Elements in the precipitation of S. Paulo City (Brazil)

Rainwater samples in S. Paulo city were collected on an event basis from October 1983 to October 1985 covering two dry and two rainy periods. Bulk samples only were obtained. At the same site and period, fine, coarse and inhalable particles were also collected. Na⁺, Ca²⁺, K⁺, Mg²⁺, NO₃⁻, SO₄²⁻ and NH₄⁺ contents were determined in rainwater samples, while Na, Ca, K, Cl and S concentrations were measured in aerosol samples. Rainwater is slightly acid (mean pH = 5.0), and contains high concentrations of Ca²⁺, NO₃⁻, SO₄²⁻ and NH₄⁺. Dry and wet fluxes and washout ratios were determined for some elements. Results obtained suggest that the atmospheric composition in this city is strongly influenced by anthropogenic sources.     

A chemical characterization of atmospheric aerosol in Sapporo

Monthly mean chemical composition of aerosol with diameter less than 8 μm was identified in Sapporo in 1982. The mass of aerosol was made up of nine components: elemental C, organics, SO₄²⁻, NO₃⁻, NH₄⁺, Cl⁻, Na⁺, soil particles and water. The concentrations of carbonaceous particles (elemental C and organics) was relatively high (12.7–16.0μ m⁻³) in autumn and winter (October–February) due to emission from domestic heating and comprised 36–41% of total aerosol mass. Higher concentration of soil particles was observed in spring (March–May) (9.7–13.1 μg m⁻³) and comprised 22–29% of total aerosol mass due to suspension by strong wind. On the other hand, the concentration of excess SO₄²⁻ (non-sea salt SO₄²⁻), which ranged from 2.6–5.2 μg m⁻³, did not change remarkably with season, and the fraction of excess sulfate increased to 21% in summer (July–August) probably due to photochemical transformation from SO₂. Nitrate concentration was far less than that of SO₄²⁻ throughout the year in Sapporo.     

Rainwater composition in Athens,Greece

Wet precipitation-only samplers were used to collect wet deposition at two sites in the Athens basin, Greece for the period March 1986–February 1987.Concentrations of major cations (H⁺, NH⁺₄, Na⁺, K⁺, Ca²⁺ and Mg²⁺) and major anions (Cl⁻, NO⁻₃ and SO²⁻₄) were determined for the first time in rainwater samples in Greece. Bicarbonate concentrations were calculated. The relative importance of natural and anthropogenic sources were estimated by a chemical balance. The majority of rain collected has a neutral or alkaline character. Acidity was due to the presence of H₂SO₄ and HNO₃. The statistical analysis of the correlation between the concentration of chemical species confirm the influence of natural and anthropogenic sources. In all samples, SO²⁻₄ concentrations exceed NO⁻₃ concentrations despite the dominance of low S oil burning in the region. The wet flux of S was calculatd to be 0.34 gm⁻²a⁻¹.     

Transfer of atmospheric constituents into an alpine snow field

Simultaneous aerosol and snow sampling was performed during a field campaign at the Alpine site Weissfluhjoch Davos, Switzerland (2540 m a.s.1.) from 1 January through 30 March 1988. In addition, a snow pit was sampled on 30 March 1988. Very good agreement between the new snow and pit snow samples was found for the measured major ions as well as for the stable isotopes δ¹⁸O and δD. Thus, snow pit samples obtained at this site during the winter months yield representative deposition patterns with a conserved stratigraphy. Generally, concentrations in snow were very low, with 3.5, 8.5, 5.2 and 2.4 μeq ℓ⁻¹ for Cl⁻, NO₃⁻, SO₄²⁻, respectively. The ³⁶Cl and ¹⁰Be concentrations as well as the ¹⁰Be/³⁶Cl ratios were comparable to the ones measured at Arctic sites. With the exception of NO₃⁻, no linear relation was obtained between atmospheric and snow concentrations, showing that the concept of scavenging ratios must be used with caution when looking at single snowfall events. The following precipitation-weighted mean scavenging ratios were found: 300 for NH₄⁺, 350 for SO₄²⁻, 940 for total NO₃⁻(NO₃⁻+HNO₃), 175 for ²¹⁰Pb, and 750 for ¹⁰Be.     

