Rainwater Sulfate Research Articles

Variability of sulfur and oxygen isotope values within wet precipitation and its correlation with diminished anthropogenic sulfur dioxide (SO2) emission

Atmospheric sulfate (SO42−) aerosols have the capacity to scatter solar radiation, thus exerting a cooling effect on the climate. It is widely acknowledged that SO42− deposition significantly contributes to ecosystem effect in aquatic and terrestrial environments worldwide. Over the course of several decades, considerable efforts have been undertaken to mitigate anthropogenic sulfur dioxide (SO2) emissions in China, leading to remarkably low SO2 concentrations. Nevertheless, the implications of reduced anthropogenic SO2 emission on atmospheric sulfate transformation and compositions of isotope values (δ34S-SO42–, δ18O-SO42–) remain inadequately understood. To address this knowledge gap, we conducted multiple rainfall sampling instances between 2010 and 2022 (n = 191), encompassing the period of transitioning anthropogenic SO2 emission from high to low levels. Remarkably, we observed a significant reduction in the volume-weighted mean value (VWMV) of SO42− concentrations, declining from 20.86 mg L−1 in 2010 to 2.41 mg L−1 in 2022, and the VWMV of SO42−/NO3− molar ratios also decreased from 12.90 in 2010 to 0.55 in 2022, reflecting the synchronously decreasing annual SO2 emissions and annual SO2 concentrations from 2010 to 2022. In contrast to the declining trends in VWMV of SO42− concentrations, the VWMV of δ34S-SO42– values exhibited a different pattern from 6.6‰ in 2010 to −0.1‰ in 2017 and slightly increased to 2.5‰ in 2022. Furthermore, the VWMV of δ18O-SO42– values demonstrated an increase from 8.8‰ in 2010 to 14.5‰ in 2018, but subsequently decreased to 5.4‰ in 2022. We attributed the sharply dropping VWMV of δ34S-SO42– values to the reduction in the input of primary sulfate with enriched δ34S-SO42– values. The strict desulfurization reduced SO2 emissions, leading to oxidation of these trace SO2 with negative δ34S values, resulting in low sulfate concentrations and negative δ34S-SO42– values. In addition, the monthly average δ18O-SO42– values exhibited a positive correlation with monthly mean δ18O-H2O values (p < 0.05), strongly indicating the water incorporation during SO2 heterogeneous oxidation. More importantly, during spring rainfall, positive δ18O-SO42– values but relatively negative δ34S-SO42– values were influenced by SO2 heterogeneous oxidation facilitated by air oxygen catalyzed under metal ions in dry weather condition, attributed to the low relative humidity (RH) coupled with high deuterium excess (dexcess) values. Conversely, in summer, negative δ18O-SO42– values but relatively positive δ34S-SO42– values resulted from the SO2 heterogeneous oxidation with H2O2 due to high RH and low dexcess values. Moreover, the VWMV of δ18O-H2O exhibited variations from −3.7‰ in 2019 to −9.7‰ in 2021, and displayed a positive correlation with annual temperature (p < 0.01) and a negative correlation with annual precipitation (p < 0.05), making it a valuable indicator of climate change alongside δ18O-SO42– values. Our findings underscore the importance of continued monitoring of atmospheric wet depositions in response to changes in anthropogenic SO2 emission activities. Furthermore, they highlight the substantial impact of variations in δ34S values of SO2 and primary sulfate on rainwater sulfate concentrations and isotope values.

Measurement report: Closure analysis of aerosol–cloud composition in tropical maritime warm convection

