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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.

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Documents

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Intercomparison of number concentration measurements by various aerosol particle counters Intercomparison of number concentration measurements by various aerosol particle counters

Date added: 07/31/2002
Date modified: 07/02/2009
Filesize: 535.01 kB

Ankilov, A., A Baklanov, M. Colhoun, K-H. Enderle, J. Gras, Yu Jualanov, D. Kaller, A. Linder, A.A. Lushnikov, R. Mavliev, F. McGovern, A. Mirme, T.C. O'Connor, J. Podzimek, O. Prining, G.P. Reischl, R. Rudolf, G.J. Sem, W.W. Szymanski, E. Tamm, A.E. Vrtala, P.E. Wagner, W. Winklmayr and V. Zagaynov, Intercomparison of number concentration measurements by various aerosol particle counters. Atmos. Res. 62, 177-208, 2002.


Abstract

 

Total aerosol particle number concentrations, as measured by means of 16 different measurement systems, have been quantitatively compared during an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (ICCP-IUGG). The range of measuring instruments includes Pollak counters (PCO) in use already for several decades, presently available commercial particle counters, as well as laboratory prototypes. The operation of the instruments considered was based on different measurement principles: (1) adiabatic expansion condensation particle counter, (2) flow diffusion condensation particle counter, (3) turbulent mixing condensation particle counter, (4) laser optical particle counter, and (5) electrostatic particle measurement system. Well-defined test aerosols with various chemical compositions were considered: DEHS, sodium chloride, silver, hydrocarbons, and tungsten oxide. The test aerosols were nearly monodispersed with mean particle diameters between 4 and 520 nm, the particle number concentrations were varied over a range from about 4 × 101 to 7 × 106 cm-3. A few measurements were performed with two-component aerosol mixtures. For simultaneous concentration measurements, the various instruments considered were operated under steady state conditions in a linear flow system. A series of at least 10 single concentration measurements was performed by each individual instrument at each set of test aerosol parameters. The average of the concentration data measured by the various instruments was defined as a common reference. The number concentrations obtained from the various instruments typically agreed within a factor of about two over the entire concentration range considered. The agreement of the measured concentrations is notable considering the various different measurement principles applied in this study, and particularly in view of the broad range of measurement instruments used. Significant deviations and nonlinear response were observed only in a few cases and are possibly related to calibration errors. For certain conditions, a dependence of aerosol counter response on particle composition has been found. The scatter of the number concentrations obtained from each individual instrument during measurements with constant test aerosol typically did not exceed 20% to 25%. At concentrations below 103 cm-3, however, several of the instruments, including electrostatic particle measurement systems, tend to show increased experimental scatter.

Seasonal characteristics of the physicochemical properties of North Atlantic... Seasonal characteristics of the physicochemical properties of North Atlantic...

Date added: 08/06/2007
Date modified: 07/23/2009
Filesize: 725.93 kB

Yoon, Y. J., et al. (2007), Seasonal characteristics of the physicochemical properties of North Atlantic marine atmospheric aerosols, J. Geophys. Res., 112, D04206, doi:10.1029/2005JD007044.


Abstract


Seasonal physicochemical characteristics of North Atlantic marine aerosols are presented for the period from January 2002 to June 2004. The aerosol size distribution modal diameters show seasonal variations, 0.031 μm in winter and 0.049 μm in summer for the Aitken mode and 0.103 μm in winter and 0.177 μm in summer for the accumulation mode. The accumulation mode mass also showed a seasonal variation, minimum in winter and maximum in summer. A supermicron sized particle mode was found at 2 μm for all seasons showing 30% higher mass concentration during winter than summer resulting from higher wind speed conditions. Chemical analysis showed that the concentration of sea salt has a seasonal pattern, minimum in summer and maximum in winter because of a dependency of sea-salt load on wind speeds. By contrast, the non-sea-salt (nss) sulphate concentration in fine mode particles exhibited lower values during winter and higher values during midsummer. The water soluble organic carbon (WSOC) and total carbon (TC) analysis also showed a distinctive seasonal pattern. The WSOC concentration during the high biological activity period peaked at 0.2 μgC m−3, while it was lower than 0.05 μgC m−3 during the low biological activity period. The aerosol light scattering coefficient showed a minimum value of 5.5 Mm−1 in August and a maximum of 21 Mm−1 in February. This seasonal variation was due to the higher contribution of sea salt in the MBL during North Atlantic winter. By contrast, aerosols during late spring and summer exhibited larger angstrom parameters than winter, indicating a large contribution of the biogenically driven fine or accumulation modes. Seasonal characteristics of North Atlantic marine aerosols suggest an important link between marine aerosols and biological activity through primary production of marine aerosols.

 

The First Condensation Nucleus Conference And Research In Dublin The First Condensation Nucleus Conference And Research In Dublin

Date added: 08/07/1985
Date modified: 08/18/2008
Filesize: 711.16 kB
 O Connor, The First Condensation Nucleus Conference And Research In Dublin, J Rech. Atmos., 19 (1985) 

The influence of the complex index of refraction on the volume extinction, scattering and absorption The influence of the complex index of refraction on the volume extinction, scattering and absorption

Date added: 08/01/1977
Date modified: 07/08/2009
Filesize: 496.46 kB
The influence of the complex index of refraction on the volume extinction, scattering and absorption coefficient of particle size distributions. Topical Optical Society of America Meeting on Optical Propagation Through Turbulence, Rain and Fog, Boulder, Colorado, U.S.A., pp. WD  7-1  to  7-4.

Abstract

 


Source assessment of particulate air pollutants measured at the southwest european coast Source assessment of particulate air pollutants measured at the southwest european coast

Date added: 08/05/1996
Date modified: 07/23/2009
Filesize: 841.66 kB

Pio, C.A., L.M. Castro, M.A. Cerqueira, I.M. Santos, F. Belchior, and M. L. Salgueiro,(1996), Source assessment of particulate air pollutants measured at the southwest , European coast, Atmos. Environ., 30, 3309-3320


Abstract


Aerosol particles and gaseous species were measured in air masses transported to the west coast of Portugal, between November 1993 and August 1994. Samples were taken during four monitoring campaigns distributed along the various seasons of the year, integrated in the EC Project : BMCAPE. Aerosol particles were collected with separation in two size fractions and analysed in relation to total mass, water soluble ions, trace elements and black/organic carbon. Local micro-meteorological parameters and air mass backward trajectories were compared with analytical results in order to define characteristic air mass types and to evaluate the origin of pollutants. Average concentrations on the Portuguese west coast, even in maritime air masses, are higher than values observed in remote oceanic locations. This is probably a consequence of continental European air masses recirculation through the eastern Atlantic Ocean, reinforced by situations of mesoscale transport from the Iberian Peninsula. Principal Component Analysis permitted the identification of five source groups for the fine and coarse aerosol fractions, namely combustion plus road traffic, sea salt spray, secondary aerosol production, soil and possibly non-ferrous metallurgy industries. In the aerosol fine fraction road traffic and combustion contribute on average with 250% of the total fine aerosol mass, while sea spray and secondary production represent 14% and 31%, respectively of the mass loading. Sea spray is by far the major contributor to the coarse fraction with an average of 88% of the suspended coarse aerosol mass.

 

Sub-micron sea-spray fluxes Sub-micron sea-spray fluxes

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 134.74 kB
Geever, M., C. O’Dowd, S. van Ekeren, R. Flanagan, D. Nilsson, G. de Leeuw and U. Rannik, Sub-micron sea-spray fluxes. Geophysical Research Letters, Geophys. Res. Lett., 32, L15810, doi:10.1029/2005GL023081, 2005.

Abstract


Eddy covariance aerosol flux measurements were conducted at the Mace Head coastal station in the North East Atlantic. Footprint and micrometeorological analysis under clean marine air mass conditions indicated that fluxes representative of open ocean conditions could be derived during high tide conditions and an oceanic fetch. Sea-spray fluxes were derived for total particle sizes larger than 10 nm and total particle sizes larger than 100 nm (i.e. covering the Aitken and Accumulation mode). The source fluxes (F) were found to be strongly correlated with both wind speed (U) and friction velocity (u*), following, by convention, an exponential relationship (Log F = a U + c) relationship. Comparison of source fluxes at sizes larger than 10 nm and larger than 100 nm demonstrates that approximately 50% of the number flux can be attributed to the accumulation mode and 50% to the Aitken mode. At 10 ms−1 wind speeds, the total primary marine aerosol flux is of the order of 2 × 106 m−2 s−1, increasing to 20 × 106 m−2 s−1 at 20 ms−1.

Marine particle nucleation Observation at Bodega Bay, California Marine particle nucleation Observation at Bodega Bay, California

Date added: 08/06/2006
Date modified: 07/24/2009
Filesize: 1.48 MB

Wen, J., Y. Zhao, and A. S. Wexler (2006), Marine particle nucleation: Observation at Bodega Bay, California, J. Geophys. Res., 111, D08207, doi:10.1029/2005JD006210.


Abstract


A TSI nano-SMPS was installed in a lab at Bodega Bay, about 50 m from the coastline and 5 m above sea level. On the basis of measurements conducted from June to December 2001 and from January to June 2003, we have observed two kinds of nucleation events, i.e., long-term (a few hours) and short-term (a few minutes) particle bursts. The long-term events mostly occur during daytime in the summer, lasting from 0.5 to 8 hours. Narrow spikes (short-term events) that occur year-round, both day and night, last only a few minutes to a half hour but contain particle number concentrations comparable to some of the long-term events. Wind direction and speed affect the occurrence and intensity of the particle burst. Nucleation mostly takes place during northwesterly onshore wind for both long- and short-term events, and the probability of nucleation occurrence is higher at higher wind speed. However, in contrast to what has been observed at Mace Head, Ireland, nucleation at Bodega Bay does not correlate with tidal height. Instead, the seasonal and interannual variations of ultrafine particle number concentration N3–10nm appear to correlate with ocean upwelling, a characteristic of currents along the west coast of the United States that brings up nutrients from subsurface waters, promoting plant productivity. Simultaneous measurements of nucleation at the coast and 1.6 km out suggest that nucleation is a coastal phenomenon, supporting the contention that it is related to direct or biogenic emission of precursor gases from the coastal area during the sea upwelling periods.

