Evaluation of the Atmospheric Deposition in an Urban Region in South Brazil

The purpose of the present study is to analyse the chemical composition of bulk and wet atmospheric deposition samples in the Guaíba Hydrographic Basin (GHB), in south Brazil. Samples of bulk and wet deposition were analysed during a 1-year's period (January to December 2002) at three different stations, i.e., 8^° Distrito and CEASA stations in the city of Porto Alegre, and Charqueadas station, in Charqueadas city. Conductivity, pH, Cl^?, NO₃ ^?, F^?, SO₄ ^{2 ?}, Na⁺, K⁺, Mg^{2 +}, NH₄ ⁺ and Ca^{2 +} were determined. The pH presented an average value between 4.75 and 7.45. Enrichment factor was characterised based on groups of acid (pH < 5.65) and alkaline (pH > 5.65) samples. For most of the studied ions, EF in bulk deposition was higher in alkaline samples, while in wet deposition there was little difference between acid and alkaline samples. The Multivariate Analysis technique, i.e. the Canonical Correlation Analysis (CCA), determined relationships between the two different data set (chemical and meteorological), identified the source (anthropogenic or natural) of the studied variables.     

Chemical and Statistical Analysis of Precipitation in Singapore

The results of chemical analyses of precipitation samples collected in Singapore between August 1997 and July 1998 are presented. Major inorganic and organic ions were determined in 169 rain samples collected using an automated wet-only sampler. The daily sample pH values ranged from 3.49 to 6.54 with a volume-weighted mean of 4.50, and about 88% of the samples had pH values less than 5.0 Nss-SO₄ ^2? accounted for about 53 % of the sum of anions in rain, whereas chloride, nitrate, formate, and acetate accounted for the remainder. Rain chemistry data were analyzed using principal component analysis to find possible sources of the measured chemical species. Three components that accounted for 83.5% of the total variance were extracted: sea-spray (Na⁺, Cl^? and and Mg²⁺) and soil particles (Ca²⁺ and K⁺), acid factor (nss-SO₄ ^2?, NO₃ ^?, NH₄ ⁺, and H⁺), and biomass burning (HCOO^? and CH₃COOO^?).     

Long Term Trend of Chemical Constituents in Tokyo Metropolitan Area in Japan

In recent years, acid rain has been a social problem all over the world. In Japan, it is also a big problem especially in the metropolitan area. Then, we have measured major ions such as H⁺, Na⁺, NH₄ ⁺, K⁺, Mg²⁺, Ca²⁺, Cl^?, NO₃ ^?, and SO₄ ^2? in precipitation and dry deposition samples which had been collected at 9 sampling sites at Hiyoshi, Mita, Kashiwa, Shiki, Fujisawa, Yokosuka, Mitaka, Hachiouji, and Ashikaga in Tokyo Metropolitan area for 10 years since 1990. The average pH of precipitation in their sites was 4.56 (n=1906). As the results of multiple regression analysis showed that pH of precipitation was determined by 5 ions such as NH₄ ⁺, nssCa²⁺(non sea salt calcium), nssCl^?(non sea salt chloride), NO₃ ^?, nssSO₄ ^2?(non sea salt sulfate) in the most of the sampling sites. Therefore, it is very important to investigate the behavior of these ions to understand the acidification of rain in Tokyo Metropolitan area. In this study, a long term trend of each ion concentration in precipitation and wet deposition was also investigated the base on the data we had observed at 7 sites for 10 years by the statistical method.     

Deposition of air pollutants in a wind-exposed forest edge

The atmospheric deposition of air pollutants at a forest edge was studied by means of monitoring canopy throughfall at the edge and at five different parallel lines in the forest behind the edge. The investigation was carried out at a pine forest on the Swedish west coast. Throughfall and bulk deposition samples were analyzed for volume, SO ₄ ^2? , NO ₃ ^? , Cl^?, NH ₄ ⁺ , Na⁺, K⁺, Mg²⁺, Ca²⁺, and for pH. The results show that the throughfall flow at the edge was increased substantially for most ions. The ratios in throughfall flows between the edge and the line 50 m into the forest were for SO ₄ ^2? , 1.5, NO ₃ ^? 2.9, NH ₄ ⁺ 2.7, and Na⁺ 3.1. Since this effect is not only valid for forest edges but also for hillsides, hilltops, and edges between stands of different age, etc., there might be substantial areas which get much larger total deposition than the normally considered closed forest.     

