Non-sea Salt Sulfate Research Articles

Single-Particle Characterization of Summertime Antarctic Aerosols Collected at King George Island Using Quantitative Energy-Dispersive Electron Probe X-ray Microanalysis and Attenuated Total Reflection Fourier Transform-Infrared Imaging Techniques

Single-particle characterization of Antarctic aerosols was performed to investigate the impact of marine biogenic sulfur species on the chemical compositions of sea-salt aerosols in the polar atmosphere. Quantitative energy-dispersive electron probe X-ray microanalysis was used to characterize 2900 individual particles in 10 sets of aerosol samples collected between March 12 and 16, 2009 at King Sejong Station, a Korean scientific research station located at King George Island in the Antarctic. Two size modes of particles, i.e., PM(2.5-10) and PM(1.0-2.5), were analyzed, and four types of particles were identified, with sulfur-containing sea-salt particles being the most abundant, followed by genuine sea-salt particles without sulfur species, iron-containing particles, and other species including CaCO(3)/CaMg(CO(3))(2), organic carbon, and aluminosilicates. When a sulfur-containing sea-salt particle showed an atomic concentration ratio of sulfur to sodium of >0.083 (seawater ratio), it is regarded as containing nonsea-salt sulfate (nss-SO(4)(2-)) and/or methanesulfonate (CH(3)SO(3)(-)), which was supported by attenuated total reflection Fourier transform-infrared imaging measurements. These internal mixture particles of sea-salt/CH(3)SO(3)(-)/SO(4)(2-) were very frequently encountered. As nitrate-containing particles were not encountered, and the air-masses for all of the samples originated from the Pacific Ocean (based on 5-day backward trajectories), the oxidation of dimethylsulfide (DMS) emitted from phytoplanktons in the ocean is most likely to be responsible for the formation of the mixed sea-salt/CH(3)SO(3)(-)/SO(4)(2-) particles.

The impact of anthropogenic emissions on atmospheric sulfate production pathways, oxidants, and ice core Δ<sup>17</sup>O(SO<sub>4</sub><sup>2–</sup>)

Abstract. We use a global three-dimensional chemical transport model to quantify the influence of anthropogenic emissions on atmospheric sulfate production mechanisms and oxidant concentrations constrained by observations of the oxygen isotopic composition (Δ17O = &delta17O–0.52 × &delta18O) of sulfate in Greenland and Antarctic ice cores and aerosols. The oxygen isotopic composition of non-sea salt sulfate (Δ17O(SO42–)) is a function of the relative importance of each oxidant (e.g. O3, OH, H2O2, and O2) during sulfate formation, and can be used to quantify sulfate production pathways. Due to its dependence on oxidant concentrations, Δ17O(SO42–) has been suggested as a proxy for paleo-oxidant levels. However, the oxygen isotopic composition of sulfate from both Greenland and Antarctic ice cores shows a trend opposite to that expected from the known increase in the concentration of tropospheric O3 since the preindustrial period. The model simulates a significant increase in the fraction of sulfate formed via oxidation by O2 catalyzed by transition metals in the present-day Northern Hemisphere troposphere (from 11% to 22%), offset by decreases in the fractions of sulfate formed by O3 and H2O2. There is little change, globally, in the fraction of tropospheric sulfate produced by gas-phase oxidation (from 23% to 27%). The model-calculated change in Δ17O(SO42–) since preindustrial times (1850 CE) is consistent with Arctic and Antarctic observations. The model simulates a 42% increase in the concentration of global mean tropospheric O3, a 10% decrease in OH, and a 58% increase in H2O2 between the preindustrial period and present. Model results indicate that the observed decrease in the Arctic Δ17O(SO42–) – in spite of increasing tropospheric O3 concentrations – can be explained by the combined effects of increased sulfate formation by O2 catalyzed by anthropogenic transition metals and increased cloud water acidity, rendering Δ17O(SO42–) insensitive to changing oxidant concentrations in the Arctic on this timescale. In Antarctica, the Δ17O(SO42–) is sensitive to relative changes of oxidant concentrations because cloud pH and metal emissions have not varied significantly in the Southern Hemisphere on this timescale, although the response of Δ17O(SO42–) to the modeled changes in oxidants is small. There is little net change in the Δ17O(SO42–) in Antarctica, in spite of increased O3, which can be explained by a compensatory effect from an even larger increase in H2O2. In the model, decreased oxidation by OH (due to lower OH concentrations) and O3 (due to higher H2O2 concentrations) results in little net change in Δ17O(SO42–) due to offsetting effects of Δ17O(OH) and Δ17O(O3). Additional model simulations are conducted to explore the sensitivity of the oxygen isotopic composition of sulfate to uncertainties in the preindustrial emissions of oxidant precursors.

