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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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Segregation and Interpretation of Ozone and Carbon Monoxide Measurements by Air Mass Origin at Segregation and Interpretation of Ozone and Carbon Monoxide Measurements by Air Mass Origin at

Date added: 08/07/1997
Date modified: 07/23/2009
Filesize: 252.17 kB

Simmonds, PG, Seuring, S, Nickless, G, et al , Segregation and interpretation of ozone and carbon monoxide measurements by air mass origin at the TOR Station Mace Head, Ireland from 1987 to 1995, J ATMOS CHEM, 1997, Vol: 28, Pages: 45 - 59, ISSN: 0167-7764


Abstract


Three independent methods have been used to sort the ozone, carbon monoxide, and other radiatively important trace gases measured at Mace Head, Ireland, and thereby distinguish clean air masses transported over the North Atlantic from the more polluted air masses which have recently travelled from the European continent. Over the period April 1987-June 1995 the Northern Hemisphere surface ozone baseline concentrations exhibited a mean concentration of 34.8 ppb, with a small positive trend (+0.19 ppb yr-1), while the corresponding trend in air originating from the polluted European areas was negative (-0.39 ppb yr-1). Carbon monoxide measurements from March 1990 to December 1994 showed negative trends for both the unpolluted (-0.17 ppb yr-1) and polluted data (-13.6 ppb yr-1). Overall the continent of Europe was shown to be a small net sink of 2.6 ppb for all occasions when European air was transported to the North Atlantic.

 

Atmospheric mercury distribution in Northern Europe and in Atmospheric mercury distribution in Northern Europe and in

Date added: 08/06/2001
Date modified: 06/30/2009
Filesize: 238.69 kB

I. Wangberg, J. Munthe, N. Pirrone, A. Iverfeldt, E. Bahlman, P. Costa, R. Ebinghaus, X. Feng, R. Ferrara, K. Gardfeldt, H. Kock, E. Lanzillotta, Y. Mamane, F. Mas, E. Melamed, Y. Osnat, E. Prestbo, J. Sommar, S. Schmolke, G. Spain, F. Sprovieri, G. Tuncel, Atmospheric mercury distribution in Northern Europe and in the Mediterranean region, Atmospheric EnvironmentVolume 35, Issue 17, , June 2001, Pages 3019-3025.


Abstract

 

Mercury species in air have been measured at five sites in Northwest Europe and at five coastal sites in the Mediterranean region during measurements at four seasons. Observed concentrations of total gaseous mercury (TGM), total particulate mercury (TPM) and reactive gaseous mercury (RGM) were generally slightly higher in the Mediterranean region than in Northwest Europe. Incoming clean Atlantic air seems to be enriched in TGM in comparison to air in Scandinavia. Trajectory analysis of events where high concentrations of TPM simultaneously were observed at sites in North Europe indicate source areas in Central Europe and provide evidence of transport of mercury on particles on a regional scale.

 

MEASUREMENTS OF NON METHANE HYDROCARBONS, DIMETHYL. SULPHIDE AND LIGHTWEIGHT OXYGENATED VOLATILE ORG MEASUREMENTS OF NON METHANE HYDROCARBONS, DIMETHYL. SULPHIDE AND LIGHTWEIGHT OXYGENATED VOLATILE ORG

Date added: 09/04/2008
Date modified: 07/09/2009
Filesize: 5.33 kB

J. Hopkins, K. Read , A. Lewis , J. Stanton and M. Pilling, MEASUREMENTS OF NON METHANE HYDROCARBONS, DIMETHYL. SULPHIDE AND LIGHTWEIGHT OXYGENATED VOLATILE ORGANIC COM-. POUNDS DURING NAMBLEX


Abstract


Marine boundary layer concentrations of C2-C7 non methane hydrocarbons (NMHCs) and lightweight oxygenated volatile organic compounds (o-VOCs) were measured during the NAMBLEX campaign, Mace Head, Ireland during the summer of 2002. A multi-bed, Peltier-cooled adsorbent trap was used to acquire samples every hour and were analysed using an in-situ dual column gas chromatograph coupled with two flame ionisation detectors (GC-FID). The equipment ran almost continuously for the seven weeks of the campaign, between 24th July and 3rd September, and collected data in a variety of meteorological conditions with diverse airmass origins. Average concentrations of acetylene, methanol, acetone and acetaldehyde at the site ranged from 40, 1051, 603 and 256 pptV respectively under clean south-westerly conditions and 154, 1693, 1133 and 530 pptV respectively in polluted easterly air masses. OVOCs were found to dominate the mass of organic species observed at the site under all atmospheric conditions and were also found to be the major organic loss route for hydroxyl radicals. Secondary production through hydrocarbon oxidation was found to be a major source of the measured o-VOCs. The variance of short lived oxygenates such as acetaldehyde was significantly less than for a hydrocarbon species with equivalent OH reactivity. Modelling studies indicate that this may be caused by significant oxygenate production occurring 2-10 days downwind from point of original surface emission. The extended time period over which acetaldehyde is produced appears to result from degradation of longer lived organic reservoir species such as a alcohols and peroxides formed during hydrocarbon oxidation. Evidence of a direct terrestrial emission source for acetaldehyde and acetone was observed during polluted easterly periods. No oceanic source was observed for these compounds.

Interannual and seasonal variability in atmospheric N 2 O Interannual and seasonal variability in atmospheric N 2 O

Date added: 08/06/2007
Date modified: 07/02/2009
Filesize: 673.42 kB

Nevison, C. D., N. M. Mahowald, R. F. Weiss, and R. G. Prinn (2007), Interannual and seasonal variability in atmospheric N2O, Global Biogeochem. Cycles, 21, GB3017, doi:10.1029/2006GB002755.


Abstract


The increase in atmospheric N2O observed over the last century reflects large-scale human perturbations to the global nitrogen cycle. High-precision measurements of atmospheric N2O over the last decade reveal subtle signals of interannual variability (IAV) superimposed upon the more prominent growth trend. Anthropogenic sources drive the underlying growth in N2O, but are probably too monotonic to explain most of the observed IAV. The causes of both seasonal and interannual variability in atmospheric N2O are explored on the basis of comparisons of a 1993–2004 atmospheric transport simulation to observations of N2O at five stations of the Advanced Global Atmospheric Gases Experiment (AGAGE). The complementary tracers chlorofluorocarbons (CFCs) 11 and 12 and SF6 also are examined. The model simulation does not include a stratospheric sink and thus isolates the effects of surface sources and tropospheric transport. Both model and observations yield correlations in seasonal and interannual variability among species, but only in a few cases are model and observed variability correlated to each other. The results suggest that tropospheric transport contributes substantially to observed variability, especially at Samoa station. However, some features of observed variability are not explained by the model simulation and appear more consistent with a stratospheric influence. At Mace Head, Ireland, N2O and CFC growth rate anomalies are weakly correlated to IAV in polar winter lower stratospheric temperature, a proxy for the strength of the mean meridional stratospheric circulation. Seasonal and interannual variability in the natural sources of N2O may also contribute to observed variability in atmospheric N2O.

 

A model prediction of the yield of CCN from coastal nucleation events A model prediction of the yield of CCN from coastal nucleation events

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 352.77 kB
Liisa Pirjola, Colin O'Dowd, Markku Kulmala, A model prediction of the yield of CCN from coastal nucleation events, J. Geophys. Res., 107, 10.1029/2000JD000213, 2002.

Abstract


The formation and evolution of new particles during coastal nucleation events are examined using the aerosol dynamic and gas-phase chemistry model AEROFOR2. Coastal regions are known to be a strong source of natural aerosol particles and are also strong sources of biogenic vapors which can condense onto aerosol particles, thus resulting in particle growth. A number of model simulations were performed to determine the instantaneous nucleation rate along with the source rate of a generic biogenic vapor leading to the observed particle size distributions which indicate the rapid appearance of ∼105–106 cm−3 nucleation mode particles in this environment. Model calculations suggest values of 3 × 105 cm−3 s−1 to 3 × 106 cm−3 s−1 for the instantaneous nucleation rate and a value of 5 × 107 cm−3 s−1 for the condensable vapor source rate in order to reproduce the observed concentrations. A significant fraction of these new particles survive to grow into cloud condensation nuclei (CCN) sizes for supersaturations typically encountered in boundary layer clouds during subsequent evolution over 3 days under clear-sky conditions, thus contributing to the indirect radiative effect of aerosols. The amount of CCN is mainly affected by coagulation between particles and condensation of the biogenic vapor and, to a lesser extent, by condensation of sulphuric acid formed by DMS oxidation. In all simulated cases, an increase of more than 100% in CCN concentration, for supersaturations >0.35% was observed.

Mass Measurements Of Aerosol at macehead on the west coast of Ireland Mass Measurements Of Aerosol at macehead on the west coast of Ireland

Date added: 07/31/1994
Date modified: 07/24/2009
Filesize: 1.91 MB

McGovern F.M., Krasenbrink, A., Jennings, S.G., Georgi, B., Spain, T.G., Below, M., and O'Connor , T.C. (1994) Mass measurements of aerosol at Mace Head on the west coast of Ireland. Atmos. Environ, 28, 1311 -1318.