 

Aerosol Optical Depth in Clean and Polluted Northeast Atlantic Air Aerosol Optical Depth in Clean and Polluted Northeast Atlantic Air

Date added: 11/06/2009
Date modified: 11/06/2009
Filesize: 250.56 kB

Mulcahy, J. P., C. D. O’Dowd, and S. G. Jennings (2009), Aerosol optical depth in clean marine and continental northeast Atlantic air, 114, D20204, doi:10.1029/2009JD011992. J. Geophys. Res.


Abstract.

The aerosol optical depth (AOD) and A ° ngstro¨m exponent for the period 2002–2004 is evaluated for clean marine and continentally influenced air masses over the northeast Atlantic region. Measurements were carried out at the Mace Head atmospheric research station on the west coast of Ireland using a precision filter radiometer which measures the aerosol optical depth at four wavelengths centered at 368, 412, 500, and 862 nm. The clean marine AOD at 500 nm is characterized by a mean value of 0.14 ±0.06, exhibiting relatively small temporal variability. The A ° ngstro¨m exponent was less than 1 for the majority of cases, having an average value of 0.40 ± 0.29 in clean marine conditions. The latter is consistent with the presence of relatively large supermicron particles, such as sea salt dominating the marine aerosol size distribution. The A ° ngstro¨m exponent shows a distinct seasonal cycle in clean marine air, with maximum values being derived in the summer months and minimum values in the winter. In continental air masses, while the range and standard deviation of the AOD is larger than in clean marine conditions, the overall mean AOD (

t500 = 0.19 ± 0.12) is comparable with the clean marine AOD. The continental A ° ngstro¨m exponent is larger, having a mean value of 1.07 ± 0.32. This is attributed to a dominating accumulation mode in the presence of urban-industrial aerosol particles originating mainly from continental Europe. These results demonstrate how the natural marine AOD can rival polluted AOD over the northeast Atlantic region and highlight the importance of the natural marine aerosol contribution over oceans.

Emissions of CH3Br, organochlorines, and organoiodines from temperate macroalgae Emissions of CH3Br, organochlorines, and organoiodines from temperate macroalgae

Date added: 08/05/2001
Date modified: 07/01/2009
Filesize: 249.05 kB

Baker1 J.M.; Sturges W.T.1; Sugier J.; Sunnenberg G.; Lovett A.A.; Reeves C.E.; Nightingale P.D.; Penkett S.A., Emissions of CH3Br, organochlorines, and organoiodines from temperate macroalgae, Chemosphere: Global Science Change, Volume 3, Number 1, January 2001 , pp. 93-106(14)


Abstract


The production rates of a range of low molecular weight halogenated organics have been determined in cultures of five temperate species of macroalgae collected from the north coast of Norfolk, England. Compounds studied included CH3Br, the chlorinated organics CH3Cl, CH2Cl2 and CHCl3, and the iodinated organics CH3I, C2H5I, and CH2ClI. Measurements of a wider range of halocarbon concentrations in an isolated rockpool and in air over the seaweed bed were also conducted to evaluate the local impact of the seaweeds on halocarbon concentrations in the natural environment. Estimates for the global emissions of some of the key halogenated compounds from macroalgae have been derived. In general macrophytes appear not to be globally significant producers of the particular halocarbons studied. In coastal regions, however, the impact on local atmospheric composition and chemistry could be greater.

 

Measurements Of Global Radiation Using Black And White Atmometers Measurements Of Global Radiation Using Black And White Atmometers

Date added: 08/07/1955
Date modified: 07/03/2009
Filesize: 1.43 MB
TC O Connor ,Measurements Of Global Radiation Using Black And White Atmometers , Geofiscica Pura E Applicata -Milano Vol 30 p 130-136 (1955)

Abstract

 

The difference in the evaporation from black and white Livingston atmometers was compared with the global radiation as measured by a Bellani spherical pyranometer. Results show that one unit (cm^3) of difference in the evaporation corresponds to 20+/- 3 cal/cm^2 of global radiation. The total of 95 daily values of radiation measured by pairs of atmometers differed from the corresponding Bellani figure by 2.3%. The operation of the atmometers and the accuracy of the results are discussed. The method is considered sufficiently accurate for the general climatological purposes.

A two-column method for long-term monitoring of non-methanehydrocarbons (NMHCs) and oxygenated volat A two-column method for long-term monitoring of non-methanehydrocarbons (NMHCs) and oxygenated volat

Date added: 08/31/2003
Date modified: 07/23/2009
Filesize: 174.39 kB

Hopkins, J. R., Read, K. A., and Lewis, A. C.: A Two Column Method for Long-term Monitoring of Non-Methane Hydrocarbons (NMHCs) and Oxygenated Volatile Organic Compounds, J. Envir. Mon., 5, 8–13, 2003.


Abstract


 

A method has been developed for concurrent analysis of C2–C7 hydrocarbons and C2–C5 oxygenated volatile organic compounds (o-VOCs) including alcohols, aldehydes, ketones and ethers. A multi-bed, Peltier-cooled adsorbent trap, consisting of Carboxen 1000 and Carbopack B, was used to acquire one sample per hour. Upon injection the sample was split in an approximately 50 : 50 ratio between a 50 m aluminium oxide (Al2O3) porous layer open tubular (PLOT) column and a 10 m LOWOX column. Eluents from each column were then analysed using flame ionisation detection (FID). Regular calibration of the system was performed using a standard cylinder mixture at the parts per billion by volume (ppbV) level for non-methane hydrocarbons (NMHCs) and a permeation tube method for the oxygenated species. The system is fully automated with NMHC detection limits between 1 and 10 parts per trillion by volume (pptV) and o-VOC detection limits between 10 and 40 pptV.

The regional aerosol-climate model REMO-HAM The regional aerosol-climate model REMO-HAM

Date added: 03/22/2013
Date modified: 03/22/2013
Filesize: 1.96 MB

Pietikäinen, JP, D O'Donnell, C Teichmann, U Karstens, S Pfeifer, J Kazil, R Podzun, S Fiedler, H Kokkola, W Birmili, C O'Dowd, U Baltensperger, E Weingartner, R Gehrig, G Spindler, M Kulmala, J Feichter, D Jacob, A Laaksonen, The regional aerosol-climate model REMO-HAM, Geosci. Model Dev., 5, 1323-1339, doi: 10.5194, 2012.


Abstract. REMO-HAM is a new regional aerosol-climate model. It is based on the REMO regional climate model and includes most of the major aerosol processes. The structure for aerosol is similar to the global aerosol-climate model ECHAM5-HAM, for example the aerosol module HAM is coupled with a two-moment stratiform cloud scheme. On the other hand, REMO-HAM does not include an online coupled aerosol-radiation nor a secondary organic aerosol module. In this work, we evaluate the model and compare the results against ECHAM5-HAM and measurements. Four different measurement sites were chosen for the comparison of total number concentrations, size distributions and gas phase sulphur dioxide concentrations: Hyyti¨al¨a in Finland, Melpitz in Germany, Mace Head in Ireland and Jungfraujoch in Switzerland. REMO-HAM is run with two different resolutions: 50×50 km2and 10×10 km2. Based on our simulations, REMO-HAM is in reasonable agreement with the measured values. The differences in the total number concentrations between REMO-HAM and ECHAM5-HAM can be mainly explained by the difference in the nucleation mode. Since we did not use activation nor kinetic nucleation for the boundary layer, the total number concentrations are somewhat underestimated. From the meteorological point of view, REMO-HAM represents the precipitation fields and 2m temperature profile very well compared to measurement. Overall, we show that REMO-HAM is a functional aerosol-climate model, which will be used in further studies.

Determination of biogenic volatile organic compounds (C8–C16) in the coastal atmosphere at Mace Determination of biogenic volatile organic compounds (C8–C16) in the coastal atmosphere at Mace

Date added: 08/07/2001
Date modified: 07/27/2009
Filesize: 357.39 kB

Determination of biogenic volatile organic compounds (C8 - C16) in the coastal atmosphere at Mace Head, Ireland (2001) J. Sartin, C.J. Halsall, B. Davison, S. Owen and C.N. Hewitt, Analytica Chimica Acta, 428, 61-72


Abstract


A methodology describing the sampling and analysis of biogenic volatile organic compounds (VOCs) in ambient coastal air is presented. Air samples were collected during a field campaign (September 1998) at Mace Head on the west coast of Ireland. In addition, air samples from seaweed enclosures were taken to assess the VOC source potential of macro-algae at low tide. VOC identification was confirmed using GC-MS and an n-alkane retention index, with quantification carried out using GC-FID. A suite of compounds (C8-C16) were routinely quantified; these included a series of n-alkanes (C11-C16) and oxygenated hydrocarbons (C8-C14). Their mixing ratios in coastal air ranged from <10-400 parts per trillion (pptv). The most abundant oxygenates included 2-ethyl-1-hexanol (mean = 175 pptv) and two ubiquitous ketones (geranyl acetone and 6-methyl-5-hepten-2-one) with average mixing ratios of 123 and 28 pptv, respectively. Air mass back trajectories indicated higher levels of the oxygenates when air flow was off the land (easterly continental) rather than from the ocean, although the opposite was observed for the n-alkanes. Mixing ratios of the n-alkanes (>C12) were significantly higher in the seaweed enclosure air than in ambient air, suggesting seaweed to be a source of long chain n-alkanes. Oxygenates, however, did not show a significant difference between enclosure and ambient air. Unlike studies carried out in the vicinity of woodlands, no monoterpenes or sesquiterpenes were detected in this study.