Abstract. Cloud droplet chemical composition is a key observable property that can aid understanding of how aerosols and clouds interact. As part of the Clouds, Aerosols and Monsoon Processes – Philippines Experiment (CAMP2Ex), three case studies were analyzed involving collocated airborne sampling of relevant clear and cloudy air masses associated with maritime warm convection. Two of the cases represented a polluted marine background, with signatures of transported East Asian regional pollution, aged over water for several days, while the third case comprised a major smoke transport event from Kalimantan fires. Sea salt was a dominant component of cloud droplet composition, in spite of fine particulate enhancement from regional anthropogenic sources. Furthermore, the proportion of sea salt was enhanced relative to sulfate in rainwater and may indicate both a propensity for sea salt to aid warm rain production and an increased collection efficiency of large sea salt particles by rain in subsaturated environments. Amongst cases, as precipitation became more significant, so too did the variability in the sea salt to (non-sea salt) sulfate ratio. Across cases, nitrate and ammonium were fractionally greater in cloud water than fine-mode aerosol particles; however, a strong covariability in cloud water nitrate and sea salt was suggestive of prior uptake of nitrate on large salt particles. A mass-based closure analysis of non-sea salt sulfate compared the cloud water air-equivalent mass concentration to the concentration of aerosol particles serving as cloud condensation nuclei for droplet activation. While sulfate found in cloud was generally constrained by the sub-cloud aerosol concentration, there was significant intra-cloud variability that was attributed to entrainment – causing evaporation of sulfate-containing droplets – and losses due to precipitation. In addition, precipitation tended to promote mesoscale variability in the sub-cloud aerosol through a combination of removal, convective downdrafts, and dynamically driven convergence. Physical mechanisms exerted such strong control over the cloud water compositional budget that it was not possible to isolate any signature of chemical production/loss using in-cloud observations. The cloud-free environment surrounding the non-precipitating smoke case indicated sulfate enhancement compared to convective mixing quantified by a stable gas tracer; however, this was not observed in the cloud water (either through use of ratios or the mass closure), perhaps implying that the warm convective cloud timescale was too short for chemical production to be a leading-order budgetary term and because precursors had already been predominantly exhausted. Closure of other species was truncated by incomplete characterization of coarse aerosol (e.g., it was found that only 10 %–50 % of sea salt mass found in cloud was captured during clear-air sampling) and unmeasured gas-phase abundances affecting closure of semi-volatile aerosol species (e.g., ammonium, nitrate and organic) and soluble volatile organic compound contributions to total organic carbon in cloud water.

Trifluoroacetic acid deposition from emissions of HFO-1234yf in India, China, and the Middle East

Abstract. We have investigated trifluoroacetic acid (TFA) formation from emissions of HFO-1234yf (CF3CFH2), its dry and wet deposition, and rainwater concentration over India, China, and the Middle East with GEOS-Chem and WRF-Chem models. We estimated the TFA deposition and rainwater concentrations between 2020 and 2040 for four previously published HFO-1234yf emission scenarios to bound the possible levels of TFA. We evaluated the capability of GEOS-Chem to capture the wet deposition process by comparing calculated sulfate in rainwater with observations. Our calculated TFA amounts over the USA, Europe, and China were comparable to those previously reported when normalized to the same emission. A significant proportion of TFA was found to be deposited outside the emission regions. The mean and the extremes of TFA rainwater concentrations calculated for the four emission scenarios from GEOS-Chem and WRF-Chem were orders of magnitude below the no observable effect concentration. The ecological and human health impacts now, and the continued use of HFO-1234yf in India, China, and the Middle East, are estimated to be insignificant based on the current understanding, as summarized by Neale et al. (2021).

The abatement of acid rain in Guizhou province, southwestern China: Implication from sulfur and oxygen isotopes