The role of organic horizons and canopy to modify the chemistry of acidic deposition in some forest ecosystems

To clarify the mechanisms of pH buffering in forest ecosystems, field observations of pH and ionic concentrations in precipitation (R), throughfall (Tf), stemflow (Sf), and leachates from organ c horizons (Lo) were conducted for three years at three stands in Tomakomai (TK) and Teshio (TS) in Hokkaido, northern Japan. Weighted mean rates of H⁺ input as wet deposition at TK and TS were estimated in the range from 0.3 to 1.0 and 0.4–0.6 kmol_c ha^?1 y^?, respectively. While the net H⁺ flux was reduced significantly by the forest canopy, net fluxes of other ions by throughfall, especially for Na⁺, Cl^?, and SO₄ ^2?, were apparently greater than those by precipitation. The canopy modification of the H⁺ flux was more remarkable under deciduous stands than under coniferous stands, suggesting that the efficiency of conifers as the collectors of dry deposition is greater than that of deciduous ones. More than 50% of H⁺ flux due to throughfall was absorbed by the organic horizons and the weighted mean pH of Lo at TK and TS was in the range from 4.9 to 5.5 and 5.0–5.5, respectively. Results from field observation and field leaching experiments, showed that the major H⁺ sinks of the organic horizons are exchange reaction of Ca²⁺, Mg²⁺ and K⁺. Organic acids or organo-metallic complexes of lower pK(=5.0–5.5) played a significant role as counter anions in O horizons leachate in coniferous forests. Our results indicate the importance of biogeochemical modifications in the canopy and organic horizon in acid buffering mechanisms of forest ecosystems.     

Nature and Magnitude of Atmospheric Fluxes of Total Inorganic Nitrogen and Other Inorganic Species to the Tampa Bay Watershed, FL, USA

We estimated the total inorganic fluxes of nitrogen (N), sulfur (S), chloride (Cl^?, sodium (Na⁺, calcium (Ca²⁺, magnesium (Mg²⁺, potassium (K⁺ and hydronium (H⁺. The resistance deposition algorithm that is programmed as part of the CALMET/CALPUFF modeling system was used to generate spatially-distributed deposition velocities, which were then combined with measurements of urban and rural concentrations of gas and particle species to obtain dry deposition rates. Wet deposition rates for each species were determined from rainfall concentrations and amounts available from the National Acid Deposition Program (NADP) monitoring network databases. The estimated total inorganic nitrogen deposition to the Tampa Bay watershed (excluding Tampa Bay) was 17 kg-N ha^?1 yr^?1 or 9,700 metric tons yr^?1, and the ratio of dry to wet deposition rates was ～2.3 for inorganic nitrogen. The largest contributors to the total N flux were ammonia (NH₃ and nitrogen oxides (NO _x at 4.6 kg-N ha^?1 yr^?1 and 5.1 kg-N ha^?1 yr^?1, respectively. Averaged wet deposition rates were 2.3 and 2.7 kg-N ha^?1 yr^?1 for NH₄ ⁺ and NO₃ ^?, respectively.     