 

Study of water-soluble atmospheric humic matter in urban and marine envirorments Study of water-soluble atmospheric humic matter in urban and marine envirorments

Date added: 08/01/2008
Date modified: 07/07/2009
Filesize: 406.61 kB
Krivácsy, Z., Kiss, G., Ceburnis, D., Jennings, G., Maenhaut, W., Salma, I., Shooter, D.,
Study of water-soluble atmospheric humic matter in urban and marine environments,
Atmospheric Research 87 (2008) 1–12.

Abstract


Recently, atmospheric humic matter or humic-like substances (HULIS) have been found in the water-soluble fraction of atmospheric aerosol sampled at different locations. Most of these locations were continental, non-urban sites. Therefore, in this work HULIS was studied in urban and marine environments. The atmospheric concentration varied over a wide range from 0.40 to 5.44 μg m-3, from the clean marine air (Mace Head, Ireland) to the heavily polluted winter urban atmosphere (Christchurch, New Zealand). In terms of carbon, ratio of HULIS was 19-51% of water-soluble organic carbon, and 10-22% of total carbon. Different spectroscopic techniques were applied for the physico-chemical characterisation of HULIS including relative aromaticity and molecular weight. Specific absorbance was observed to be much less variable than specific fluorescence, and consequently UV-VIS spectroscopy at λ>330 nm was recommended for rapid, semi-quantitative determination of HULIS in the water extracts of atmospheric aerosol. Application of a dual filter sampling system at one of the sampling sites has revealed a significant positive sampling artefact which calls for further systematic studies on this subject, and also supports the idea of a secondary organic aerosol formation mechanism of HULIS.

Characteristic features of air ions at Mace Head on the west coast of Ireland Characteristic features of air ions at Mace Head on the west coast of Ireland

Date added: 08/07/2008
Date modified: 07/27/2009
Filesize: 917.86 kB

Marko Vana, Mikael Ehn, Tuukka Petaja, Henri Vuollekoski, Pasi Aalto, Gerrit de Leeuw, Darius Ceburnis, Colin D. O'Dowd, Markku Kulmala, Characteristic features of air ions at Mace Head on the west coast of Ireland, Atmospheric Research


Abstract


Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.34–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameters smaller than 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in the marine coastal environment. Intermediate ion concentrations were generally close to zero, but during some nucleation episodes the concentrations increased to several hundreds per cm3. Nucleation events occurred during most of the measurement days. We classified all days into one of seven classes according to the occurrence and type of new particle formation. Nucleation events were observed during 207 days in 2006, most prominently in the spring and summer months. Rain-induced events, in turn, were observed during 132 days. Particle formation and growth events mostly coincided with the presence of low tide. Also small cluster ions (0.34–1.6 nm) were characterized. Average concentrations of small ions were 440 cm− 3 for the negative ions and 423 cm− 3 for the positive ions. Average mean mobilities of small ions were 1.86 cm2V− 1s− 1 and 1.49 cm2V− 1s− 1 for the negative and positive polarities, respectively. Concentrations of small ions were observed to be strongly dependent on the variations of meteorological parameters including wind speed and direction.

 

Submicron Particle, Radon and Soot Carbon Characteristics over Northeast Atlantic Submicron Particle, Radon and Soot Carbon Characteristics over Northeast Atlantic

Date added: 08/01/1993
Date modified: 07/23/2009
Filesize: 1 MB

O'Dowd, C. D., M. H. Smith, and S. G. Jennings (1993), Submicron Particle, Radon, and Soot Carbon Characteristics Over the Northeast Atlantic, J. Geophys. Res., 98


Abstract


Atmospheric aerosol particles (0.05μm ≤ rdry ≤ 1.5μm), 222Rn, and soot carbon mass were measured on a cruise over the Northeast Atlantic (63°N, 8°W) during October and November 1989. An accumulation mode (AM) was present in all particle data and was characterized by a lognormal size distribution with parameters N cm−3 (total number concentration), rg μm (geometric mean radius) and σg (geometric standard deviation). For aerosol associated with the “cleanest” Northeast Atlantic maritime and Arctic air masses, the AM parameters were found to be 16 cm−3 ≤ N ≤ 48 cm−3, 1.32 ≤ σg ≤ 1.46, and 0.08 μm < rg < 0.09 μm, leading to AM masses of between 0.20 μg m−3 and 0.38 μg m−3. Clean background levels of soot carbon mass for maritime and Arctic air were estimated to be around 20 ng m−3 and were associated with particle size radii r ≤ 0.15 μm. Soot carbon mass showed an excellent correlation with AM number concentration (∝=0.93), demonstrating its usefulness as an air mass tracer and as an indicator of anthropogenic pollutant transport. By comparison, radon, which is often used for this purpose, exhibited a significantly poorer correlation (∝=0.60) for this region. Approximately 9% of the total AM mass was accounted for by soot carbon, regardless of air mass origin, suggesting that early winter marine aerosol in the remote North Atlantic is primarily of anthropogenic origin.

The influence of evaporation and drop-interaction on a rainshaft : Comments and Notes The influence of evaporation and drop-interaction on a rainshaft : Comments and Notes

Date added: 09/14/1974
Date modified: 07/08/2009
Filesize: 326.53 kB

Brazier-Smith, P.R., and Jennings, S.G., and Latham, J. (1974)- The influence of evaporation and drop-interaction on a rainshaft Reply. Quart. J. Roy. Met. Soc., 99, 704-722.


Abstract


Calculations have been made of the variations with fall-depth z of the liquid water content, L, rainfall rate, p, radar reflectivity, Z, drop concentration, NT, and raindrop size distribution n(r), within a steady-state rainshaft as a result of the evaporation and interaction of the drops. The interactions were described by a generalized stochastic equation which takes account, as described by Brazier-Smith, Jennings and Latham (1973), of the variation of coalescence efficiency s with drop radii R, r and the fact that satellite drops are produced when drops separate after collision. The relative humidity is assumed to fall linearly from 100 per cent at cloud base (z = 0, T = 8°C) with a gradient 8. The lapse rate within the rainshaft was taken to be 8°C krn- and the initial size distribution was generally given by the Marshall-Palmer equation. Calculations were made for 3 different situations in order to isolate the physical processes which most affect the rainfall:
(l), evaporation without interaction; (2) interaction without evaporation; (3) both interaction and evaporation. The calculations for Case (1) indicate that the numbers of drops in all size classes are diminished with increasing Z, with a preferential reduction at the small-radius end of the spectrum. In Case (2) the interactions of the raindrops introduce considerable detail into n(r), with bimodal curves associated with satellite drop production, the highly efficient consumption of small drops by larger ones and the variations of E and fall-velocity V with drop-radius r.
The main feature of the calculations for Case (3) is the rBle of coalescence in preserving within the spectrum a considerable amount of liquid water that would otherwise be lost by evaporation. For example, whereas the rainwater content at z = 1.5 km for 8 = 20 per cent km- and Lo = 1.0 gm m- is 0.28 gm m-3 if interactions are absent, their presence elevates L to 0.57 gm m-3 at this level. This retention effect is significant for all values considered of 8, L, p, and the initial slope of the raindrop size distribution (varied from half to twice that of the Marshall-Palmerequation). It is alsofound that the structure introduced into the size distributions as a result of interactions is partially smoothed out by evaporation, which replaces a substantial proportion of the smallest drops consumed by coalescence.

Size Mobility Charge of multi charged Ions Size Mobility Charge of multi charged Ions

Date added: 08/07/1955
Date modified: 07/23/2009
Filesize: 4.14 MB
PJ Nolan and TC O'Connor ,Size Mobility Charge of multi charged Ions,  14 Dec 1955
Abstract

 

The experiments of J.J Nolan and J.G O'Keefe (1933) on multiply charged ions produced in various ways indicated that the mobility of these ions was independent of the charge. they suggusted the following way out of the difficulty: "It is possible that a nucleus on receiving a large electric charge, may in a moist atmosphere rapidly grow and adapt its size to its charge in such a way as to have approximately a constant mobility". the present research was designed to elucidate the problem by measureing the size as well as the mobility and charge of multiply charged ions. One of the methods of producing multiply charged ions used by Nolan and O'Keefe was the spraying of water. We found that production by bubblling was more convenient than production by spraying. During the course of the work certain features of the ionisation produced by bubbling were investigated. These investigations were not exhaustive since they were only incidental to the main purpose of the research.

Some Characteristics of condensation Nuclei stored in a large vessel Some Characteristics of condensation Nuclei stored in a large vessel

Date added: 08/07/1955
Date modified: 07/07/2009
Filesize: 1.44 MB
TC OConnor, Some Characteristics of condensation Nuclei stored in a large vessel ,Geofisica Pura E Apllicata- Milano Vol 31 pp 107-114 (1955)

Abstract

 

THe Coagulation coefficent, size and charge distribution of condensation nuclei from room air when stored in a 4000 litre rubber balloon gasometer were studied. The results indicate that the acquisation of water vapour contributes to the growth of stored nuclei. A preliminary trial was made to see if Junge's Approximate rule that the number of particles in an aerosol varies inversely as the third power of their radius, also holds for Aitken nuclei. Further cnfirmation of the relationship between the percentage of stored nuclei electrically charged and their average radius were obtained.