The high frequency of acid rain in southern China has captured public and official concern since 1980s. Subsequently, gas emission reduction measures have been implemented to improve the air quality. Variations in SO2 emission intensities can influence the sulfur and oxygen isotopic compositions of sulfate in rainwater, since atmospheric sulfate is mainly formed via the oxidation of sulfur gases from natural and anthropogenic sources. To evaluate the impacts of emission reduction measures on atmospheric sulfate, the seasonal and long-term trends in stable isotopic compositions of sulfate in rainwater in Guizhou province, southwestern China have been investigated based on rainwater samples collected from June 2016 to June 2018 and literature investigation (2000–2010).The results reveal that coal combustion remains a major contributor to sulfate in rainwater, although its SO2 emission has significantly decreased over the past two decades. The δ34Ssulfate and δ18Osulfate values in rainwater are negatively correlated and have significant seasonal changes. The seasonality in δ34Ssulfate has been interpreted as due to the changes in contributions of dimethyl sulfide and coal combustion, while the seasonal pattern of δ18Osulfate is consistent with that of δ18Owater values, indicating sulfate in rainwater is mainly formed by heterogeneous oxidation of SO2. Combined with the data from previous studies (Xiao and Liu, 2002; Liu, 2007; Xiao et al., 2009; Xiao et al., 2014), we found that the volume weighted mean δ34S values of sulfate in rainwater in Guizhou province show a marked increase between 2001 and 2018, indicating that the 34S-depleted SO2 emission from coal combustion has declined during this period. Furthermore, the synchronous changes in δ34S values, sulfate concentration and pH values of rainwater suggest that the frequency of acid rain in Guizhou province has dropped over the past two decades, which is likely to result from the emission reduction measures taken in Guizhou province.

The Influence of Meteorology and Atmospheric Transport Patterns on the Sulfate Levels in Raiwater in Orizaba Valley, Veracruz, Mexico

This work assessed the relationship between synoptic circulation patterns, meteorological conditions and sulfate levels in rainwater in Orizaba Valley, Veracruz, Mexico during 2015. Samples were collected by using an automatic deposition sampler considering three climatic periods: Cold fronts or Nortes, Dry and Rainy seasons. Sulfate in rainwater was determined by turbidimetry (NMX-AA-SCFI-074-1981). A backward trajectory model (HYSPLIT) was used to characterize the potential source regions and transport pathways for air parcels arriving to Orizaba Valley; trajectories extended five days during 2015 were calculated. Mean concentrations of sulfate were 105.33, 37.5, and 52.5 μEq·l-1, for Cold Fronts, Dry and Rainy seasons, respectively. An evident dilution pattern was observed with lower concentration levels when rainfall increased. Mean values for sulfate concentration exceeded the background hemispheric value reported by Galloway et al. (1982) for remote sites (10 μEq·l-1), exceeding almost 10, 3.7 and 5.2 times, during the Nortes, Rainy and Dry seasons, respectively. From the obtained results, it was concluded that the high sulfate levels in the rainwater measured in Orizaba Valley had their origin in different upwind regional sources as a result of long-range transport during Rainy and Nortes seasons.

Atmospheric Corrosion of Corrugated Iron Roofing Sheet in Oil Producing Locations in Southeastern Nigeria

The study evaluated the atmospheric corrosion of corrugated iron roofing sheets in rural, urban, and marine environments using rain water harvested from roofs of various ages. Corrosion study was based on the weathering processes leading to high levels of sulphate, chloride and nitrate in rainwater in the three areas. Results showed that roofs below one year and 2 years in age were more susceptible to rusting than roofs above 15 years. The mean corrosion rates were higher in marine (Ibeno) ranging between 0.16 × 103 μm/yr and 2.94 × 103 μm/yr followed by rural (Okobo) 0.08 × 103 - 1.88 × 103 μm/yr, and the least was urban (Uyo) 0.031 × 103 μm/yr - 0.79 × 103 μm/yr. Sulphates, nitrates and chlorides were high in the marine environment, which also coincided with the area of gas flare by Mobil Oil exploration activities. Increase in temperature and acid rain formations in this area led to increased acid rainstorm. This could manifest in the erosion of beach and wetland, inundates low-lying areas (Ibeno, Ibaka (James town), Oron, Utan brama, Utan-Effiong and Mbe-Ndoro) flooding and loss of coastal land and mangrove forests. Above all, gas flaring affects atmospheric water quality in which soil, crops, fruits, streams, and rivers are affected.

MC ICP-MS δ(34)S(VCDT) measurement of dissolved sulfate in environmental aqueous samples after matrix separation by means of an anion exchange membrane.

