based Retrieval of Continental and Marine Warm Cloud Microphysics

Date added: 08/05/2011
Date modified: 08/05/2011
Filesize: 3.85 MB

Martucci, G. and C.D. O’Dowd, Ground-based Retrieval of Continental and Marine Warm Cloud Microphysics. Atmos, Meas. Techs.. Diss., 4, 4825-4865, doi:10.5194/amtd-4-4825-2011,, 2011


Abstract. A technique for retrieving warm cloud microphysics using synergistic ground based remote sensing instruments is presented. The SYRSOC (SYnergistic Remote Sensing Of Cloud) technique utilises a Ka-band Doppler cloud RADAR, a LIDAR-ceilometer and a multichannel microwave radiometer. SYRSOC retrieves the main microphysical parameters such as cloud droplet number concentration (CDNC), droplets effective radius (reff), cloud liquid water content (LWC), and the departure from adiabatic conditions within the cloud. Two retrievals are presented for continental and marine stratocumulus formed over the Mace Head Atmospheric Research Station. Whilst the continental case exhibited high CDCN (N = 382 cm−3; 10th-to-90th percentile [9.4–842.4] cm−3) and small mean effective radius (reff = 4.3; 10th-to-90th percentile [2.9–6.5] μm), the marine case exhibited low CDNC and large mean effective radius (N = 25 cm−3, 10th-to-90th percentile [1.5–69] cm−3; reff = 25.6 μm, 10th-to-90th percentile [11.2–42.7] μm) as expected since the continental air at this location is typically more polluted than marine air. The large reff of the marine case was determined by the contribution of drizzle drops (large radii and few occurrences) and in fact the modal radius was reffMOD = 12 μm (smaller radius and large occurrences). The mean LWC was comparable for the two cases (continental: 0.19 g m−3; marine: 0.16 g m–3) but the 10th–90th percentile range was wider in marine air (continental: 0.11–0.22 g m−3; marine: 0.01–0.38 g m−3). The calculated algorithm uncertainty for the continental and marine case for each variable was, respectively, σN=141.34 cm−3 and 11.5 cm−3, σreff=0.8 μm and 3.2 μm, σLWC = 0.03 g m−3 and 0.03 g m−3. The retrieved CDNC are compared to the cloud condensation nuclei concentrations and the best agreement is achieved for a super-saturation of 0.1 % in the continental case and between 0.1 %–0.75 % for the marine stratocumulus. The retrieved reff at the top of the clouds are compared to the MODIS satellite reff: 7 μm (MODIS) vs 6.2 μm (SYRSOC) and 16.3 μm (MODIS) vs. 17 μm (SYRSOC) for continental and marine cases, respectively. The combined analysis of the CDNC and the reff, for the marine case shows that the drizzle modifies the droplet size distribution and reff especially if compared to reffMOD. The study of the cloud subadiabaticity and the LWC shows the general sub-adiabatic character of both clouds with more pronounced departure from adiabatic conditions in the continental case due to the shallower cloud depth and more significant mixing with dry tropospheric air.

Optical and Thermal Measurements of Black CArbon Aerosol Content.....of the Specific Attenuation Cross-section, Sigma. Jennings, Liousse, Cachier Optical and Thermal Measurements of Black CArbon Aerosol Content.....of the Specific Attenuation Cross-section, Sigma. Jennings, Liousse, Cachier

Date added: 07/31/1993
Date modified: 07/03/2009
Filesize: 2.92 MB

Louisse, C., Cachier, H., and Jennings, S.G. (1993). - Optical and thermal measurements of black carbon aerosol contents in different environments: variation of the specific attenuation cross-section. Atmos. Environ., 27A, 1203 - 1211.


Abstract


In optical analysers devoted to the analysis of atmospheric black carbon concentration, the specific attenuation cross-section, a is the factor used to convert the attenuation of a light beam due to the absorption of aerosols deposited on a filter into their black carbon content. We have tried to gain further insight for a suitable choice of sigma value, using both optical analysis (with an aethalometer) and thermal analysis of black carbon aerosols and comparison of the two sets of results. Samples which were investigated originate from varying environments, including suburban areas, tropical areas where biomass buming was prevalent and from more remote locations. In a given type of atmospheric environment, a values are found to be constant

Averaging periods for indoor-outdoor ratios of pollution in naturally ventilated non-domestic buildings near a busy road Averaging periods for indoor-outdoor ratios of pollution in naturally ventilated non-domestic buildings near a busy road

Date added: 08/01/2003
Date modified: 06/30/2009
Filesize: 387.68 kB

Ni Riain, C, Mark, D., Davies, M., Harrison, R.M. and Byrne, M.A. Averaging periods for indoor-outdoor ratios of pollution in naturally ventilated non-domestic buildings near a busy road. Atmos Env, Vl 37, pp 4121-4132 , 2003.


Abstract

 

Continuous measurements of carbon monoxide (CO) and particulate matter (PM10, PM2.5 and PM1) were made inside and outside two naturally ventilated (NV) and two mechanically assisted (MV) spaces overlooking the same six-lane highway in Central London. The indoor/outdoor (I/O) ratio was calculated for each site for the whole monitoring period in the usual way, and then cumulatively at each hourly time-step from the start of monitoring up to the whole period in order to track the evolution of the I/O ratio with length of monitoring or averaging period. Hourly data were also sorted by wind speed and direction and I/O ratios calculated for each direction/speed set from ensemble means. I/O ratios for the whole period were generally lower in the NV spaces than the MV, however, the indoor-outdoor relationship in the NV spaces was found to vary substantially with wind direction. For a constant above-roof wind speed, I/O ratios of CO varied by 50-60% about the mean value with direction, and by 20-30% for particulate matter. Consequently, I/O ratios for NV spaces depended on the distribution of wind direction within the calculation period and, hence, on the length of monitoring period. The I/O ratio in one NV space changed by a factor of three between the early stages and final stages of monitoring, with a stable final value (±5%) achieved after 900 h of monitoring. By contrast, in the MV spaces under constant fan speed, constant values for the I/O ratio were achieved for CO within 4 h of the start of monitoring. It is argued here that field assessments of the filtration performance of naturally ventilated spaces need to consider exposure to and distribution of natural ventilation drivers within the monitoring period in order to draw meaningful comparisons for design and exposure assessment purposes.

Seasonal cycle of N2O Analysis of data Seasonal cycle of N2O Analysis of data

Date added: 08/06/2007
Date modified: 07/23/2009
Filesize: 599.77 kB

Jiang, X., W. L. Ku, R.-L. Shia, Q. Li, J. W. Elkins, R. G. Prinn, and Y. L. Yung (2007), Seasonal cycle of N2O: Analysis of data, Global Biogeochem. Cycles, 21, GB1006, doi:10.1029/2006GB002691


Abstract


We carried out a systematic study of the seasonal cycle and its latitudinal variation in the nitrous oxide (N2O) data collected by National Oceanic and Atmospheric Administration–Global Monitoring Division (NOAA-GMD) and the Advanced Global Atmospheric Gases Experiment (AGAGE). In order to confirm the weak seasonal signal in the observations, we applied the multitaper method for the spectrum analysis and studied the stations with significant seasonal cycle. In addition, the measurement errors must be small compared with the seasonal cycle. The N2O seasonal cycles from seven stations satisfied these criteria and were analyzed in detail. The stations are Alert (82°N, 62°W), Barrow (71°N, 157°W), Mace Head (53°N, 10°W), Cape Kumukahi (19°N, 155°W), Cape Matatula (14°S, 171°W), Cape Grim (41°S, 145°E) and South Pole (90°S, 102°W). The amplitude (peak to peak) of the seasonal cycle of N2O varies from 0.29 ppb (parts-per-billion by mole fraction in dry air) at the South Pole to 1.15 ppb at Alert. The month at which the seasonal cycle is at a minimum varies monotonically from April (South Pole) to September (Alert). The seasonal cycle in the Northern Hemisphere shows the influence of the stratosphere; the seasonal cycle of N2O in the Southern Hemisphere suggests greater influence from surface sources. Preliminary estimates are obtained for the magnitude of the seasonally varying sources needed to account for the observations.

 

An analysis of condensation nuclei levels at Mace Head, Ireland An analysis of condensation nuclei levels at Mace Head, Ireland

Date added: 07/31/1999
Date modified: 07/27/2009
Filesize: 737.83 kB

Mc Govern, F.M. (1999). An analysis of condensation nuclei levels at Mace Head, Ireland. Atmos. Environ., 33, 1711-1723.