Chemical characterization of acid precipitation in Albany,New York

Chemical composition of precipitation in Albany, NY from July 1986 to December 1988 has been studied. Mean volume-weighted concentrations (μeq^ℓ−1) were: acidity, 104.0; alkalinity, −63.7; SO₄²⁻, 52.8; NO₃⁻, 29.8; Cl⁻, 5.6; F⁻, 0.50; NH₄⁺, 19.3; Ca²⁺, 6.5; Mg²⁺, 2.8; Na⁺, 3.5; and K⁺, 1.4. Mean pH was 4.2 . Seasonal patterns were pronounced for most species. Concentrations of H⁺, SO₄²⁻, NO₃⁻, NH₄⁺ and Ca²⁺ peaked in the summer and spring. Deposition was related to rainfall amount by a power law relationship in which the exponent of the equation was ∮.6. Wet SO₄²⁻ deposition was 2.35 keq ha⁻¹ over a 30-month period. The SO₄²⁻ and NO₃⁻ deposition rates observed at Albany indicate that transport from midwestern sources have a major influence at this site. On the average, free H⁺ ion concentrations determined from pH measurements accounted for 51% of the measured total acidity. There were unknown species, most likely organic acids, that could contribute to the acidity. Correlation and regression analyses indicated that major anions, SO₄²⁻ and NO₃⁻, were closely associated with H⁺ and NH₄⁺ ions. Factor analysis revealed four common factors which are related to fossil-fuel combustion, sea spray, cement factory and biomass burning.     

Fogwater chemistry at Riverside,California

Fog, aerosol, and gas samples were collected during the winter of 1986 at Riverside, California. The dominant components of the aerosol were NH₄⁺, NO₃⁻, and SO₄₂₋. Gaseous NH₃ was frequently present at levels equal to or exceeding the aerosol NH₄⁺. Maximum level were 3800, 3100, 690 and 4540 neq m⁻³ for NH₄⁺, NO₃²⁻ and NH_3(g), respectively. The fogwater collected at Riverside had very high concentrations, particularly of the major aerosol components. Maximum concentrations were 26,000 29,000 and 6200 μM for NH₄⁺, NO₃⁻ and SO₄²⁻, respectively. pH values in fogwater ranged from 2.3 to 5.7. Formate and acetate concentrations as high as 1500 and 580 μM, respectively, were measured. The maximum CH₂O concentration was 380 μM. Glyoxal and methylglyoxal were found in all the samples; their maximum concentrations were 280 and 120 μM, respectively. Comparison of fogwater and aerosol concentrations indicates that scavenging of precursor aerosol by fog droplets under the conditions at Riverside is less than 100% efficient.The chemistry at Riverside is controlled by the balance between HNO₃ production from NO_x emitted throughout the Los Angeles basin and NH₃ emitted from dairy cattle feedlots just west of Riverside. The balance is controlled by local mixing. Acid fogs result at Riverside when drainage flows from the surrounding mountains isolate the site from the NH₃ source. Continued formation of HNO_3(g) in this air mass eventually depletes the residual NH_3(g). A simple box model that includes deposition, fog scavenging, and dilution is used to assess the effect of curtailing the dairy cattle feedlot operations. The calculations suggest that the resulting reduction of NH₃ levels would decrease the total NO₃⁻ in the atmosphere, but nearly all remaining NO₃⁻ would exist as HNO₃. Fogwater in the basin would be uniformly acidic.     

青岛大气气溶胶水溶性无机离子研究:季节分布特征

为了全面了解当前青岛地区大气气溶胶中水溶性组分的特征及来源,于2008年1～12月在青岛市区连续采集了总悬浮颗粒物(TSP)样品,运用离子色谱法对其主要的水溶性阴阳离子进行了分析.结果表明,SO24-、NO3-、NH4+和Cl-是TSP中水溶性离子的主要成分,四者质量浓度之和占总水溶性离子质量浓度的86.9%.TSP及其水溶性组分存在明显的季节变化,其来源也存在多源性.Na+、NH4+、Ca2+、F-、Mg2+均为冬季最高,夏季最低,K+、PO34-为秋季最高,夏季最低,Cl-为冬季最高,秋季最低,NO3-则为春季最高,夏季最低,而SO24-为春季最高,秋季最低.不同天气对颗粒物和气溶胶中水溶性离子影响很大.颗粒物浓度在晴天时最低,其次是雾天,再次是烟雾和霾,沙尘天气下质量浓度最高.Na+、Mg2+、Ca2+、F-、Cl-和PO34-在烟雾天气下的平均浓度最高,而NH4+、K+、NO3-和SO24-则是在霾天气下质量浓度最高.     