Analysis of 34S/32S of sulfate in rainwater and soil solutions can be seen as a powerful tool for the study of the sulfur cycle. Therefore, it is considered as a useful means, e.g., for amelioration and calibration of ecological or biogeochemical models. Due to several analytical limitations, mainly caused by low sulfate concentration in rainwater, complex matrix of soil solutions, limited sample volume, and high number of samples in ecosystem studies, a straightforward analytical protocol is required to provide accurate S isotopic data on a large set of diverse samples. Therefore, sulfate separation by anion exchange membrane was combined with precise isotopic measurement by multicollector inductively coupled plasma mass spectrometry (MC ICP-MS). The separation method proved to be able to remove quantitatively sulfate from matrix cations (Ca, K, Na, or Li) which is a precondition in order to avoid a matrix-induced analytical bias in the mass spectrometer. Moreover, sulfate exchange on the resin is capable of preconcentrating sulfate from low concentrated solutions (to factor 3 in our protocol). No significant sulfur isotope fractionation was observed during separation and preconcentration. MC ICP-MS operated at edge mass resolution has enabled the direct 34S/32S analysis of sulfate eluted from the membrane, with an expanded uncertainty U (k = 2) down to 0.3 ‰ (a single measurement). The protocol was optimized and validated using different sulfate solutions and different matrix compositions. The optimized method was applied in a study on solute samples retrieved in a beech (Fagus sylvatica) forest in the Vienna Woods. Both rainwater (precipitation and tree throughfall) and soil solution δ34SVCDT ranged between 4 and 6 ‰, the ratio in soil solution being slightly lower. The lower ratio indicates that a considerable portion of the atmospherically deposited sulfate is cycled through the organic S pool before being released to the soil solution. Nearly the same trends and variations were observed in soil solution and rainwater δ34SVCDT values showing that sulfate adsorption/desorption are not important processes in the studied soil.Graphical abstractSulfate separation by means of an anion exchange resin on a plastic membraneElectronic supplementary materialThe online version of this article (doi:10.1007/s00216-015-9053-z) contains supplementary material, which is available to authorized users.

Spatial Distribution of Sulfate Concentration in Groundwater of South-Punjab, Pakistan

Sulfate causes various health issues for human if on average daily intake of sulfate is more than 500 mg from drinking-water, air, and food. Moreover, the presence of sulfate in rainwater causes acid rains which has harmful effects on animals and plants. Food is the major source of sulfate intake; however, in areas of South-Punjab, Pakistan, the drinking-water containing high levels of sulfate may constitute the principal source of intake. The spatial behavior of sulfate in groundwater is recorded for South-Punjab province, Pakistan. The spatial dependence of the response variable (sulfate) is modeled by using various variograms models that are estimated by maximum likelihood method, restricted maximum likelihood method, ordinary least squares, and weighted least squares. The parameters of estimated variogram models are utilized in ordinary kriging, universal kriging, Bayesian kriging with constant trend, and varying trend and the above methods are used for interpolation of sulfate concentration. The K-fold cross validation is used to measure the performances of variogram models and interpolation methods. Bayesian kriging with a constant trend produces minimum root mean square prediction error than other interpolation methods. Concentration of sulfate in drinking water within the study area is increasing to the Northern part, and health risks are really high due to poor quality of water.

Source Identification of Sulfur in Uncultivated Surface Soils from Four Chinese Provinces

The analysis of stable isotopes of sulfur (δ34S) is a useful tool for identifying sources of sulfur in soils. Concentrations and sulfur (S) isotopes of water-soluble sulfate (WSS), adsorbed sulfate (AS), residual sulfur (RS), and total sulfur (TS) in uncultivated surface soils of four Chinese provinces were systematically analyzed for identifying sources of S in the soils. Green and healthy mosses (Haplocladium microphyllum) were sampled as bioindicators. The mean WSS concentration (27.8 ± 23.4 mg kg−1) in the surface soils was lower than those of AS (101.4 ± 57.0 mg kg−1) and RS (381.5 ± 256.7 mg kg−1). The mean δ34S values of WSS and AS were very similar (about 2.0%), lower than those of RS (8.0%) and TS (6.1%). A significant linear correlation was found between the δ34S values of AS and WWS (y = 1.0002x – 0.0557, P < 0.0001), indicating that sulfate adsorption in the soils did not markedly fractionate S. All S species in the soils of Guizhou Province were characterized by the lowest δ34S values, consistent with the most 34S-depleted rainwater sulfate reported at Guiyang of Guizhou Province. The δ34S values of sulfate in mosses and rainwater previously reported were significantly linearly correlated with those of both WWS and AS in surface soils, suggesting that atmospheric S input was an important source for soil WSS and AS. However, there were no significant correlations between isotopic composition of rainwater sulfate and RS or TS. The slopes of all these significant linear correlations (soil/rainwater or soil/moss isotopic ratio) were 0.4–0.6, indicating that inorganic sulfate in the surface soils should be a result of mixing of deposited atmospheric sulfate with a more 34S-depleted sulfate component possibly from mineralization of RS.