Evalution of Acid Deposition in Korea

This study was carried out to evaluate acid depositions and to understand their effect. Wet precipitation has been collected at twenty-four sites in Korea for one year of 1999. The ion concentrations such as H⁺, Na⁺, K⁺, Mg²⁺, NH₄ ⁺, Ca²⁺, Cl^?, NO₃ ^? and SO₄ ^2? were chemically analyzed and determined. Precipitation had wide range of pH(3.5～8.5), and volume-weighted average was 5.2. The contribution amounts of Cl^?, SO₄ ^2? and NO₃ ^? in anion were shown to be 54%, 32%, and 14%, respectively and those of Na⁺ and NH₄ ⁺ in cation were 32% and 25%. The ratios of Cl^? and Mg²⁺ to Na⁺ in precipitation were similar to those of seawater, which imply that great amount of Cl^? and Mg²⁺ in precipitation could be originated from seawater. The concentration of H⁺ is little related with SO₄ ^2?, NO₃ ^? and Cl^? ions, whereas nss^?SO₄ ^2? and NO₃ ^? are highly correlated with NH₄ ⁺, which could suggest that great amount of SO₄ ^2? and NO₃ ^? exist in the form of ammonium associated salt. The annual wet deposition amounts (g m^?2year^?1) of SO₄ ^2?, NO₃ ^?, Cl^?, H⁺, NH₄ ⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺ were estimated as 0.88～4.89, 0.49～4.37, 0.30～9.80, 0.001～0.031, 0.06～2.15, 0.27～4.27, 0.10～3.81, 0.23～1.59 and 0.03～0.63.     

Relationships between Acid Ions and Carbonaceous Fly-Ash Particles in Deposition at European Mountain Lakes

The concentrations of major ions and spheroidal carbonaceous fly-ash particles (SCPs) in bulk deposition were determined in weekly samples from six European mountain lakes during 1997/98. SCPs are produced only from high temperature combustion of fossil-fuels and therefore provide an unambiguous indicator of atmospheric deposition from this source. Positive correlations were observed between SCPs and SO₄ ^2?, NO₃ ^? and NH₄ ⁺ at all sites except for some determinands at Jorisee (Switzerland) and Starolesnienske (Slovakia). Correlations between SCPs and SO₄ ^2? + NO₃ ^? were always more positive than for SCPs with 'total acid ions' (SO₄ ^2? + NO₃ ^? + NH₄ ⁺). This is in agreement with the expectation that the contribution to NH₄ ⁺ deposition made by fossil-fuels is negligible. Good positive correlations between SCPs and all acid anions were observed at Estany Redo (Pyrenees); lower but still positive correlations were observed for all acid ions with SCPs at Gossenköllesee (Austria), Lochnagar and Kårvatn (central Norway), whilst little trend in correlation was observed for Jorisee and Starolesnienske. It is suggested that this gradient reflects the influence of fossil-fuels on acid deposition in these areas. A high positive correlation was observed between SCP and Cl^? at Gossenkollesee possibly as a result of HCl from coal combustion.     

Stability of Ionic Components in Precipitation Samples — A Case Study in Taipei

The changes in ionic contents were studied in acidic precipitation samples collected for precipitation events in Taipei, which is near the sea. The storage cases under investigation include filtration, refrigeration, and light. Thus the experimental design leads all precipitation samples collected in the same rain event stored under different conditions. They were then analyzed six times successively within two months to provide the information containing potential ionic composition change. The measured constituents are H⁺, K⁺, Na⁺, Ca²⁺, Mg²⁺, NH₄ ⁺, NO₃ ^?, SO₄ ^2?, and Cl^?. The comparison of measured ionic concentrations corresponding to different storage methods yield no significant difference. The increases of NO₃ ^? and decreases of NH₄ ⁺ with time were observed to be of similar magnitude, while the variation of pH values is significant. The presented study indicated the important role played by sample storage in determining the ionic composition of precipitation samples.     