The measurements were carried out by means of the Pollak-Murphy improved version of the photo-electric nucleus counter. A statistical analysis based on over a thousand comparisions of two identical models shows that the agreement of individual readings is better than 10% of nucleus concentrations in 80% of all cases. Excessive differences have now been eliminated.

Sources and source variations for aerosol at Mace Head, Ireland Sources and source variations for aerosol at Mace Head, Ireland

Date added: 08/07/2001
Date modified: 07/23/2009
Filesize: 575.5 kB

JR Huang S., Arimoto R., Rahn K. A. (2000) Sources and source variations for aerosol at Mace Head, Ireland. Atmos. Environ. 35, 1421-1437.


Abstract


The sources and source variations for aerosol at Mace Head, Ireland, were studied by applying positive matrix factorization (PMF), a variant of factor analysis, to a 5-yr data set for bulk aerosol. Signals for the following six sources were evident year round: (1) mineral dust, (2) sea salt, (3) general pollution, (4) a secondary SO42--Se signal that is composed of both natural (marine) and pollution (coal) components, (5) ferrous industries, (6) and a second marine (possibly biogenic) source. Analyses of seasonally stratified data suggested additional sources for iodine and oil emissions but these were present only in certain seasons, respectively. The marine signal is particularly strong in winter. The main pollution transport from Europe to Mace Head occurs in May, but the influence of continental European emissions is evident throughout the year. Mineral aerosol evidently follows a transport pathway similar to that of pollution aerosol, i.e., recirculation via the westerlies brings pollutants mixed with dust to the site from nearby land, i.e., Ireland, the United Kingdom, and the Belgium, Netherlands, and Luxemburg (Benelux) region, with some inputs from Scandinavia, Western Europe, Eastern Europe, and even the Mediterranean region. Compared with Bermuda, aerosol at Mace Head has stronger marine sources (especially marine-derived secondary SO42- and Se) but weaker crustal and oil signals. Transport across the North Atlantic, especially in winter, cannot be ruled out.

Aerosol physico-chemical characteristics over a boreal forest determined by volatility analysis Aerosol physico-chemical characteristics over a boreal forest determined by volatility analysis

Date added: 07/31/2000
Date modified: 06/30/2009
Filesize: 154.04 kB

O'Dowd, C.D., E. Becker, J.M. Makela, M. Kulmala, Aerosol physic-chemical characteristics over a boreal forest determined by volatility analysis, Boreal Environment Research, 4, 337-348, 2000


Abstract


A thermal volatility technique was used in the boreal forest environment to examine accumulation mode (0.05–0.35 µm radius) physico-chemical properties as a function of air mass origin. Three primary aerosol species were identified in all air masses: (1) a semi-volatile organic component, (2) ammonium sulphate, and (3) a non-volatile component thought to comprise mostly of soot carbon. Under some conditions, sulphuric acid was also identified, as was sea salt. Following nucleation and growth of new particles into accumulation mode sizes, the organic fraction of accumulation mode aerosol, by mass, was observed to increase from 30%, prior to and during the nucleation event, up to 75% by the end of the growth period, indicating a substantial fraction of organic mass condensing onto newly formed particles.

The effect of physical and chemical aerosol properties on warm cloud droplet activation The effect of physical and chemical aerosol properties on warm cloud droplet activation

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 1.02 MB

McFiggans, G., P. Artaxo, U. Baltensperger, H. Coe, M. C. Facchini, G. Feingold, S. Fuzzi, M. Gysel,, A. Laaksonen, U. Lohmann, T. F. Mentel, D. M. Murphy, C. D. O'Dowd, J. R. Snider and E. Weingartner, The effect of physical and chemical aerosol properties on warm cloud droplet activation, Atmospheric Chemistry and Physics Discussions, Vol. 5, pp 8507-8647, 2005.


Abstract


The effects of atmospheric aerosol on climate forcing may be very substantial but are quantified poorly at present; in particular, the effects of aerosols on cloud radiative properties, or the "indirect effects" are credited with the greatest range of uncertainty amongst the known causes of radiative forcing. This manuscript explores the effects that the composition and properties of atmospheric aerosol can have on the activation of droplets in warm clouds, so potentially influencing the magnitude of the indirect effect. The effects of size, composition, mixing state and various derived properties are assessed and a range of these properties provided by atmospheric measurements in a variety of locations is briefly reviewed. The suitability of a range of process-level descriptions to capture these aerosol effects is investigated by assessment of their sensitivities to uncertainties in aerosol properties and by their performance in closure studies. The treatment of these effects within global models is reviewed and suggestions for future investigations are made.

New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei

Date added: 10/01/2008
Date modified: 07/28/2009
Filesize: 178.38 kB

Baerbel Langmann, Claire Scannell, Colin O'Dowd, New Directions: Organic matter contribution to marine aerosols and cloud condensation nuclei, Atmospheric Environment, Volume 42, Issue 33, October 2008, Pages 7821-7822, ISSN 1352-2310, DOI: 10.1016/j.atmosenv.2008.09.002.


Abstract

 

Aerosols in the marine atmosphere influence solar irradiation over the world’s ocean directly by backscattering incoming solar radiation and indirectly, by forming cloud condensation nuclei (CCN) thereby affecting the cloud albedo. Charlson et al. (1987) suggested the existence of a feedback mechanism between climate change and the flux of oceanic dimethyl sulfide (DMS), commonly known as the CLAWhypothesis after the four founding authors. According to this hypothesis, DMS produced by marine phytoplankton is ventilated into the marine boundary layer (MBL) and ultimately oxidised to sulfate aerosol which form CCNs.

Atmospheric inputs of trace metals to the Northeast Atlantic Ocean The importance of southeaste Atmospheric inputs of trace metals to the Northeast Atlantic Ocean The importance of southeaste

Date added: 08/06/2001
Date modified: 07/27/2009
Filesize: 209.3 kB

Spokes et al., 2001 L. Spokes, T. Jickells and K. Jarvis, Atmospheric inputs of trace metals to the northeast Atlantic Ocean: the importance of southeasterly flow, Marine Chemistry 76 (2001), pp. 319–330


Abstract


The study of aerosols and rainwater presented here demonstrates that episodic atmospheric deposition events associated with southeasterly flow are quantitatively significant for large areas of the North Atlantic Ocean. This paper considers aluminium and manganese, with predominantly crustal sources, and lead and zinc, which are mobilised into the atmosphere primarily through anthropogenic activity. High levels of all trace metals are associated with southeasterly flow from Europe as the air passes over heavily populated and industrialised regions before reaching the northeast Atlantic Ocean. Fluxes calculated using the 1% HNO3 acid soluble metal concentration show that, although the climatological norm for this area is westerly flow, short-lived southeasterly transport events dominate the input of trace metals to this ocean region. This material may be toxic to phytoplankton or may be represent a new source of nutrients to the biological community. A significant decrease in atmospheric lead levels in polluted air is seen between June 1996 and May 1997, reflecting the decrease in use of leaded fuels in Europe. Comparing atmospheric flux values to sediment trap metal fluxes shows that the atmosphere represents the dominant source of zinc to the deep ocean, whereas an additional, non-atmospheric, manganese source this required, perhaps from mobilisation of sedimentary material from the continental shelf or long range advection of manganese rich Saharan material.

 

Coastal CCN measurements at Mace Head with enhanced concentrations in strong winds Coastal CCN measurements at Mace Head with enhanced concentrations in strong winds

Date added: 07/31/1998
Date modified: 07/27/2009
Filesize: 166.47 kB

Jennings, S.G., Geever, M., and O'Connor, T.C. (1998)- Coastal CCN measurements at Mace Head with enhanced concentrations in strong winds. Atmos. Res.,46,243-252.


Abstract


Surface measurements of cloud condensation nuclei (CCN) number concentration (cm-3) are presented for unmodified marine air and for polluted air at Mace Head, for the years 1994 and 1995. The CCN number concentration active at 0.5% supersaturation is found to be approximately log-normal for marine and polluted air at the site. Values of geometric mean, median and arithmetic mean of CCN number concentration (cm-3) for marine air are in the range 124-135, 140-150 and 130-157 for the two years of data. Analysis of CCN number concentration for high wind speed, U, up to 20 m s-1 show enhanced CCN production for U in excess of about 10-12 m S- Approximately 7% increase in CCN per 1 m s-1increase in wind speed is found, up to 17 m s-1. A relationship of the form log10CCN = a+bU is obtained for the periods March 1994 and January, February 1995 for marine air yielding values a of 1.70; 1.90 and b of 0.035 for both periods.

Sulphur and nitrogen compounds in variable marine continental air masses at the southwest Europ Sulphur and nitrogen compounds in variable marine continental air masses at the southwest Europ

Date added: 08/05/1996
Date modified: 07/07/2009
Filesize: 1.16 MB

Pio et al., 1996. A.C. Pio, M.A. Cerqueira, L.M. Castro and M.L. Salgueiro , Sulphur and nitrogen compounds in variable Marine/Continental air masses at the Southwest European Coast. Atmospheric Environment 30 18 (1996), pp. 3115–3127.