Sources and meteorological factors that control seasonal variation of δ34S values in rainwater

Sulfate concentrations and sulfur isotopic compositions were measured in rainwater in Guiyang city in Southwest China between October 2008 and September 2009 to identify sulfur sources and their impacts on sulfur isotopic composition. The δ34S values of 1235 samples collected during this period ranged from−12.0 to +9.4‰, with a volume-weighted mean of−2.8±9.8‰, suggesting that rainwater sulfate in Guiyang was mainly derived from SO2 produced during coal combustion. The δ34S values of rainwater sulfate increased from 1987 to 2009, with an increment of about +0.16‰ per year, reflecting a gradual reduction in 34S-depleted SO2 emitted during coal combustion. Seasonal variations in δ34S values were pronounced, with higher values in winter than in summer. Long-distance transport of SO2 from coal burned in northern cities (which was higher than the component from southern cities), and more importantly, the aqueous oxidation of SO2 during transport affected the seasonal variation of rainwater δ34S values in Guiyang. Temperature-dependent aqueous oxidation of SO2 suggested that lower rainwater δ34S coincides with higher temperature.

Spectrophotometric flow-injection determination of sulfate in rainwater

A flow-injection system is proposed for the spectrophotometric determination of low concentrations of sulfate in rainwater using barium dimethylsulfonazo(III) (Ba-DMSA). Selectivity is enhanced by including a Dowex 1-X8 anionic resin mini-column into the manifold, aiming at sulfate in-line concentration and separation from potential interfering chemical species. The proposed system is robust and provides precise results (r.s.d. < 5.0%) at an analytical frequency of 40 h−1. About 0.09 mg DMSA is consumed per determination. The analytical curve is linear up to 2.0 mg L−1 SO42− and the detection and quantification limits were estimated as 0.01 and 0.04 mg L−1 SO42−, respectively. Results are in agreement with those obtained by ion chromatography at the 95% confidence level.

Carbon System Measurements and Potential Climatic Drivers at a Site of Rapidly Declining Ocean pH

We explored changes in ocean pH in coastal Washington state, USA, by extending a decadal-scale pH data series, by reporting independent measures of dissolved inorganic carbon (DIC), spectrophotometric pH, and total alkalinity (TA), by exploring pH patterns over larger spatial scales, and by probing for long-term trends in environmental variables reflecting potentially important drivers of pH. We found that pH continued to decline in this area at a rapid rate, that pH exhibited high natural variability within years, that our measurements of pH corresponded well to spectrophotometric pH measures and expected pH calculated from DIC/TA, and that TA estimates based on salinity predicted well actual alkalinity. Multiple datasets reflecting upwelling, including water temperature, nutrient levels, phytoplankton abundance, the NOAA upwelling index, and data on local wind patterns showed no consistent trends over the period of our study. Multiple datasets reflecting precipitation change and freshwater runoff, including precipitation records, local and regional river discharge, salinity, nitrate and sulfate in rainwater, and dissolved organic carbon (DOC) in rivers also showed no consistent trends over time. Dissolved oxygen did not decline over time, indicating that long-term changes did not result from shifts in contributions of respiration to pH levels. These tests of multiple potential drivers of the observed rapid rate of pH decline indicate a primary role for inorganic carbon and suggest that geochemical models of coastal ocean carbon fluxes need increased investigation.