Sequential sampling and variability of acid precipitation in Hampton,Virginia

Rain samples were collected sequentially by amount (≈2.7 mm each) from individual events at a single, relatively isolated, suburban site from August 1977 to July 1980. Rain pH's for ≤ 3 mm samples closely fit a monomodal Gaussian distribution with a median of 4.50 and a standard deviation of 0.39. The variability in pH was primarily interevent as opposed to intraevent. The 3-yr volume-weighted pH was 4.35 ± 0.02 for 3.16 m collected; annual pH's were 4.31, 4.37, and 4.38, and cumulative H⁺ deposition was 141 mg H⁺ m^?2. Event-averaged rain pH and meteorological and air quality data were correlated. Low pH was associated with low rainfall volume and rate; rain after several dry days; rains with northeast surface winds; high SO₂, NO₂, and O₃ in the ambient atmosphere; and high, strongly correlated, SO₄ ⁼ and NO₃ ^? rainwater concentrations. The lowest 3-yr seasonal average pH (4.31) occurred during summer; values for other seasons were ≈4.37. Average intraevent H⁺ molarity (volume-weighted) was accurately characterized by 6.89 E^{?5 *}(mm ram)^?0.215. The relative merits of composite (e.g., whole event) and sequential sampling are examined.     

Dry deposition to snow in an urban area

Ambient particle and gas concentrations, wet deposition and dry deposition were measured in Warren, MI between December 18, 1983 and April 6, 1984. Dry deposition was measured to various surfaces in a cutoff bucket, including a snow surface, a snow/water surface during melting and a deionized water surface. Dry deposition velocities were calculated for various species from the ratio of the dry flux to the ambient concentrations. The dry deposition velocities measured to a snow surface were 0.082 cm s^?1 SO₂ 2.0 for HNO₃, 0.083 for NH₄ ⁺, 2.0 for Ca⁺⁺ and 4.3 for Cl^?. The values were not significantly different for a snow/water surface during melting compared to a snow surface. However, higher values of 0.69 cm s^?1 for SO₂, 6.2 for HNO₃, 0.33 for NH₄ ⁺, and 4.2 for Ca⁺⁺ were found to a deionized water surface in the spring. These higher values could be due to the higher air temperature, the pH of the liquid or to increased atmospheric mixing during this period.     

Nutrient Input Through Occult and Wet Deposition into a Subtropical Montane Cloud Forest

Chemical composition of fog and rain water was studied during a 47-day experimental period. The differences between the fog and rain water were found to be significantly for most analyzed ions. H⁺, NH₄ ⁺, NO₃ ^?, and SO₄ ^2? made up 85% of the total median ion concentration in fog and 84% in rain water. The total mean equivalent concentration was 15 times higher in the fog than in the rain water. The fog water samples were classified according to their air mass history. The analysis of the 120 h backward trajectory led to the identification of three advection regimes. Significant differences of ion concentrations between the respective classes were found. Air masses of class I travelled exclusively over the Pacific Ocean, class II were carried over the Philippines, and class III were advected from mainland China. The turbulent fog water deposition was determined by the means of the eddy covariance method. The total (turbulent plus gravitational) fog water fluxes ranged between +31.7 mg m^?2 s^?1 and ?56.6 mg m^?2 s^?1. Fog water droplets with mean diameters between 15 μm and 25 μm contributed most to the liquid water flux. The sample based nutrient input was calculated on the basis of the occult and wet deposition, and the concentrations of the simultaneously collected fog and rainwater samples, respectively. The nutrient input through wet deposition was about 13 times higher than through occult deposition.     

An analysis of spatial variability of the dominant ions in precipitation in the eastern United States

Data of the Multistate Atmospheric Power Production Pollution Study (MAP3S) and the National Atmospheric Deposition Program (NADP) were utilized to develop wet deposition spatial distribution patterns for the eastern United States for 1979. The ions of SO₄ ^?, NO₃ ^?, H⁺, and NH₄ ⁺ were selected for study since they are the most prominent ones found in precipitation. Total wet deposition for 1979 was normalized to one centimeter of precipitation and objectively analyzed using the Synagraphic Mapping System (SYMAP) technique. Gradients of SO₄ ^? and NO₃ ^? were found to be essentially uniform, both to the east and west of the major pollution regions. An increased gradient in normalized deposition for SO₄ ^?, NO₃ ^?, and H⁺ was found in the Appalachian Mountain region. Estimates of total wet deposition were obtained by using the normalized deposition values in conjunction with precipitation as reported by the National Climatic Center. SYMAP analyses of the estimated total wet deposition were localized in nature due to precipitation variations between sites.     

