Detection of sulphur dioxide in the air using Scotch pine needles

Air quality is especially important in surface layers, for it is this layer that provides the living components of environment with the needed oxygen and carbon dioxide. Various air polluting gases penetrate cells affecting and contaminating them. Chloroplast shell of some pine species, for instance, doubles under the impact of carbon dioxide which is followed by tillacoids swelling and reduction.Literature provides opinions of some authors, who consider Scotch pine needle to be a biological indicator of sulphur dioxide. Others object to it basing on the observations of physiological development.The property of a Scotch pine as that of biological indicator manifests in SO₂ absorption by its needles. The analysis of total content of SO₂ in the needles shows an increase of SO₂ concentration.Sulphur in the needles is found in the form of organically bound sulphur, aminoacids, hormones as well as in the form of sulphates.Basing on our previous analysis we have generalized the data on the correlation concentrations of sulphur dioxide in the air and general concentrations of sulphur in the needles. We have supplemented the observations with the analyses of organically bound sulphur and concentrations of nonorganic sulphur. According to research data, needles contain a characteristic and rather stable quantity of organically bound sulphur.So we may state that the SO _inf4 ^sup2– concentration and the amount of SO₂ absorbed from the air are interdependent.Some authors state that SO _inf4 ^sup2– content in the soil doesn't affect sulphur content in pine needles. That is why we studied the affect of SO _inf4 ^sup2– content in the soil on sulphur content in Scotch pine needles.We could prove this statement by means of various kinds of analyses only partially. The ion transport is affected by the presence of other ions, pH and a lot of other factors.What may be said for sure is that different qualities of soils gave only minor and insignificant deviations.Hence our assumption about the SO₂ contamination from air, proved by its effect on the soils, turns to suit approximate measurements.     

Sulphate-sulphur levels of topsoils related to atmospheric sulphur dioxide pollution

Sulphate-sulphur levels were determined in topsoils from areas of varying vehicular traffic densities, population densities and industrial activities in Ibadan City, Nigeria. The factors of traffic and population densities, as well as industrial activities, had been shown to correlate positively with ambient sulphur dioxide levels.The soil-SO ₄ ⁼ levels correlated positively with gradients in the factors tested. Vehicular traffic density variations had the most pronounced and significant effect on the SO ₄ ⁼ level trend. The results indicate that soil-SO ₄ ⁼ levels may be indirectly empirically related to ambient sulphur dioxide levels derived from diffuse sources.     

The effect of metals and ammonia on SO2 oxidation to sulphates in the ambient air

The effect of metals and ammonia on the relationship between mass concentrations of sulphur dioxide and sulphate in the air was studied near an aluminium plant over a 1-year period. Sulphur dioxide, sulphates and ammonia in the air as well as metals (Pb, Fe, Mn, Zn, Cu, Cd and Al) in the deposit were measured at four measuring sites.The levels of mass concentrations of SO₂ were low at all measuring sites while the levels of mass concentrations of sulphates in the air and concentrations of metals in the deposit were high. The levels of ammonia were found to decrease in relationship to the distance from the source of pollution.The relationship between the mass concentrations of sulphate and SO₂ can be described by the equation y=ax ^b ;where y is the percentage of sulphate sulphur in the total sulphur (sulphate and SO₂) and x is the mass concentration of the total sulphur in the air. The values of the coefficients a and b are characteristic of individual areas.As the results show the coefficients a and b obtained at a measuring site close to the plant and outside the urban area are characteristic of an industrial area. At control sites in the urban area the coefficients are characteristic of an urban area. At the measuring site close to the industrial zone and the centre of the urban area the interaction of the effects occurs. Therefore, the coefficient a is characteristic of an urban area and b of an industrial one.     