Indicating atmospheric sulfur by means of S-isotope in leaves of the plane, osmanthus and camphor trees

Foliar δ 34S values of three soil-growing plant species ( Platanus Orientalis L., Osmanthus fragrans L. and Cinnamomum camphora) have been analyzed to indicate atmospheric sulfur. The foliar δ 34S values of the three plant species averaged −3.11 ± 1.94‰, similar to those of both soil sulfur (−3.73 ± 1.04‰) and rainwater sulfate (−3.07 ± 2.74‰). This may indicate that little isotopic fractionation had taken place in the process of sulfur uptake by root or leaves. The δ 34S values changed little in the transition from mature leaves to old/senescing leaves for both the plane tree and the osmanthus tree, suggestive of little isotope effect during sulfur redistribution in plant tissues. Significantly linear correlation between δ 34S values of leaves and rainwater sulfate for the plane and osmanthus trees allowed the tracing of temporal variations of atmospheric sulfur by means of foliar sulfur isotope, while foliage δ 34S values of the camphor is not an effective indicator of atmospheric sulfur.

Colorimetric Determination of micro amounts of Sulfate in Rainwater by Reagents of 2-Aminoperimedine coupled to Dinitrosulfonazo III

Colorimetric Determination of micro amounts of Sulfate in Rainwater by Reagents of 2-Aminoperimedine coupled to Dinitrosulfonazo III

Long-Term Temporal Variability in Hydrogen Peroxide Concentrations in Wilmington, North Carolina USA Rainwater

Measurements of hydrogen peroxide (H(2)O(2)), pH, dissolved organic carbon (DOC), and inorganic anions (chloride, nitrate, and sulfate) in rainwater were conducted on an event basis at a single site in Wilmington, NC for the past decade in a study that included over 600 individual rain events. Annual volume weighted average (VWA) H(2)O(2) concentrations were negatively correlated (p < 0.001) with annual VWA nonseasalt sulfate (NSS) concentrations in low pH (<5) rainwater. Under these conditions H(2)O(2) is the primary aqueous-phase oxidant of SO(2) in the atmosphere. We attribute the increase of H(2)O(2) to decreasing SO(2) emissions which has had the effect of reducing a major tropospheric sink for H(2)O(2). Annual VWA H(2)O(2) concentrations in low pH (<5) rains showed a significant increase over the time scale of this study, which represents the only long-term continuous data set of H(2)O(2) concentrations in wet deposition at a single location. This compositional change has important implications because H(2)O(2) is a source of highly reactive free radicals so its increase reflects a higher overall oxidation capacity of atmospheric waters. Also, because rainwater is an important mechanism by which H(2)O(2) is transported from the atmosphere to surface waters, greater wet deposition of H(2)O(2) could influence the redox chemistry of receiving watersheds which typically have concentrations 2-3 orders of magnitude lower than rainwater.

Turbidimetric determination of sulfate in rainwater employing a LED based photometer and multicommuted flow analysis system with in-line preconcentration

In the present work, an automatic procedure for turbidimetric determination of sulfate in rainwater, based on the multicommuted flow analysis approach, is proposed. The photometer set-up was developed at the laboratory, and includes: a LED (λ = 420 nm), a long pathlength flow cell (100 mm), and a photodiode. A preconcentration step is included in order to improve sensitivity. After establishing the adequate operational conditions, the proposed procedure presented the following useful features: a linear response ranging from 0.1 mg L-1 up to 2.0 mg L-1 sulfate, a detection limit (3σ criterion) of 0.04 mg L-1 sulfate, a relative standard deviation of 1.5% for 0.5 mg L-1 sulfate solution (n = 7), barium chloride consumptions of 17.0 mg per determination, and waste generation of 7.3 mL per determination. Accuracy assessment was achieved by applying the paired t-test between results obtained using the proposed procedure and ICP-OES and showed that there is no significant difference at 95% confidence level.