Throughfall and canopy buffering in three sitka spruce stands in Denmark

Throughfall was studied in three even-aged sitka spruce stands in Denmark during the years 1989 to 1994. Deposition of sea salts dominated the fluxes of substances in varying degrees between years and sites. During the study period, non-marine S deposition did not change substantially. At the site most affected by animal husbandry, fluxes of NH₄ ⁺ and NO₃ ^? increased over the years. Elevated fluxes of TOC, K⁺, and PO₄ ^3? occurred in the growing season due to canopy leaching caused by attacks by the green spruce aphid. Fluxes of Cl^?, SO₄ ^2?, Na⁺, Ca²⁺, and Mg²⁺ were highest in the dormant season. Buffering of. pH was affected by the nitrogen dynamics in the canopy, and also, at least during the summer, by elevated levels of organic compounds.     

Long-term development of element budgets in a Norway spruce (Picea abies (L.) Karst.) forest of the German solling area

To evaluate ecosystem response to changing atmospheric deposition, element budgets were established over the period from 1973 to 1991 for a Norway Spruce (Picea abies (L.) Karst.) site. Budgets for Na⁺, Cl^?, Ca²⁺, Mg²⁺, N, S and H⁺ were based on total deposition and seepage water fluxes. The deposition of Ca²⁺, Mg²⁺, particularly, of S and H⁺ decreased with time, while calculated N deposition remained constant at a high level. The decrease in Ca²⁺ deposition led to a reduction of Ca²⁺ fluxes with seepage water. The decrease of Mg²⁺ deposition did not have an effect on the output fluxes of Mg²⁺. The reversibility of soil and seepage water acidification by reduced S deposition was delayed by the release of previously accumulated soil SO ₄ ^2? . The highest NO ₃ ^? fluxes were observed during the period of 1986 to 1988; NO ₃ ^? fluxes in general demonstrated a considerable annual and periodic variation. Total N accumulation in the ecosystem amounted to nearly 590 kg ha^?1 yr^?1 during the observation period. The major sink of N in the spruce site is the aggrading humus layer. The results emphasize the need for measurements over several years to make conclusions regarding the function of ecosystems in response to atmospheric deposition.     

A comparison of measured and theoretical soil acidity diffusion coefficients over a wide range of pH

The soil acidity diffusion coefficients have been measured at two P_co2 levels with values in the range 2–70 × 10^?9 cm² s^?1. The coefficient passed through an ill-defined minimum in the pH range 5–6.5. Theoretical values, calculated on the basis that the only significant acid-base carriers in the soil were the H₃O⁺ -H₂O and H₂CO₃-HCO^?₃ pairs, agreed well with the experimental values over the whole pH range at P_co2= 0.005 atm. Agreement was not so good however at a CO₂ pressure of 0.0003 atm., especially in the neutralalkaline pH range. This was thought to be due to difficulties in maintaining this level of CO₂ throughout the soil samples.     

Fog- and Rainwater Chemistry in the Tropical Seasonal Rain Forest of Xishuangbanna, Southwest China

Fogwater, fog drip and rainwater chemistry were examined at a tropical seasonal rain forest in Xishuangbanna, southwest China between November 2001 and October 2002. During the period of observation, 204 days with the occurrence of radiation fog were observed and the total duration of fog was 1949 h, of which 1618 h occurred in the dry season (November to April), accounting for 37.0% of the time during the season. The mean pH of fogwater, fog drip and rainwater were 6.78, 7.30, and 6.13, respectively. The ion with the highest concentration for fog- and rainwater was HCO₃ ^?, which amounted to 85.2 and 37.3 μeq l^?1, followed by Ca²⁺, Mg²⁺ and NH₄ ⁺. Concentrations of NO₃ ^?, HCO₃ ^?, NH₄ ⁺, Ca²⁺, and K⁺ in fogwater samples collected in the dry season were significantly greater when compared to those collected in the rainy season. It was found that the ionic concentrations in fog drip were higher than those in fogwater, except for NH₄ ⁺ and H⁺, which was attributed to the washout of the soil- and ash-oriented ions deposited on the leaves and the alkaline ionic emissions by the leaves, since biomass burns are very common in the region and nearby road was widening.     