Roadside Concentration of Gaseous and Particulate Matter Pollutants and Risk Assessment in Dar-Es-Salaam, Tanzania

This study used manual air sampling method to assess the contribution of road traffic to air pollution level in Dar-es-Salaam City, Tanzania. Samples were collected from 11 different sites. Parameters measured were: sulphur dioxide using pararosaniline method, nitrogen dioxide using saltzman method, particulate matter and particulate lead using filtration method and atomic absorption spectrometric method, respectively. Results showed that hourly average sulphur dioxide concentration range from 127 to 1385 g/m³. The measured values of sulphur dioxide were above the recommended WHO guidelines with an hourly objective value of 350 g/m³ at 87% of the sampling sites. The hourly average nitrogen dioxide concentration ranged from 18 to 53 g/m³. The maximum hourly nitrogen dioxide concentration at 53 g/m³ was below the WHO guideline value of 200 g/m³. The hourly average suspended particulate matter (SPM) ranged from 98 to 1161 g/m³, exceeding the recommended value of 230 g/m³ by WHO at 87% of the sampling sites. The hourly average lead concentration was found to range from 0.60 to 25.6 g/m³, exceeding again the WHO guideline value of 1.5 g/m³at 83% of the sampling sites. Results predicted by Gaussian model when compared with the measured values were found to have a correlation coefficient of 0.8, signifying a good correlation. The risk assessment was undertaken considering the people who spend a significant portion of their time near the roads, such as the Uhuru primary school pupils and the adult population who reside by the roadside. The unit risk realised was 18.2 × 10^–6 for adult population and 2.2 × 10^–6 for pupils, both scenarios showing risk higher than the United Sates of America Environmental Protection Agency (USEPA) acceptable limit of 1× 10^–6. Considering the magnitude of the problem at hand, this study recommends an introduction of mandatory emission tests of SPM, lead and sulphur dioxide (SO₂). The study further recommends the introduction of continuous and/or regular air quality monitoring and the use non-leaded petrol in Tanzania.     

In search of a recyclable sulphur dioxide sponge—a new look at an old system

The sulphur dioxide content and thermal stability of the quinol-SO₂ clathrate have been studied by thermogravimetric analysis (TG), its derivative (DTG) and differential scanning calorimetry (DSC). These analyses demonstrated the thermal recoverability of the quinol from the clathrate and hence its potential use as a sponge for SO₂ present in the environment as a pollutant. Similarly, Bu₄N⁺I^- was found to occlude NO₂ and SO₂ at 50°C in solution.     

Using Archive Data to Investigate Trends in the Sources and Composition of Urban PM10 Particulate Matter: Application to Edinburgh (U.K.) Between 1992 and 1997

By extending the method of Stedman (1998), daily dataof atmospheric concentrations of gravimetricPM₁₀, black smoke (BS) and sulphate aerosol (SA)from national networks were analysed to determine thetrends in time of the contribution of different sources of particulate matter to total PM₁₀ measured in central Edinburgh. Since BS is an indicator of combustion-related primary sources of particulate matter, the quantity obtained by subtraction of daily BS from daily PM₁₀ is indicative of the contribution to total PM₁₀ from other primary sources and from secondary aerosol. This PM₁₀-BS statistic was regressed on SA, since SA is an indicator of variation in secondary aerosol source. For Edinburgh, SA is a considerably better indicator of PM₁₀-BS during summer than winter (reflecting the much greater photochemical generation of secondary aerosol in summer) and there is evidence that the contribution of other secondary aerosol (presumably nitrate aerosol) has increased relative to SA between 1992 and 1997. The concentration of non-combustion primary particulate material (marine aerosol, suspended dust) to PM₁₀ in Edinburgh has not changed over this period but is about twice that calculated as the U.K. national average. The increasing input to PM₁₀ from secondary aerosol sources at regional rather than urban scale has important implications for ensuring local air quality compliance. The method should have general applicability to other locations.     