Factor analysis of trends in Texas acidic deposition

Precipitation chemistry data collected between 1980 and 1987 for 11 NADP/NTN sites in Texas have been analyzed using factor analysis and a trend analysis of monthly averages. Factor analysis identified four major factors which differed significantly from site to site: (1) a Gulf factor of Na⁺, Cl^-, and Mg²⁺; (a) a soil factor of Ca²⁺, K⁺, Na⁺, and Mg²⁺; (3) an acid factor of H⁺, NO₋³, and SO₄⁴⁻; and (4) an aged aerosol factor of NO₃⁻, SO₄²⁻, and NH₄⁺. At Longview, the acid and Gulf factors accounted for 18 and 46%, respectively, of the variation of the data. A trend analysis was performed on the logarithm of the monthly averages at the Longview and Victoria sites, the two sites with the largest and most complete data. Results suggest that hydrogen ions have been increasing at both sites, while calcium ions have been decreasing.     

Chemical composition of rain in Thessaloniki,Greece, in relation to meteorological conditions

Wet precipitation was collected in Thessaloniki, Greece, during the period March 1989–December 1990 by using an automatic wet-only precipitation sampler.Rainwater samples were analysed for major cations (H⁺, NH₄⁺, Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (Cl⁻, NO₃⁻, SO₄²⁻), in addition to acidity and conductivity measurements. The majority of rain had a neutral or alkaline character as a result of neutralization, primarily caused by calcareous soil dust and secondarily by atmospheric ammonia. In all rain, SO₄²⁻ concentration exceeded NO₃⁻ concentration. The contribution of maritime sources to the total SO₄²⁻ concentration was very low (<2%).The chemical composition of precipitation was analysed in conjunction with meteorological variables (season of the year, precipitation type, airflow patterns) to evaluate temporal variations and chemical source influence. Rain caused by weak, localized flows showed the highest acidity and the minimum influence of neutralization processes.     

Spatial and temporal patterns in summertime sulfate aerosol acidity and neutralization within a metropolitan area

A study of sulfate aerosol acidity in Metropolitan Toronto was conducted during the summer of 1986. Fine-fraction aerosol (<2.5-μm) were collected using Teflon membrane filters and analyzed for major ionic species (H⁺, NH⁺₄, NO⁻₃, SO²⁻₄). Samples were collected for 6 weeks at three study sites: one in the Center City and the others 13 km (WNW) and 20 km (NE) away. There were very strong correlations among the three sites with respect to measured aerosol species (r² > 0.9 for 24-h data). However, spatial variations in the magnitude of aerosol acidity were observed during sulfate episodes. For example, the peak concentrations for all sites occurred on 25–26 July 1986. While the 24-h data for sulfate were quite uniform at the three sites (34, 34 and 35 μg m⁻³), H⁺ concentrations were 9.4, 8.3 and 6.0 μg m⁻³ (as H₂SO₄) for the NE, WNW and Center City sites, respectively. For most of the summertime episodes, the downtown area also had lower aerosol acidity compared to the two sites in suburban areas.     

A comparison of urban and suburban precipitation chemistry

Precipitation samples at an urban Chicago site and a nearby suburban site were compared in order to examine the influence of emissions within a large urban area on local precipitation chemistry. Precipitation samples were collected from June 1981 to May 1982, initially for events and subsequently weekly, and precipitation-weighted concentrations (PWCs) of the major chemical constituents were calculated from concurrent urban-suburban pairs of samples, stratified according to the estimated mixed-layer wind quadrant. Overall, PWCs at the urban site were higher than those at the suburban site for Ca²⁺, Mg²⁺, NH₄⁺, NO₃⁻ and Cl⁻; approximately equal for Na⁺ and SO₄²⁻; and lower for H⁺. For precipitation in southwesterly flow, in which the suburban site was upwind of the urban site and most urban emissions, PWCs of all species except Na⁺ were higher at the urban site. For the few precipitation cases in northeasterly flow, however, differences between sites did not have a pattern consistent with a reversal in the upwind-downwind relationship.     