Abstract


Aerosol mass/size measurements have been carried out at the Mace Head research station, on the west coast of Ireland, for a period of over two years. Mass/size distributions were obtained in the size range 0.06-10 μm using Berner low-pressure cascade impactor systems. The distributions obtained reflect the different types of air mass which are encountered at Mace Head. Westerly winds are dominant at the site with the associated air masses being typically maritime. Unimodal mass/size distributirns with the peak mass concentration occurring principally in the 2-4 μm size range were characteristic if these conditions. Continental air masses from Europe are typified by mass/size distributions which have peak values in the submicron size range

Particle deposition in ventilation duct onto three-dimensional roughness elements Particle deposition in ventilation duct onto three-dimensional roughness elements

Date added: 08/01/2002
Date modified: 07/03/2009
Filesize: 133.69 kB
A.C.K. Lai, M.A. Byrne, A.J.H. Goddard, Particle deposition in ventilation duct onto three-dimensional roughness elements, Building and Environment, 37, No .10, 939-945, 2002.

Abstract


Gaining insights on particle deposition onto ventilation duct has many important applications. One key pathway by which outdoor polluted air enters the indoor environment is through mechanical ventilation ducts. An experimental system was designed for the study of particle 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 0.7–7.1 μm. The Reynolds number for the test conditions was 44,000 in the 150 mm square duct. Four different types of uniform roughness elements were tested. Compared to earlier measurements in the same duct system involving smooth or ribbed surfaces, a significant increase (up to 74 times) in deposition velocity onto the regular roughness elements is observed.

Intercomparison of formaldehyde measurements in clean and polluted atmospheres Intercomparison of formaldehyde measurements in clean and polluted atmospheres

Date added: 08/06/2000
Date modified: 07/24/2009
Filesize: 222.47 kB

Cardenas, L.M., Brassington, D.J., Allan, B.J., Coe, H., Alicke, B., Platt, U., Wilson, K.M., Plane, J.M.C. and Penkett, S.A., 2000. Intercomparison of formaldehyde measurements in clean and polluted atmospheres. Journal of Atmospheric Chemistry 37, pp. 53–80.


Abstract


Three different techniques used tomeasure atmospheric formaldehyde were compared duringa field campaign carried out at a clean maritime siteon the West coast of Ireland. Two spectroscopictechniques Differential Optical AbsorptionSpectroscopy (DOAS) and Tunable Diode Laser AbsorptionSpectroscopy (TDLAS), together with a glass coil/Hantzschreaction/fluorescence technique, wereemployed for measurements of atmospheric formaldehydeof the order of a few hundred pptv. The betteragreement was observed between the fluorescence andDOAS instruments.Two DOAS instruments were compared to the glasscoil/Hantzsch reaction/fluorescence technique at asemi-polluted site on the North Norfolk coast, U.K.,where concentrations of formaldehyde were observed atlevels up to 4 ppbv. A very good agreement wasobserved between the two instruments.The glass coil/Hantzsch reaction/fluorescence and theTDLAS instruments were also deployed simultaneously inorder to measure indoor air inside a mobile laboratorylocated at the Imperial College Silwood Park site nearAscot, U.K. The doors of the mobile laboratory wereleft open in order to obtain the backgroundformaldehyde concentrations. Closing them afterwardsallowed us to observe the increase in concentrationsas a result of indoor emissions. The agreement betweenthe two instruments was outstanding (correlationcoefficient was 99%).The results from this study showed that of the fourinstruments included in this intercomparison the glasscoil/Hantzsch reaction/fluorescence technique provedthe most suitable for continuous measurements offormaldehyde in the background atmosphere.

On the formation, growth and composition of nucleation mode particles On the formation, growth and composition of nucleation mode particles

Date added: 08/06/2001
Date modified: 07/03/2009
Filesize: 428.69 kB

Kulmala, M.,M. Dal Maso, J.M. Mäkelä, L. Pirjola, M. Väkevä, P. Aalto, P. Miikkulainen, K. Hämeri and C.D. O'Dowd, On the Formation, growth and composition of nucleation mode particles, Tellus B, 53, 479-490,, 2001


Abstract


Taking advantage of only the measured aerosol particles spectral evolution as a function of time, a new analytical tool is developed to derive formation and growth properties of nucleation mode aerosols. This method, when used with hygroscopic growth‐factors, can also estimate basic composition properties of these recently‐formed particles. From size spectra the diameter growth‐rate can be obtained, and aerosol condensation and coagulation sinks can be calculated. Using this growth‐rate and condensation sink, the concentration of condensable vapours and their source rate can be estimated. Then, combining the coagulation sink together with measured number concentrations and apparent source rates of 3 nm particles, 1 nm particle nucleation rates and concentration can be estimated. To estimate nucleation rates and vapour concentration source rates producing new particle bursts over the Boreal forest regions, three cases from the BIOFOR project were examined using this analytical tool. In this environment, the nucleation mode growth‐rate was observed to be 2–3 nm hour−1, which required a condensable vapour concentration of 2.5–4×107 cm−3 and a source rate of approximately 7.5–11×104 cm−3 s−1 to be sustained. The formation rate of 3 nm particles was ≈1 particle cm−3 s−1 in all three cases. The estimated formation rate of 1 nm particles was 10–100 particles cm−3 s−1, while their concentration was estimated to be between 10,000 and 100,000 particles cm−3. Using hygroscopicity data and mass flux expressions, the mass flux of insoluble vapour is estimated to be of the same order of magnitude as that of soluble vapour, with a soluble to insoluble vapour flux ratio ranging from 0.7 to 1.4 during these nucleation events.

 

Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents

Date added: 07/31/1979
Date modified: 07/06/2009
Filesize: 512.02 kB
Jennings, S.G., Pinnick, R.G., and Gillespie, J.B. (1979)- Relation between absorption coefficient and imaginary index of atmospheric aerosol constituents. Appl. Opt., 18, 1368-1371.

Abstract


The absorption coefficient per unit mass α(cm2g-l) for aerosols in the wavelength range λ = 1.06–10.6 µm is shown to be a sensitive function of particle size distribution and of both imaginary and real indexes of refraction. Hence the imaginary index of refraction cannot be accurately determined from absorption measurements on an aerosol sample as attempted by S. A. Schleusener et al., Appl. Opt. 15, 2546 (1976), unless the size distribution and real index of the aerosol material are known. Similar difficulties arise in attempts to infer imaginary index from transmission measurements through aerosol samples as done by F. E. Volz, Appl. Opt. 11, 755 (1972); 12, 564 (1973) and K. Fischer, Beitr. Phys. Atmos. 43, 244 (1970). In addition, scattering losses can further complicate the determination of imaginary index from transmission measurements.

Explaining global surface aerosol number concentrations in terms of primary emissions and particle f Explaining global surface aerosol number concentrations in terms of primary emissions and particle f

Date added: 01/31/2011
Date modified: 01/31/2011
Filesize: 972.89 kB

Spracklen, D. V., K. S. Carslaw, J. Merikanto, G. W. Mann, S. Pickering, J. A. Ogren, B. Andrews, U. Baltensperger, E. Weingartner, M. Boy, M. Kulmala, H. Lihavainen, J. Hatakka, N. Mihalopoulos, G. Kouvarakis, S. G. Jennings, C. O’Dowd, W. Birmili, A. Wiedensohler, R. Weller, J. Gras, P. Laj, R. Griffin, B. Bonn, and B. Bandy, Explaining global surface aerosol concentrations in terms of primary emissions and particle formation, Atmos. Chem. Phys., 10, 4775–4793, doi:10.5194/acp-10-4775-2010, 2010


 

Abstract

 

We synthesised observations of total particle number (CN) concentration from 36 sites around the world. We found that annual mean CN concentrations are typically 300–2000 cm−3 in the marine boundary layer and free troposphere (FT) and 1000–10 000 cm−3 in the continental boundary layer (BL). Many sites exhibit pronounced seasonality with summer time concentrations a factor of 2–10 greater than wintertime concentrations. We used these CN obser-vations to evaluate primary and secondary sources of particle  number in a global aerosol microphysics model. We found that emissions of primary particles can reasonably reproduce the spatial pattern of observed CN concentration (R2=0.46) but fail to explain the observed seasonal cycle (R2=0.1). The modeled CN concentration in the FT was biased low (normalised mean bias, NMB=−88%) unless a secondary source of particles was included, for example from binary homogeneous nucleation of sulfuric acid and water (NMB=−25%). Simulated CN concentrations in the continental BL were also biased low (NMB=−74%) unless the number emission of anthropogenic primary particles was increased or a mechanism that results in particle formation in the BL was included. We ran a number of simulations where we included  an empirical BL nucleation mechanism either using the activation-type mechanism (nucleation rate, J , proportional to gas-phase sulfuric acid concentration to the power one) or kinetic-type mechanism (J proportional to sulfuric acid to the power two) with a range of nucleation coefficients. We found that the seasonal CN cycle observed at continental BL sites was better simulated by BL particle formation (R2=0.3) than by increasing the number emission from primary anthropogenic sources (R2=0.18). The nucleation constants that resulted in best overall match between model and observed CN concentrations were consistent with values derived in previous studies from detailed case studies at individual sites. In our model, kinetic and activation-type nucleation parameterizations gave similar agreement with observed monthly mean CN concentrations.

 

On the photochemical production of biogenic new particles in the coastal boundary layer On the photochemical production of biogenic new particles in the coastal boundary layer

Date added: 08/05/1999
Date modified: 08/05/2008
Filesize: 4.86 MB
O'Dowd, C.D., G. McFiggans, D.J. Creasey, L. Pirjola, C. Hoell, M.H. Smith, B.J. Allan, J.M.C. Plane, D.E. Heard, J.D. Lee, M.J. Pilling, and M. Kulmala, On the photochemical production of biogenic new particles in the coastal boundary layer, Geophys. Res. Lett., 26, 1707-1710, 1999, (Ser. No. ACP072).