南京北郊气溶胶散射特性观测研究

南京北郊是重工业区,空气污染严重。该文利用浊度仪对大气气溶胶散射系数进行了四季观测,研究了该区气溶胶散射系数、后向散射比、质量散射系数及散射系数与能见度的关系,结果表明,观测期间散射系数波动较大,平均值为344.84 Mm^-1,标准差为215.99 Mm^-1,散射系数季节差异明显,主要受气象条件和外界污染排放的影响;后向散射比平均值为0.139,春季变化剧烈,夏、秋、冬季在波动中缓慢上升,大气中细粒子污染严重且含量有增加的趋势;散射系数与PM_2.5质量浓度相关系数达到0.91,质量散射系数平均值为1.87m²/g;散射系数与能见度之间存在-0.66的相关性,两者呈负幂函数关系。     

Field Survey of Trans-boundary Air Pollution with High Time Resolution at Coastal Sites on the Sea of Japan during Winter in Japan}

An intensive field survey, with 6-h measurement intervals, of concentrations of chemical species in particulate matter and gaseous compounds was carried out at coastal sites on the Sea of Japan during winter. The concentration variation of SO₂(g) and HNO₃(g) were well correlated, whereas the NH₃(g) concentration variation had no correlation with those of SO₂(g) and HNO₃(g). The NH₄ ⁺ (p)/non-sea-salt- (nss-)SO₄ ^{2 −}(p) ratio in particulate matter was mainly affected by the location of the sampling site. One or more concentration peaks of nss-Ca^{2 +} for survey period were observed. Backward trajectories analyses for the highest nss-Ca^{2 +} concentration peaks showed some inconsistency in pathways. We consider that insufficient mixing of the atmosphere and/or insufficient time for the transported air pollutants to react with those discharged locally are the most likely explanations for the discrepancies between the measured products [HNO₃][NH₃] and the calculated values.     

Comparisons of Geochemical Signatures of Biotransformation of Fuel Hydrocarbons in Groundwater

Biotransformation processes play an active role in reducing the environmental impact of fuel hydrocarbon releases to groundwater. Because monitoring data at release locations are typically sparse, spatial variations in geochemical indicator parameters are often called upon as indirect evidence of biotransformation. These parameters include concentrations of electron acceptors (O₂, NO₃ ^-, SO> ₄ ^2- , reduced redox reaction by-products (Fe²⁺, Mn²⁺, CH₄), as well as bicarbonate alkalinity, pH and E_h. However, background variability in a number of these parameters complicates the task of data interpretation, particularly in the case of small data sets. In this study, correlation analyses are applied to geochemical indicator data at six hydrocarbon groundwater contamination sites in California to identify which parameters are the most reliable indicators. The results of the analyses suggest that the most direct indicators of the local redox environment – Fe²⁺, Mn²⁺, CH₄, E_h – yield the most consistent evidence of hydrocarbon biotransformation. Indicators which rely largely on mass balance – O₂, NO ₃ ^- , SO ₄ ^2- , alkalinity – appear to be less reliable. These findings may provide guidance in both the collection and interpretation of groundwater monitoring data at hydrocarbon contamination sites.     

The characteristics of size distribution of suspended particulates in the air for sulphates and selected metals in different areas and seasons

The characteristics of the distribution of particles by size were investigated for sulphates and selected metals (Pb, Fe, Mn, and Cu) in the air in two urban and an industrial area during the winter and summer periods using an Andersen cascade impactor.In the case of metals, but not sulphates, the character of the area affected the value of mass median diameter. Lowest values were obtained in a sparsely populated urban area, whereas in a densely populated urban area and in the industrial area the values were higher.In the industrial area a high correlation coefficient was found between sulphate and manganese, and between sulphate and lead, as well as a high value of the equivalent Mn²⁺/SO _inf4 ^sup2- ratio for the total sample. It may therefore be assumed that in the industrial area manganese produces a catalytic effect on SO₂ conversion to sulphate. Among the investigated metals lead stands out as a dominant cation which binds to the sulphate ion in the industrial and densely populated areas.     