Origin of soluble chemical species in bulk precipitation collected in Tokyo,Japan: Statistical evaluation of source materials

An iterative least-squares method with a receptor model was applied to the analytical data of the precipitation samples collected at 23 points in the suburban area of Tokyo, and the number and composition of the source materials were determined. Thirty-nine monthly bulk precipitation samples were collected in the spring and summer of 1987 from the hilly and mountainous area of Tokyo and analyzed for Na⁺, K⁺, NH₄⁺, Mg²⁺, Ca²⁺, F⁻, Cl⁻, Br⁻, NO₃⁻ and SO₄²⁻ by atomic absorption spectrometry and ion chromatography. The pH of the samples was also measured. A multivariate ion balance approach (Tsurumi, 1982, Anal. Chim. Acta138, 177–182) showed that the solutes in the precipitation were derived from just three major sources; sea salt, acid substance (a mixture of 53% HNO₃, 39% H₂SO₄ and 8% HCl in equivalent) and CaSO₄. The contributions of each source to the precipitation were calculated for every sampling site. Variations of the contributions with the distance from the coast were also discussed.     

A comparison of two cloudwater/fogwater collectors: The rotating arm collector and the caltech active strand cloudwater collector

A side-by-side comparison of the Rotating Arm Collector (RAC) and the Caltech Active Strand Cloudwater Collector (CASCC) was conducted at an elevated coastal site near the eastern end of the Santa Barbara Channel in southern California. The CASCC was observed to collect cloudwater at rates of up to 8.5 ml min⁻¹. The ratio of cloudwater collection rates was found to be close to the theoretical prediction of 4.2:1 (CASCC:RAC) over a wide range of liquid water contents (LWC). At low LWC, however, this ratio climbed rapidly, possibly reflecting a predominance of small droplets under these conditions, coupled with a greater collection efficiency of small droplets by the CASCC. Cloudwater samples collected by the RAC had significantly higher concentrations of Na⁺, Ca²⁺, Mg²⁺ and Cl⁻ than those collected by the CASCC. These higher concentrations may be due to differences in the chemical composition of large vs small droplets. No significant differences were observed in concentrations of NO₃⁻, SO₄²⁻ or NH₄⁺ in samples collected by the two instruments.     

Scavenging ratios and deposition of sulphur,nitrogen and chlorine species in eastern England

Measurements of wet deposited NH₄⁺, SO₄²⁻, NO₃⁻ and Cl⁻, as well as airborne concentrations of these species and gaseous HNO₃, HCl and NH₃, have been made at a site in eastern England. Scavenging ratios based solely upon aerosol-associated species and upon aerosol plus gaseous airborne species are presented and compared with literature values. It appears that HCl and HNO₃ have only a rather minor influence upon wet deposition at our site. Gaseous NH₃ influences ground-level air chemistry appreciably, but scavenging ratios for NH₄⁺ are low, even when based upon aerosol NH₄⁺ concentrations alone, presumably due to altitudinal gradients in this species. The problems inherent in interpretation of scavenging ratios are discussed. Deposition of nitrogen in various chemical forms is estimated from rainwater and air composition. If a transport-limited deposition velocity is assumed for ammonia gas, dry deposition of this species accounts for around 40% of total nitrogen deposition to the ground.     