Ion mass budgets for small forested catchments in Finland

Ion mass and H⁺ budgets were calculated for three pristine forested catchments using bulk deposition, throughfall and runoff data. The catchments have different soil and forest type characteristics. A forest canopy filtering factor for each catchment was estimated for base cations, H⁺, Cl^? and SO ₄ ^2? by taking into account the specific filtering abilities of different stands based on the throughfall quality and the distribution of forest types. Output fluxes from the catchments were calculated from the quality and quantity of the runoff water. Deposition, weathering, ion exchange, retention and biological accumulation processes were taken into account to calculate catchment H⁺ budgets, and the ratio between external (anthropogenic) and internal H⁺ sources. In general, output exceeded input for Na⁺, K⁺, Ca²⁺, Mg²⁺, HCO ₃ ^? (if present) and A^? (organic anions), whereas retention was observed in the case of H⁺, NH ₄ ⁺ , NO ₃ ^? and SO ₄ ^2? . The range in the annual input of H⁺ was 22.8–26.3 meq m^?2 yr^?1, and in the annual output, 0.3–3.9 meq m^?2 yr^?1. Compared with some forested sites located in high acid deposition areas in southern Scandinavia, Scotland and Canada, the catchments receive rather moderate loads of acidic deposition. The consumption of H⁺ was dominated by base cation exchange plus weathering reactions (41–79 %), and by the retention of SO ₄ ^2? (17–49 %). The maximum net retention of SO ₄ ^2? was 87% in the HietajÄrvi 2 catchment, having the highest proportion of peatlands. Nitrogen transformations played a rather minor role in the H⁺ budgets. The ratio between external and internal H⁺ sources (excluding net base cation uptake by forests) varied between 0.74 and 2.62, depending on catchment characteristics and acidic deposition loads. The impact of the acidic deposition was most evident for the southern Valkeakotinen catchment, where the anthropogenic acidification has been documented also by palaeolimnological methods.     

Spatio-temporal variations in nutrient concentration in soil solution under greenhouse tomato

The aim of this trial was to study the spatio-temporal variability in solution nutrient concentration under intensive greenhouse tomato production, to determine the number of suction-cups needed to obtain a representative sample and the influence by the position in the greenhouses. Twenty sampling points were selected within the greenhouse with one suction-cup per sampling point. One soil solution were sampled per point at weekly intervals to analyze for pH, electrical conductivity, chloride, nitrate, phosphate, sulfate, sodium, potassium, calcium, and magnesium (EC, Cl^?, NO₃^?, H₂PO₄^?, SO₄^2—, Na⁺, K⁺, Ca²⁺, and Mg²⁺) concentrations. The pH, Cl^?, H₂PO₄^?, and SO₄^2? concentrations showed no spatio-temporal variation but EC, NO₃^?, and K⁺ showed temporal variation. The spatial variability in EC, K⁺_, Na⁺, Mg²⁺, and Ca²⁺ can be influenced by microclimate and topography. The numbers of suction cups required for a representative sample ranged from 1 to 10 depending on nutrient.     

Calculations of ion activities in soil solutions from humic horizons

Concentrations of the main components and activities of Ca²⁺, Na⁺, Cl^?, and NO₃^? were determined in soil solutions displaced from chernozem samples (A₁ horizon). To calculate ion activity in these solutions, it was necessary to consider formation of Ca²⁺, Mg² and Na⁺ complexes with organic anions. If 1 : 1-composition of these complexes was assumed, dependence of their stability constants on the ionic strengths was found; this allowed a 17% average error for Ca²⁺ activity and 8% for Na⁺ activity in the calculations. As followed from the computations, 68–80% of the Ca²⁺ and Mg²⁺ were included in ion pairs and complexes with 91–97% of these amounts bound with organic anions. The values for the calcite solubility product were close to those for pure saltwater systems.