제주도 해안과 산간 지역 대기 에어러솔의 이온조성 비교

The ionic compositions of atmospheric aerosols were investigated and characterized in coastal and mountainous sites of Jeju Island, which were Gosan and Mt. Halla-1100 sites respectively. It was found that the concentrations of nss- (non-sea salt sulfate) and at two measurement sites were almost similar and they showed high concentrations in June at the same time. The concentration of soil-originated nss- (non-sea salt calcium) was generally associated with that of anthropogenic and its concentration was increased during spring season. From the comparison of time-series variation and regression analysis of ionic species between two measurement sites, TSP (total suspended particulate) in Gosan site was directly influenced by sea salt particles and the concentration levels of nss-, , nss-, , and were mainly related with long-range transported air pollutants rather than local pollution sources.

Nitrate records of a shallow ice core from East Antarctica: Atmospheric processes, preservation and climatic implications

High-resolution records of nitrate (NO3−), oxygen isotope (δ 18O) and non-sea salt sulphate (nssSO42− ) were studied using an ice core collected from central Dronning Maud Land in East Antarctica to identify the influence of environmental variability on accumulation of NO3− over the past 450 years. The results confirmed that multiple processes were responsible for the production and preservation of NO3− in Antarctic ice. Correlation between NO3− and nssSO42− peaks revealed that sulphate aerosols released during major volcanic eruptions might have activated the production of nitric acid, which was scavenged by ion-induced nucleation in polar ice sheets. The correlation between the nitrate and δ18 O records further suggest that enhanced NO3− preservation in the ice occurred during periods of lower atmospheric temperature. Major shifts in the NO3− record of the ice core presently studied and its comparison with 10Be record from a core collected from South Pole suggest that a reduction in solar activity influenced the NO3− accumulation in Antarctica through enhanced production of odd nitrogen species.

Ten-year observation of sulfur isotopic composition of sulfate in aerosols collected at Tsuruoka, a coastal area on the Sea of Japan in northern Japan

Atmospheric aerosol samples were collected from 1993 to 2003 at Tsuruoka, Japan, a coastal area on the Sea of Japan. Concentration of water-soluble chemical components and sulfur isotopic ratios of sulfate in aerosol samples were measured to evaluate the temporal variation and identify the source. The samSO4 2‐ and nssSO4 2‐ concentrations range from 7.6 to 354.4 and 3.7 to 335.6 neq m ‐3 , respectively, and there was no clear seasonal variation. Sulfur isotope ratios of total sulfate (samδ 34 S) and non-sea salt sulfate (nssδ 34 S) in aerosols are +1.0 to +15.1 with a mean value of +5.7‰ and ‐4.4 to +14.5 with a mean value of +4.1‰, respectively. The values of samδ 34 S and nssδ 34 S are relatively low in summer and high in the other three seasons. The nssδ 34 S values of aerosols in fall to spring agree with the average sulfur isotope ratios of coal used in northern China, considering the isotope fractionation. These results indicate the possibility of long-range transport of sulfate from the Asian continent to Japan. The variations of atmospheric samSO4 2‐ and nssSO4 2‐ concentrations decreased gradually and reach a minimum in 1999. The decline of SO2 emission in China due to reduction in industrial coal use, a slowdown of the Chinese economy, and the closure of small and inefficient plants would be among the causes of this decreasing observed trend. On the other hands, the variation ranges of samδ 34 S and nssδ 34 S values abruptly changed after 2000. The introduction of fuel-gas desulfurization technologies to industrial plants of coke production and thermal power stations would be one of the most important causes of this change.

Isotopic evidence of boron in precipitation originating from coal burning in Asian continent

The boron concentration and isotopic composition (δ11B) of precipitation collected from December 2002 to March 2006 at three sites on the Japan Sea coast were measured. Those sites have been considerably affected by the long-range transport of air pollutants from the Asian continent during winter and spring when the airflows from the Asian continent are predominant. The boron concentration in the precipitation increased primarily during winter whereas the δ11B decreased during winter or spring. It is assumed that this decrease in δ11B is not associated with a Rayleigh distillation process, because the previous δD values of the precipitation collected at a site on the Japan Sea coast did not decrease in the same manner. A weak correlation (r2 = 0.13-0.24, P < 0.01) was observed between δ11B and the nonsea-salt sulfate (nss-SO42-)/B ratio at each site, suggesting that boron in the precipitation originate primarily from two sources. The first source, which is characterized by high δ11B and nss-SO42-/B = 0, is seawater. At the northern site, the enrichment factor for boron in the precipitation relative to seawater approached unity during winter. This implies that much of the boron in the precipitation is derived from unfractionated sea salts rather than gaseous boron evaporated from seawater. The second source is characterized by low δ11B and high nss-SO42-/B ratio. Most of the nss-SO42- in the precipitation originates from anthropogenic combustion activities in the Asian continent based on the previous model calculations. Coal accounts for a major portion of the total primary energy supply in China. Moreover, coal enriches boron and represents generally negative δ11B values. Hence, we propose that the emission of boron from coal burning is the most likely second source. Thus, boron isotopes may be useful as tracers of coal-burning plumes from the Asian continent.