Abstract


Measurements of atmospheric sulphur and nitrogen species were made on the west coast of Portugal, within the framework of BMCAPE project. Four research intensive campaigns took place between November 1993 and August 1994 and revealed pronounced seasonal cycles for DMS and MSA. Surprisingly high levels of DMS were detected during autumn (mean concentration : 776ngSm-3), possibly as a consequence of a later algae bloom or local marsh emissions. COS displayed a slight seasonal variation with mean concentrations ranging from 741 ngSm-3 in autumn up to 903 ngS m-3 in summer. On the basis of backward air mass trajectories and local meteorological data, samples were assigned into different classes of air masses. The lowest concentrations of SO2, nssSO42-, NH3, NH4+, HNO3, NO3- and NO2were found in air masses transported over the Atlantic Ocean and were about 3-10 times lower than those recorded in air masses from continental origin. Nevertheless, for many of the species, the mean concentrations in maritime air were still significantly higher than those previously recorded in remote marine sites, presumably owing to long-range transport of pollutants or contamination induced by mesoscale wind circulation.

 

Influence of an increased sea surface temperature on North Atlantic cyclones Influence of an increased sea surface temperature on North Atlantic cyclones

Date added: 09/23/2008
Date modified: 07/23/2009
Filesize: 2.79 MB

Semmler, S. Varghese, R. McGrath, P. Nolan, S. Wang, P. Lynch, C. O'Dowd, Influence of an increased sea surface temperature on North Atlantic cyclones, J. Geophys. Res, D02107, doi/2006JD008213, 2008.


Abstract

 

The influence of an increased sea surface temperature (SST) on the frequency and intensity of cyclones over the North Atlantic is investigated using two data sets from simulations with the Rossby Centre regional climate model RCA3. The model domain comprises large parts of the North Atlantic and the adjacent continents. RCA3 is driven by reanalysis data for May to December 1985–2000 at the lateral and lower boundaries, using SST and lateral boundary temperatures. A realistic interannual variation in tropical storm and hurricane counts is simulated. In an idealized sensitivity experiment, SSTs and boundary condition temperatures at all levels are increased by 1 K to ensure that we can distinguish the SST from other factors influencing the development of cyclones. An increase in the count of strong hurricanes is simulated. There is not much change in the location of hurricanes. Generally weaker changes are seen in the extratropical region
and for the less extreme events. Increases of 9% in the count of extratropical cyclones and 39% in the count of tropical cyclones with wind speeds of at least 18 m/s are found.

Ten years of CO2, CH4,CO and N2O fluxes over Western Europe inferred from atmospheric..,Ireland Ten years of CO2, CH4,CO and N2O fluxes over Western Europe inferred from atmospheric..,Ireland

Date added: 08/01/2008
Date modified: 07/23/2009
Filesize: 2.45 MB

Messager, C., Schmidt, M., Ramonet, M., Bousquet, P., Simmonds, P., Manning, A., Kazan, V., Spain, G., Jennings, S. G., and Ciais, P.: Ten years of CO2, CH4, CO and N2O fluxes over Western Europe inferred from atmospheric measurements at Mace Head, Ireland, Atmos. Chem. Phys. Discuss., 8, 1191-1237, 2008


Abstract


We estimated CO2, CH4, CO and N2O emission fluxes over the British Isles and Western Europe using atmospheric radon observations and concentrations recorded at the Mace Head Atmospheric Research Station between 1996 and 2005. We classified hourly concentration data into either long-range European or regional sources from Ireland and UK, by using local wind speed data in conjunction with 222Rn and 212Pb threshold criteria. This leads to the selection of about 7% of the total data for both sectors. We then used continuous 222Rn measurements and assumptions on the surface emissions of 222Rn to deduce the unknown fluxes of CO2, CH4, CO and N2O. Our results have been compared to the UNFCCC, EMEP and EDGAR statistical inventories and to inversion results for CH4. For Western Europe, we found yearly mean fluxes of 4.1±1.5 106 kg CO2 km−2 yr−1 , 11.9±2.0 103 kg CH4 km−2 yr−1, 12.8±4.2 103 kg CO km−2 yr−1 and 520.2±129.2 kg N2O km−2 yr−1, respectively, for CO2, CH4, CO and N2O over the period 1996–2005. The method based upon 222Rn to infer emissions has many sources of systematic errors, in particular its poorly known and variable footprint, uncertainties in 222Rn soil fluxes and in atmospheric mixing of air masses with background air. However, these biases are likely to remain constant in the long-term, which makes the method quite efficient to detect trends in fluxes. Over the last ten years period, the decrease of the anthropogenic CH4, CO and N2O emissions in Europe estimated by inventories (respectively −30%, −35% and −23%) is confirmed by the Mace Head data within 2%. Therefore, the 222Rn method provides an independent way of verification of changes in national emissions derived from inventories. Using European-wide estimates of the CO/CO2 emission ratio, we also found that it is possible to separate the fossil fuel CO2 emissions contribution from the one of total CO2 fluxes. The fossil fuel CO2 emissions and their trends derived in that manner agree very well with inventories.

Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 354.52 kB
Markku Kulmala, Pekka Korhonen, Ismo Napari, Robert Jansson, Harald Berresheim, and Colin O'Dowd, Aerosol formation during PARFORCE: Ternary nucleation of H2SO4, NH3 and H2O, J. Geophys. Res., 107, 10.1029/2001JD000900, 2002.

Abstract


A new version of a ternary nucleation (sulphuric acid-ammonia-water) model based on classical nucleation theory, but with an improved ability to predict nucleation rates over a larger temperature range (258–303 K) compared with previous work, is presented. The modeled nucleation rates are given as a function of temperature and ambient acid and ammonia concentrations. For the first time the predicted ternary nucleation rates are compared to the observed particle production rates using measured ambient sulphuric acid and ammonia concentrations as input data. The ambient gas concentrations were measured simultaneously to aerosol formation rates during the 1999 New Particle Formation and Fate in the Coastal Environment (PARFORCE) coastal field campaign at Mace Head. According to the results, daytime ambient acid and ammonia concentrations were significantly higher than required by model calculations to induce the formation of new particles by homogeneous ternary nucleation. However, binary nucleation of sulphuric acid-water molecules is not able to predict new particle formation since the binary nucleation rate is far too small. We conclude that all particle formation events observed at coastal sites can be initiated by ternary nucleation of sulphuric acid, ammonia, and water vapor. However, related studies illustrate that ambient sulphuric acid concentrations are, nevertheless, insufficient to explain observed rapid growth of particles from 1 to 3 nm sizes which can be detected by current instrumentation.

IOP  John A McClelland IOP John A McClelland

Date added: 08/07/2002
Date modified: 08/07/2008
Filesize: 3.28 MB
 pg 176 - 185 by Tom O Connor

The Hohenpeissenberg aerosol formation experiment (HAFEX): a long-term study including size-resolved The Hohenpeissenberg aerosol formation experiment (HAFEX): a long-term study including size-resolved

Date added: 07/27/2003
Date modified: 07/27/2009
Filesize: 514.79 kB

Birmili W, Berresheim H, Plass-Dulmer C, Elste T, Gilge S, Wiedensohler A, Uhrner U, 2003. The Hohenpeissenberg aerosol formation experiment (HAFEX): a longterm study including size-resolved aerosol, H2SO4, OH, and monoterpenes measurements. Atmos. Chem. Phys. 3: 361–376.


Abstract

 

Ambient aerosol size distributions (> 3 nm) and OH, H2SO4, and terpene concentrations were measured from April 1998 to August 2000 at a rural continental site in southern Germany. New particle formation (NPF) events were detected on 18% of all days, typically during midday hours under sunny and dry conditions. The number of newly formed particles correlated significantly with solar irradiance and ambient levels of H2SO4. A pronounced anticorrelatation of NPF events with the pre-existing particle surface
area was identified in the cold season, often associated with the advection of dry and relatively clean air masses from southerly directions (Alps). Estimates of the particle formation rate based on observations were around 1 cm−3 s−1, being in agreement with the predictions of ternary homogeneous H2SO4-NH3-H2O nucleation within a few orders of magnitude. The experimentally determined nucleation mode particle growth rates were on average 2.6 nm h−1, with a fraction of 0.7 nm h−1 being attributed to the cocondensation of H2SO4-H2O-NH3. The magnitude of nucleation mode particle growth was neither significantly correlated
to H2SO4, nor to the observed particle formation rate. Turn-over rate calculations of measured monoterpenes and aromatic hydrocarbons suggest that especially the oxidation products of monoterpenes have the capacity to contribute to the growth of nucleation mode particles. Although a large number of precursor gases, aerosol and meteorological parameters were measured, the ultimate key factors controlling the occurence of NPF events could not be identified.

The efficency with which drizzle and precipitation sized drops collide with aerosol particles The efficency with which drizzle and precipitation sized drops collide with aerosol particles

Date added: 07/31/1991
Date modified: 07/10/2009
Filesize: 3.81 MB

McGann, B.T., and Jennings, S.G. (1991) - The efficiency with which drizzle and precipitation sized drops collide with aerosol particles. Atmos. Environ., 25A, 791 - 800.


Abstract


Vlaues of collision efficency and scavenging rates for drops interacting with aerosol particles are presented using more accurate flow fields than previous work and for a much greater number of drops than hitherto obtained. All calculations are performed at an Ambient temperature of 10C andatmospheric pressure of 900mb. Computations of collision efficency are performed for a drop radius range from 50 to 500 micrometre (um), for particle radius from 0.005 to 10um, for relative humidity values of 50,75,95 and 100% and for particle density of 1,1.5,2.0 and 2.5 x 10^3 kgm^-3. In addition the collision effiicency was also calculated fro elctric charges on the drop and particle and for an electric field, representive of typical thundercloud values. Combined use is made of a rigorous trajectory model together with a flux model and comparision is made between them in the overlap size region . Precipitation scavenging rates and the percentage of aerosol particles scavenged by precipitation drops described by Marshall-Palmer size distribution is also calculated.