An analysis of rapid increases in condensation nuclei concentrations at a remote coastal site i An analysis of rapid increases in condensation nuclei concentrations at a remote coastal site i

Date added: 08/06/1999
Date modified: 07/27/2009
Filesize: 885.01 kB

Grenfell, J.L., R.M. Harrison, A.G. Allen, J.P. Shi, S.A. Penkett, C.D. O'Dowd, M.H. Smith, M.K. Hill, L. Robertson, C.N. Hewitt, B. Davison, A.C. Lewis, D.J. Creasey, D.E. Heard, K. Hebestreit, B. Alicke and J. James, An analysis of rapid increases in condensation nuclei concentrations at a remote site on the West Irish Coast, J. Geophys.Res., 104, 13,771-13,780, 1999, (Ser. No. ACP073).


Abstract


Massive bursts in condensation nuclei (CN) concentration were recorded at a remote site on the west Irish coast during campaigns in summer 1996 and spring/summer 1997. Number concentrations of 3-7 nm diameter CN were observed to rise daily from 102-103 up to ∼105 /cm3 for 1-3 hours. Data were collected as part of the Atmospheric Chemistry Studies in the Oceanic Environment program. In a previous paper the burst phenomenon was linked to the movement of the tide, and it was suggested that enhanced biogenic emissions occurred near low tide with concomitant rapid homogeneous gas phase CN formation. In this paper possible chemical mechanisms for the burst phenomenon are investigated. Two approaches are adopted. First, by assuming a 20:80 sulfate:water molar composition and calculating the number distribution using data from condensation particle counters, the total mass of CN formed during a burst is evaluated. This is compared with that mass of sulfate produced by OH-initiated dimethyl sulfide (DMS) oxidation. The procedure is termed mass balance. Second, a variety of chemical species are coplotted with tidal height. DMS oxidation is not believed to play a major role in CN formation at this site because (1) the mass balance calculations imply ambient DMS concentrations higher than those observed, and (2) gas phase HCI, HNO3. SO2, and NH3 did not exhibit any discernible correlation with tidal height. Further, none of the suite of observed nonmethane hydrocarbons or DMS showed a tidal relation. No mechanism has to date been convincingly identified for the burst phenomenon.

 

Atmospheric CO2 concentration variations recorded at Mace Head, Ireland, from 1992 to 1994 Atmospheric CO2 concentration variations recorded at Mace Head, Ireland, from 1992 to 1994

Date added: 07/31/1997
Date modified: 07/27/2009
Filesize: 491.17 kB

Bousquet, P., Gaudry. A., Ciais, P., Kazan, V., Monfray, P., Simmonds, P.G., Jennings, S.G., and O'Connor, T.C. (1997). Atmospheric CO2 concentration variations recorded at Mace Head, Ireland from 1992 to 1994. Phys. Chem. Earth, 21, 447-481.


Abstract


Atmospheric CO 2 has been monitored continuously at the Irish station of Mace-Head (MHD) since July 1992. The mean rate of increase is 1.85 ppmv yr -t with a peak-to-peak amplitude of 15.1+1.1 ppmv. The record also shows important short-term variations from the smoothed curve due to both European and oceanic influences and amplified by day/night local effects. Two different baseline conditions are defined in order to remove local perturbations. Restricted Baseline Conditions (RBC) keep data only representing atmospheric background conditions from the West. Extended Baseline Conditions (EBC) add stable air masses coming from all angular sectors to RBC selection. The contrast between western and eastern air masses coming respectively from North-Atlantic ocean and Europe is studied. For air masses arriving from the West, a systematic depletion in 1992-93 is found relative to all surrounding stations within the North- Atlantic basin. The partition of this depletion between European biospheric uptake and the North-Atlantic ocean cannot be performed as long as other tracers are not sampled regularly, or during intensive campaigns at Mace Head (13C/12C, Radon-222 and O2/N2). In contrast, Eastern air masses present strong positive anomalies in CO2 that reflect European sources.

Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site

Date added: 08/07/1999
Date modified: 07/27/2009
Filesize: 210.82 kB

A.C. Lewis J.B. McQuaid, N. Carslaw, M.J. Pilling.,; Short Communication Diurnal cycles of short-lived tropospheric alkenes at a north Atlantic coastal site,. Atmospheric Environment 33 (1999) 2417Ð2422 2419


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.

 

Increased rates of rainfall production in Electrified clouds Increased rates of rainfall production in Electrified clouds

Date added: 07/30/1973
Date modified: 07/22/2009
Filesize: 822.23 kB

Brazier-Smith, P.R., Jennings, S.G., and Latham, J. (1973)- Increasing rates of rainfall production in electrified clouds. Quart. J. Roy. Met. Soc., 99, 776-779


Abstract

A dedicated study of new particle formation and fate in the coastal environment (PARFORCE) Overview of objectives and initial achievements A dedicated study of new particle formation and fate in the coastal environment (PARFORCE) Overview of objectives and initial achievements

Date added: 07/31/2002
Date modified: 07/27/2009
Filesize: 448.25 kB
C. D. O'Dowd, K. Hämeri, J.M. Mäkelä, M. Kulmala, L. Pirjola, H. Berresheim, S.G. Jennings, H-C Hansson, G. de Leeuw, A.G. Allen, C.N. Hewitt, A. Stroh, and Y. Viisanen. A dedicated study of new particle formation and fate in the coastal environment (PARFORCE): Overview of objectives and initial achievements. J. Geophys. Res. 107, 10.1029/2001000555, 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 order of 105–106 cm−3 s−1 and occurred for sulphuric acid concentrations above 2 × 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.

Seasonal variation of the aerosol light scattering coefficient in marine air of the North-East Atlan Seasonal variation of the aerosol light scattering coefficient in marine air of the North-East Atlan

Date added: 11/17/2011
Date modified: 11/17/2011
Filesize: 677.22 kB

Vaishya, A., S.G. Jennings and C.D. O'Dowd, Seasonal variation of the aerosol light scattering coefficient in marine air of the North-East Atlantic, Adv. Met., Volume 2011, Article ID 170490, doi:10.1155/2011/170490, 2011.

 

  


Aerosol light scattering measurements were carried out using a TSI 3563 Nephelometer at the Mace Head Atmospheric Research Station, on the west coast of Ireland from year 2001–2010. A strong seasonal trend in the aerosol light scattering coefficient at 550nm (σscat), for clean marine air masses, is observed with a high σscat value, [average (geometric mean)] of 35.3Mm1 (29.5Mm1), in January and a low σscat value of 13.7Mm1 (10.2Mm1), in July. This near threefold increase in the σscat value during the winter season is because of the large contribution of wind-speed generated sea-salt particles in the marine boundary layer. A high positive correlation coefficient of 0.82 was found between the percentage occurrence of relatively large A° ngstro¨m exponent (A° ) values (>1.2) and the percentage occurrence of lower σscat values (5–15Mm1) in the summer season. σscat and wind-speed have a high positive correlation coefficient of 0.88 whereas °Aand wind-speed have a negative correlation coefficient of 0.89. °A values during the summer months indicate the dominance of sub-μm particles thus indicating the contribution of non-sea-salt sulphate and organics towards the σscat as these species show an enhanced concentration during the summer months

 

Marine biogenic and anthropogenic contributions to non-sea-salt sulfate in the marine boundary Marine biogenic and anthropogenic contributions to non-sea-salt sulfate in the marine boundary

Date added: 08/06/2002
Date modified: 07/24/2009
Filesize: 376.92 kB

Savoie, D. L., R. Arimoto, W. C. Keene, J. M. Prospero, R. A. Duce, and J. N. Galloway (2002), Marine biogenic and anthropogenic contributions to non-sea-salt sulfate in the marine boundary layer over the North Atlantic Ocean, J. Geophys. Res., 107(D18), 4356, doi:10.1029/2001JD000970.


Abstract


As a part of the Atmosphere/Ocean Chemistry Experiment (AEROCE), daily aerosol samples were collected in the marine boundary layer at Barbados, West Indies (13.17°N, 59.43°W), Bermuda (32.27°N, 64.87°W), and Mace Head, Ireland (53.32°N, 9.85°W), and in the free troposphere at Izaña, Tenerife, Canary Islands (28.30°N, 16.48°W; 2360 m asl). In this report, we use multiple variable regression analyses with methanesulfonate (MSA) and Sb and/or NO3 as the independent variables to assess the relative contributions of the marine biogenic and anthropogenic sources to the total non-sea-salt (nss) SO42− concentrations at the AEROCE sites. On the basis of 2 years of data at Bermuda and Barbados, the marine nss SO42−/MSA mass ratios (19.6 ± 2.1 and 18.8 ± 2.2) were consistent throughout the year and comparable to those at American Samoa in the tropical South Pacific (18.1 ± 0.9). At Mace Head (based on 1 year of data), this ratio was about 3.01 (±0.53). An analysis of the residuals and an assessment of the root mean square deviations indicate that the ratio at Mace Head can also be reasonably applied throughout the year. However, there is enough uncertainty during the winter that we cannot rule out a significant increase (to about 20) during periods with low concentrations of both MSA and NO3. The results from 4 years indicate that the marine contribution is too low to permit a reasonable assessment of the biogenic nss SO42−/MSA ratio at Izaña. The continental nss SO42−/Sb mass ratio varies significantly from one location to another. At Bermuda, where North American sources are expected to dominate, the ratio is about 29,000, about a factor of 2 higher than the average of 13,500 at Mace Head where European sources dominate. Intermediate values occurred at Barbados (18,000) and Izaña (24,000) where both European and North African sources are significant. Estimates based on these ratios indicate that, on an annual basis, the contributions from anthropogenic sources account for about 50% of the total nss SO42− in aerosols at Barbados, 70% at Bermuda, 85–90% at Mace Head, and about 90% at Izaña. If the same biogenic nss SO42−/MSA ratios are applicable to rainwater, then the relative contributions in precipitation at Barbados and Bermuda are comparable to those in aerosols.