Ammonium and non-sea salt sulfate in the EPICA ice cores as indicator of biological activity in the Southern Ocean

Sulfate (SO 4 2−) and ammonium (NH 4 +) flux records over the last 150,000 years from both Antarctic EPICA ice cores (European Project for Ice Coring in Antarctica) are presented. The ice core record from Dome C is influenced by the Indian sector of the Southern Ocean (SO), whereas Dronning Maud Land is facing the Atlantic sector. Generally, they reflect the past atmospheric aerosol load and, thus, potentially reveal the fingerprint of marine biogenic sources from the SO. The most important feature of both, the nssSO 4 2− as well as NH 4 + flux records, is the absence of any significant glacial cycles, in contrary to the distinct transitions for mineral dust and sea salt aerosol over the last 150,000 years. This finding challenges the iron fertilization hypothesis on long time scales, as the significant changes in dust, e.g. from the last glacial maximum toward the Holocene have neither an impact on nssSO 4 2− nor on NH 4 + fluxes found in interior Antarctica. The inter-site correlation of both species is weak, r 2 = 0.42 for the nssSO 4 2− flux and r 2 = 0.12 for the NH 4 + flux respectively, emphasizing the local source characteristics of biogenic aerosol from the SO. Millennial variability in NH 4 + and nssSO 4 2− is within the uncertainty of our flux estimates. Correlation with mineral dust and sea ice derived sodium shows only a very weak influence of dust deposition on those insignificant changes in nssSO 4 2− flux for the Atlantic sector of the Southern Ocean, but also small transport changes or terrigeneous sulfate contributions may contribute to those variations at EDML.

Decadal trends in aerosol chemical composition at Barrow, Alaska: 1976–2008

Abstract. Aerosol measurements at Barrow, Alaska during the past 30 years have identified the long range transport of pollution associated with Arctic Haze as well as ocean-derived aerosols of more local origin. Here, we focus on measurements of aerosol chemical composition to assess (1) trends in Arctic Haze aerosol and implications for source regions, (2) the interaction between pollution-derived and ocean-derived aerosols and the resulting impacts on the chemistry of the Arctic boundary layer, and (3) the response of aerosols to a changing climate. Aerosol chemical composition measured at Barrow, AK during the Arctic haze season is compared for the years 1976–1977 and 1997–2008. Based on these two data sets, concentrations of non-sea salt (nss) sulfate (SO4=) and non-crustal (nc) vanadium (V) have decreased by about 60% over this 30 year period. Consistency in the ratios of nss SO4=/ncV and nc manganese (Mn)/ncV between the two data sets indicates that, although emissions have decreased in the source regions, the source regions have remained the same over this time period. The measurements from 1997–2008 indicate that, during the haze season, the nss SO4= aerosol at Barrow is becoming less neutralized by ammonium (NH4+) yielding an increasing sea salt aerosol chloride (Cl−) deficit. The expected consequence is an increase in the release of Cl atoms to the atmosphere and a change in the lifetime of volatile organic compounds (VOCs) including methane. In addition, summertime concentrations of biogenically-derived methanesulfonate (MSA−) and nss SO4= are increasing at a rate of 12 and 8% per year, respectively. Further research is required to assess the environmental factors behind the increasing concentrations of biogenic aerosol.

Surface-Level Fine Particle Mass Concentrations: From Hemispheric Distributions to Megacity Sources

Since 1990, basic knowledge of the “chemical climate” of fine particles, has greatly improved from Junge’s compilation from the 1960s. A worldwide baseline distribution of fine particle concentrations on a synoptic scale of approximately 1000 km can be estimated at least qualitatively from measurements. A geographical distribution of fine particle characteristics is deduced from a synthesis of a variety of disparate data collected at ground level on all continents, especially in the northern hemisphere. On the average, the regional mass concentrations range from 1 to 80 μg/m3, with the highest concentrations in regions of high population density and industrialization. Fine particles by mass on a continental and hemispheric spatial scale are generally dominated by non-sea salt sulfate (0.2 to ∼20 μg/m3, or ∼25%) and organic carbon (0.2->10 μg/m3, or ∼25%), with lesser contributions of ammonium, nitrate, elemental carbon, and elements found in sea salt or soil dust. The crustal and trace metal elements contribute a varied amount to fine particle mass depending on location, with a larger contribution in marine conditions or during certain events such as dust storms or volcanic disturbances. The average distribution of mass concentration and major components depends on the proximity to areal aggregations of sources, most of which are continental in origin, with contributions from sea salt emissions in the marine environment. The highest concentrations generally are within or near very large population and industrial centers, especially in Asia, including parts of China and India, as well as North America and Europe. Natural sources of blowing dust, sea salt, and wildfires contribute to large, intermittent spatial-scale particle loadings beyond these ranges. A sampling of 10 megacities illustrates a range of characteristic particle composition, dependent on local and regional sources. Long-range transport of pollution from spatially aggregated sources over hundreds of kilometers creates persistent regional- and continental-scale gradients of mass concentration, sulfate, and carbon species especially in the northern hemisphere. Data are sparse in the southern hemisphere, especially beyond 45° S, but are generally very low in mass concentrations.