PM10 Concentration Measurements In Dublin City PM10 Concentration Measurements In Dublin City

Date added: 07/31/1998
Date modified: 07/03/2009
Filesize: 4.08 MB

Jennings, S.G. (1998). How dirty is Dublin air? Technology Ireland, 30, 40-43.


Abstract


Mass concentration of ambient particulate matter with an aerodynamic diameter less than 10μm (PM10) are reported for the first time for a range of sites in Dublin City over a 6 month period from January 1st 1996 to June 30th 1996. PM10 gravimetric mass concentration measurements are made with low flow Partisol 2000 air samplers using an impaction type PM10 inlet and 47mm diameter glass fibre filters. In addition, much finer time resolution measurements (minimum sampling frequency of 30 minutes) are made using a tapered element oscillating microbalance (TEOM) PM10 mass monitor. These PM10 mass concentrations methods are also compared with mass concentration inferred using the standard black smoke method. Analysis of the ambient mass concentration data with reference to traffic density and meteorological influences are presented. Results for the first six months of 1996 show that the average PM10 values range from a high of 49 μg/m3 at the Dublin city centre site to 14 μg/m3 at one of the suburban sites. Intercomparison between PM10 and black smoke mass concentrations show that the relationship is site specific. Statistical analysis between PM10 levels and car traffic number show a positive correlation while a weak negative correlation is found between PM10 levels and rainfall amount, wind speed and air temperature.

Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements

Date added: 07/31/2001
Date modified: 06/30/2009
Filesize: 527.45 kB
Lai, A.C.K., Byrne, M.A. and Goddard, A.J.H. Aerosol deposition in turbulent channel flow on a regular array of three-dimensional roughness elements. J. Aerosol Sci., 32, 121-137, 2001.

Abstract


Understanding particle deposition onto rough surfaces is important for many engineering and environmental applications. An experimental system was designed for the study of aerosol deposition on regular arrays of uniform elements (in the form of discrete protrusions) in a turbulent ventilation duct flow using monodisperse tracer small particles, in the range 0.7-7.1mum. The Reynolds number for the test conditions was 44,000 in the 150 mm square duct. The roughness elements were arranged at two different orientations with respect to the airflow direction and the aerosol deposition velocity and pressure drop were measured for both orientations. Compared to earlier measurements in the same duct system involving smooth or ribbed surfaces, a significant increase in deposition velocity onto the regular roughness elements is observed. In addition, the associated pressure loss penalty is lower than in the presence of the roughness elements than in the presence of the ribbed surfaces. This may be attributable to the small dimensionless roughness height of the elements, which results only in a moderate distortion of the flow structure near the surfaces.

Short-lived alkyl iodides and bromides at Mace Head, Ireland Links to biogenic sources and halo Short-lived alkyl iodides and bromides at Mace Head, Ireland Links to biogenic sources and halo

Date added: 08/05/1999
Date modified: 07/23/2009
Filesize: 944.76 kB

Carpenter, L., Hebestreit, K., Sturges, W., Penkett, S., Liss, P., Alicke, B., and Platt, U.: Observation of short-lived alkyl iodides and bromides at Mace Head, Ireland: links to biogenic sources and halogen oxide production, J. Geophys. Res., 104, 1679–1689, 1999. 6080, 6108


Abstract


Automated in situ gas chromatograph/mass spectrometer (GC/MS) measurements of a range of predominantly biogenic alkyl halides in air, including CHBr3, CHBr2Cl, CH3Br, C2H5Br, CH3I, C2H5I, CH2ICl, CH2I2, and the hitherto unreported CH2IBr were made at Mace Head during a 3-week period in May 1997. C3H7I and CH3CHICH3 were monitored but not detected. Positive correlations were observed between the polyhalomethane pairs CHBr3/CHBr2Cl and CHBr3/CH2IBr and between the monohalomethane pair CH3I/C2H5I, which are interpreted in terms of common or linked marine sources. During periods when air masses were affected by emissions from local seaweed beds, the concentrations of CHBr3, CH2ICl, and CH2IBr not only showed remarkable correlation but also maximized at low water. These are the first field observations to provide evidence for a link between the tidal cycle, polyhalomethanes in air, and potential marine production. The calculated total flux of iodine atoms into the boundary layer at Mace Head from organic gaseous precursors was dominated by photolytic destruction of CH2I2. Photolysis of CH3I contributed less than 3%. The calculated peak flux of iodine atoms during the campaign coincided with the highest measured levels of iodine oxide radicals, as determined using Differential Optical Absorption Spectrometry (DOAS).

 

Steady state modelling of hydroxyl radical concentrations at Mace Head during the EASE '97 camp Steady state modelling of hydroxyl radical concentrations at Mace Head during the EASE '97 camp

Date added: 08/06/2001
Date modified: 07/23/2009
Filesize: 564.23 kB
Savage, N.H., R.M. Harrison, P.S. Monks, and G. Salisbury, Steady state modelling of hydroxyl radical concentrations at Mace Head during the EASE '97 campaign. May 1997, Atmos.Env., 35(3), 515-524, 2001, (Ser. No. ACP111).

Abstract

 

Two different steady-state methods are applied to calculate OH radical concentrations based on the rates of known source and sink processes. The first method, which calculates only OH radical concentrations from measured data including HO2 gives good correlation with measured OH concentrations but overpredicts by 30%. The second method applied calculates OH, HO2 and RO2 radical concentrations simultaneously. This second method overestimates the measured concentrations of OH by almost 3 times. This apparent overprediction may be a result of calculated concentrations of HO2 which appear too high and may be indicative of a gap in our understanding of the relevant peroxy radical chemistry or a result of the limited peroxy radical chemistry assumed by the method.

Recent Tropospheric Growth Rate and Distribution of HFC-134a (CF3CH2F) Recent Tropospheric Growth Rate and Distribution of HFC-134a (CF3CH2F)

Date added: 08/06/1996
Date modified: 07/23/2009
Filesize: 488.65 kB

Oram, D.E., Reeves, C.E., Sturges, W.T., Penkett, S.A., Fraser, P.J. and Langenfelds, R.L. 1996. Recent tropospheric growth rate and distribution of HFC-134a (CF3CH2F). Geophysical Research Letters 23:1949-1952.


Abstract


Air samples collected at Cape Grim, Tasmania (41°S) between 1978 and 1995, and at Mace Head, Ireland (53°N) between July 1994 and May 1995, have been analysed by GC-MS to determine recent trends of HFC-134a, an important CFC replacement, in the background atmosphere. Until 1990, the concentration of HFC-134a at Cape Grim was below detection limits, the first quantifiable level (0.01 pptv) appearing in May 1990. Between 1992 and mid-1995 the concentration grew exponentially at ∼200 % yr-1 with the concentration at the end of 1994 reaching 0.43 pptv. At Mace Head, HFC-134a grew at a rate of 1.24 ± 0.11 pptv yr-1 between July 1994 and May 1995, with the concentration at the end of 1994 being 1.48 pptv. In the absence of industrial production and release estimates for HFC-134a, the observations have been used in conjunction with a 2-D global model to estimate recent emissions. The model indicates that significant emissions (250 tonnes) began in 1991, increasing rapidly to a level of ∼8 ktonnes in 1994.

 

Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties

Date added: 09/12/2008
Date modified: 07/06/2009
Filesize: 257.12 kB

Sellegri, K., P. Villani, D. Picard, R. Dupuy, C. O’Dowd and P. Laj, Role of the Volatile Fraction of Submicron Marine Aerosol on its Hygroscopic Properties, Atmos. Res., in press, 2008.


Abstract


The hygroscopic growth factor (HGF) of 85 nm and 20 nm marine aerosol particles was measured during January 2006 for a three-week period within the frame of the EU FP6 project MAP (Marine Aerosol Production) winter campaign at the coastal site of Mace Head, using the TDMA technique. The results are compared to aerosol particles produced in a simulation tank by bubbling air through sea water sampled near the station, and through synthetic sea water (inorganic salts). This simulation is assimilated to primary production. Aitken and mode particles (20 nm) and accumulation mode particles (85 nm) both show HGF of 1.92 and 2.01 for particles generated through bubbling in natural and artificial sea water respectively. In the Aitken mode, the marine particles sampled in the atmosphere shows a monomodal HGF slightly lower than the one measured for sea salt particles artificially produced by bubble bursting in natural sea water (HGF = 1.83). This is also the case for the more hygroscopic mode of accumulation mode particles. In addition, the HGF of 85 nm particles observed in the atmosphere during clean marine sectors exhibits half of its population with a 1.4 HGF. An external mixture of the accumulation mode marine particles indicates a secondary source of this size of particles, a partial processing during transport, or an inhomogeneity of the sea water composition. A gentle 90 °C thermo-desorption results in a significant decrease of the number fraction of moderately hygroscopic (HGF = 1.4) particles in the accumulation mode to the benefit of the seasalt mode, pointing to the presence of semi-volatile compounds with pronounced hydrophobic properties. The thermo-desorption has no effect on the HGF of bubble generated aerosols, neither for synthetic or natural sea water, nor on the atmospheric Aitken mode, indicating that these hydrophobic compounds are secondarily integrated in the particulate phase. No difference between night and day samples is observed on the natural marine aerosols regarding hygroscopicity, but a more pronounced sensitivity to volatilization of the 1.4 HGF mode in the accumulation mode is observed during the day.

Novel Biogenic Iodine-Containing Trihalomethanes and Other Short-Lived Halocarbons in the Coast Novel Biogenic Iodine-Containing Trihalomethanes and Other Short-Lived Halocarbons in the Coast

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 1.05 MB

Carpenter, L. J., G. Malin, P. S. Liss, and F. C. Küpper (2000), Novel Biogenic Iodine-Containing Trihalomethanes and Other Short-Lived Halocarbons in the Coastal East Atlantic, Global Biogeochem. Cycles, 14(4), 1191–1204.