Abstract


Condensation nuclei (CN) concentrations measured at Mace Head between 1990 and 1992 are presented. The background CN concentration was found to typically range from 100 to 700 cm-3. Concentration values were in this range for 55% of the measurement period. No seasonal cycle was observed in the CN concentration values. Concurrent equivalent black carbon (EBC) measurements are used to examine anthropogenic influences on the background CN concentration. Evidence that transatlantic air mass transport influenced the background CN concentration contributing to increased CN and EBC levels, is shown. During polluted conditions the CN concentration was generally higher than 1000 cm-3. The principal source for high pollution levels was European air masses arriving at the site. Very high CN concentrations, greater than 50 000 cm-3, are attributed to local gas-to-particle conversion processes. The characteristics of a number of particle production events are considered. These show that these events are highly photochemical and occur during both clean and polluted conditions. Such production events though infrequent contributed significantly to the total aerosol number concentration.

Iodine Oxide Homogeneous Nucleation An Explanation for Coastal New Particle Production Iodine Oxide Homogeneous Nucleation An Explanation for Coastal New Particle Production

Date added: 07/31/2001
Date modified: 07/24/2009
Filesize: 423.83 kB

Hoffmann, T, CD O'Dowd, JH Seinfeld, Iodine oxides and new particle formation, Geophys. Res. Letts., 27, 1949-1952, 2001.


Abstract


A series of laboratory experiments on the chemical composition of aerosol particles formed after photodissociation of CH2I2, a major volatile alkyl halide released from macroalgae, have been performed in a laboratory scale reaction chamber using on-line atmospheric pressure chemical ionization mass spectrometry (APCI/MS). Based on the mass spectrometric results and the molecular properties of iodine oxides, we suggest that the self-nucleation of iodine oxides provides an efficient source of natural condensable material in coastal environments and discuss this concept focusing on OIO as one potential key species for new particle formation. The presented hypothesis not only fits the measured enrichment of iodine species in submicrometer particles, but also can explain the frequently observed nucleation bursts in the coastal boundary layer.

Air Pollution Measurements at Macehead Air Pollution Measurements at Macehead

Date added: 08/07/1988
Date modified: 07/27/2009
Filesize: 2.14 MB

Hydroxyl Radical Concentrations Estimated from Measurements of Trichloroethylene during the EAS Hydroxyl Radical Concentrations Estimated from Measurements of Trichloroethylene during the EAS

Date added: 08/05/1999
Date modified: 07/24/2009
Filesize: 161.63 kB

Derwent, R.G., N. Carslaw, P. G. Simmonds, M. Bassford, S. O’Doherty, D.B. Ryall, M.J. Pilling, A.C. Lewis, and J.B. McQuaid, Hydroxyl radical concentrations estimated from measurements of trichloroethylene during the EASE/ACSOE campaign at Mace Head, Ireland during July 1996, J. Atmos Chem, 34, 185-205, 1999, (Ser. No. ACP107).


Abstract


During the EASE/OXICOA campaign of the NERC ACSOE programme, trichloroethylene and a wide range of man-made halocarbons and radiatively-active trace gases were monitored with high precision and high frequency throughout July 1996 at Mace Head on the Atlantic Ocean coast of Ireland. Trichloroethylene concentrations in concert with many other trace gases became elevated as regionally-polluted and photochemically-aged air masses reached Mace Head. However, as the anticyclonic air masses retreated during 19 and 20 July, trace gas concentrations remained elevated for a significant period. During this 2-4 day period, trichloroethylene concentrations decayed significantly, though the concentrations of the other more chemically-inert trace gases did not. A detailed interpretation of this behaviour using a Lagrangian dispersion model has allowed the estimation of average and peak OH radical concentrations of 3 and 9 × 106 molecule cm-3, respectively, during the travel from the source areas in the U.K. and the low countries out to Mace Head. Using a simple box model, the available Mace Head measurements, when combined into a detailed chemical mechanism, generated OH radical concentrations which peaked at 7 × 106 molecule cm-3, in close agreement with the estimates based on trichloroethylene decay.

 

Number size distributions and seasonality of submicron particles in Europe 2008–2009 Number size distributions and seasonality of submicron particles in Europe 2008–2009

Date added: 08/04/2011
Date modified: 08/05/2011
Filesize: 11.95 MB

Asmi, A.,  A. Wiedensohler, P. Laj, A.-M. Fjaeraa, K. Sellegri, W. Birmili, E. Weingartner, U. Baltensperger, V. Zdimal, N. Zikova, J.-P. Putaud, A. Marinoni, P. Tunved, H.-C. Hansson, M. Fiebig, N. Kivekäs, H. Lihavainen, E. Asmi, V. Ulevicius, P. P. Aalto, E. Swietlicki, A. Kristensson, N. Mihalopoulos, N. Kalivitis, I. Kalapov, G. Kiss, G. de Leeuw, B. Henzing, R. M. Harrison, D. Beddows, C. O'Dowd, S. G. Jennings, H. Flentje, K. Weinhold, F. Meinhardt, L. Ries, and M. Kulmala.

Number size distributions and seasonality of submicron particles in Europe 2008–2009, Atmos. Phys. Chem. 11, 5505-5538, doi:10.5194/acp-11-5505, 2011

 


 

  

Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community. We also show that the aerosol number concentrations of  Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes) are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types. The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000ma.s.l.) with a strong seasonal cycle in aerosol number concentrations, high variability, andvery low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional coverage of these results. Aerosol number concentrations over the Britain and Ireland had very high varianceand there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The greatest concentrations were observed at the Ispra station in Northern Italy with high accumulation mode number concentrations n the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-A° lesund in Svalbard have also a strong seasonal cycle, with greater concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied.Analysis products are made for open-access to the research

 

 

community, available in a freely accessible internet site. The

results give to the modelling community a reliable, easy-touse

and freely available comparison dataset of aerosol size

distributions.

Marine organohalogens in the atmosphere over the Atlantic and Southern Oceans Marine organohalogens in the atmosphere over the Atlantic and Southern Oceans

Date added: 08/06/2003
Date modified: 07/24/2009
Filesize: 564.21 kB

Carpenter, L. J., P. S. Liss, and S. A. Penkett (2003), Marine organohalogens in the atmosphere over the Atlantic and Southern Oceans, J. Geophys. Res., 108(D9), 4256, doi:10.1029/2002JD002769.


Abstract


Reactive halogen species (RHS) such as the halogen oxide radicals IO and BrO influence tropospheric oxidation processes in both polar and temperate regions. Oceanic photolabile halocarbons have been shown to be strong sources of RHS in midlatitudes. However, the global source strengths of these halocarbon precursors and the relative importance of the coastal and pelagic oceans on their concentrations are highly uncertain. Here we present atmospheric measurements of the reactive organic halogens CH3I, CH2I2, CH2ClI, CH2IBr, CHIBr2, CHBr3, CH2Br2, and CHBr2Cl made at Mace Head, Ireland, during the Particle Formation and Fate in the Coastal Environment campaign in September 1998 and at Cape Grim, Tasmania, during the Southern Ocean Atmospheric Photochemistry Experiment 2 campaign in January/February 1999. Mace Head is strongly influenced by local macroalgae, whereas Cape Grim, owing to its cliff-top location, suffers much less impact from seaweeds. The very reactive halocarbons CH2I2, CH2IBr, and CHIBr2 observed at Mace Head were below detection limits at Cape Grim, although CH2ClI was detected at both locations. Mixing ratios of CH3I, CH2ClI, CHBr3, CHBr2Cl, and CH2Br2 at Cape Grim were on average 25–50% of those at Mace Head. Concentrations of the polybromomethanes correlated well at both sites. Using these correlations, we estimate molar source strengths of CHBr2Cl and CH2Br2 to be between 3 and 6% and between 15 and 25% of the global CHBr3 flux, respectively. These values fall within ranges estimated independently from concentration and lifetime data.

 

Aircraft Measurements During NAMBLEX (the SNAP campaign) Aircraft Measurements During NAMBLEX (the SNAP campaign)

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 33.65 kB
Purvis R.M., Lewis A.C., McQuaid J.B. & Lee J.D. "Aircraft Measurements During NAMBLEX (the SNAP campaign)." Geophys Res. Abs. 6 (2004):

Abstract

 

The spatial distribution of a number of trace species has been determined in marine boundary layer (MBL) and free troposphere (FT) air around the Mace Head Atmospheric Research Station, Ireland. CO and ozone measurements were made onboard the NERC Dornier 228-101 research aircraft operated by the Airborne Remote Sensing Facility during the SNAP (Supporting NAMBLEX from an Airborne Platform) campaign in August 2002. High frequency whole air samples taken from onboard the aircraft with ground analysis using GC-FID were used for C2 - C6 hydrocarbons mixing ratios. The campaign was conducted in conjunction with the ground based NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign carried out at Mace Head during the summer of 2002. The distribution of trace species was investigated in both coastal regions and above the deep waters beyond the continental shelf. A vertical gradient in concentration of hydrocarbon and sulphur species with known oceanic sources was observed in the MBL over both oceanic regions when compared to anthropogenic tracers such as acetylene and CO. Under clear sky conditions typical maximum mixing ratios were MBL ethene 78 pptV: FT ethene 10 pptV: MBL DMS: 89 pptV: FT DMS 21 pptV.