Compositions and source apportionments of atmospheric aerosol during Asian dust storm and local pollution in central Taiwan

A study has been carried out on water soluble ions, trace elements, as well as PM2.5 and PM2.5–10 elemental and organic carbon samples collected daily from Central Taiwan over a one year period in 2005. A source apportionment study was performed, employing a Gaussian trajectory transfer coefficient model (GTx) to the results from 141 sets of PM2.5 and PM2.5–10 samples. Two different types of PM10 episodes, local pollution (LOP) and Asian dust storm (ADS) were observed in this study. The results revealed that relative high concentrations of secondary aerosols (NO 3 − , SO 4 2− and NH 4 + ) and the elements Cu, Zn, Cd, Pb and As were observed in PM2.5 during LOP periods. However, sea salt species (Na+ and Cl−) and crustal elements (e.g., Al, Fe, Mg, K, Ca and Ti) of PM2.5–10 showed a sharp increase during ADS periods. Anthropogenic source metals, Cu, Zn, Cd, Pb and As, as well as coarse nitrate also increased with ADS episodes. Moreover, reconstruction of aerosol compositions revealed that soil of PM2.5–10 elevated approximately 12–14% in ADS periods than LOP and Clear periods. A significantly high ratio of non-sea salt sulfate to elemental carbon (NSS-SO 4 2− /EC) of PM2.5–10 during ADS periods was associated with higher concentrations of non-sea-salt sulfates from the industrial regions of China. Source apportionment analysis showed that 39% of PM10, 25% of PM2.5, 50% of PM2.5–10, 42% of sulfate and 30% of nitrate were attributable to the long range transport during ADS periods, respectively.