Abstract


Reactive halogen photochemistry and its impact on tropospheric oxidant levels have recently attracted intense research interest following the observation of the iodine oxide radical at midlatitudes. During September 1998, short-lived organoiodines including CH3I, C2H5I, CH2ICl, CH2IBr, CH2I2, and the hitherto undetected CHIBr2, as well as the organobromines CHBr3, CH2Br2, CHBr2Cl, CH3Br, and C2H5Br, were measured in air and seawater at and around Mace Head, on the west coast of Ireland. The release rates of organic bromines and iodines from seaweeds were determined from incubations of 10 species of brown, red, and green macroalgae collected in the intertidal or subtidal zones of the rocky shore. For all the brown algae studied, iodine was released mainly as CH2I2. However, for several seaweeds, the novel iodine-containing trihalomethanes CHIBr2 and CHI2Cl represented a significant fraction of the released organic iodine. The macroalgae incubation experiments as well as monitoring of the in situ concentrations in a rock pool indicated that natural halocarbon production by seaweeds was stimulated by incident light. The halocarbon fluxes derived from the seaweed incubations, coupled with published detailed biomass surveys, enabled coastal organohalogen seawater concentrations to be estimated. The CHBr3, CH2Br2, and CHBr2Cl concentrations calculated by this method compared well with coastal surface seawater measurements, implying that macroalgae were the major sources of the polybromomethanes. Measured CH3Br, CH3I, and CH2ICl levels were higher than calculated, which may be due to the existence of additional sources. CH3Br production by macroalgae accounted for less than 10% of measured levels in coastal waters. Short-lived iodocarbons such as CH2I2 and CHIBr2 were depleted in surface seawater compared to calculated levels, implying their photolytic loss within the upper water column.

 

Statistical Analysis of Eight Surface Ozone Measurement Series for various sites in Ireland, Statistical Analysis of Eight Surface Ozone Measurement Series for various sites in Ireland,

Date added: 02/08/2011
Date modified: 02/08/2011
Filesize: 1.81 MB

Tripathi, O. P., Jennings S. G., O’Dowd, C. D., Coleman, L., Leinert, S., O’Leary, B., Moran, E., O’Doherty, S. J., and Spain, T. G., Statistical Analysis of Eight Surface Ozone Measurement Series for various sites in Ireland, J. Geophys. Res., 115, D19302, doi:10.1029/2010JD014040., 2010


Abstract: Data from various stations having different measurement record periods between 1988 and 2007 are analyzed to investigate the surface ozone concentration, long‐term trends, and seasonal changes in and around Ireland. Time series statistical analysis is performed on the monthly mean data using seasonal and trend decomposition procedures and the Box‐Jenkins approach (autoregressive integrated moving average). In general, ozone concentrations in the Irish region are found to have a negative trend at all sites except at the coastal sites of Mace Head and Valentia. Data from the most polluted Dublin city site have shown a very strong negative trend of −0.33 ppb/yr with a 95% confidence limit of 0.17 pp/yr (i.e., −0.33 ± 0.17) for the period 2002−2007, and for the site near the city of Cork, the trend is found to be −0.20 ± 0.11 ppb/yr over the same period. The negative trend for other sites is more pronounced when the data span is considered from around the year 2000 to 2007. Rural sites of Wexford and Monaghan have also shown a very strong negative trend of −0.99 ± 0.13 and −0.58 ± 0.12, respectively, for the period 2000−2007. Mace Head, a site that is representative of ozone changes in the air advected from the Atlantic to Europe in the marine planetary boundary layer, has shown a positive trend of about +0.16 ± 0.04 ppb per annum over the entire period 1988−2007, but this positive trend has reduced during recent years (e.g., in the period 2001−2007). Cluster analysis for back trajectories are performed for the stations having a long record of data, Mace Head and Lough Navar. For Mace Head, the northern and western clean air sectors have shown a similar positive trend (+0.17 ± 0.02 ppb/yr for the northern sector and +0.18 ± 0.02 ppb/yr for the western sector) for the whole period, but partial analysis for the clean western sector at Mace Head shows different trends during different time periods with a decrease in the positive trend since 1988 indicating a deceleration in the ozone trend for Atlantic air masses entering Europe.

A High Temperature Volatility technique for determination of atmospheric aerosol composition A High Temperature Volatility technique for determination of atmospheric aerosol composition

Date added: 07/31/1992
Date modified: 06/30/2009
Filesize: 2.32 MB
O'Dowd, C.D., Jennings, S.G., Smith M.H., and Cooke, W.F. (1992) - A high temperature volatility technique for determination of atmospheric aerosol composition. J. Aerosol Sci., 23, S905 - S908.

Abstract


Size segregated atmospheric aerosol composition, over the radius range 0.05μm ≤ r ≤ 1.5μm, is inferred using an optical particle counter equipped with a high temperature heater tube cycling through temperatures from 20°C to 870°C. The volatility system infers the presence of common atmospheric constituents such as H2SO4, (NH4)2SO4, NaCl, and soot carbon. This system has been successfully used to determine the physico-chemical characteristics of accumulation mode aerosol associated with air masses of different origin. Results from ship-borne and ground based measurements are presented. For continental and modified maritime air, (NH4)2SO4 was observed to be the dominant species, whilst H2SO4 was more abundant in Arctic aerosol. Sea-salt aerosol accounts for ≈75% of accumulation mode particle concentration for maritime aerosol in periods of high wind speeds. We also show that soot carbon can be identified in polluted air using this technique.

A Photoelectric Condensation Nucleus Counter On High Precision A Photoelectric Condensation Nucleus Counter On High Precision

Date added: 08/07/1955
Date modified: 07/13/2009
Filesize: 4.73 MB
L.w Pollak & Tc O'Connor, A Photoelectric Condensation Nucleus Counter On High Precision, Geofisica Pura E Applicata Milano Vol. 32 pp 139-146

Abstract

 

A new model of the direct beam photo-electrix condensation nucleus counter and itsproperties are described. the main feature of the construction is the reduction of the fog tube diameter which resulted in the elimination of all uncertainties in the measurement of the light intensity after the fog is formed by adiabatic expansion.- Individual measurements with two identical of this design which incorporate all previous improvements, agree to better than 5% in 70% in all cases, their aver absolute difference being 2%. Deviations of more than one division of meter reading (or 10% of concentration) were not observed, This agreement is maintained over long periods. - A calibration curve of the latest model of the photo-electric nucleus counter is given

Characterization of individual airborne particles by using aerosol time-of-flight mass spectrom Characterization of individual airborne particles by using aerosol time-of-flight mass spectrom

Date added: 08/06/2004
Date modified: 07/27/2009
Filesize: 425.52 kB

Dall'Osto, M., D. C. S. Beddows, R. P. Kinnersley, R. M. Harrison, R. J. Donovan, and M. R. Heal (2004), Characterization of individual airborne particles by using aerosol time-of-flight mass spectrometry at Mace Head, Ireland, J. Geophys. Res., 109, D21302, doi:10.1029/2004JD004747.


Abstract


An aerosol time-of-flight mass spectrometer was deployed at Mace Head (Ireland) during August 2002. The measurements provide qualitative chemical composition and size distribution (0.3–3 μm) information for single particles. Three broad categories of particles: sea salt, dust, and carbon-containing particles were identified and apportioned, and their temporal evolution (1 hour resolution) is described. Aerosol sources were correlated with meteorological factors and with air mass trajectories, demonstrating long-range transport of different continental air masses from Europe, Africa, and America. The major class of particles was derived from sea salt and was subdivided into pure, mixed, and aged sea salt according to the extent of displacement of chloride by nitrate. Two types of dust particles were found mainly in the coarse mode (>1 μm); the former, thought to originate from the Sahara, presented an aluminium/silicon signature, while the latter, of more local origin, had a calcium-rich composition. Carbon-containing particles were mainly distributed in the fine mode (<1 μm) and associated with different chemical species in different size modes, suggesting different mechanisms of formation.

 

An important source of marine secondary organic aerosol from biogenic amines, An important source of marine secondary organic aerosol from biogenic amines,

Date added: 04/08/2009
Date modified: 07/23/2009
Filesize: 548.79 kB

Facchini, M.C., S. Decesari, M. Rinaldi, C. Carbone, E. Finessi, M. Mircea, S. Fuzzi, F. Moretti, E. Tagliavini, D. Ceburnis and C. D. O’Dowd, An important source of marine secondary organic aerosol from biogenic amines, Env. Sci. & Tech., 10.1021/es8018385, 2008


Abstract

 

Relevant concentrations of dimethyl- and diethylammonium salts(DMA+andDEA+)weremeasured in submicrometer marine aerosol collected over the North Atlantic during periods of high biological activity (HBA) in clean air masses (median concentration (minimum-maximum))26 (6-56) ngm-3). Much lower concentrations were measured during periods of low biological activity (LBA): 1 (<0.4-20) ng m-3 and when polluted air masses were advected to the sampling site: 2 (<0.2-24) ngm-3.DMA+ andDEA+ are the most abundant organic species, second only to MSA, detected in fine marine particles representing on average 11% of the secondary organic aerosol (SOA)fraction and a dominant part (35% on average) of the watersoluble organic nitrogen (WSON). Several observations support the hypothesis that DMA+ and DEA+ have a biogenic oceanic source and are produced through the reaction of gaseous amines with sulfuric acid or acidic sulfates. Moreover, the water-soluble fraction of nascent marine aerosol particles produced by bubble-bursting experiments carried out in parallel to ambient aerosol sampling over the open ocean showed WSON, DMA+, and DEA+ concentrations always below the detection limit, thus excluding an important primary sea spray source.