Elevated mixing ratios of species with oceanic origin were observed in the lower most  FT in regions experiencing strong convective activity associated with cumulus cells. Vertical profiles centred over the field site showed good agreement between ground based and airborne hydrocarbon measurements taken within the MBL. The MBL upwind of Mace Head appeared well mixed with respect to both NMHCs,CO and ozone. Above 2 km showed distinct layers with free  tropospheric ozone values of 50 ppbV contrasting typical MBL values of less than 30 ppbV. Flights indicate a boundary layer height of approximately 1200 m. The observations confirm that for these species the surface site measurements are generally representative of the marine boundary layer as a whole but not of the air mass above.

Nitrogen deposition to the eastern Atlantic Ocean The importance of southeasterly flow Nitrogen deposition to the eastern Atlantic Ocean The importance of southeasterly flow

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 782.42 kB

Spokes, L.J., Yeatman, S.G., Cornell, S.E. and Jickells, T.D., 2000. Nitrogen deposition to the eastern Atlantic Ocean. The importance of south-easterly flow. Tellus 52B, pp. 37–49.


Abstract


Converting measured concentrations into fluxes and using estimates of biological productivity in the coastal waters of the eastern Atlantic Ocean enables us to determine the role of the atmosphere as a source of biologically essential species, including nitrate and ammonium, to the marine biota. To understand the effects of the atmosphere as a source of nitrogen capable of promoting new production, we need to know both the seasonality of the input as well as the effects of extreme high deposition events which, while small in overall annual budget terms, maybe able to extend, or even promote, phytoplankton growth under nutrient depleted summer conditions. Aerosols and rainwater were collected at both Mace Head and at sea aboard RRS Challenger. Temporal patterns have been interpreted using airmass back trajectories which give the predicted air path prior to arrival at the sampling site. Low levels of both nitrate and ammonium are seen associated with marine westerly flow across the Atlantic and northerly air originating in the Arctic region. As expected, marine derived sodium, chloride, magnesium and seasalt sulphate are high during these periods. High concentration nitrate and ammonium events are seen associated with south-easterly flow where the airmass passes over the UK and northern Europe prior to arrival on the west coast of Ireland. In the polluted atmosphere, nitrate exists as nitric acid and as fine mode (< 1 μm diameter) ammonium nitrate aerosol. In the coastal zone, nitric acid reacts with coarse mode seasalt aerosols to form coarse mode (> 1 μm diameter) sodium nitrate: HNO3(g) + NaCl(s) → NaNO3(s) + HCl(g). This seasalt displacement reaction not only enhances dry nitrate deposition through more efficient gravitational settling of large particles, but also increases the efficiency of precipitational scavenging via inertial impaction. By looking at the size distribution of nitrate, we can see evidence for the seasalt displacement reaction. Under the polluted south-easterly flow, ∼40-60% of the nitrate occurs in the coarse mode fraction. Under clean marine conditions, the seasalt displacement reaction results in almost complete conversion of nitrate from the fine to the coarse aerosol mode. By converting measured wet and dry nitrate, ammonium and organic nitrogen concentrations into fluxes and comparing the data with estimates of biological productivity in the surface waters, our data suggest that ∼ 30% of new production in eastern Atlantic surface waters off Ireland can be supported by atmospheric inputs in May 1997 and that most of the input occurs during short lived, high-concentration, south-easterly transport events.

 

Home Environment and Childhood Asthma Home Environment and Childhood Asthma

Date added: 07/31/1994
Date modified: 07/02/2009
Filesize: 224.33 kB

Leen, M.G., O'Connor, T.C., Kelleher, C.C., Loftus, B.G. & Mitchell, C. (1994)- Home environment and childhood asthma. The Irish Medical Journal, Vol. 87, No. 5, pp. 142-144.


Abstract


The prevalence of childhood asthma has increased dramatically in the past 20 years. The reasons for the increase are unclear but many authors suggest that changes in the home environment favourable to proliferation of the house dust mite are to blame. Our study aimed to compare home environment of children with asthma and controls. A questionnaire on home environment was administered to the parents of 134 children with asthma and 118 controls. Detailed studies of home temperature, humidity and dust mite allergen (DERpI) levels were performed in 20 homes (10 from each group). The questionnaire response rate was 86%. There were no significant differences between asthma and control homes with respect to social class, type of housing, smoking habits, pets, insulation, home heating, bedding, carpeting and domestic cleaning habits. A first degree family history of atopy wasobtained in 42% of asthmatic families and in 16% of controls. Temperature, humidity and dust mite allergen levels were similar in both groups. The majority gave readings exceeding recommended norms. Values for DERpI were above thresholds by a factor of 5 in 48%. Home environment does not significantly differ in children with or without asthma. The home environment is now generally mite friendly, and large segments of the childhood population are now exposed to high levels of DERpI. This may account for the increasing prevalence as more and more children with an atopic background develop overt symptoms in response to high levels of allergen load.

Marine aerosol chemistry gradients Elucidating primary and secondary processes and fluxes Marine aerosol chemistry gradients Elucidating primary and secondary processes and fluxes

Date added: 08/01/2008
Date modified: 07/24/2009
Filesize: 260.53 kB

Ceburnis, D., C. D. O'Dowd, G. S. Jennings, M. C. Facchini, L. Emblico, S. Decesari, S. Fuzzi, and J. Sakalys (2008), Marine aerosol chemistry gradients: Elucidating primary and secondary processes and fluxes, Geophys. Res. Lett., 35, L07804, doi:10.1029/2008GL033462.


Abstract


Production mechanisms of aerosol chemical species, in terms of primary and secondary processes, were studied using vertical concentration gradient measurements at the coastal research station in Mace Head, Ireland. Total gravimetric PM1.0 mass, sea salt and water insoluble organic carbon (WIOC) concentration profiles showed a net production at the surface (i.e. primary production), while nssSO4 and water soluble organic carbon (WSOC) concentration profiles showed a net removal at the surface. These observations indicate that WSOC was predominantly of secondary origin and that WIOC was predominantly of primary origin. Derived PM1 mass fluxes compared reasonably well with those previously obtained from an eddy covariance (EC) technique following a power law relationship with the wind speed (F PM1 = 0.000096*U 4.23). For cases with clear primary organic mass fluxes in the flux footprint WIOM mass fluxes ranged between 0.16 and 1.02 ng m−2 s−1 and WIOM/sea salt mass ratio was 0.34–3.6, in good agreement with previous measurements at Mace Head.

Production Of Cn by Gaseous Reactions Production Of Cn by Gaseous Reactions

Date added: 08/07/1963
Date modified: 07/23/2009
Filesize: 4.02 MB
Tom OConnor ,Production Of Cn by Gaseous Reactions, Journal de Recherches Atmospherique, pg 127 - 133 (1963)
Abstract

 

The production of condensation Nuclei as a result of gaseous reactions is discussed.  A Portable nucleus counter used to investigate sources of nuclei in the littoral zone is described. Laboratory experiments show that decaying seaweed emits a gas which forms condensation nuclei on irradiation with ultra violet or sunlight. It also emits H2S and the significance of this in the natural cycle of sulphur in the atmosphere is considered. Electrically heated wires produce very small condensation nuclei and also NO2.

New Particle Formation Nucleation Rates and Spatial Scales in the Clean Coastal Environment New Particle Formation Nucleation Rates and Spatial Scales in the Clean Coastal Environment

Date added: 08/06/1998
Date modified: 07/23/2009
Filesize: 492.74 kB

O’Dowd, C. D., M. Geever, M. K. Hill, M. H. Smith, and S. G. Jennings (1998), New Particle Formation: Nucleation Rates and Spatial Scales in the Clean Marine Coastal Environment, Geophys. Res. Lett., 25(10), 1661–1664.