수원지역 강우의 화학적 특성

최근 급속한 산업화가 진행되고 있는 중국의 편서풍 영향하에 위치한 우리나라의 경우에는 장거리 이동에 따른 강우의 산성도 변화 및 예상되는 피해에 대한 대책 마련을 위하여 강우의 화학성에 대한 지속적인 모니터링이 필요하다. 본 연구는 경기도 수원지역 강우의 산성도 및 주요 이온조성을 평가하기 위하여 wet sampling 방식의 자동채취기를 사용하여 2006년 4월부터 12월까지의 빗물 42점을 채취하였다. 각 시료의 pH 및 주요 이온 성분에 대한 강우량 가중평균치의 월별 변화를 조사하였으며, pH 분포와EC의 계절적 특성을 평가하였다. 빗물 중 양이온과 음이온의 균형비(ion balance)와 전기전도도 균형비(electrical conductivity balance)가 1에 가까운 값을 보여 분석의 높은 신뢰성을 나타내었다. 조사기간 중 평균 pH값은 4.7을 보였다. 빗물의 EC는 조사기간 평균 <TEX>$17.6{\mu}S\;cm^{-1}$</TEX>을 나타냈으며, 월별로는7월에 <TEX>$9.1{\mu}S\;cm^{-1}$</TEX>로 조사기간 중 가장 낮은 값을 보였으며, 11월 이후에 급격히 높아져 EC의 계절적 특성을 보였다. 빗물의 조성에서 양이온 구성은 <TEX>$Na^+</TEX><TEX>></TEX><TEX>NH_4{^+}</TEX><TEX>></TEX><TEX>Ca^{2+}</TEX><TEX>></TEX><TEX>H^+</TEX><TEX>></TEX><TEX>Mg^{2+}</TEX><TEX>></TEX><TEX>K^+$</TEX>의 순이었으며, <TEX>$Na^+$</TEX> 와 <TEX>NH_4{^+}$</TEX>가 전체 양이온 함량의 65% 이상을 차지 하였다. 음이온은 <TEX>$SO_4{^{2-}}</TEX><TEX>></TEX><TEX>NO_3{^-}</TEX><TEX>></TEX><TEX>Cl^-$</TEX> 순으로 <TEX>$SO_4{^{2-}}$</TEX>가 약 67%를 차지하였다. 조사기간 중 평균 sulfate 함량은 <TEX>$119.0{\mu}eq\;L^{-1}$</TEX>이었으며, 이중 비해염 sulfate(nss-<TEX>$SO_4$</TEX>) 함량은 평균 94%로 빗물 중에 함유된 sulfate의 대부분이 인위적인 발생원에서 기인되었다. To evaluate the acidity and chemical characteristics of rainwater in Korea, its pH and ion concentrations were investigated in Suwon from April to December, 2006. In addition, to estimate the contribution of ions on its acidity, ion composition and neutralization effect of major cations were investigated. Ion balance and electrical conductivity balance between measured and estimated values showed a high correlation. The mean pH and EC in rainwater collected during the investigation periods were 4.7 and <TEX>$17.6{\mu}S\;cm^{-1}$</TEX>, respectively. The monthly variation in EC showed a clear seasonal pattern, which had the lowest value of <TEX>$9.1{\mu}S\;cm^{-1}$</TEX> in July and increased remarkably in November. <TEX>$Na^+$</TEX> was the most abundant cation and followed by <TEX>$NH_4{^+}</TEX><TEX>></TEX><TEX>Ca^{2+}</TEX><TEX>></TEX><TEX>H^+</TEX><TEX>></TEX><TEX>Mg^{2+}</TEX><TEX>></TEX><TEX>K^+$</TEX>. Among them, <TEX>$Na^+$</TEX> and <TEX>$NH_4{^+}$</TEX> accounted for more than 65% of the total cations. In case of anions, the relative abundance was <TEX>$SO_4{^{2-}}</TEX><TEX>></TEX><TEX>NO_3{^-}</TEX><TEX>></TEX><TEX>Cl^-$</TEX>. About 67% of the total anions in rainwater was <TEX>$SO_4{^{2-}}$</TEX>, which showed <TEX>$119.0{\mu}eq\;L^{-1}$</TEX> as mean value during the monitoring periods. Furthermore, 94% of the soluble sulfate in rainwater was identified as nss-<TEX>$SO_4{^{2-}}$</TEX>(non-sea salt sulfate). We also found that <TEX>$NH_4{^+}$</TEX> and <TEX>$Ca^{2+}$</TEX> contributed greatly in neutralizing the rain acidity, especially in dry season.

DMS and MSA measurements in the Antarctic Boundary Layer: impact of BrO on MSA production

Abstract. In situ measurements of dimethyl sulphide (DMS) and methane sulphonic acid (MSA) were made at Halley Station, Antarctica (75°35' S, 26°19' W) during February 2004–February 2005 as part of the CHABLIS (Chemistry of the Antarctic Boundary Layer and the Interface with Snow) project. DMS was present in the atmosphere at Halley all year (average 38.1±43 pptV) with a maximum monthly average value of 113.6±52 pptV in February 2004 coinciding temporally with a minimum in sea extent. Whilst seasonal variability and interannual variability can be attributed to a number of factors, short term variability appeared strongly dependent on air mass origin and trajectory pressure height. The MSA and derived non-sea salt sulphate (nss-SO42−) measurements showed no correlation with those of DMS (regression R2=0.039, and R2=0.001 respectively) in-line with the complexity of DMS fluxes, alternative oxidation routes, transport of air masses and variable spatial coverage of both sea-ice and phytoplankton. MSA was generally low throughout the year, with an annual average of 42 ng m−3 (9.8±13.2 pptV), however MSA: nss-SO42− ratios were high implying a dominance of the addition oxidation route for DMS. Including BrO measurements into MSA production calculations demonstrated the significance of BrO on DMS oxidation within this region of the atmosphere in austral summer. Assuming an 80% yield of DMSO from the reaction of DMS+BrO, an atmospheric concentration of BrO equal to 3 pptV increased the calculated MSA production from DMS by a factor of 9 above that obtained when considering only reaction with the hydroxyl radical. These findings have significant atmospheric implications, but may also impact on the interpretation of ice cores which previously relied on the understanding of MSA and nss-SO42− chemistry to provide information on environmental conditions such as sea ice extent and the origins of sulphur within the ice.