 

Atmospheric measurements of OH, HO2 and NO by laser-induced fluorescence spectroscopy Atmospheric measurements of OH, HO2 and NO by laser-induced fluorescence spectroscopy

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 16.18 kB

Bloss, W. J.; Floquet, C.; Gravestock, T. J.; Heard, D. E.; Ingham, T.; Johnson, G. P.; Lee, J. D.,Atmospheric measurements of OH, HO2 and NO by laser-induced fluorescence spectroscopy using a compact all solid-state laser system,EGS - AGU - EUG Joint Assembly, Abstracts from the meeting held in Nice, France, 6 - 11 April 2003, abstract #10521


Abstract


Free-radicals are key intermediates that control the budgets of many trace gases, for example ozone, greenhouse gases and harmful pollutants. Measurement of radicals and comparison with model calculations constitutes an important test of our understanding of the underlying chemistry. There is a greater need for compact and lightweight instruments for the in situ measurement of free-radical species that are suitable for deployment from a number of field-platforms. A new field instrument has been developed that incorporates an all solid-state Nd:YAG pumped titanium sapphire laser that is capable of generating radiation at high pulse-repetition-frequency for the detection of OH, HO_2, NO and IO radicals in the atmosphere by laser induced fluorescence (LIF). The system offers advantages of wide wavelength tunability, compactness, low weight, greater long-term stability (fibre-optic delivery) and short warm-up time. The instrument was successfully deployed during 2002 in the NAMBLEX field campaign at Mace Head with detection limits for OH and HO_2 (measured simultaneously with laser operation at 308 nm) of 3.1 x 10^5 molecule cm-3 (0.012 ppt) and 2.6 x 10^6 molecule cm-3 (0.09 pptv) respectively. Diurnal profiles of OH have been recorded over a period of 5 weeks. NO controls the HO_2/OH ratio and is the critical parameter in the production of tropospheric ozone, yet measurements in the boundary layer are restricted to a single indirect technique based on chemiluminescent analysers. Measurements of NO in the atmosphere have been made by LIF using the new instrument operating at 226 nm, with absolute concentrations in good agreement with simultaneous measurements made using a commercial chemiluminescent analyser. Whilst operating at 445 nm, the instrument has detected the IO radical in the laboratory, with a projected detection limit that is well below previously measured atmospheric concentrations of IO. A second instrument to be deployed on an aircraft platform is currently being developed.

Ionization Equibrium of maritime Air Ionization Equibrium of maritime Air

Date added: 08/07/1960
Date modified: 07/24/2009
Filesize: 5.83 MB
O'Connor, T.C, Sharkey, W.P, Ionization Equilibrium In Maritime Air, Procedding of the Royal irish Academy, Volume 61, Section A, No. 3
Abstract

Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction Effects of particulate complex refractive index and particle size distribution variations on atmospheric extinction

Date added: 08/01/1978
Date modified: 07/01/2009
Filesize: 851.05 kB
Jennings, S.G., and Pinnick, R.G.  (1978)- Effects of particulate refractive index and particle size distribution variations on atmospheric extinction and absorption for visible to middle-IR wavelengths. American Meteorological Society Third Conference on Atmospheric Radiation, Davis, California, 6-9.

Abstract


A comprehensive sensitivity study has been made, using Mie theory, to determine the effect of realistic variations in values of real and imaginary parts of the complex index of refraction on volume extinction and absorption coefficients for a wide range of lognormal particle size distributions (defined by geometric mean radius r sub g and geometric standard deviation sigma sub g). Wavelengths lambda from visible (0.55 micrometers) through middle-infrared (10.6 micrometers) were considered. Extinction is independent of complex index to within 20 percent for the majority of realistic particle size distributions, providing lambda < or = 2 micrometers. However, changes in extinction by up to an order of magnitude are caused by realistic variations in refractive indexes for 2 < or = lambda < or = 10.6 micrometers, with real index being more important in affecting extinction than imaginary index.

A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to l A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to l

Date added: 08/07/2005
Date modified: 06/30/2009
Filesize: 181.92 kB

P.G. Simmonds,A. J.Manning,R.G. Derwent, P. Ciais,M.Ramonet, V. Kazan and D. Ryall, A burning question. Can recent growth rate anomalies in the greenhouse gases be attributed to large-scale biomass burning events?, Atmos. Environ., 2005, 39, 2513–2517.


Abstract


Simultaneous in situ measurements of carbon dioxide (CO2) and the principal gases linked to biomass burning at the Mace Head Observatory, Ireland, reveal a strong correlation in 1998-99 and 2002-03, both periods with intense global fires. CO2, carbon monoxide (CO), methane (CH4), hydrogen (H2), ozone (O3) and methyl chloride (CH3Cl), all have similar rates of accumulation during these time frames. These perturbations imply a causal relationship between large-scale biomass burning events and the interannual variability of these gases.

 

Growth Rates During Coastal and Marine New Particle Formation in Western Ireland Growth Rates During Coastal and Marine New Particle Formation in Western Ireland

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 1.75 MB

Ehn, M., H. Vuollekoski, T. Petäjä, V.-M. Kerminen, M. Vana, P. Aalto, G. de Leeuw, D. Ceburnis, R. Dupuy, C. D. O’Dowd and M. Kulmala, Growth Rates During Coastal and Marine New Particle Formation in Western Ireland, J. Geophys. Res., doi:10.1029/2010JD014292, 2010.


Growth rates of new particles during coastal and marine secondary aerosol particle

formation events were studied in western Ireland, both at the Mace Head atmospheric

research station and onboard the R/V 

Production project. Strong new particle formation events are frequently detected at Mace

Head caused by the emission of precursor gases from exposed seaweed during low tide.

Although these events were usually only detected as a mode of particles at a certain size, we

were able to link the size of the mode to the growth time of these particles after the initial

formation by combining data from several events measured between January 2006 and

November 2007 with an air ion spectrometer. Typically, the early growth rates were

extremely high, reaching values of several hundred nanometers per hour during the first

seconds. The growth rates rapidly decreased and reached values below 1 nm h 

1 h after nucleation. Our results were reproduced with box model calculations. All the

obtained growth rates could be explained by the model either by varying the precursor

formation time (typically a few seconds) or allowing multiple precursor vapor additions.

From the ship

ocean new particle formation detected in this region. In total, four events were detected

during this period, with three having a variable continental influence. An estimated

average growth rate in marine conditions was 3 nm h

Celtic Explorer as part of the Marine Aerosol 1 within borne measurements, we report the first observations of purely open 1 for these events.

Condensation Nuclei as indicators of air pollution Condensation Nuclei as indicators of air pollution

Date added: 07/31/1984
Date modified: 07/27/2009
Filesize: 2.52 MB

O'Connor, T.C. & O'Dea, J.J.(RTC Sligo) (1984)- Indicators of Air Pollution, Irish Journal of Environmental Science, III, pp. 32-39


Abstract


Condensation Nuclei (CN) are Submicron sized particles found in the atmosphere at concentrations of 10^2 to 10^6 particles per cm^3. They arise from a variety of sources but are mainly produced by combustion processes. Sensitive and reliable CN counters have been developed in Ireland to determine their concentration and size. Results from a variety of locations are presented to illustratetheir use as a general indicator of air pollution levels. The Use of CN measurement as a tool for air quality management is discussed.

Isentropic airflow probability analysis Isentropic airflow probability analysis

Date added: 08/06/1994
Date modified: 07/24/2009
Filesize: 1.32 MB

Merrill, J. T. (1994), Isentropic airflow probability analysis, J. Geophys. Res., 99(D12), 25,881–25,889.


Abstract

 

Trajectory analysis has been used to identify possible sources in both short-and long-range atmospheric transport. Here the focus is on the climatological pathway of airflow to the Atmosphere/Ocean Chemistry Experiment sites, determined by superposition of ensembles of isentropic trajectories. The trajectories are prepared from wind fields on surfaces of constant potential temperature interpolated from the National Meteorological Center global analysis, calculated twice daily for each site for the period from 1986 to 1993. At Bermuda there is a notable seasonal variation, with the months of May–November dominated by flow around the subtropical anticyclone, while flow from the northwest and west is more common in the cooler months of December–April. Flow from the west predominates at Mace Head, Ireland, in the months from April–September, while flow from the east (over Great Britain and western Europe) is of increased importance during October–March. At Izaña the flow is most commonly from the west; flow from the east, over Africa and southern Europe, is most common during the months of July–September. The winds at Barbados, West Indies, are much steadier than at the other sites, and there is little seasonal variation in the general pattern of flow. The circulation during precipitation events, evaluated as the airflow weighted by rainfall amount, showed a striking difference from the general pattern of airflow at Mace Head, especially during October–March: in the absence of rain the winds are much more common from the east, over polluted continental areas, than during rain events, when the dominance of flow from the west is greater.