Abstract


Nucleation of new, ultra-fine, aerosol particles has been observed in the clean marine coastal atmosphere under a variety of conditions. These nucleation events were observed to occur frequently over spatial scales of 10’s-100’s of metres and temporal scales of seconds to minutes. Two conditions appeared to be necessary for nucleation event to occur: low tide and solar irradiation. The requirement of low tide conditions suggests that the exposed shore area provides the source of new particle precursors. It is speculated that VOC and/or alkyl halide derivatives contribute to nucleation under these conditions. Nucleation rates were calculated to be ≈ 10³ −104 cm−3 s−1, suggesting that the coastal zone is an important source of atmospheric nuclei.

 

Comparison of calculated and measured peroxide data collected in marine air to investigate prom Comparison of calculated and measured peroxide data collected in marine air to investigate prom

Date added: 08/06/1998
Date modified: 07/27/2009
Filesize: 1007.98 kB

Penkett, S.A., Reeves, C.E., Bandy, B.J., Kent, J.M., and Richer, H.R., Comparison of calculated and measured peroxide data collected in marine air to investigate prominent features of the annual cycle of ozone in the troposphere, J. Geophys. Res., 103 (D11): 13377-13388, 1998.


Abstract


Large amounts of data on the concentration of peroxides have been collected in vertical profiles over the North Atlantic Ocean by a Hercules aircraft. The measured peroxide concentrations have been compared with concentrations calculated by a simple algorithm derived assuming that the standing peroxide concentration is in equilibrium with its production and loss processes. In clean air where the peroxide and ozone concentrations are anticorrelated throughout the profile measured and calculated peroxide concentrations coincide, whereas in layers of polluted air within the profile, as determined from positive ozone peroxide correlations, calculated peroxide concentrations are greatly in excess of measured values. Using the degree of correlation between measured and calculated peroxide concentrations as a diagnostic, it is possible to show that many aspects of the seasonal cycle of ozone are caused by in situ tropospheric chemistry. Thus the summer minimum in the seasonal cycle of ozone, observed at clean marine ground-based sites such as Mace Head, is due to photochemical destruction, and elevated levels of ozone are associated with the transport of polluted air, on occasion over thousands of kilometers. Of particular interest if our analysis is correct, the broad maximum of ozone occurring between March and May at ground-based sites has a large contribution from ozone formed by tropospheric as well as stratospheric chemistry.

 

Modelling of indoor exposure to nitrogen dioxide in the UK Modelling of indoor exposure to nitrogen dioxide in the UK

Date added: 08/31/2001
Date modified: 07/03/2009
Filesize: 346.84 kB

Dimitroulopoulou, C., Ashmore, M.R., Byrne, M.A. and Kinnersley, R.P. Modelling of indoor exposure to nitrogen dioxide in the UK. Atmos. Environ., 35, 269-279, 2001.


Abstract


A dynamic multi-compartment computer model has been developed to describe the physical processes determining indoor pollutant concentrations as a function of outdoor concentrations, indoor emission rates and building characteristics. The model has been parameterised for typical UK homes and workplaces and linked to a time-activity model to calculate exposures for a representative homemaker, schoolchild and office worker, with respect to NO2. The estimates of population exposures, for selected urban and rural sites, are expressed in terms of annual means and frequency of hours in which air quality standards are exceeded. The annual mean exposures are estimated to fall within the range of 5-21 ppb for homes with no source, and 21-27 ppb for homes with gas cooking, varying across sites and population groups. The contribution of outdoor exposure to annual mean NO2 exposure varied from 5 to 24%, that of indoor penetration of outdoor air from 17 to 86% and that of gas cooking from 0 to 78%. The frequency of exposure to 1 h mean concentrations above 150 ppb was very low, except for people cooking with gas.

Behavior of ultrafine particles in continental and marine air masses at a rural site in the Uni Behavior of ultrafine particles in continental and marine air masses at a rural site in the Uni

Date added: 08/06/2000
Date modified: 07/09/2009
Filesize: 1.44 MB

Coe H., P. I. Williams, G. McFiggans, M. W. Gallagher, K. M. Beswick, K. N. Bower and T. W. Choularton Behavior of ultrafine particles in continental and marine air masses at a rural site in the United Kingdom. J. Geophys. Res., 105, 26891-26905, 2000


Abstract


Particle size distribution measurements were made at a coastal site in the United Kingdom. These are presented, and the behavior of recently formed ultrafine particles is discussed. No ultrafine particles were observed in maritime air masses; however, 3 to 7 nm particles were frequently observed at enhanced concentrations when the wind direction was from the land. Their formation was favored at lower temperatures, when 1 ppbv or more of SO2 was present and in air masses that had not been aged extensively. On days when enhanced ultrafine particle concentrations were observed, 3 nm particles increased sharply in the morning, approximately 30 to 90 min after the UV solar flux first increased. By early afternoon the ultrafine particle concentration had returned to background levels. Rapid measurements of 5 nm particles showed no correlation with turbulence parameters, although the boundary layer mixing scales were similar to growth times of freshly nucleated particles to 5 nm diameter. However, ultrafine particle concentrations do correlate with the availability of sulphuric acid vapor. A delay of approximately an hour between the increase of H2SO4 in the morning and a large increase in ultrafine particle concentrations is due to the growth of particles to observable sizes, not the nucleation process itself. An analysis of the timescales for growth showed that coagulation may be important immediately after the particles have nucleated but its effectiveness reduces as number concentration falls. Conversely, growth by condensation is initially slow due to the Kelvin effect but increases in importance as the particles reach observable sizes.

 

Eastern Atlantic Spring Experiment 1997 (EASE97) 2 Comparisions of model concentrations of OH... Eastern Atlantic Spring Experiment 1997 (EASE97) 2 Comparisions of model concentrations of OH...

Date added: 08/06/2002
Date modified: 07/27/2009
Filesize: 640.01 kB

Carslaw,m N.; Creasey, D.J.; Heard, D.E.; Jacobs, P.; Lee, J.D.L.; Lewis, A.C.; McQuaid, J.B.; Pilling, M.J.; Bauguitte, S.; Penkett, S.A.; Monks, P.S.; Salisbury, G. (2002) Eastern Atlantic Spring Experiment 1997 (EASE97) - 2. Comparisons of model concentrations of OH, HO2, and RO2 with measurements, Journal of Geophysical Research, 107, pp.4190/ ACH5


Abstract


An observationally constrained box model has been used to investigate the chemistry of the marine boundary layer at the Mace Head Atmospheric Research Station, a remote site on the west coast of Ireland. The model aims to simulate concentrations of the hydroxyl (OH) and hydroperoxy (HO2) radicals measured by an in situ fluorescence assay by gas expansion instrument, and the sum of peroxy radicals ([HO2] + Σ[RO2]) as determined by a peroxy radical chemical amplification instrument. The model has been constructed based on observed concentrations of nonmethane hydrocarbons, measured in situ during the campaign by gas chromatography. The chemical mechanism for the model is a subset of a comprehensive master chemical mechanism. This paper details comparisons of the concentrations of modeled and measured radical species from a field campaign held at Mace Head during spring 1997. The air masses arriving at the site have been split into three categories depending on their origin and chemical characteristics and model-measurement comparisons carried out for each air mass. The average model-measurement ratios are 2.4 for [OH], 3.6 for [HO2], and 0.9 for ([HO2] + Σ[RO2]), respectively, between 1100 and 1500 hours: the level of agreement is better for all three sets of radicals in the cleanest air mass. Possible reasons for the observed discrepancies are discussed. In addition, a rate of production analysis is used to identify key OH and HO2 reactions in the three air masses. The rate of OH production from HO2 with NO exceeds that from ozone photolysis by factors of 2–6 in the polluted air masses studied. In cleaner air from the northern polar region, primary production from ozone photolysis exceeds that from HO2 + NO by a factor of 2.5. HO2 and CH3O2 dominate the peroxy radical composition in all air masses, but peroxy radicals derived from the oxidation of nonmethane hydrocarbons are more important in polluted air masses.

 

Dimethyl sulfide, methane sulfonic acid and physicochemical aerosol properties in Atlantic air Dimethyl sulfide, methane sulfonic acid and physicochemical aerosol properties in Atlantic air

Date added: 08/06/1996
Date modified: 07/01/2009
Filesize: 1.18 MB

Davison, B.M., C.N. Hewitt, R.M. Harrison, M. Schwikowski, U. Baltensperger, C. O'Dowd and M.H. Smith. Dimethyl sulfide, methane sulfonic acid and physico-chemical aerosol properties in Atlantic air from the United Kingdom to Halley Bay. J. Geophys. Res., 101, 22855-22874, 1996.