Clouds and aerosols in Puerto Rico – a new evaluation

Abstract. The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and behaviour of clouds and their influence on climate. In an attempt to better understand warm cloud formation in a tropical marine environment, a period of intensive measurements took place in December 2004 in Puerto Rico, using some of the latest developments in online instrumentation such as aerosol mass spectrometers, cloud condensation nuclei counters and a hygroscopicity tandem differential mobility analyser. Simultaneous online measurements of aerosol size distributions, composition, hygroscopicity and optical properties were made near the lighthouse of Cape San Juan in the north-eastern corner of the island and at the top of East Peak mountain (1040 m a.s.l.), the two sites separated by 17 km. Additional measurements of the cloud droplet residual and interstitial aerosol properties were made at the mountain site, accompanied by measurements of cloud droplet size distributions, liquid water content and the chemical composition of cloud and rain water samples. Both aerosol composition and cloud properties were found to be sensitive to wind sector. Air from the east-northeast (ENE) was mostly free of anthropogenic influences, the submicron fraction being mainly composed of non-sea salt sulphate, while that from the east-southeast (ESE) was found to be moderately influenced by populated islands upwind, adding smaller (&lt;100 nm), externally mixed, carbonaceous particles to the aerosol that increased the number concentrations by over a factor of 3. This change in composition was also accompanied with a reduction in the measured hygroscopicity and fractional cloud activation potential of the aerosol. At the mountain site, the average cloud droplet concentrations increased from 193 to 519 cm−3, median volume diameter decreased from 20 to 14 μm and the liquid water content increased from 0.24 to 0.31 g m−3 when the winds shifted from the ENE to ESE. Larger numbers of interstitial particles were recorded, most notably at sizes greater than 100 nm, which were absent during clean conditions. The average size of the residual particles and concentrations of cloudwater nitrate, sulphate and insoluble material increased during polluted conditions. Previous studies in Puerto Rico had reported the presence of a significant non-anthropogenic organic fraction in the aerosols measured and concluded that this was a factor controlling the in situ cloud properties. However, this was not observed in our case. In contrast to the 1.00±0.14 μg m−3 of organic carbon measured in 1992 and 1995, the organic matter measured in the current study of 0.17±0.35 μg m−3 is many times lower, most of which can be attributed to anthropogenic sources. During clean conditions, the submicron aerosol was observed to be almost entirely inorganic, an observation supported by the hygroscopicity measurements. This suggests that organic aerosols from marine sources may not be completely ubiquitous (either spatially or temporally) in this environment and requires further investigation to quantify their true extent and implications, with more extensive, longer-term sampling in conjunction with wind field analyses.

Chemical trends in background air quality and the ionic composition of precipitation for the period 1980–2004 from samples collected at Valentia Observatory, Co. Kerry, Ireland

A major Irish study, based upon more than 8000 samples collected over the measurement period of 22 years, for sulfur dioxide (SO2-S), sulfate (SO4-S) and nitrogen dioxide (NO2-N) concentrations (microg m(-3)) within air, and the ionic composition of precipitation samples based on sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), chloride (Cl-), sulfate (SO4-S), non-sea salt sulfate (nssSO4-S), ammonium (NH4-N), and nitrate (NO3-N) weighted mean concentrations (mg l(-1)), has been completed. For the air samples, the sulfur dioxide and sulfate concentrations decreased over the sampling period (1980-2004) by 75% and 45%, respectively, whereas no significant trend was observed for nitrogen dioxide. The highest concentrations for sulfur dioxide, sulfate and nitrogen dioxide were associated with wind originating from the easterly and northeasterly directions i.e. those influenced by Irish and European sources. The lowest concentrations were associated with the westerly directions i.e. for air masses originating in the North Atlantic region. This was further verified with the use of backward (back) trajectory analysis, which allowed tracing the movement of air parcels using the European Centre for Medium range Weather Forecasting (ECMWF) ERA-40 re-analysis data. High non-sea salt sulfate levels were being associated with air masses originating from Europe (easterlies) with lower levels from the Atlantic (westerlies). With the precipitation data, analysis of the non-sea salt sulfate concentrations showed a decrease by 47% since the measurements commenced.

Seasonal variability of crustal and marine trace elements in the aerosol at Neumayer station, Antarctica

Atmospheric trace element concentrations were measured from March 1999 to December 2003 at the Air Chemistry Observatory of the German Antarctic station Neumayer, by inductively coupled plasma–quadrupol mass spectrometry (ICP–QMS) and ion chromatography (IC). This continuous five-year long record derived from weekly aerosol sampling revealed a distinct seasonal summer maximum for elements linked with mineral dust entry (Al, La, Ce, Nd) and a winter maximum for the mostly sea salt derived elements Li, Na, K, Mg, Ca and Sr. The relative seasonal amplitude was around 1.7 and 1.4 for mineral dust (La) and sea salt aerosol (Na), respectively. On average, a significant deviation regarding mean ocean water composition was apparent for Li, Mg and Sr, which could hardly be explained by mirabilite precipitation on freshly formed sea ice. In addition, we observed all over the year, a not clarified high variability of element ratios Li/Na, K/Na, Mg/Na, Ca/Na and Sr/Na. We found an intriguing co-variation of Se concentrations with biogenic sulphur aerosols (methane sulphonate and non-sea salt sulphate), indicating a dominant marine biogenic source for this element, linked with the marine biogenic sulphur source.