Atmospheric dry deposition on pines in the Eastern Brook Lake Watershed,Sierra Nevada,California

Atmospheric dry deposition to branches of Pinus contorta and P. albicaulis was measured during summer 1987 in a sub-alpine zone at Eastern Brook Lake Watershed (EBLW), eastern Sierra Nevada, California. Results are presented as deposition fluxes of NO₃⁻, SO₄²⁻, PO₄³⁻, Cl⁻, F⁻, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺, Zn²⁺, Fe³⁺, Mn²⁺, Pb²⁺ and H⁺, and compared with other locations in California and elsewhere. Deposition fluxes of anions and cations to the pine branches were low, several times lower than the values determined near the Emerald Lake Watershed (ELW), another sub-alpine location in the western Sierra Nevada. The sums of deposition fluxes of the measured cations and anions to pine surfaces were similar, in contrast to the ELW location where the sums of cation fluxes were much higher than the sums of anion fluxes. A strong positive correlation between depositions of NO₃⁻ and NH₄⁺, as well as SO₄²⁻ and Ca²⁺, suggested that large portions of these ions might have originated from particulate NH₄NO₃ and CaSO₄ deposited on pine surfaces. An estimated total N dry deposition (surface deposition of NO₃⁻ and NH₄⁺ and internal uptake of NO₂ and HNO₃) to the forested area of the EBLW was 29.54 eq ha⁻¹ yr⁻ (about 414 g H ha⁻¹ yr⁻¹).     

The chemical composition of intercepted cloudwater in the Sierra Nevada

The chemical composition of cloudwater in the Sierra Nevada is dominated by NO₃⁻, SO₄²⁻, and NH₄⁺. Cloudwater pH is determined largely by the balance between the concentrations of these three species, although inputs of formic and acetic acid also are believed to be important, particularly when anthropogenic inputs are small. Cloudwater samples collected in Sequoia National Park (SNP) exhibited pH values ranging from 3.9 to 6.5; Yosemite National Park (YNP) cloudwater samples had pH values ranging from 3.8 to 5.2. Samples collected at YNP were more acidic than those collected at SNP. The difference in pH between the two regions appears to be due to relatively small differences in inputs of NO₃⁻, SO₄²⁻, and NH₄⁺. In the absence of inputs of NH₃, cloudwater pH values in the Sierra may fall below 3.Over 250 h of cloud interception were observed during a 12 month period at a cloud monitoring site at 1856 m elevaton in SNP. Estimates of cloudwater deposition of NO₃⁻, SO₄²⁻, and NH₄⁺ indicate that cloud interception contributes significantly to regional acid deposition for closed forest canopies. Cloud interception may be the dominant deposition mechanism for isolated conifers and ridgetop canopies, where wind speeds are higher and cloudy air parcels can impact directly on foliar surfaces.     

Cloud chemistry at Mt Rigi,Switzerland: Dependence on drop size and relationship to precipitation chemistry

The chemical composition of winter and spring cloud water sampled at 1620 masl elevation on Mt Rigi in central Switzerland was dominated by NO₃⁻, SO₄²⁻, NH₄⁺ and H⁺. A wide range of concentration levels was observed, with maxima of 3700, 1800 and 4600 micronormal for NO₃⁻, SO₄²⁻ and NH₄⁺, respectively. Concentrations at a lower elevation (1030 masl) site on the mountain were higher due to lower cloud liquid water contents and higher pollutant levels at that site. The lowest pH observed was 2.95; large concentrations of NH₃ in the region prevented pH values from falling even lower. A comparison of simultaneously sampled cloud water and precipitation revealed much higher concentrations for most species in the cloud water, except in one case of extreme precipitation riming when the concentrations in the two phases converged. An exception to the pattern was H⁺; at times the precipitation was more acidic than the cloud water. The chemical composition of the cloud drops varied with drop size. Drops smaller than 10 μm diameter were enriched in NO₃⁻, SO₄²⁻ and NH₄⁺ relative to larger drops. Since the larger drops are the ones most effeciently captured by snow crystals, knowledge of their composition is essential to understanding the chemical implications of accretional growth of precipitation.     