Abstract


The concentrations of dimethyl sulfide in air were obtained during a cruise between the United Kingdom and the Antarctic in the period October 1992 to January 1993 using a method of sampling and analysis optimized to avoid interferences from oxidants. In equatorial regions (30°N to 30°S) the atmospheric DMS concentration ranged from 3 to 46 ng (S) m-3, with an average of 18 ng (S) m-3, In the polar waters and regions south of the Falkland Islands, concentrations from 3 to 714 ng (S) m-3 were observed, with a mean concentration of 73 ng (S) m-3. The concentrations of a range of DMS oxidation products were also obtained. No clear relationships between reactant and product concentrations were seen. Information on particle number concentration, Fuchs surface area and the thermal volatility characteristics of the ambient aerosol was obtained, but again no clear relationships with sulfur concentrations were observed. Accumulation mode particle concentrations averaged 25 cm-3 in the clean marine and polar air masses south of 58°S while background condensation nuclei (CN) concentrations were of the order of 400-600 cm-3. Simplistic calculations suggest that a particle source strength of about 20-60 particles cm-3 d-1 is required to sustain this background CN concentration. It is not clear whether boundary layer nucleation of new CN or entrainment from the free troposphere provided the source of CN. Periods of elevated CN concentrations (>4000 cm-3) were regularly observed in the boundary layer over the Weddell Sea and were attributed to bursts of new particle formation. However, shortly after these nucleation events the CN concentration rapidly decayed to the background level through coagulation losses, suggesting little impact on the background CN or cloud condensation nuclei (CCN) concentration.

 

In situ measurement of the ratio of aerosol absorption to extinction coefficient In situ measurement of the ratio of aerosol absorption to extinction coefficient

Date added: 07/31/1980
Date modified: 07/02/2009
Filesize: 558.49 kB

Bruce, C.W., Yee, Y.P., and Jennings, S.G. (1980)- In situ measurements of the ratio of aerosol absorption to extinction coefficients. Appl. Opt., 19, 1893-1894.


Abstract


A knowledge of the proportion of absorbed to scattered radiation for countermeasure smokes is necessary for modeling battlefield effects. Measurement of the total scattered component, however, is difficult. This report presents results obtained by using a new and simpler approach focussing on the extinction and the absorption coefficients (the total scattering coefficient is the difference quantity). Measurements of the absorption and extinction coefficients due to smoke produced by the combustion of 'red phosphorous' are simultaneously obtained in a small test chamber. The same CO2 laser beam at lambda = 9.55 micron is used to produce both results. A form of aerosol spectrophone cell was used to measure the absorption coefficient while functioning as a transmission cell from which the extinction coefficient was calculated. The ratio of the absorption to extinction coefficients was then compared with estimates of the same quantities based on calculated particle sizes, the particle size estimates being obtained from characteristics of the settling process. The ratio agreed with that predicted within the experimental error.

Quantification of carbon dioxide, methane, nitrous oxide and chloroform emissions over Ireland from atmospheric observations at Mace Head Quantification of carbon dioxide, methane, nitrous oxide and chloroform emissions over Ireland from atmospheric observations at Mace Head

Date added: 08/01/2002
Date modified: 07/23/2009
Filesize: 738.69 kB

Biraud, S., Ciais, Philippe, Ramonet, Michel, Simmonds, Peter, Kazan, Victor, Monfray, Patrick, O’Doherty, Simon, Spain, Gerard, and Jennings, S. Gerard. 2002. Quantification of carbon dioxide, methane, nitrous oxide, and chloroform emissions over Ireland from atmospheric observations at Mace Head, Tellus, 54B, pp. 41-60.


Abstract


Flux estimates of CO2, CH4, N2O and CHCl3 over Ireland are inferred from continuous atmospheric records of these species. We use radon-222 (222Rn) as a reference compound to estimate unknown sources of other species. The correlation between each species and 222Rn is calculated for a suite of diurnal events that have been selected in the Mace Head record over the period 1995-1997 to represent air masses exposed to sources over Ireland. We established data selection criteria based on 222Rn and 212Pb concentrations. We estimated flux densities of 12 × 103 kg CH4 km-2 yr-1, 680 kg N2O km-2 yr-1 and 20 kg CHCl3 km-2 yr-1 for CH4, N2O and CHCl3, respectively. We also inferred flux densities of 250 x 103 kg C km-2 yr-1 for CO2 during wintertime, and of 760 x 103 kg C km-2 yr-1 for CO2 during summer night-time. Our CH4 inferred flux compare well with the CORINAIR90 and CORNAIR94 inventories for Ireland. The N2O emission flux we inferred is close to the inventory value by CORINAIR90, but twice the inventory value by CORINAIR94 and EDGAR 2.0. This discrepancy may have been caused by the use of the revised 1996 IPCC guidelines for national greenhouse gas inventories in 1994, which include a new methodology for N2O emissions from agriculture. We carried out the first estimation of CHCl3 emission fluxes over Ireland. This estimation is 4 times larger than the CHCl3 emission fluxes measured close to the Mace Head station over peatlands. Our CHCl3 emission fluxes estimate is consistent with the interpretation of the same data by Ryall (personal communication, 2000), who obtained, using a Lagrangian atmospheric transport model, CHCl3 fluxes of 24 ± 7 kg CHCl3 km-2 yr-1. Our estimates of CO2 emission fluxes during summer night-time and wintertime are close to those estimated from inventories and to one biogeochemical model of heterotrophic respiration.

Atmospheric bromoform at Mace Head, Ireland seasonality and evidence for a peatland source Atmospheric bromoform at Mace Head, Ireland seasonality and evidence for a peatland source

Date added: 08/07/2005
Date modified: 07/27/2009
Filesize: 692.16 kB

Carpenter, L. J., Wevill, D. J., O'Doherty, S., Spain, G., and Simmonds, P. G.: Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source, Atmos. Chem. Phys., 5, 2927-2934, 2005.


Abstract


In situ atmospheric observations of bromoform (CHBr3) made over a 2.5 year period at Mace Head, Ireland from May 2001- Dec 2003, including during the NAMBLEX (North Atlantic Marine Boundary Layer Experiment) campaign, show broad maxima from spring until autumn and winter minima, with mixing ratios of 5.3+1.0 pptv (mid March - mid October) and 1.8+0.8 pptv (December-February). This indicates that, unlike CHCl3, which has a summer minimum and winter maximum at Mace Head, local biological sources of CHBr3 have a greater influence on the atmospheric data than photochemical decay during long-range transport. The emission sources are predominantly macroalgal, but we find evidence for a small terrestrial flux from peatland ecosystems, which so far has not been accounted for in the CHBr3 budget. Sharp increases in CHCl3 and CHBr3 concentrations and decreases in O3 concentrations occurred at night when the wind direction switched from an ocean- to a land-based sector (land breeze) and the wind speed dropped to below 5 ms-1. These observations infer a shallow atmospheric boundary layer with increased O3 deposition and concentration of local emissions of both CHCl3 and CHBr3. The ratio of ΔCHCl3/ΔCHBr3 varied strongly according to the prevailing wind direction; from 0.60+0.15 in south-easterly (100-170° and northerly (340-20°) air to 2.5+0.4 in north-easterly (40-70°) air. Of these land-sectors, the south-easterly air masses are likely to be strongly influenced by macroalgal beds along the coast and the emission ratios probably reflect those from seaweeds in addition to land sources. The north-easterly airmasses however had an immediate fetch inland, which locally is comprised of coastal peatland ecosystems (peat bogs and coastal conifer plantations), previously identified as being strong sources of atmospheric CHCl3 under these conditions. Although we cannot entirely rule out other local land or coastal sources, our observations also suggest peatland ecosystem emissions of CHBr3. We use correlations between CHCl3 and CHBr3 during the north-easterly land breeze events in conjunction with previous estimates of local wetland CHCl3 release to tentatively deduce a global wetland CHBr3 source of 20.4(0.4-948) Gg yr-1, which is approximately 7% of the total global source.

An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire

Date added: 08/06/1998
Date modified: 07/27/2009
Filesize: 1.36 MB
McArdle N. ; Liss P. ; Dennis P.  1998, An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire, J. Geophys. Res. Vol. 103 , No. D23 , p. 31,079 (98JD01664)

Abstract


Sulphur isotope measurements made on aerosol and precipitation samples collected at three sites in Wales and Mace Head, Eire, between March 1993 and 1994, had highest non-sea-salt sulphate δ34S values, up to 11.9‰ for aerosol and 9.7‰ for precipitation, during the summer months. Aerosol methanesulphonate shows a clear summer peak with values up to 3-4 nmol m-3. Assuming samples contained only sulphur from terrestrial/anthropogenic, sea salt, and marine biogenic (from the oxidation of dimethylsulphide) sources, we used the sulphur isotope values to determine the contribution of dimethylsulphide-derived sulphate to total sulphate. In general the biogenic contribution was small, < 10%, although in samples from marine air masses it was as high as 40%. A comparison of aerosol and precipitation δ34S values found no evidence for large isotopic fractionations during the oxidation of sulphur dioxide.