Coupling between dimethylsulfide emissions and the ocean - atmosphere exchange of ammonia

Environmental context. Dimethylsulfide (DMS) is recognised as a potentially significant climate-forcing gas, owing to its role in particle and cloud formation in the marine atmosphere, where it is the dominant source of acidity. Ammonia, the dominant naturally occurring base in the atmosphere, plays an important role in neutralising particles formed from DMS oxidation products and may even enhance the formation rate of new particles. A biogeochemical coupling has previously been proposed between DMS and ammonia fluxes from the ocean to the atmosphere, in the form of coproduction of the two gases in seawater. We revise this suggestion by introducing the concept of ‘co-emission’ of the gases, where DMS emission controls the rate of emission of ammonia from the ocean by acidifying the atmosphere. Abstract. A strong correlation between aerosol ammonium and non-sea salt sulfate is commonly observed in the remote marine boundary layer. It has been suggested that this relationship implies a biogeochemical linkage between the nitrogen (N) and sulfur (S) cycles at the cellular biochemical level in phytoplankton in the ocean, or a linkage in the atmosphere (see P. S. Liss and J. N. Galloway, Interactions of C, N, P and S biogeochemical cycles and global change (Springer, 1993), and P. K. Quinn et al. in J. Geophys. Res. – Atmos. 1990, 95). We argue that an oceanic linkage is unlikely and draw on mechanistic and observational evidence to make the argument that the atmospheric connection is based on simple physical chemistry. Drawing on an established analogous concept in terrestrial trace gas biogeochemistry, we propose that any emission of dimethylsulfide (DMS) from the ocean will indirectly influence the flux of NH3 from the ocean, through the neutralisation of acidic DMS oxidation products and consequent lowering of the partial pressure of NH3 in the atmosphere. We present a simple numerical model to investigate this hypothesised phenomenon, using a parameterisation of the rate and thermodynamics of gas-to-particle conversion of NHx and explicitly modelled ocean–atmosphere NH3 exchange. The model indicates that emission of acidic sulfur to the atmosphere (e.g. as a product of DMS oxidation) may enhance the marine emission of NH3. It also suggests that the ratio of ammonium to non-sea salt sulfate in the aerosol phase is strongly dependent on seawater pH, temperature and wind speed – factors that control the ocean–atmosphere ammonia flux. Therefore, it is not necessary to invoke a stoichiometric link between production rates of DMS and ammonia in the ocean to explain a given ammonium to non-sea salt sulfate ratio in the aerosol. We speculate that this mechanism, which can provide a continuous resupply of ammonia to the atmosphere, may be involved in a series of biogeochemical-climate feedbacks.

Optical and chemical properties of marine aerosols over the central equatorial Pacific Ocean during the 2003 R/V Mirai cruise

The optical and chemical properties of atmospheric aerosols were measured over the central equatorial Pacific Ocean (from 150°E to 160°W longitude, near the equator) during the R/V Mirai cruise of January 2003. In the area from 165°E to 160°W along the equator, concentrations of anthropogenic chemical components were low; the average concentration of nonsea salt sulfate was 0.28 μg m−3, that of vanadium was less than the detection limit, and those of elemental carbon and organic carbon were 0.009 and 0.09 μg‐C m−3. The scattering coefficients were low (3.2 × 10−6 m−1 on average), and the absorption coefficients were also extremely low (0.06 × 10−6 m−1 on average). The mean value of single scattering albedo was 0.98, with a standard deviation of 0.01, indicating that the measured aerosols were transparent and had low variability. The measurement results suggest that nonsea salt sulfate and organic carbon were from natural sources. Sea salt particles and nonsea salt sulfate composed a large fraction (94%) of the water‐soluble components of fine particles. Thus the water‐soluble components and organic materials from natural sources were primarily responsible for the scattering of solar radiation. The measurement results give typical values of the optical and chemical properties of aerosols in the unpolluted central equatorial Pacific Ocean.