 

Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean

Date added: 08/06/2000
Date modified: 07/27/2009
Filesize: 1.44 MB

Baker, A. R., S. M. Turner, W. J. Broadgate, A. Thompson, G. B. McFiggans, O. Vesperini, P. D. Nightingale, P. S. Liss, and T. D. Jickells (2000), Distribution and Sea-Air Fluxes of Biogenic Trace Gases in the Eastern Atlantic Ocean, Global Biogeochem. Cycles, 14(3), 871–886.


Abstract


A number of atmospherically important trace gases (dimethyl sulphide (DMS), methyl iodide (CH3I), and nonmethane hydrocarbons (NMHCs)) were measured simultaneously in the eastern Atlantic Ocean during May 1997. This investigation was part of the U.K. Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) Community Research Program and covered a 200 by 200 nautical mile (1 nautical mile is 1.852 km) area to the west of the Mace Head Atmospheric Research Station on the coast of Ireland. Different spatial and temporal patterns were observed for each of the gases, showing that distinct sources dominate their production in this region: specific species of phytoplankton (DMS), macroalgae (CH3I), total phytoplankton biomass (isoprene), and photochemistry (ethene). Sea-to-air fluxes of the gases are calculated for near and offshore domains, and their temporal variations are discussed. A simple photochemical box model has been used to assess the contributions of the gas fluxes to the levels of the gases observed at Mace Head. Results show that the area studied may constitute a substantial source of DMS, a weak source of CH3I, a small source of ethene at night, and an insignificant source of isoprene to atmospheric levels of these gases measured at Mace Head in western Ireland.

 

Atmospheric histories of halocarbons from analysis of Antarctic firn air Major Montreal Protocol species Atmospheric histories of halocarbons from analysis of Antarctic firn air Major Montreal Protocol species

Date added: 08/01/2002
Date modified: 06/30/2009
Filesize: 832.27 kB
Sturrock, G. A., D. M. Etheridge, C. M. Trudinger, P. J. Fraser, and A. M. Smith (2002), Atmospheric histories of halocarbons from analysis of Antarctic firn air: Major Montreal Protocol species, J. Geophys. Res., 107(D24), 4765, doi:10.1029/2002JD002548.
Abstract

 

Air samples extracted from Antarctic firn at Law Dome have been analyzed for the suite of halocarbons that contribute most of the anthropogenic chlorine and about half the anthropogenic bromine presently released into the stratosphere. The species, all included in the Montreal Protocol, are the chlorofluorocarbons (CFCs -11, -12, -113, -114, -115), hydrochlorofluorocarbons (HCFCs -22, -141b, -142b), halons (H -1211, -1301), CH3CCl3 (methyl chloroform) and CCl4 (carbon tetrachloride). The measurements were used to reconstruct the atmospheric history of these species since the 1930s, providing a record considerably predating existing in situ records or other conventional air archives, encompassing virtually the entire history of anthropogenic emissions of CFCs, HCFCs, and halons and giving early 20th century levels for CH3CCl3 and CCl4. Significant features of this study are (1) the narrow age spread (spectral width 5 years) of the individual firn air samples, which reveals rapid atmospheric changes, (2) the use of inversion techniques to infer past atmospheric composition with associated uncertainties, and (3) the low analytical detection limit (<0.1 ppt), which, together with the narrow air age spread, detects early background levels and resolves the time that industrial emissions first appeared in the southern hemisphere atmosphere. Integrity of the data is demonstrated by successful intercomparison of data from independent firn sites on Law Dome with common time-series. An upper limit is given for the potential contribution to atmospheric levels of CH3CCl3 from nonindustrial sources. The atmospheric records produced from firn air are compared to calculations based on the history of their global emissions.

Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö fie Concentrations and fluxes of aerosol particles during the LAPBIAT measurement campaign at Värriö fie

Date added: 08/01/2007
Date modified: 07/10/2009
Filesize: 2.65 MB

Ruuskanen, T.M., M. Kaasik, P. P. Aalto, U. Hõrrak, M. Vana, M. Mårtensson, Y. J. Yoon, P. Keronen, D. Nilsson, C. O’Dowd, M. Noppel, T. Alliksaar, J. Ivask, M. Sofiev, M. Prank, M. Kulmala, Concentrations and fluxes of aerosols particles during the LAPBIAT measurement campaign in the Varrio field station. Atmos. Chem. And Phys., 7, 3683–3700, 2007.


Abstract

 

The LAPBIAT measurement campaign took place in the V¨arri¨o SMEAR I measurement station located in Eastern
Lapland in the spring of 2003 between 26 April and 11 May. In this paper we describe the measurement campaign,
concentrations and fluxes of aerosol particles, air ions and trace gases, paying special attention to an aerosol particle
formation event broken by a air mass change from a clean Arctic air mass with new particle formation to polluted one
approaching from industrial areas of Kola Peninsula, Russia, lacking new particle formation. Aerosol particle number
flux measurements show strong downward fluxes during that time. Concentrations of coarse aerosol particles were  high for 1–2 days before the nucleation event (i.e. 28–29 April), very low immediately before and during the observed aerosol particle formation event (30 April) and increased moderately from the moment of sudden break of the event. In general particle deposition measurements based on snow samples show the same changes. Measurements of the mobility distribution of air ions showed elevated concentrations of intermediate air ions during the particle formation event. We estimated the growth rates in the nucleation mode size range. For particles <10 nm, the growth rate increases with size on 30 April. Dispersion modelling made with model SILAM support the conclusion that the nucleation event was interrupted by an outbreak of sulphate-rich air mass in the evening of 30 April that originated from the industry at Kola Peninsula.

Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new

Date added: 11/10/2010
Date modified: 11/10/2010
Filesize: 672.69 kB

Rinaldi,M., S.Decesari, E. Finessi, L.Giulianelli, C.Carbone, S.Fuzzi, C.D. O'Dowd, D.Ceburnis and M.C. Facchini, Primary and secondary organic marine aerosol and oceanic biological activity: recent results and new perspectives for future studies, Adv. in Meteorol., Volume 2010, Article ID 310682, doi:10.1155/2010/243701, 2010.

 


 

One of the most important natural aerosol systems at the global level is marine aerosol that comprises both organic and inorganic components of primary and secondary origin. The present paper reviews some new results on primary and secondary organic marine aerosol, achieved during the EU project MAP (Marine Aerosol Production), comparing them with those reported in the recent literature.Marine aerosol samples collected at the coastal site ofMaceHead, Ireland, show a chemical composition trend that is influenced by the oceanic biological activity cycle, in agreement with other observations. Laboratory experiments show that seaspray  aerosol from biologically active sea water can be highly enriched in organics, and the authors highlight the need for further studies on the atmospheric fate of such primary organics. With regard to the secondary fraction of organic aerosol, the average  chemical composition and molecular tracer (methanesulfonic-acid, amines) distribution could be successfully characterized by adopting a multitechnique analytical approach.

Modelling Iodine Particle Formation and Growth from Seaweed in a Chamber Modelling Iodine Particle Formation and Growth from Seaweed in a Chamber

Date added: 08/01/2005
Date modified: 07/23/2009
Filesize: 520.58 kB

Pirjola, L., C. O’Dowd, Y. J. Yoon, K. Sellegri, Modelling Iodine Particle Formation and Growth from Seaweed in a Chamber. Environ. Chem. 2, 271. doi:10.1071/EN05075, 2005.


Abstract


A sectional atmospheric chemistry and aerosol dynamics box model (AEROFOR) was further developed and used to simulate ultra-fine particle formation and growth from seaweed in a chamber flushed with particle-free atmospheric air. In the model, thermodynamically stable clusters were formed by dimer nucleation of OIO vapour, whose precursor was assumed to be molecular I2 emitted by seaweed. Fractal geometry of particles was taken into account. For the I2 fluxes of (0.5–1.5) × 109 cm-3 s-1 the model predicted strong particle bursts, the steady state concentrations of I2 vapour and particles larger than 3 nm were as high as 4 × 109–1.2 × 1010 cm-3 and 5.0 × 106–9.2 × 106 cm-3 respectively. The steady state was reached in less than 150 s and the predicted growth rates of 3–6 nm particles varied in the range of 1.2–3.6 nm min-1. Sensitivity of the size distribution against I2O3 cluster formation, an extra condensable vapour, the photolysis rate of the OIO vapour as well as against the density of (OIO)n-clusters was discussed. The modelled results were in good agreement with the chamber measurements performed during the BIOFLUX campaign in September, 2003, in Mace Head, Ireland, confirming that I2 emissions and nucleation of iodine oxides can largely explain the coastal nucleation phenomenon.

Advance, 12 the growth of snowflakes and hail Advance, 12 the growth of snowflakes and hail

Date added: 06/01/1972
Date modified: 08/01/2008
Filesize: 330.33 kB

Organic aerosol formation via sulphate cluster activation Organic aerosol formation via sulphate cluster activation

Date added: 08/06/2004
Date modified: 07/03/2009
Filesize: 667.33 kB

Kulmala, M., V.-M. Kerminen, T. Anttila, A. Laaksonen, and C. D. O'Dowd (2004), Organic aerosol formation via sulphate cluster activation, J. Geophys. Res., 109, D04205, doi:10.1029/2003JD003961.