Gas-to-particle conversion of sulphur and nitrogen compounds as studied at marine stations in N Gas-to-particle conversion of sulphur and nitrogen compounds as studied at marine stations in N

Date added: 08/05/1996
Date modified: 07/02/2009
Filesize: 935.92 kB

V. L. Foltescu, E. Selin Lindgren, J. Isakson, M. Oblad, J. M. Pacyna, S. Benson, Gas-to-particle conversion of sulphur and nitrogen compounds as studied at marine stations in Northern Europe, Atmospheric EnvironmentVolume 30, Issue 18, , September 1996, Pages 3129-3140.


Abstract


The present work provides insights into the N- and S-pollution behaviour at rural and remote sites in Northern Europe. Formation of SO42- and NO3- from their precursor gases receives special attention in order to understand the significance of chemical conversion in shaping the distributions of concentration and deposition monitored at our sites : Säby-on the Swedish west coast, Lista-on the Norwegian south coast and South Uist-on the Hebride Islands in Northern Scotland. Owing mainly to the complexity of the problem, the approach is semiquantitative. Concentration patterns of S- and N-compounds for air mass transport between the sites were investigated for 10 periods (13d), within continental(6d) and oceanic (7 d) air masses. The observations spanned over both winter and summer days and conclusions could be drawn in some cases with respect to seasonality. The measurements were performed during the BMCAPE (Background Maritime Contribution to Atmospheric Pollution in Europe) project in 1993 and 1994. S- and N-ratios were used as indicators of air mass age, chemical conversion efficiency and en-route deposition. The S-ratio is defined as the ratio of particulate S (as SO42-) to total S (as SO2 and SO42-). The N-ratio is taken as the ratio of gaseous HNO3-N over particulate NO3--N. S-ratios at Säby and Lista agreed very well in those cases when no or insignificant precipitation occurred. Higher S-ratios and lower N-ratios were typical for conditions of high relative humidity. It is conceivable that condensed phase chemistry was of major importance in the SO2 oxidation and that HNO3 was absorbed onto the wet aerosol particles. Stagnation of the air masses over source regions of high emission densities and rates resulted in accumulation of pollution, the S-ratios in such conditions being high due to the longer transport time. The S-ratios for marine air flow at Säby and Lista no longer agreed (higher at Lista) as in the case of continental air masses. The reason is likely to be the proximity of the Lista station to the sea. Lista was highly affected by sea spray produced by the strong westerly winds. The N-ratio remained very low in the case of maritime air masses due to unexpectedly high NO3- concentrations. It is conceivable that the high load of NO3- is due to sea spray of surface water. More efficient SO2 deposition over land than over sea has been observed in the westerly airflow by the relative loss of SO2 while the flow swept over land.

 

Primary Marine Organic Aerosol: A Dichotomy of Low Hygroscopicity and High CCN Activity Primary Marine Organic Aerosol: A Dichotomy of Low Hygroscopicity and High CCN Activity

Date added: 11/17/2011
Date modified: 11/17/2011
Filesize: 532.27 kB

Ovadnevaite, J., D. Ceburnis, J. Bialek, C. Monahan, G. Martucci, M. Rinaldi, M.C. Facchini, H. Berresheim, D. R. Worsnop and C. O’Dowd. Primary Marine Organic Aerosol: A Dichotomy of Low Hygroscopicity and High CCN Activity, Geophys. Res. Letts, 38, L21806, doi:10.1029/2011GL048869., 2011


Abstract. High-time resolution measurements of primary marine organic sea-spray physico-chemical properties reveal an apparent dichotomous behavior in terms of water uptake: specifically sea-spray aerosol enriched in organic matter possesses a low hydroscopic Growth Factor (GF~1.25) while simultaneously having a cloud condensation nucleus/condensation nuclei (CCN/CN) activation efficiency of between 83% at 0.25% supersaturation and 100% at 0.75%. In contrast, the activation efficiency of particles dominated by non-sea-salt (nss)-sulfate ranged between 48-100% over supersaturation range of 0.25%-1%. Simultaneous retrieval of Cloud Droplet Number Concentration (CDNC) during primary organic aerosol plumes reveals CDNC concentrations of 350 cm-3 for organic mass concentrations 3-4 mg m-3. It is demonstrated that the retrieved high CDNCs under clean marine conditions can only be explained by organic sea-spray and corroborates the high CCN activation efficiency associated with primary organics. It is postulated that marine hydrogels are responsible for this dichotomous behavior.

On condensation nuclei produced at heated surfaces On condensation nuclei produced at heated surfaces

Date added: 08/31/1959
Date modified: 07/03/2009
Filesize: 1.59 MB

O'Connor, T.C, Sharkey, W.P.F., and O Brolchain, C. (1959)- On condensation nuclei produced at heated surfaces, Geofisia pura e applicata, 42, 109-116.


Abstract

 

An investigation of heated surfaces of glass, metal and oil as sources of condensation nuclei is reported. Below a certain transition temperature the nucleus production is of a temporary nature and decreases to zero with the continued heating of the surface. Above this temperature, however, the nucleus production does not change with time. The transition temperature varies with the material of the surface and is not always associated with the onset of incandescence. The nuclei produced at the lower temperatures have a radius of about 10–5 cm and, on production, are mainly uncharged. Electric light bulbs can produce appreciable numbers of these nuclei.

Halogenated greenhouse gases at the Swiss High Alpine Site of Jungfraujoch (3580 m asl) Continu Halogenated greenhouse gases at the Swiss High Alpine Site of Jungfraujoch (3580 m asl) Continu

Date added: 08/06/2004
Date modified: 07/24/2009
Filesize: 1.93 MB

Reimann, S., D. Schaub, K. Stemmler, D. Folini, M. Hill, P. Hofer, B. Buchmann, P. G. Simmonds, B. R. Greally, and S. O'Doherty (2004), Halogenated greenhouse gases at the Swiss High Alpine Site of Jungfraujoch (3580 m asl): Continuous measurements and their use for regional European source allocation, J. Geophys. Res., 109, D05307, doi:10.1029/2003JD003923.


Abstract


At the high Alpine site of Jungfraujoch (3580 m asl), 23 halogenated greenhouse gases are measured quasi-continuously by gas chromatography-mass spectrometry (GCMS). Measurement data from the years 2000–2002 are analyzed for trends and pollution events. Concentrations of the halogenated trace gases, which are already controlled in industrialized countries by the Montreal Protocol (e.g., CFCs) were at least stable or declining. Positive trends in the background concentrations were observed for substances which are used as CFC-substitutes (hydrofluorocarbons, hydrochlorofluorocarbons). Background concentrations of the hydrofluorocarbons at the Jungfraujoch increased from January 2000 until December 2002 as follows: HFC 134a (CF3CH2F) from 15 to 27 ppt, HFC 125 (CF3CHF2) from 1.4 to 2.8 ppt, and HFC 152a (CHF2CH3) from 2.3 to 3.2 ppt. For HFC 152a, a distinct increase of its concentration magnitude during pollution events was observed from 2000 to 2002, indicating rising European emissions for this compound. Background concentrations of all measured compounds were in good agreement with similar measurements at Mace Head, Ireland. On the other hand, peak concentrations were significantly higher at the Jungfraujoch. This finding is due to the proximity to potent European sources, foremost in southern Europe. The average ratio of halocarbons versus carbon monoxide (CO) concentrations above their baseline values was used to estimate source strengths for the part of Europe which most influences the Jungfraujoch during pollution events. HFCs emission estimates from Jungfraujoch tend to be higher than figures at Mace Head (Ireland) from the end of the 1990s, which either reflects the increased use of these compounds or the closer location of Jungfraujoch to major southern European sources. Transport of polluted European boundary layer air masses to the high Alpine site was observed especially during frontal passages, foehn events, and thermal lifting of air masses in summer. The measurement data during the periods when the Jungfraujoch was under the influence of the polluted boundary layer were used in combination with concurrent air mass trajectories to allocate above baseline halocarbon concentrations to specific European source regions.

 

Observation of diurnal cycles in short-lived tropospheric alkenes at a North Atlantic coastal s Observation of diurnal cycles in short-lived tropospheric alkenes at a North Atlantic coastal s

Date added: 08/05/1999
Date modified: 07/22/2009
Filesize: 210.82 kB

A. C. Lewis, J. B. McQuaid, N. Carslaw, M. J. Pilling, Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site, Atmospheric EnvironmentVolume 33, Issue 15, , 1 July 1999, Pages 2417-2422.