태안지역 강우의 이온 조성

태안지역에서 영농기간중 강우의 화학적 특성을 알아보기 위하여 2005년 4월부터 10월까지 26점의 강우를 채수하여 pH 및 화학적 성분조성을 조사하였다. 강우량을 고려한 가중평균(volume-weighted mean)이온농도 변화와 알카리성 물질들에 의한 강우의 산성도 중화를 평가한 결과는 다음과 같다. 시료분석의 신뢰성을 검토한 전기전도도 수지 평가에서는 높은 상관을 나타내어 분석 이온들에 대한 신뢰가 인정되었다. 조사기간 중 태안지역에 내린 강우의 pH별 분포는 pH <TEX>$4.5{\sim}5.0$</TEX> 범위가 가장 많았으며, 월별로는 6월이 다른 조사기간에 비해 산성도가 낮았다. 강우량과 강우의 EC 관계에서는 강우기가 비강우기인 6월 이전에 비해 EC가 낮은 계절적 특성을 보였다. 강우의 조성에서 양이온 구성은 <TEX>$Na^+>H^+>Ca^{2+}>NH_4^+>K^+>Mg^{2+}$</TEX>의 순이었으며, <TEX>$Na^+,\;NH_4^+,\;Ca^{2+}$</TEX> 및 <TEX>$H^+$</TEX>가 전체 양이온 함량의 94% 이상을 차지하였다. 음이온은 <TEX>$SO_4^{2-}>NO_3^->Cl^-$</TEX> 순으로 <TEX>$SO_4^{2-}$</TEX> 및 <TEX>$NO_3^-$</TEX>가 약 80%를 차지하였다. 조사기간 중 강우산성도 중화는 6월이 다른 기간에 비해 높았음을 보였다. 총 sulfate 함량 중 nss-<TEX>$SO_4^{2-}$</TEX> 함량은 78%로 강우 중에 함유된 sulfate의 대부분이 인위적인 발생원에서 기인되었으며, 월별로는 9월까지 점차 낮아지다. 10월에 다시 높아지는 계절적 변이를 보였다. The issue of acid precipitation and related environmental problems in East Asia has been emerging. To evaluate the acidity and chemical characteristics of rainwater in Korea, its chemical properties during cultivation season from April to October in 2005 were investigated at Taean. Also, to estimate the contribution of ions on acidity, ion composition characteristics and neutralization effects by cations were determined. The electrical conductivity balance between measured and estimated values showed a high correlation. Rainwater was highly distributed in the range of pH <TEX>$4.5{\sim}5.0$</TEX>. The acidity of rainwater was relatively low during the month of June compared with other monitored periods. <TEX>$Na^+$</TEX> was the main cation, followed by <TEX>$H^+>Ca^{2+}>NH_4^+>K^+>Mg^{2+}$</TEX>. Among these ions, <TEX>$Na^+,\;NH_4^+,\;Ca^{2+}$</TEX> and <TEX>$H^+$</TEX> comprised over 94% of the total cations. Rainwater anion composition was more than 80% with <TEX>$SO_4^{2-}$</TEX> and <TEX>$NO_3^-$</TEX>. In rainwater samples, <TEX>$NH_4^+$</TEX> and <TEX>$Ca^{2+}$</TEX> contributed greatly to neutralizing the rain acidity. The sulfate content decreased until September, and sea salt derivatives were higher in May and October than during other monitored periods. Also, 78% of the soluble sulfate in rainwater was nss-<TEX>$SO_4^{2-}$</TEX> (non-sea salt sulfate).

Temporal Trends of Non-sea Salt Sulfate and Nitrate in Wet Deposition in Japan

Temporal trends of non-sea salt (nss-) sulfate and nitrate were analyzed from nationwide precipitation chemistry measurements provided by the Ministry of the Environment (MOE) for the 1988–2002 fiscal years (April–March). The concentrations and deposition of nss-sulfate were found to be decreasing, and those of nitrate were stable or slightly increasing at most sites. These deposition trends were discussed from the viewpoint of emissions of SO2 and NOX during the period of interest. Because monitoring techniques have changed in the number of active sites, samplers, and analytical methods during the operation period, the median of all annual depositions measured in Japan in a specific year was selected as the annual representative. The contribution of specific emission sources was also calculated for 1990 on the basis of the nss-sulfate and nitrate deposition in Japan obtained with a model simulation in which the model did not include volcanic emissions from Mt. Oyama, Miyakejima Island, which began to erupt suddenly and violently in 2000. For nss-sulfate, the calculated deposition agrees well with the intensity and trends of the median up to 1999. After 2000, a higher deposition than calculated in the preceding years was evident, which is attributable to the volcanic SO2 from Mt. Oyama. For nitrate, both the calculated and observed depositions were slightly increasing; however, the calculation was found to exceed the observation.

Determination of the deposition of cosmogenic radionuclide 35S and sulfate in a heavy-snowfall area facing the Sea of Japan

Summary In connection with the investigation of acid depositions, a reliable method for the determination of the cosmogenic radionuclide 35S in precipitation was developed, and atmospheric depositions of 35S and SO42- have been measured every ten days at Tatsunokuchi,in a heavy-snowfall area facing to the Sea of Japan for two years during 1998-1999. Consistent seasonal cycles were found for the atmospheric depositions of 35S and non-sea salt sulfate (nss-SO42-), in which both depositions were high in winter and low in other seasons. A similar wet scavenging mechanism was suggested to be involved in the association of 35S and SO42-.