Abstract


The formation of aerosols, and subsequent cloud condensation nuclei, remains one of the least understood atmospheric processes upon which global climate change critically depends. Under atmospheric conditions, the process of homogeneous nucleation (formation of stable clusters ∼ 1 nm in size), and their subsequent growth into new particles (>3 nm), determines the aerosol and cloud nuclei population, yet, hitherto, no theory has elucidated the new particle formation phenomenon in detail. In this study, we present a new theory which provides a mechanistic explanation for new particle formation via activation of stable inorganic clusters by organic vapors. The new nano-particle activation theory is analogous to Köhler theory which describes cloud formation in a supersaturated water vapor field but differs in that it describes the activation of inorganic stable nano-clusters into aerosol particles in a supersaturated organic vapor which initiates spontaneous and rapid growth of clusters. Inclusion of the new theory into aerosol formation models predicts that increases in organic vapor densities lead to even greater increases in particle production, which, in turn, will influence the global radiative cooling effect of atmospheric aerosols.

 

Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the ma Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the ma

Date added: 08/06/2001
Date modified: 07/23/2009
Filesize: 1.44 MB

Salisbury, G., et al. (2001), Production of peroxy radicals at night via reactions of ozone and the nitrate radical in the marine boundary layer, J. Geophys. Res., 106(D12), 12,669–12,687.


Abstract


In this paper, a substantial set of simultaneous measurements of the sum of peroxy radicals, [HO2+RO2], NO3, hydrocarbons (HCs), and ozone, taken at Mace Head on the Atlantic coast of Ireland in spring 1997, is presented. Conditions encountered during the experiment ranged from semipolluted air masses advected from Britain and continental Europe to clean air masses off the North and mid-Atlantic, where mixing ratios of pollution tracers approached Northern Hemispheric background mixing ratios. Average mixing ratios of peroxy radicals varied from 2.5 to 5.5 parts per trillion by volume (pptv) at night depending on wind sector, and were observed to decay only very slowly from late afternoon to early morning (0.1–0.5 pptv h−1). Measurements of OH and HO2 on two nights using the Fluorescence Assay by Gas Expansion (FAGE) technique give an upper limit for [OH] of 2.5×105 molecules cm−3 and an average upper limit [HO2]/[HO2+RO2] ratio of 0.27. A modeling study of the 1/e lifetimes of the peroxy radicals, assuming no radical production at night, yielded mean lifetimes of between ∼ 8–23 min for HO2 and 3–18 min for CH3O2. Given these lifetimes, it may be concluded that the peroxy-radical mixing ratios observed could not be maintained without substantial production at night. No significant correlation is observed between measured [HO2+RO2] and [NO3] under any conditions. Calculation of the reaction rates for ozone and NO3 with hydrocarbons (HCs) shows that the ozone-initiated oxidation routes of HCs outweighed those of NO3 in the NE, SE and NW wind sectors. In the SW sector, however, the two mechanisms operated at similar rates on average, and oxidation by NO3 was the dominant route in the westerly sector. The oxidation of alkenes at night by ozone was greater by a factor of 4 than that by NO3 over the whole data set. The HC degradation rates from the three “westerly” sectors, where tracer mixing ratios were relatively low, may be representative of the nighttime oxidative capacity of the marine boundary layer throughout the background Northern Hemisphere. Further calculations using literature values for OH yields and inferred RO2 yields from the ozone-alkene reactions show that peroxy radicals derived from the ozone reactions were likely to make up the major part of the peroxy-radical signal at night (mean value 66%). However, the NO3 source was of similar magnitude in the middle of the night, when [NO3] was generally at its maximum. The estimated total rates of formation of peroxy radicals are much higher under semipolluted conditions (mean 8.0×104 molecules cm−3 s−1 in the SE wind sector) than under cleaner conditions (mean 2.4×104 molecules cm−3 s−1 in the westerly wind sector). A model study using a campaign-tailored box model (CTBM) for semipolluted conditions shows that the major primary sources of OH, HO2, and CH3O2 (the most abundant organic peroxy radical) were the Criegee biradical intermediates formed in the reactions of ozone with alkenes.

 

Extinction and liquid water content of fog at visible wavelengths Extinction and liquid water content of fog at visible wavelengths

Date added: 07/31/1983
Date modified: 07/01/2009
Filesize: 2.27 MB

Jennings, S.G. (1983)- Extinction and liquid water content of fog at visible wavelengths. Appl. Opt., 22, 2514-2515.


Abstract


Aerosol generation by waves breaking on small islands and rocks near the mace head research sta Aerosol generation by waves breaking on small islands and rocks near the mace head research sta

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 150.69 kB

Kunz, GJ, CD O'Dowd, G de Leeuw, Aerosol generation by waves breaking on small islands and rocks near the Mace Head research station. European Aerosol Conference, 2000, J. Aerosol. Sci., Suppl 1., 656-657, 2000. [36] Kleefeld, C., S O'Rielly, SG Jennings, E Becker, C O'Dowd, G Kunz and G de Leeuw, Aerosol scattering: relation to primary and secondary aerosol production in the coastal atmosphere during the PARFORCE campaign, European Aerosol Conference, 2000, J. Aerosol. Sci., Suppl 1., 658-659, 2000.


Abstract


Two coastal field experiments (September 1998 and in June 1999) were conducted at Mace Head, Ireland, under the EU-funded PARFORCE (New P__._~icle Formation and Fate in the Coastal Environment) programme which was designed to elucidate the processes which control and promote homogeneous heteromolecular nucleation in the coastal boundary layer. During conditions of westerly winds and after sufficiently long fetch, the Mace Head station is regularly exposed to pure maritime and clean arctic atmospheres. Under these conditions the generation and growth of new particles due to photochemical conversion of biological emissions is seen to occur on almost a daily basis (e.g., O'Dowd et al., 1998 and O'Dowd et al., 1999). During the PARFORCE experiments the TNO Physics and Electronics Laboratory (TNO-FEL) undertook to measure boundary layer dynamics, as determined from the aerosol structures measured with a lidar (light detection and ranging) system. The results revealed the generation of large amounts of sea spray Aerosol by waves breaking on the islands and roCks near the Mace Head station. The location, size and dynamics of these locally generated aerosol plumes were determined from series of consecutive horizontal and vertical scans. The horizontal extent of these aerosol plumes is highly coherent over distances of several kilometres and the vertical extent is generally between a few tens of meters to a few hundreds of meters. In some occasions the aerosol was observed to be taken aloft to the top of the mixed layer at an altitude of about one kilometre.

Observation and interpretation of the seasonal cycles in the surface concentrations of ozone an Observation and interpretation of the seasonal cycles in the surface concentrations of ozone an

Date added: 08/07/1998
Date modified: 07/23/2009
Filesize: 1.37 MB

Derwent, RG, Simmonds, PG, Seuring, S, et al , Observation and interpretation of the seasonal cycles in the surface concentrations of ozone and carbon monoxide at Mace Head, Ireland from 1990 to 1994, ATMOS ENVIRON, 1998, Vol: 32, Pages: 145 - 157, ISSN: 1352-2310


Abstract


In this study, three independent methods have been applied to the sorting of the daily and hourly mean concentrations of ozone and carbon monoxide measured at Mace Head, Ireland. From the entire 1990-1994 dataset, 61% of the hourly data points have been assigned to Northern Hemisphere mid-latitude background air. The mean ozone and carbon monoxide concentrations in these air masses have been estimated as 35±4.3 and 125±27 ppb, respectively. We have characterised the seasonal variations of ozone and carbon monoxide in these air masses and found them to exhibit spring-time maxima and summer-time minima in monthly mean concentrations. Similar seasonal cycles have been found in the monthly mean concentrations of a number of trace gases in Northern Hemisphere mid-latitude background air at Mace Head, in addition to ozone and carbon monoxide. The occurrence of spring-time maxima is not unique to ozone and spring-time maxima are observed for many trace gases whether or not they have stratospheric sources.

 

Importance of organic and black carbon in atmospheric aerosols at Mace Head, on the West Coast of Ireland (53°19′N, 9°54′W) Importance of organic and black carbon in atmospheric aerosols at Mace Head, on the West Coast of Ireland (53°19′N, 9°54′W)

Date added: 07/31/2002
Date modified: 07/24/2009
Filesize: 146.78 kB

Kleefeld, S., Hoffer, A., Krivacsy, and Jennings, S.G., 2002. Importance of organic and black carbon at Mace Head, on the west coast of Ireland (53 019’N, 9 054’W), Atmos. Environ., 36, pp. 4479-4490.


Abstract


The mass concentrations of total organic carbon (TC) and its chemical fractions, water-soluble organic carbon (WSOC), water-insoluble organic carbon (WISOC), and black carbon (BC), were determined in marine aerosols, which were collected during the period July 1998-September 1999 at the Mace Head Atmospheric Research Station on the west coast of Ireland. In addition, mass concentrations of major inorganic ions, like non-sea-salt (NSS) sulphate, and mass concentrations of dicarboxylic acids have been measured separately within the water-soluble aerosol fraction. The aerosol samples were classified into clean marine aerosol samples and modified marine aerosol samples according to the origin of air masses arriving at Mace Head, and using BC as a tracer for anthropogenic pollution. Following this classification, the data set was further divided into samples taken during summertime and wintertime. An average TC mass concentration of 591±75 ng/m3 was determined for all aerosol samples taken at Mace Head. WSOC was found to be the dominating fraction in modified marine aerosol samples, followed by WISOC and BC, whereas in clean marine aerosol samples WISOC was the main fraction, followed by WSOC, and BC. A comparison of the mass concentration of the water-soluble organic matter to the main water-soluble inorganic component, NSS sulphate, gave an average ratio of 0.72±0.10, which increased to 1.59±0.23 when considering solely clean marine aerosol samples. The dominating dicarboxylic acid found in carbonaceous aerosols at Mace Head was oxalic acid, followed by malonic acid. Both diacids were responsible for about 14±2% of the WSOC (in terms of carbon).

Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO

Date added: 08/06/2003
Date modified: 07/27/2009
Filesize: 184.19 kB
W. J. Bloss, T. J. Gravestock, D. E. Heard, T. Ingham,G. P. Johnson and J. D. Lee, "Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO2, NO and IO by laser-induced fluorescence", Journal of Environmental Monitoring., 5, 21-28 (2003).

Abstract

 

A tuneable, high pulse-repetition-frequency, solid state Nd:YAG pumped titanium sapphire laser capable of generating radiation for the detection of OH, HO2, NO and IO radicals in the atmosphere by laser induced fluorescence (LIF) has been developed. The integration of the laser system operating at 308 nm into a field measurement apparatus for the simultaneous detection of hydroxyl and hydroperoxy radicals is described, with detection limits of 3.1 6 105 molecule cm23 (0.012 pptv in the boundary layer) and 2.6 6 106 molecule cm23 (0.09 pptv) achieved for OH and HO2 respectively (30 s signal integration, 30 s background integration, signalto- noise ratio ~ 1). The system has been field tested and offers several advantages over copper vapour laser pumped dye laser systems for the detection of atmospheric OH and HO2 radicals by LIF, with benefits of greater tuning range and ease of use coupled with reduced power consumption, instrument footprint and warm-up time. NO has been detected in the atmosphere at y 1 ppbv by single photon LIF using the A 2S1 B X 2P1/2 (0,0) transition at 226 nm, with absolute concentrations in good agreement with simultaneous measurements made using a chemiluminescence analyser. With some improvements in performance, particularly with regard to laser power, the theoretical detection limit for NO is projected to be y 2 6 106 molecule cm23 (0.08 pptv). Whilst operating at 445 nm, the laser system has been used to readily detect the IO radical in the laboratory, and although it is difficult to project the sensitivity in the field, an estimate of the detection limit is v 1 6 105 molecule cm23 (v 0.004 pptv), well below previously measured atmospheric concentrations of IO.

PRODUCTION OF METHANOL, ACETONE AND. ACETALDEHYDE DURING LONG-RANGE. TRANSPORT PRODUCTION OF METHANOL, ACETONE AND. ACETALDEHYDE DURING LONG-RANGE. TRANSPORT

Date added: 08/07/2003
Date modified: 08/07/2008
Filesize: 32.63 kB
Stanton, J.C.; Pilling, M.J.; Hopkins, J.R.; Lewis, A.C.Production of methanol, acetone and acetaldehyde during long-range transport [EGU04-A-07457].

Mace Head Atmospheric Research Station-characterization of aerosol radiative parameters Mace Head Atmospheric Research Station-characterization of aerosol radiative parameters

Date added: 08/01/2003
Date modified: 07/24/2009
Filesize: 1.51 MB

Mace Head Atmospheric Research Station – characterization of aerosol radiative parameters S. Gerard Jennings, C. Kleefeld, C. D. O'Dowd, C. Junker, T.G. Spain, P. O'Brien, A.F Roddy, and T.C. O'Connor Boreal Environ. Res., 8, 303-314, 2003.


Abstract


A fairly concise description and a short history of the Mace Head atmospheric research station, at 53°N, 10°W, on the west coast of Ireland is reported. The relatively high latitude site is representative of background marine air in the Northern Atlantic on the western periphery of Europe. The site is ideally located to measure the prevailing (about 52% of the time) westerly-southwesterly air from the Atlantic, as well as polluted air under anticyclonic conditions from sources east of the site within Ireland, from the UK and from mainland Europe. Three years of aerosol radiative data, over a period from January 2000 to December 2002, are indicative of the medium to longterm measurement programme at the site. These include aerosol scattering coefficient, aerosol absorption coefficient, aerosol optical depth and single scattering albedo, supported by meteorological and air mass trajectory input. Variability in aerosol parameters are shown to be dependent on air mass origin, season and meteorological conditions. Measurements indicate that the dominant contribution to aerosol optical depth is due to scattering, with single scattering albedo in the range 0.941 to 0.997. Measured aerosol optical depth for marine air over the 3 year period varies between 0.03 and 0.38 with a mean value of 0.11 and standard deviation of ±0.06. These values are in fair agreement with other data for the North Atlantic region.

Analysis of PM2.5 particulate mass concentrations during 1999 at Mace Head Analysis of PM2.5 particulate mass concentrations during 1999 at Mace Head

Date added: 08/07/2000
Date modified: 07/27/2009
Filesize: 148.23 kB

Kleefeld S.; Jennings S.G., Analysis of PM2.5 particulate mass concentrations during 1999 at Mace Head, Journal of Aerosol Science, Volume 31, Supplement 1, September 2000 , pp. 731-732(2)


Abstract


In recent years, the quality of air we breathe has become a significant factor in the environment, with ncreasing interest in the properties of both indoor and outdoor air. Ambient air particles, in addition to gaseous species, are important components in the assessment of air quality, since there is increasing evidence for an association between adverse health effects and the levels of particulate air pollution. Especially the finer particle fraction PMz.5 (particulate mass concemrations with a 50% cut-off diameter of 2.5 pro) is able to penetrate deep into the respiratory system of humans and is best correlated with acute mortality and morbidity findings in urban areas (Oberd6rster et al., 1995). Few measurements of PM2.5 mass concentrations exist for urban areas (e.g. Chan et al., 1999, Chow et al., 1996), but no information is available so far for clean marine air concentrations in the North Atlantic region. Information on background concentrations of PM2.~ mass concentrations as well as on their sources is essential in the interpretation of urban particulate air pollution. Within this study PMz.~ mass concentrations are presented for a clean air site at the Atmospheric Research Station at Mace Head, Cama, (53019 ' N, 9054 ' W) on the west coast of Ireland for the year 1999, and a source identification is performed.

On the representativeness of coastal aerosol studies to open ocean On the representativeness of coastal aerosol studies to open ocean

Date added: 02/12/2010
Date modified: 02/13/2010
Filesize: 1.01 MB

Rinaldi, M., M. C. Facchini, S. Decesari, C. Carbone, E. Finessi, M. Mircea, S. Fuzzi, D. Ceburnis, M. Ehn, M. Kulmala, G. de Leeuw and C. D. O’Dowd, On the representativeness of coastal aerosol studies to open ocean studies: Mace Head – a case study, Atmos. Chem. & Phys., 9, 9635-9646, 2009


Abstract.  

A unique opportunity arose during the MAP project to compare open ocean aerosol measurements with those undertaken at the Mace Head Global Atmosphere Watch Station, a station used for decades for aerosol process research and long-term monitoring. The objective of the present study is to demonstrate that the key aerosol features and processes observed at Mace Head are characteristic of the open ocean, while acknowledging and allowing for spatial and temporal gradients. Measurements were conducted for a 5-week period at Mace Head and offshore, on the Research Vessel Celtic Explorer, in generally similar marine air masses, albeit not in connected-flow scenarios. The results of the study indicate, in terms of aerosol number size distribution, higher nucleation mode particle concentrations at Mace Head than offshore, pointing to a strong coastal  source of new particles that is not representative of the open ocean. The Aitken mode exhibited a large degree of similarity, with no systematic differences between Mace Head and the open ocean, while the  zcumulation mode showed averagely 35% higher concentrations at Mace Head. The higher accumulation mode concentration can be attributed equally to cloud processing and to a coastal enhancement in concentration. Chemical analysis showed similar or even higher offshore concentrations for dominant species, such as nss-SO
2 4 , WSOC, WIOC and MSA. Sea salt concentration differences determined a 40% higher supermicron mass at Mace Head, although this difference can be attributed to a higher  wind speed at Mace Head during the parison period.        Moreover, the relative chemical composition as a function of size illustrated remarkable  similarity. While differences to varying degrees were observed between offshore and coastal  measurements, no convincing evidence was found of local  coastal effects, apart from nucleation mode aerosol, thus confirming the integrity of previously reported marine aerosol characterisation studies at Mace Head.

An automated system for near-real time monitoring of trace atmospheric halocarbons An automated system for near-real time monitoring of trace atmospheric halocarbons

Date added: 08/05/1998
Date modified: 07/27/2009
Filesize: 122.2 kB

An Automated System for Near-Real-Time Monitoring of Trace Atmospheric Halocarbons, Bassford, M.R., Simmonds, P.G., and Nickless, G.,Anal. Chem., 70, 5, 958 - 965, 1998,  10.1021/ac970861z


Abstract


A new gas chromatographic method developed to quantitatively determine important atmospheric halocarbons is described. Target compounds include replacement CFCs, chlorinated solvents, and biosynthesized (naturally produced) organohalogens, all trace gases in the atmosphere at concentrations ranging from 0.1 to 600 pptv (where pptv = 1 part in 10-12 by volume). A combination of ultralow concentrations and relatively small electron attachment cross sections renders these compounds very difficult to routinely measure in the background air typical of remote atmospheric monitoring stations. Detection is achieved by preconcentration of a 200-mL air sample using an adsorbent-filled microtrap and enhancement of electron capture detector response by oxygen doping one of two detectors connected in series. Oxygen doping specifically targets halocarbons with relatively poor electron attachment rate coefficients. The work described here details construction of a novel analytical system, laboratory trials, and optimization followed by an extended field campaign at a remote atmospheric monitoring station, Mace Head, Ireland. A calibration standard or ambient air sample was acquired every hour using a cyclic, automated procedure without employing cryogenic preconcentration or refocusing. Overall precision of the analytical method for the target compounds is between 0.3 and 1.5%.