Abstract


Observation of diurnal cycles in atmospheric concentrations of reactive alkenes are reported from measurements performed at a North Atlantic coastal site (Mace Head, Eire 53°19'34N; 9°54'14W). Species seen to exhibit distinct cycles included isoprene, ethene, propene, 1-butene, iso-butene and a substituted C6 alkene. Five hundred and thirty air mass classified measurements were performed over a 4 week period at approximately hourly frequency and demonstrate that during periods when air flow resulted from unpolluted oceanic regions a clear daily cycle in concentrations existed, peaking at around solar noon for all species. These observations support the proposed mechanism of production via photochemical degradation of organic carbon in sea water. The observed concentrations showed strong correlation (propene R2 > 0.75) with solar flux, with little relationship to other meteorological or chemical parameters. The species' short atmospheric lifetimes indicate that the source of emission was from local coastal waters within close proximity of the sampling site. At solar noon concentrations of reactive alkenes from oceanic sources were responsible for up to 88% of non-methane hydrocarbon reaction with the hydroxyl radical at this coastal marine site.

 

Measurements of the number concentration of aitken nuclei at mountain and rural sites Measurements of the number concentration of aitken nuclei at mountain and rural sites

Date added: 08/01/1975
Date modified: 07/03/2009
Filesize: 1.25 MB
Jennings, S.G.  (1975)- Measurements of condensation Aitken nuclei at rural and mountain sites. Jnl. de Rech. Atmos., No. 2,  59-66.

Abstract

 

A study of the number concentration at Aitken nuclei has been carried out using automated Nolan Pollak photoelectric nucleus ountain site, a sparsely populated site and in a rural envirorment. It has been found that the nucleus counter assembly operates very satisfactorily over long periods under field conditions.

The appuratus has proven to be particularly senstive in detecting pertubations in the background count due to localized nuclei sources. Frequency distribution curves of the individual observations follow closely a log-normal distribution for each measurement period. It is shown that te two minute sampling frequency can be increased by about an order of magnitude without causing a significant change in the nuclei number distribution.

AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001 AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001

Date added: 08/01/2004
Date modified: 07/27/2009
Filesize: 593.54 kB

Simmonds, P.; Derwent, R.; Manning, A.; Fraser, P.; Krummel, P.; O'Doherty, S.; Prinn, R.; Cunnold, D.; Miller, B.; Wang, H.; Ryall, D.; Porter, L.; Weiss, R.; Salameh, P. ,AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998–2001, Journal of Atmospheric Chemistry, pg 1573-0662


Abstract


In situ AGAGE GC-MS measurements of methyl bromide (CH3Br) and methyl chloride (CH3Cl) at Mace Head, Ireland and Cape Grim, Tasmania (1998–2001) reveal a complex pattern of sources. At Mace Head both gases have well-defined seasonal cycles with similar average annual decreases of 3.0% yr−1 (CH3Br) and 2.6% yr−1 (CH3Cl), and mean northern hemisphere baseline mole fractions of 10.37 ± 0.05 ppt and 535.7 ± 2.2 ppt, respectively. We have used a Lagrangian dispersion model and local meteorological data to segregate the Mace Head observations into different source regions, and interpret the results in terms of the known sources and sinks of these two key halocarbons. At Cape Grim CH3Br and CH3Cl also show annual decreases in their baseline mixing ratios of 2.5% yr−1 and 1.5% yr−1, respectively. Mean baseline mole fractions were 7.94 ± 0.03 ppt (CH3Br) and 541.3 ± 1.1 ppt (CH3Cl). Although CH3Cl has astrong seasonal cycle there is no well-defined seasonal cycle in the Cape Grim CH3Br record. The fact that both gases are steadily decreasing in the atmosphere at both locations implies that a change has occurred which is affecting a common, major source of both gases (possibly biomass burning) and/or their major sink process (destruction by hydroxyl radical).

Concurrent observations of alkyl halides and dimethyl sulphide in marine air Implications for s Concurrent observations of alkyl halides and dimethyl sulphide in marine air Implications for s

Date added: 08/05/1999
Date modified: 07/27/2009
Filesize: 560.08 kB

Bassford, M.R., G. Nickless, P. Simmonds, A.C. Lewis, M.J. Pilling, M.J. Evans and J.A. Pyle, Concurrent observations of alkyl halides and dimethyl sulphide in marine air: Implications for sources of atmospheric methyl iodide, Atmos Environ, 33, 2373-2383, 1999, (Ser. No. ACP106).


Abstract


Continuous atmospheric measurements of methyl iodide and dimethyl sulphide were carried out at Mace Head, western Ireland, over a 4-week period in July 1996. The concurrent observations of methyl iodide and dimethyl sulphide reported here display a clear association, indeed statistical analysis indicated a very signiÞcant degree of covariance. A simple yet informative use of modelled 5-day back trajectories was employed in tandem with examination of local meteorology to illuminate the geographical source regions of methyl iodide and dimethyl sulphide. The  interpretation of the atmospheric observations in terms of air-mass ßow has elucidated part of the global methyl iodide cycle and provides evidence for two distinct source regions of methyl iodide:
1. Under certain synoptic meteorological conditions, long-range transport of methyl iodide and dimethyl sulphide was observed from discrete areas of the sub-tropical Atlantic Ocean located in a region between 30Ð50¡N and 20Ð50¡W.

2. Measurements taken under di¤erent conditions led us to believe that there was an additional source of methyl iodide that inßuenced the Mace Head atmosphere, most likely produced by coastal macroalgae which inhabit waters o¤ the western coast of Ireland.

Evasion of mercury from coastal and open waters of the Atlantic Ocean and the Mediterranean Sea Evasion of mercury from coastal and open waters of the Atlantic Ocean and the Mediterranean Sea

Date added: 08/07/2003
Date modified: 07/24/2009
Filesize: 240.1 kB

Gardfeldt, K., Sommar, J., Ferrara, R., Ceccarini, C., Lanzillotta, E., Munthe, J., Wangberg, I., Lindqvist, O., Pirrone N., Sprovieri, F., Pesenti, E. (2003)   Evasion of mercury from coastal and open waters of the Atlantic Ocean and the Mediterranean Sea. Atmospheric Environment. Vol. 37-S1, 73-84.


Abstract


Dissolved gaseous mercury (DGM) was measured in coastal Atlantic seawater and in the Mediterranean Sea. The Atlantic measurements were performed during September 1999 at the Mace Head Atmospheric Research Station, situated on the Irish west coast. The measurements in the Mediterranean Sea were made along a 6000 km cruise path from 14 July to 9 August 2000 in the framework of the Med-Oceanor project. Total gaseous mercury (TGM) concentrations in air were continuously measured with a 5 min time resolution using an automated mercury analyser (Tekran 2537A) during both expeditions. Paired TGM and DGM samples from all campaigns showed that the surface water was supersaturated with elemental mercury. The mercury evasion was estimated using a gas exchange model (J. Geophys. Res. 97 (1992) 7373), which uses salinity, wind speed and water temperature as independent parameters. The predicted average mercury evasion from the coastal Atlantic water was 2.7 ng m-2h-1 implying that the concentration of TGM in the Atlantic air is enhanced by mercury evasion from the sea. Measurements in different regions of the Mediterranean Sea showed spatial variations in DGM concentrations. The highest DGM concentration (∼90 pg l-1) was observed at a location in the Strait of Sicily (37° 16N 11° 52E). The mercury evasion in the eastern sector of the Mediterranean Sea (area: 32-36°N, 17-28 E) was generally higher (7.9 ng m-2h-1) than that observed in the Tyrrhenian Sea (4.2 ng m-2h-1) or in the western sector (2.5 ng m-2h-1) (areas: 38-42°N, 8-13°E and 38-41°N, 7-8°E, respectively). Estimations of mercury evasion were also made at Mediterranean coastal sites using a dynamic chamber technique. In addition, a newly developed method making continuous in situ DGM measurements possible was tested.