The spatial distribution and particle size of some inorganic nitrogen,sulphur and chlorine species over the North Sea

The use of filter packs and a cascade impactor during a series of research cruises in the southern area of the North Sea has yielded detailed spatial distribution patterns of aerosol concentrations, Cl⁻, NO₃⁻, SO₄²⁻¹ and NH₄⁺ and gaseous concentrations, HCl, HNO₃ and NH₃. The overall distribution of the atmospheric concentrations closely parallels published modelled results for metallic species. The chemical transformations of these aerosols and gases are investigated together with their interactions with the seasalt aerosol. Aerosol chloride loss is greatest in the more polluted areas, whilst concentrations products of NH₃ with HNO₃ and HCl appear insufficient to sustain the existence of NH₄NO₃ and NH₄Cl. Nitrate is associated predominantly with larger particles and appears to be present substantially as a surface coating on marine aerosol. The total dry deposition input for nitrogen species is calculated for the southern sector with extrapolation to the whole of the North Sea, using particle size weighted deposition velocities of 0.63 and 0.21 cm s⁻¹ for NO₃⁻¹ and NH₄⁺, respectively, and literature-derived values for the gaseous constituents. Finally the use of air-mass back trajectories illustrates the role of source regions in influencing the chemical composition of the North Sea atmosphere.     

Chemical characterization of size-resolved aerosols in four seasons and hazy days in the megacity Beijing of China

Size-resolved aerosol samples were collected by MOUDI in four seasons in 2007 in Beijing. The PM₁₀ and PM_1.8 mass concentrations were 166.0 ± 120.5 and 91.6 ± 69.7 μg/m³, respectively, throughout the measurement, with seasonal variation: nearly two times higher in autumn than in summer and spring. Serious fine particle pollution occurred in winter with the PM_1.8/PM₁₀ ratio of 0.63, which was higher than other seasons. The size distribution of PM showed obvious seasonal and diurnal variation, with a smaller fine mode peak in spring and in the daytime. OM (organic matter = 1.6 × OC (organic carbon)) and SIA (secondary inorganic aerosol) were major components of fine particles, while OM, SIA and Ca^2 + were major components in coarse particles. Moreover, secondary components, mainly SOA (secondary organic aerosol) and SIA, accounted for 46%–96% of each size bin in fine particles, which meant that secondary pollution existed all year. Sulfates and nitrates, primarily in the form of (NH₄)₂SO₄, NH₄NO₃, CaSO₄, Na₂SO₄ and K₂SO₄, calculated by the model ISORROPIA II, were major components of the solid phase in fine particles. The PM concentration and size distribution were similar in the four seasons on non-haze days, while large differences occurred on haze days, which indicated seasonal variation of PM concentration and size distribution were dominated by haze days. The SIA concentrations and fractions of nearly all size bins were higher on haze days than on non-haze days, which was attributed to heterogeneous aqueous reactions on haze days in the four seasons.     

Spatial variability of urban precipitation chemistry and deposition: Statistical associations between constituents and potential removal processes of precursor species

The precipitation chemistry of Greater Manchester, a Metropolitan County in the northwest of England, has been examined for small scale spatial variability using a network of 18 bulk precipitation collectors. Significant spatial variability was found for concentrations of non-marine SO₄²⁻, NO₃⁻, NH₄⁺, Ca²⁺ and H⁺ ions. The statistical associations between the data were investigated using correlation, partial correlation and principal components analyses. It was found that zero-order correlation coefficients were inadequate for the interpretation of the data and that the computation of first, and higher order partial correlation coefficients was necessary in order to explain the interrelationships between the data and their spatial variability. The statistical associations between the data suggest relationships between Ca²⁺ and non-marine SO₄²⁻, and NO₃⁺ in precipitation which are discussed in terms of their possible precursor species. Potential source effects were examined in conjunction with atmospheric removal processes. The dry deposition of SO₄ particles, rather than the dry deposition of SO₂, may explain the spatial variability of non-marine SO₄²⁻. The erosion of CaSO₄ formed from the reaction of SO₂ with CaCO₃ on urban surfaces with subsequent resuspension is thought to be the basis of the relationship between Ca²⁺ and non-marine SO₄²⁻ concentrations in precipitation. The wet and dry deposition of CaCO₃ particles from local sources may be partially responsible for the spatial variability of H⁺, and dry deposition and scavenging of NH₃, in conjunction with the predominant wind direction may explain the spatial variability of NO₃⁻ and NH₄⁺ ions. Ammonia is thought to originate from sources both outside the study area and within it.