 

Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combinat Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combinat

Date added: 08/06/2000
Date modified: 07/23/2009
Filesize: 1.6 MB

James, J. D. ; Harrison, Roy M. ; Savage, N. H. ; Allen, A. G. ; Grenfell, J. L. ; Allan, B. J. ; Plane, J. M. C. ; Hewitt, C. N. ; Davison, B. ; Robertson, L.  2000, Quasi-Lagrangian investigation into dimethyl sulfide oxidation in maritime air using a combination of measurements and model, J. Geophys. Res. Vol. 105 , No. D21 , p. 26,379 (2000JD900375)


Abstract


Using a combination of field measurement data and a modified photochemical box model, strong evidence is presented to suggest that the rate of daytime oxidation of dimethyl sulfide (DMS) by OH radicals is insufficient to describe the measured conversion. Quasi-Lagrangian measurements were made at two sites in the eastern Atlantic (Research Vessel and Mace Head Research Station, Ireland) as part of the Atmospheric Chemistry Studies in the Oceanic Environment (ACSOE) program. Periods of connected flow between the two sites were identified, air parcel transit times were estimated, and measurements of the main DMS oxidation products (MSA, SO2, and nss-SO42-) were compared with model predictions to establish whether the model's chemical mechanism could account for observed changes. The main finding was that during daytime periods with maritime air masses, the model failed to predict a sufficient increase in DMS oxidation products during the estimated transit time. This was despite a tendency to overprediction of the progress of nitrogen chemistry during air mass advection, and independent checks on the model estimates of hydroxyl radical concentrations through measurements. In the light of this, the involvement of halogen species (most probably halogen oxides) or heterogeneous oxidation processes is tentatively suggested as the cause of enhanced daytime DMS oxidation in the marine boundary layer (MBL). Increasing the rate constant for the OH + DMS reaction by a factor of 3.3 (as a crude way of simulating parallel channels of DMS oxidation) permitted model results to reproduce the measurements very much more closely.

 

Airborne concentrations and deposition fluxes of major and trace species at marine stations in Airborne concentrations and deposition fluxes of major and trace species at marine stations in

Date added: 08/05/1997
Date modified: 06/30/2009
Filesize: 1.36 MB

Foltescu et al (1996). V.L. Foltescu, E. Selin Lindgren, J. Isakson, M. Oblad, R. Tiede, J. Sommar, J.M. Pacyna and K. Toerseth , Airborne concentrations and deposition fluxes of major and trace species at marine stations in southern Scandinavia. Atmospheric Environment 30 22 (1996), pp. 3857–3872.


Abstract


Extensive measurements of airborne concentrations and deposition fluxes of many major and trace species were performed within the framework of the BMCAPE project (Background Maritime Contribution to Atmospheric Pollution in Europe) at two Scandinavian sites (Saby in Sweden and Lista in Norway) during four seasons in 1993 and 1994. The study focused on gaseous and particulate S-, N- and CI-species.Airborne concentration levels during the different campaigns, seasons and the various air masses encountered are presented for the following gaseous and particulate species: SO2, HCl, NOx, HNO3, NH3, SO2-4, NH+4, NO-3, S, Cl, K, Ca, V, Ni, Zn, Br, Pb and condensation nuclei. In addition, particle concentrations of Ti, Fe, Cu and Mn are discussed in the text. A time series is given for particulate and gaseous Hg. Annual flux estimates for Southern Scandinavia are given for Mn, Fe, Ni, Cu, Zn, Pb, Cl, S, non-sea-salt-sulphate-S, As, Na, K, Ca, Mg, NO-3-N and NH+4-N. Based on direct flux measurements to a water surface, dry deposition velocities are determined for nine elements: Mn, Fe, Ni, Cu, Zn, Pb, Cl, S, Ca.

 

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: 06/30/2009
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).

Black carbon measurements at Mace Head, 1989–1996 Black carbon measurements at Mace Head, 1989–1996

Date added: 07/31/1997
Date modified: 07/27/2009
Filesize: 625.86 kB

W.F. Cooke., Jennings, S.G., and Spain, T.G. (1997) Black-carbon measurements at Mace Head, 1989-1996, J. Geophys. Res.,102, 25, 339-25, 346.


Abstract


Black carbon mass concentrations have been measured using an aethalometer at Mace Head on the west coast of Ireland on an almost continuous basis from February 1989 to June 1996. The purpose of this paper is to report on the monthly averaged black carbon concentration at this site over the 7 year period and to examine the influence of air mass on the black carbon mass concentration. The seasonal variation of black carbon mass concentration for clean marine and continental air masses is also investigated.

Primary marine aerosol emissions size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions Primary marine aerosol emissions size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions

Date added: 08/01/2007
Date modified: 07/23/2009
Filesize: 1.75 MB

Nilsson, E.D., E. M. Mårtensson, J. S. Van Ekeren, G. de Leeuw, M. Moerman, and C. O'Dowd, Primary marine aerosol emissions: size resolved eddy covariance measurements with estimates of the sea salt and organic carbon fractions, Atmos. Chem. Phys. Discuss., 7, 13345-13400, 2007


Abstract


Primary marine aerosol fluxes were measured using eddy covariance (EC), a condensation particle counter (CPC) and an optical particle counter (OPC) with a heated inlet. The later was used to discriminate between sea salt and total aerosol. Measurements were made from the 25 m tower at the research station Mace Head at the Irish west coast, May to September 2002. The aerosol fluxes were dominated by upward fluxes, sea spray from bubble bursting at the ocean surface. The sea salt aerosol number emissions increased two orders of magnitude with declining diameter from 1 to 0.1 μm where it peaked at values of 105 to 107 particles m−2s−1. The sea salt emissions increased at all sizes in the wind range 4 to 22 ms−1, in consistency with a power function of the wind speed. The sea salt emission data were compared to three recent sub micrometer sea salt source parameterisations. The best agreement was with Mårtensson et al. (2003), which appear to apply from 0.1 to 1.1 μm diameters in temperate water (12°C) as well as tropical water (25°C). The total aerosol emissions were independent of the wind speed below 10 ms−1, but increased with the wind above 10 ms−1. The aerosol volume emissions were larger for the total aerosol than for the sea salt at all wind speeds, while the sea salt number emissions approached the total number emissions at 15 ms−1. It is speculated that this is caused by organic carbon in the surface water that is depleted at high wind speeds. The data are consistent with an internal aerosol mixture of sea salt, organic carbon and water. Using the aerosol model by Ellison et al. (1999) (a mono-layer of organic carbon surrounding a water-sea-salt brine) we show that the total and sea salt aerosol emissions are consistent. This predict that the organic carbon fraction increase with decreasing diameter from a few % at 1 μm over 50% at about 0.5 μm to about 90% at 0.1 μm, in consistency with simultaneous chemical data by Cavalli et al. (2004). The combined models of Mårtensson et al. (2003) and Ellison et al. (1999) reproduce the observed total aerosol emissions and offer an approach to model the organic sea spray fraction.

Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at

Date added: 08/07/2005
Date modified: 07/27/2009
Filesize: 449.95 kB

Kock, H.H.;  Bieber, E.; Ebinghaus, R.; Spain, T.G.; Thees, B. (2005): Comparison of long-term trends and seasonal variations of atmospheric mercury concentrations at the two European coastal monitoring stations Mace Head, Ireland, and Zingst, Germany. In: Atmospheric Environment . Vol. 39 (2005) 39, 7549 - 7556


Abstract

 

Monitoring of total gaseous mercury (TGM) concentrations has been carried out at Mace Head on the west coast of Ireland and at Zingst on the southern shore-line of the Baltic Sea. We have used the continuous measurements to assess long-term trends and seasonal variations of TGM concentrations over the same time period. Between 1998 and 2004 the annually averaged TGM concentrations measured at Mace Head (1.72 ng m-3) and Zingst (1.66 ng m-3) remained fairly stable. At both stations we measured higher TGM levels during winter months and lower concentrations during summer months. We also observed an unexpected West to East gradient and found that the overall mean Mace Head TGM concentration was 0.06 ng m-3 higher than those of Zingst. For the January to June period, the Mace Head TGM values (6-year mean = 1.75 ng m-3) are significantly elevated compared to the Zingst results (6-year mean-1.64 ng m-3). Since no local anthropogenic mercury sources exist near the Mace Head station, enhanced emission from the sea appears to provide the most probable explanation for the observed differences. Multiple regression analysis with the atmospheric mercury concentrations measured at Zingst were made with selected meteorological and air quality parameters (wind component, dew point, dust and NOx concentrations). The short-term variation in the TGM concentrations at Zingst shows a strong positive correlation with weather conditions and selected air quality parameters, making TGM a usable tracer of air masses originating from different source regions.

 

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