Sulfur isotopic signatures in rainwater and moss Haplocladium microphyllum indicating atmospheric sulfur sources in Nanchang City (SE China)

Sulfur source identification previously reported has been based on sulfur isotopic ratios in either rainwater or mosses. The δ 34S values of rainwater sulfate and the epilithic moss Haplocladium microphyllum in Nanchang region (China) were determined for comparisons and used to delineate atmospheric sulfur sources. At the urban and rural sites, similar mean δ 34S values were observed between rainwater sulfate (+ 1.6‰ and − 0.2‰, respectively) and epilithic mosses (+ 1.7‰ and + 0.6‰, respectively), suggesting that mosses acquire δ 34S values similar to those found for rainwater sulfate. This has further demonstrated that moss δ 34S signatures hold valuable source-specific information as rainwater δ 34S values do. The δ 34S values of both rainwater sulfate and epilithic mosses indicated that atmospheric sulfur in Nanchang region was mainly associated with coal combustion. The lower δ 34S values at the rural site can be explained by higher contribution of local coals (lower δ 34S values relative to those of north Chinese coals) and biogenic sulfur.

Modelagem dos processos de remoção sulfato e dióxido de enxofre presente no particulado em diferentes localidades da região metropolitana de São Paulo

Este artigo versa sobre a modelagem dos processos de remocao do sulfato no material particulado sulfato e o gas dioxido de enxofre, comparando as condicoes sinopticas, em diferentes locais de coleta, com o intuito de se verificar a dominância dos processos dentro e abaixo da nuvem na Regiao Metropolitana de Sao Paulo (RMSP). Tres locais de amostragens foram escolhidos: GV (Granja Viana) na periferia da RMSP, IAG-USP e no Mackenzie (RMSP centro). Baseando-se nas condicoes sinopticas, foram escolhidos grupos de eventos onde a modelagem numerica foi simulada, usando um modelo simples de remocao. Estas condicoes foram geralmente de nuvens convectivas, sendo as mais comuns na RMSP. Os resultados mostram que os processos dentro da (intra-)nuvem foram dominantes (80%) para a remocao de sulfato/dioxido de enxofre. Os processos de remocao abaixo da nuvem indicaram cerca de 20% deste total. Eventos claramente convectivos, com precipitacao total maior que 20 mm, sao mais eficientemente modelados que os eventos mais estratiformes, com um coeficiente de correlacao de 0,92. Ha tambem uma clara associacao entre eventos de maior precipitacao e a razao entre modelado e observado, com coeficiente de correlacao de 0,63. Adicionalmente, como seria de esperar a respeito da distância as fontes de poluicao, o local de amostragem GV apresentou de modo geral menores concentracoes de sulfato na agua de chuva, tanto modelado como observado, do que a regiao central, no Mackenzie, onde a caracterizacao dos eventos explica parcialmente as diferencas entre as concentracoes em agua de chuva.

Sandstone weathering in tropical climate: Results of low-destructive investigations at the temple of Angkor Wat, Cambodia

Investigations at the temple of Angkor Wat aimed at the explanation of the major weathering processes of building sandstone as well as at the role of both intrinsic factors (i.e. sandstone petrography and properties) and extrinsic factors (i.e. climatic and environmental influences). Since material sampling at the temple was limited to a few boreholes because of the high artistic rank of the building, non-destructive and low-destructive in-situ investigation methods like ultrasonic wave and drilling resistance measurements had to be applied to obtain information about the material properties of sandstone and their changes due to weathering. Moreover, hydric swelling behaviour of the sandstone was determined on undecorated pieces of fallen blocks from the walls. Additional random-test stable isotopic investigations of environmental influences and salts and thorough investigations of the spatial distribution of salts in the ashlars at two selected places with typical weathering patterns completed the set of data. The results demonstrate that the weathering process is mainly triggered by rain–dry-cycles. Salt load found in the stone is composed of gypsum and nitrate compounds. Sulphur stable isotope investigations of potential sources of gypsum lead to the conclusion that soluble components of bat droppings are the major source of salts. Influences of environmental factors like sulphate in rainwater or SO 2 from the air on salt formation are unlikely. Gypsum may reinforce the surface deterioration due to high swelling–shrinking movements of the sandstone (> 1 mm/m) during intensive wetting–drying cycles.

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.