Effects of acid deposition on watershed ecosystems of national parks in the great lakes basin

Legally protected national parks provide an appropriate substrate for essential long-term study of ecosystem structure and function, and for detecting trends in natural and human-induced stress. The absence of unplanned site manipulation in such areas is especially valuable for such research. Our present research has two major components. The first is the long-term ecosystem-level study of the effects of atmospheric contaminants on ecosystem processes. The overall objective is to evaluate ecosystem aquatic/terrestrial linkages and their role in establishing aquatic ecosystem sensitivity to anthropic atmospheric inputs. Four watershed/lake ecosystems, representative of much of the region's diversity, are under study. Two mature boreal sites on Isle Royale are characterized by first-order perennial surface stream input and lake outflow. Two additional mainland northern hardwood sites, one with shallow soils and one with soils derived from glacial till, are characterized by sensitive aquatic systems. One site is in a private reserve and the other in Pictured Rocks National Lakeshore. Surface outflow is gaged by Parshall flume and stage height recorder. Meteorological stations record variables for estimating evapotranspiration. One-tenth ha plots have been established in all watersheds and three sites have had intensive study of precipitation modification by canopy and forest soil. Five-year mean maximum and minimum lake pH varies from 6.85 to 4.94, Ca²⁺ from 1070 to 54 eq l^-1, K⁺ from 5.42 to 8.35 eq l^-1, NH ₄ ⁺ from 10.12 to 3.23 eq l^-1, HCO ₃ ^sup- from 635 to 24 eq l^-1, NO ₃ ^sup- from 3.27 to 1.54 eq l^-1, and SO ₄ ^sup2- from 110 to 52.7 eq l^-1. The relatively high NO ₃ ^sup- values observed in one lake are the result of stream drainage from a watershed dominated by Alnus rugosa, and another has high seasonal NO ₃ ^sup- inputs during spring runoff. However, owing to periodic winter thaws, significant snowpack release of nutrients generally precedes maximum spring stream runoff. Water chemistry in both sensitive and non-sensitive lakes appears to be primarily reflecting how the conterminous terrestrial system is retaining atmospheric inputs more than the quality of direct lake atmospheric input. This is especially evident for H⁺, NO ₃ ^sup- and SO ₄ ^sup2- .The second component is the assessment of watershed acidification, SO ₄ ^sup2- output and soil retention across an input gradient. An anthropic deposition gradient provides the opportunity for intersite time-trend analyses as to the effects of inputs. Our study objective was to see if the decreasing west to east input/output values for SO ₄ ^sup2- , noted in small first-order watersheds in national parks from Minnesota to Ohio, might be related to present atmospheric inputs, potential and total soil SO ₄ ^sup2- adsorption, or soil SO ₄ ^sup2- desorption from earlier higher inputs. Precipitation pH ranged from 5.05 at Fernberg, Minnesota to 4.24 at Wooster, Ohio. Minimum and maximum concentrations of NH ₄ ⁺ , NO ₃ ^sup- , SO ₄ ^sup2- and Cl^- were also found at these stations. Stream water concentrations of NO ₃ ^sup- and SO ₄ ^sup2- increase in a similar but sharper gradient. Streams are well buffered. Cation, HCO ₃ ^sup- , NO ₃ ^sup- and especially SO ₄ ^sup2- output increase west to east, but H⁺ output decreases. At the eastern site stream SO ₄ ^sup2- concentration and output exceed HCO ₃ ^sup- . Potential soil SO ₄ ^sup2- adsorption capacity increases eastward, but this capacity is filled. Crystalline Fe hydrous oxides appear more effective than amorphous Fe hydrous oxides at adsorbing SO ₄ ^sup2- . High anthropic anion inputs, inability of forest soil to adsorb additional inputs and perhaps SO ₄ ^sup2- desorption appear responsible for the replacement of HCO ₃ ^sup- by SO ₄ ^sup2- in stream water. The major cation accompanying SO ₄ ^sup2- is Ca²⁺.Contribution from Fourth World Wilderness Congress—Acid Rain Symposium, Denver (Estes Park), Colorado, September 11–18, 1987.     