 

Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland

Date added: 07/31/2000
Date modified: 07/23/2009
Filesize: 1.21 MB

O'Brien, E. W., Jennings, S.G., Geever, M., and Kleefeld, C. (2000). Relationships between condensation nuclei number concentration, tides, and standard meteorological variables at Mace Head, Ireland. J. Geophys. Res., 105, 1973-1986.


Abstract


The set of hourly averaged condensation nuclei (CN) data collected at Mace Head during 1991-1994 was examined for relationships that might exist between CN number concentrations and the more commonly measured meteorological variables, including tides. CN number concentrations at Mace Head can be characterized by typically low background levels (less than about 700 particles cm-3) when the wind is from the west, somewhat higher background levels (1000-4000 particles cm-3) when the wind is from the east, with sporadic bursts of short-lived discrete events of more than 10,000 cm-3 for several hours. These events occur typically during early afternoon and are normally associated with slack winds and anomalously warm, dry air. They appear to be independent of pressure, wind direction and precipitation. They can occur any time during the year, although the strongest events tend to occur during spring and autumn. Large-amplitude low tides also occur predominantly in the early afternoon during this observing period. We present evidence that large CN concentration events occur preferentially after exceptionally low tides during daylight. A neural network was employed to train the standard meteorological variables to predict CN concentrations. Baseline forecasts of CN counts for the final 180 days of the observing period were made using lagged values of all other variables. Further forecasts were made with some variables removed from the predictor set. The best correlation between the predicted values and the verifying data over the 180 days was 0.67, which was obtained from a 1-hour forecast using knowledge of all variables except temperature. Other variables whose removal improved the forecast (or whose presence degraded it) were pressure and wind speed. The best predictors of CN values were wind direction, relative humidity, and time of day. An elementary nearest neighbor, or historical analogue approach to predicting the same set of CN values generated lower correlations with the verifying data but generated a much more accurate probability distribution function.

Interpretation of roadside PM10 monitoring data from Sunderland, United Kingdom Interpretation of roadside PM10 monitoring data from Sunderland, United Kingdom

Date added: 09/22/2003
Date modified: 07/23/2009
Filesize: 739.63 kB

Price, M., Dowd, C., & Dixon, M. (2003). Interpretation of roadside PM10 monitoring data from Sunderland, United Kingdom. Environmental Monitoring and Assessment, 82, 225-241


Abstract


Roadside PM10 has been monitored by Partisol® at three sites in Sunderland between August 1997 and February 1998. The sites chosen were an inner city kerbside site; a roadside site adjacent to a dual carriageway on the outskirts of Sunderland with an open aspect; and a rural site. The results indicate that there is a seasonal variation in the relationship between the sites in terms of monitored PM10. In the winter there is a poor correlation between the sites whereas in the summer significant correlations are obtained. Of the sites monitored PM10 is consistently highest at the inner city roadside site. During the summer, exceedances of the U.K. 50 μg m-3 standard (DETR, 2000) are associated with conditions suitable for the build-up of photochemical pollution however during the winter period exceedances are recorded during a variety of weather conditions. At the dual carriageway site PM2.5 has also been recorded and contributions to measured PM10 are 77% in summer and 68% in winter. The results illustrate a number of inconsistencies between this study utilising the Partisol® and others reporting results where PM10 has been monitored by TEOM®.

A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE): Overview A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE): Overview

Date added: 08/01/2002
Date modified: 07/21/2009
Filesize: 448.25 kB
O’Dowd, C. D., et al., A dedicated study of New Particle Formation and Fate in the Coastal Environment (PARFORCE):Overview of objectives and achievements, J. Geophys. Res., 107(D19), 8108, doi:10.1029/2001JD000555, 2002Overview of objectives and achievements, J. Geophys. Res., 107(D19), 8108, doi:10.1029/2001JD000555, 2002

Abstract


A dedicated study into the formation of new particles, New Particle Formation and Fate in the Coastal Environment (PARFORCE), was conducted over a period from 1998 to 1999 at the Mace Head Atmospheric Research Station on the western coast of Ireland. Continuous measurements of new particle formation were taken over the 2-year period while two intensive field campaigns were also conducted, one in September 1998 and the other in June 1999. New particle events were observed on ∼90% of days and occurred throughout the year and in all air mass types. These events lasted for, typically, a few hours, with some events lasting more than 8 hours, and occurred during daylight hours coinciding with the occurrence of low tide and exposed shorelines. During these events, peak aerosol concentrations often exceeded 106 cm-3 under clean air conditions, while measured formation rates of detectable particle sizes (i.e., d > 3 nm) were of the order of 104-105 cm-3 s-1. Nucleation rates of new particles were estimated to be, at least, of the Qrder of 105-106 cm-3 s-1and occurred for sulphuric acid concentrations above 2 x 106 molecules cm-3; however, no correlation existed between peak sulphuric acid concentrations, low tide occurrence, or nucleation events. Ternary nucleation theory of the H2SO4-H2O-NH3 system predicts that nucleation rates far in excess of 106 cm-3 s-1 can readily occur for the given sulphuric acid concentrations; however, aerosol growth modeling studies predict that there is insufficient sulphuric acid to grow new particles (of ∼1 nm in size) into detectable sizes of 3 nm. Hygroscopic growth factor analysis of recently formed 8-nm particles illustrate that these particles must comprise some species significantly less soluble than sulphate aerosol. The nucleation-mode hygroscopic data, combined with the lack of detectable VOC emissions from coastal biota, the strong emission of biogenic halocarbon species, and the fingerprinting of iodine in recently formed (7 nm) particles suggest that the most likely species resulting in the growth of new particles to detectable sizes is an iodine oxide as suggested by previous laboratory experiments. It remains an open question whether nucleation is driven by self nucleation of iodine species, a halocarbon derivative, or whether first, stable clusters are formed through ternary nucleation of sulphuric acid, ammonia, and water vapor, followed by condensation growth into detectable sizes by condensation of iodine species. Airborne measurements confirm that nucleation occurs all along the coastline and that the coastal biogenic aerosol plume can extend many hundreds of kilometers away from the source. During the evolution of the coastal plume, particle growth is observed up to radiatively active sizes of 100 nm. Modeling studies of the yield of cloud-condensation nuclei suggest that the cloud condensation nuclei population can increase by ∼100%. Given that the production of new particles from coastal biogenic sources occurs at least all along the western coast of Europe, and possibly many other coastlines, it is suggested that coastal aerosols contribute significantly to the natural background aerosol population.

The concurrent observation of methyl iodide and dimethyl sulphide in marine air; implications f The concurrent observation of methyl iodide and dimethyl sulphide in marine air; implications f

Date added: 08/07/1998
Date modified: 07/23/2009
Filesize: 560.08 kB

Bassford, M.R., G. Nickless, P.G. Simmonds, A.C. Lewis, M.J. Pilling, and M.J. Evans, The concurrent observation of methyl iodide and dimethyl sulphide in marine air; implications for sources of atmospheric methyl iodide, Atmospheric Environment, 33 (15), 2373-2383, 1999.


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 significant 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 flow has elucidated part of the global methyl iodide cycle and provides evidence for two distinct source regions of methyl iodide: I. 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 30-50°N and 20-50°W. 2. Measurements taken under different conditions led us to believe that there was an additional source of methyl iodide that influenced the Mace Head atmosphere, most likely produced by coastal macroalgae which inhabit waters off the western coast of Ireland.

 

Size-differentiated volatility analysis of internally mixed laboratory-generated aerosol, Size-differentiated volatility analysis of internally mixed laboratory-generated aerosol,

Date added: 08/01/2002
Date modified: 07/23/2009
Filesize: 348.8 kB
Brooks, B.J., M.H. Smith, M.K. Hill, and C.D. O'Dowd, Size-differenciated volatility analysis of internally mixed laboratory-generated aerosol, J. Aer. Sci.,33, 555-579, 2002.

Abstract


The increased application of volatility analysis to determine the composition and structure of sub-micron aerosol requires that the thermal behaviour of chemically complex aerosol be understood. Presented here is a volatility study, utilising a tandem volatility differential mobility analyser (TVDMA), of 30, 50, and 70nm radii, internally mixed, aerosol containing ionic-salts, acids, organics, and carbon. Evidence of some size-dependent behaviour was observed with several of the single component aerosol. Internally mixed aerosol displayed complex thermal behaviours that were dependent on both size and the volume mixing ratio of source solutions

Marine Aerosol Production: a review of the current knowledge Marine Aerosol Production: a review of the current knowledge

Date added: 08/06/2007
Date modified: 07/02/2009
Filesize: 1.51 MB

O’Dowd, C.D., & G. de Leeuw, Marine Aerosol Production: a review of the current knowledge, , Phil. Trans. R. Soc. A, doi:10.1098/rsta.2007.2043, 2007


Abstract


The current knowledge in primary and secondary marine aerosol formation is reviewed. For primary marine aerosol source functions, recent source functions have demonstrated a significant flux of submicrometre particles down to radii of 20nm. Moreover, the source functions derived from different techniques up to 10μm have come within a factor of two of each other. For secondary marine aerosol formation, recent advances have identified iodine oxides and isoprene oxidation products, in addition to sulphuric acid, as contributing to formation and growth, although the exact roles remains to be determined. While a multistep process seems to be required, isoprene oxidation products are more likely to participate in growth and sulphuric acid is more likely to participate in nucleation. Iodine oxides are likely to participate in both nucleation and growth.

 

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