 

Atmospheric Composition Change – Global and Regional Air Quality Atmospheric Composition Change – Global and Regional Air Quality

Date added: 11/11/2009
Date modified: 11/11/2009
Filesize: 9.8 MB

Monks, P.S., C. Granier, S. Fuzzi, A. Stohl, M. Williams, H. Akimoto, M. Amman, A. Baklanov, U. Baltensperger, I. Bey, N. Blake, R.S. Blake, K. Carslaw, O.R. Cooper, F. Dentener, D. Fowler, E. Fragkou, G. Frost, S. Generoso, P. Ginoux, V. Grewe, A. Guenther, H.C. Hansson, S. Henne, J. Hjorth, A. Hofzumahaus, H. Huntrieser, I.S.A. Isaksen, M.E. Jenkin, J. Kaiser, M. Kanakidou, Z. Klimont, M. Kulmala, P. Laj, M.G. Lawrence, J.D. Lee, C. Liousse, M. Maione, G. McFiggans, A. Metzger, A. Mieville, N. Moussiopoulos, J.J. Orlando, C. O'Dowd, P.I. Palmer, D.D. Parrish, A. Petzold, U. Platt, U. Poeschl, A.S.H. Prévôt, C.E. Reeves, S. Reimann, Y. Rudich, K. Sellegri, R. Steinbrecher, D. Simpson, H. ten Brink, J. Theloke, G.R. van der Werf, R. Vautard, V. Vestreng, Ch. Vlachokostas and R. vonGlasow, Atmospheric Composition Change – Global and Regional Air Quality, Atmos. Environ.,  doi:10.1016/j.atmosenv.2009.08.021  , 2009


Abstract.

Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems, heritage and climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, nighttime chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed.

Relationship between visible extinction absorption and mass concentration of carbonaceous smokes Relationship between visible extinction absorption and mass concentration of carbonaceous smokes

Date added: 07/31/1980
Date modified: 07/22/2009
Filesize: 1.99 MB

Jennings, S.G., and Pinnick, R.G. (1980)- Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes. Atmos. Environ., 14, 1123-1129.


Abstract


A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σe(m−1) and mass concentration M (gm−3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σe/M = 9.5m2g−1, assuming a particle density of 2gcm−3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σa, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.

Atmospheric carbon dioxide and its stable isotope ratios, methane, carbon monoxide, nitrous oxi Atmospheric carbon dioxide and its stable isotope ratios, methane, carbon monoxide, nitrous oxi

Date added: 08/07/1998
Date modified: 07/27/2009
Filesize: 655.24 kB

Francey, R.J., L.P. Steele, R.L. Langenfelds, C.E. Allison, L.N. Cooper, B.L. Dunse, B.G. Bell, T.D. Murray, H.S. Tait, L. Thompson and K.A. Masarie, Atmospheric carbon dioxide and its stable isotope ratios, methane, carbon monoxide and hydrogen from Shetland Isles, Atmos. Environ., Vol. 32, No. 19, 3331-3338, 1998.


Abstract


Since November 1992, 0.5l glass flasks have been filled approximately monthly with dry marine air from Shetland Isles, Scotland (60.2oN, 1.2oW) and transported to CSIRO, Australia for analyses. The Shetland site is part of a CSIRO global flask network with 10-12 sites, anchored to continuous high precision in situ measurements made at the Australian Cape Grim Baseline Station (40.7oS, 144.7oE), a primary station in the Global Atmosphere Watch programme (GAW) coordinated by the World Meteorological Organisation. The methodology is summarised, and Shetland results for CO2, CH4, N2O, CO, H2 and delta13C, delta18O of CO2 presented for the period 1992-1996. We compare data to available results from surrounding stations of the NOAA cooperative network (in particular Mace Head, Ireland, 53.3oN, 9.9oW), and address issues of both trace species intercalibration and atmospheric spatial gradients. While considerable uniformity of trace-gas composition is evident in oceanic air over a 13o range of latitude, nevertheless anomalies in CO2 concentration and isotopic composition are suggested in samples representing air to the west of Shetland. The potential for remotely monitoring integrated emissions from northern Europe is also identified.

 

European emissions of mercury derived from long-term obsercations at Mace Head, on the western Irish coast European emissions of mercury derived from long-term obsercations at Mace Head, on the western Irish coast

Date added: 08/01/2006
Date modified: 07/24/2009
Filesize: 185.84 kB

Slemr F, R. Ebinghaus, P.G. Simmonds and S.G. Jennings, European emissions of mercury derived from long-term observations at Mace Head, on the western Irish coast, Atmos. Environ., 40, 6966-6974, 2006.


Abstract


Many emission inventories for mercury have been compiled but rarely constrained using observations of ambient air concentrations with a known quality. In this paper, we derive Hg/CO, Hg/halocarbon, and Hg/CH4 emission ratios from pollution episodes observed during the long-term mercury monitoring at the Mace Head Atmospheric Research Station in Ireland. The average Hg/CO emission ratio from 15 pollution episodes with air originating from the European continent observed between 1996 and 2003 was 0.0050±0.0021 ng m-3 ppbv-1, i.e. (5.5±2.3) x 10-7mol/mol, which is almost identical to the ratio reported recently for the continental plumes of eastern Asia. Mercury correlated also with CFCl3 (CFC-11), CF2Cl2 (CFC-12), CH3CCl3, CCl4, CCl2FCF2Cl (CFC-113), CHCl3, N2O, and CH4 during the pollution episodes. The mercury emissions calculated from the emission ratios and the European emissions of the above gases are in reasonable agreement with the estimated anthropogenic total mercury emissions of 250t/yr in 1995. However, the measurements encompass almost exclusively elemental mercury whose anthropogenic emissions are estimated to be only 152 t yr-1. Several hypotheses are proposed to explain this discrepancy, such as natural sources, underestimation of the emissions of elementary mercury, and erroneous speciation of anthropogenic emissions.

Particle counting and numerical models: Effect of instrumental size resolution and particle shapes o Particle counting and numerical models: Effect of instrumental size resolution and particle shapes o

Date added: 08/05/2006
Date modified: 08/05/2009
Filesize: 245.54 kB

Karine Chamaillard, S.G. Jennings, Particle counting and numerical models: Effect of instrumental size resolution and particle shapes on optical cross-sections, Journal of Quantitative Spectroscopy and Radiative Transfer, Volume 100, Issues 1-3, VIII Conference on Electromagnetic and Light Scattering by Nonspherical Particles, July-August 2006, Pages 64-76, ISSN 0022-4073, DOI: 10.1016/j.jqsrt.2005.11.064.

 


Abstract


The effect of instrumental size resolution measurements on numerical calculations of optical cross-sections is investigated. The particle counting instruments considered are a FSSP-300, a large scattering angle probe instrument similar to a ASASP-X, and, an aerodynamical system ELPI instrument. The scattering and hemispheric backscattering cross-sections, Csca and Cbk, are calculated on the basis that the full width of the instrumental size bin should be considered in modeling. An average process is applied on these quantities over the full size bin of the instrument; they are then compared to their usual estimation on the single mean diameter Dp per channel. The effect of particle shape is investigated with ellipsoids and spheres. Results show sensitivity of the optical cross-sections to the shape of the particles as well as position of the mean geometrical diameter Dp of the channels within the interferences modes of the scattering efficiencies. The value of the width of the size bins, d log D, of each channel is crucial in the results. This comparison gives a useful estimation of error important in optical particle counting instruments based on inversion process of optical quantities. In addition, accuracy of size distribution measurements is found not to be representative of accuracy in the calculations of optical cross-sections.

Biogenic coastal aerosol production and its influence on aerosol radiative properties Biogenic coastal aerosol production and its influence on aerosol radiative properties

Date added: 07/31/2001
Date modified: 07/27/2009
Filesize: 562.71 kB
O'Dowd, C.D., Biogenic coastal aerosol production and its influence on aerosol radiative properties, J. Geophys. Res., 106, 1545-1550, 2001

Abstract


Coastal zones have been shown to provide a massive source of new, tidal-related, aerosol particles in the atmospheric boundary layer with concentrations exceeding 1,000,000 cm−3 during nucleation bursts sustained over many hours [O Dowd, 200O]. While coastal regions are very strong sources of natural aerosol particles, hithertofore, it has not been demonstrated that these particles contribute to aerosol-related radiative flux. In this brief report, evidence is presented for growth of these new particles, following tidal-related particle formation, into radiatively active particle sizes (i.e. radius>50 nm) where an increase in concentration of more than 300% can be seen. This increase of radiatively active particles concomitantly results in more than a threefold enhancement in both aerosol scattering ability (thereby influencing direct radiative flux) and cloud condensation nuclei (CCN) availability (thereby influencing indirect radiative flux). These results provide direct evidence for coastal biogenic emissions significantly enhancing the radiative flux potential of atmospheric aerosols.

«StartPrev12345678910NextEnd»
Page 7 of 11
Copyright © 2017 Atmospheric Physics Research Cluster. All Rights Reserved.
Joomla! is Free Software released under the GNU/GPL License.
 
None