Evaluation of the effects of acid precipitation in eastern Canada using the raison system

Evaluations have been made of the key chemical factors in the aquatic effects upon surface waters due to acidic precipitation in eastern Canada. The region of Canada east of the Manitoba/Ontario border was divided into 22 aggregates and assessments of inorganic and organic ion chemistry appraised relative to sulphate deposition rates and distributions. Aquatic sensitivity is largely dominated by the concentration, distribution and magnitude of SO _inf4 ^sup2- (sulphate) deposition and by the prevalent geology and derived soils found in each aggregate. The RAISON system provided an adaptable and highly flexible platform to evaluate interactively, multiple data sets of divergent characteristics. Attributes usually associated with geographical information systems are significantly augmented by quantitative numerical and stochastic capabilities that were used extensively in this study.     

重庆市主城区大气水溶性离子在线观测分析

2015年12月—2016年3月期间,利用在线气体与气溶胶成分监测仪(IGAC)在重庆市大气超级站开展连续观测分析,并捕捉到2次持续时间较长的空气重污染过程。对PM_(2.5)中9种水溶性离子及5种气态前体物的观测结果分析表明:NO_3~-、NH_4~+和SO_4~(2-)是重庆市主城区PM_(2.5)中主要的水溶性离子成分,其浓度均表现出明显的日变化特征,主要以(NH4)_2SO_4和NH_4NO_3的形式存在。NH_3和SO_2是最主要的气态污染物。2次重污染过程的水溶性离子组分有明显差异,细颗粒物累积型污染的NH_4~+、SO_4~(2-)、NO_3~-浓度高,二次转化十分明显;春节期间烟花爆竹集中燃放,Cl~-、K~+浓度高,主要属于一次排放;污染期间主要离子组分的同源性特征显著。     

Visibility impairing aerosols in the urban atmosphere of Delhi

To study the visual air quality of Delhi, size fractionated aerosols – coarse and fine fractions of PM₁₀ – were collected and analysed for and EC at three sites with different background activities. The analysed species constitute a smaller portion of coarse fraction (39%) but a larger portion of fine fraction (69%). The sampling was performed from June 2003 to November 2003 which covers monsoon and post monsoon seasons.Aerosol data was used to describe the spatial variation of Visibility Range as a function of chemical composition of visibility impairing aerosols. During the study period, visibility was found to be poor varying between 4.7 and 13 km with an average value of 9.4 km. It is observed that visibility impairment was more due to carbonaceous aerosol followed by sulphate.     

Inorganic Ion Levels of Soils and Streams in some Areas of Ogoniland, Nigeria as Affected by Crude Oil Spillage

The inorganic ion concentrations of soils and streams in the three locations (Yorla, Zaakpon and Goi) in Ogoniland,Nigeria affected by crude oil spillage were investigated. In general, inorganic ion concentrations of polluted soilsand streams varied significantly (p = 0.05) from those of unpolluted soils and streams. Anions such as nitrate (NO ₃ ^- ), sulphate (SO ₄ ^2- ) and chloride(Cl^-) showed significantly (p = 0.05) higher values inthe polluted soils and steams than in the unpolluted controls. The phosphate (PO ₄ ^3- ) values were lowerin the polluted soils and streams than in the unpolluted controls.PO ₄ ^3- , NO ₃ ^- , SO ₄ ^2- and Cl^- concentrations were generally significantly (p = 0.05) higher in soils and streams from Yorla, Zaakpon and their control than in Goi North, Goi South and Goi control.Exchangeable cations and trace metal concentrations weresignificantly (p = 0.05) higher in the polluted soils andstreams than in the unpolluted controls. Yorla and Zaakponpolluted soils and streams had higher concentrations of theexchangeable cations and trace metals compared to valuesfrom Goi, except for Na. Results also showed significantlyhigher values of heavy metals (Pb, Cd, Cr and Ni) in the polluted soils compared to their controls, and values werealso significantly (p = 0.05) higher in Yorla, Zaakpon andtheir control compared to Goi North, Goi South and Goicontrol. Values obtained in polluted streams were higherthan in the unpolluted though not significant at the 5%level (p = 0.05). The anionic and cationic concentrationsof Yorla and Zaakpon soils and streams were generally higherthan those of Goi, indicating that Yorla and Zaakpon areaswere more polluted than Goi.Although the concentrations of most of the anions andcations analysed in the polluted soils and streams werewithin the World Health Organisation's permissible valuesfor the protection of humans and environment, the streams ofYorla, Zaakpon and Goi are in general being polluted withinorganic ions. This may make these soils and streamsunacceptable for domestic and industrial uses if not treated,and soils (farmlands) may also become unsuitable for agricultural purposes.     

Biochemical responses in tree foliage exposed to coal-fired power plant emission in seasonally dry tropical environment

A biomonitoring study was conducted to investigate the responses of plants exposed to power plant emission in a dry tropical environment. For this purpose, five sampling sites were selected in the prevailing wind direction (NE) at different distance to thermal power plant (TPP) within 8.0 km range and a reference site was selected in eastern direction at a distance of 22.0 km. The two most common tree species, Ficus benghalensis L. (Evergreen tree) and Dalbergia sisso Roxb. (deciduous tree) were selected as test plants. Ambient sulphur dioxide (SO(2)), nitrogen dioxide (NO(2)), suspended particulate matter (SPM), respirable suspended particulate matter (RSPM), dust-fall rate (DFR) and plant responses such as leaf pigments (chlorophyll a, chlorophyll b and carotenoids), ascorbic acid, sugar and sulphate-sulphur (SO4(2-)-S) contents were measured. Ambient SO(2), NO(2), SPM, RSPM and DFR showed significant spatial and temporal variation at different sites. Considerable reduction in pigment (chlorophyll a, chlorophyll b and carotenoids) and sugar contents were observed at sites receiving higher pollution load. Ascorbic acid exhibited significant positive correlation with pollution load. Accumulation of SO4(2-)-S in leaf tissue showed significant positive correlation with ambient SO(2) concentration at all the sites. At the same time, SO4(2-)-S showed significant negative correlation with pigment and sugar content. D. sisso Roxb. tree was found to be more sensitive as compared to F. benghalensis L. tree.     

北京市典型重污染过程中PM2.5载带水溶性无机离子污染特征分析

为研究北京地区冬季PM_(2.5)载带的水溶性无机离子组分污染特征,2013年1月在中国环境科学研究院内采用在线离子色谱(URG-9000B,AIM-IC)对PM_(2.5)中水溶性无机离子(SO_4~(2-)、NO_3~-、Cl~-、NH_4~+、Na~+、K~+、Mg~(2+)、Ca~(2+))进行监测与分析。结果表明,采样期间总水溶性无机离子(TWSI)浓度为61.0μg/m~3,其中二次无机离子SO_4~(2-)、NO_3~-、NH_4~+(SNA)占比达72.3%,在PM_(2.5)中占比为40.29%,表明北京市PM_(2.5)二次污染严重。重污染天[NO_3~-]/[SO_4~(2-)]表明,固定源污染较移动源更为显著。三元相图表明,在空气质量为优的情况下,NH_4~+(在SNA中占比为30.3%~65.5%,下同)主要以NH_4NO_3的形式存在,较少比例以(NH_4)_2SO_4存在;严重污染时,NH_4~+(47.3%~77.9%)主要以(NH_4)_2SO_4形式存在,其次以NH_4NO_3的形式存在,其余的NH_4~+以NH_4Cl的形式存在。[NO_3~-]/[SO_4~(2-)]日变化表明,早、晚机动车高峰影响北京重污染发生。     

Atmospheric Aerosols over a Southwestern Region of Texas

Speciated samples of PM_2.5 were collected at the Big Bend site from July of 2003 to June 2006 and the McDonald Observatory site from July of 2003 to August of 2005 in southwestern Texas, respectively, by the US Environmental Protection Agency. A total of 175 samples for the Big Bend site and 105 samples for the McDonald Observatory site with 52 species were measured; however, 30 and 32 species from the Big Bend and McDonald Observatory sites, respectively, were excluded because of too much below-detection-limit data. Due to the laboratory change about November 1 of 2004 and possible analytical artifacts, phosphorous was excluded as well. Among the species excluded, 31 species are common to both sites. The two data sets were analyzed by positive matrix factorization to infer the sources of PM observed at the two sites. The analysis resolved five source-related factors for Big Bend and four for McDonald Observatory. Sulfate-rich secondary aerosol, coal burning, motor vehicle/road dust, and a mixed factor were identified as common sources to both sites. The other factor identified for Big Bend is related to soil. Sulfate mainly exists as ammonium salts. The sulfate-rich secondary aerosols account for about 62% and 66% of the PM_2.5 mass concentration at the two sites, respectively. The highest concentration of Si associated with Ca, Fe, \textSO₄^{2 -} {\text{SO}}_4^{2 - } , and organic carbon at the two sites was possibly attributed to the coal-fired power plants in the region. Basically, the factor of sulfate and coal burning at the two sites showed similar chemical composition profiles and seasonal variation that reflect the regional characteristics of these sources. The regional factors of sulfate, coal burning, and soil showed predominantly low-frequency variations; however, the area-related and/or local factors showed both high and low frequency variations. The motor vehicle/road dust and the mixed factors were likely to be area-related and/or local source.     

1997—2010年北京市大气降水离子特征变化趋势研究

依据北京市环境保护监测中心1997—2010年降水监测资料,分析北京地区降水中离子特征及变化趋势,阐明北京市降水污染现状及变化特征。结合北京市特有的气象条件、地形地貌和工业分布情况,分析污染物来源及污染变化趋势。研究表明:年度降水电导率呈现波动变化,降水污染严重程度依次为南部郊区>市区>北部背景点。北京地区大气降水中的主要阳离子成分是Ca²⁺和NH₄⁺,主要阴离子成分是SO₄^2-和NO₃^-。近年来[SO₄^2-]/[NO₃^-]比值逐步下降,污染类型由典型硫酸型发展为硫酸+硝酸混合型。阳离子[Ca²⁺]/[NH₄⁺]比值下降,碱性离子缓冲能力降低。9种离子各季节浓度变化趋势基本一致,由高到低依次是春季>秋季>冬季>夏季,这种季节变化特征与气象因素密切相关。相关性及聚类分析表明:NO₃^-与SO₄^2-存在很强相关性,说明其前体物SO₂和NO_X在大气中经常一同排放且进入降水途径相同;H⁺浓度不是由某个离子决定,是所有致酸离子和中和离子相互作用的结果,而NH₄⁺来源不同于其它离子,北京地区的氨存在其单独排放源。     

重庆市黔江区降水地球化学特征

为了解生态旅游城市重庆市黔江区大气污染状况,2015年采集了91个降水样品,分析了降水中离子组分分布特征,运用富集因子法、海盐示踪法、相关性分析、主成分分析、聚类分析和HYSPLIT模型分析了降水化学组分来源。研究结果表明:黔江区域降水p H为5.66~6.96,加权平均值为6.34,降水离子组分浓度大小次序为SO_4~(2-)Ca~(2+)NH_4~+Mg~(2+)NO_3~-Cl~-Na~+K~+F~-,SO_4~(2-)、Ca~(2+)之和占总离子的63.95%;除Mg~(2+)和K+外,其余组分离子浓度与总离子浓度随季节变化(冬季春季秋季夏季)呈同样的变化特征。Ca~(2+)、Mg~(2+)和K+大部分均来源于陆源贡献,Na~+可能受到了海洋源的影响,SO_4~(2-)和NO_3~-主要来源于人为输入源的贡献,Cl~-是受土壤物质和海洋的双重影响。轨迹水汽运输结果表明:黔江区域的降水主要受到西北气团、西南季风、西风环流和极地气候共同作用输入。降水中各个离子组分均表现出显著性或极显著性关系,主成分分析结果表明,第一主成分上研究的降水离子组分中都具有相对较大正载荷,第二组分pH、降水量和气温为一类。