Bulk and wet atmospheric deposition chemistry at pallanza (N. Italy)

The chemistry of wet only and bulk depositions collected weekly at Pallanza from May, 1984 to December, 1986 is compared and discussed in relation to the composition of dust fall. The comparison shows a very good agreement between pH values (volume weighted mean values of 4.35 and 4.36, respectively, for wet only and bulk samples) and differences between 6 and 12% for ammonium, sulphate, nitrate, and Na. For Ca, Mg, and K the difference range is 30 to 50%. The amount of precipitation over Pallanza (mean value 1951–1985,1709 mm), together with the solute concentrations in atmospheric deposition, mean that there is high bulk deposition of acidifing substances. The values found during the study period were 76, 93, 143, and 81 meq m² yr^?1 for H⁺, ammonium, sulphate, and nitrate, respectively.     

An empirical equation to calculate soil solution electrical conductivity at 25°C from major ion concentrations

The electrical conductivity at 25°C (EC₂₅) of soil solutions or irrigation waters is the standard property for assessing salinity. Many models for soil salinity prediction calculate the major ion composition of the soil solution. The electrical conductivity of a solution can be determined from its composition through several different empirical equations. An assessment of these equations is necessary to incorporate the most accurate and precise equations in such models. Twelve different equations for the EC₂₅ calculation were calibrated by means of regression analyses with data from 133 saturation extracts and another 135 1:5 soil‐to‐water extracts from a salt‐affected agricultural irrigated area. The equations with better calibration parameters were tested with another data set of 153 soil solutions covering a wide range of salt concentrations and compositions. The testing was conducted using the standardized difference t‐test, which is a rigorous validation test used in this study for the first time. The equations based on the ionic conductivity decrement given by Kohlrausch's law presented the poorest calibration parameters. The equations founded on the hypothesis that EC₂₅ is proportional to analytical concentrations had worse calibration and validation parameters than their counterparts based on free‐ion concentrations and ionic activities. The equations founded on simpler mathematical relationships generally gave improved validation parameters. The three equations based on the specific electrical conductivity definition presented a mean standardized difference between observations and predictions indistinguishable from zero at the 95% confidence level. The inclusion of the charged ion‐pair concentrations in the equation based on free‐ion concentrations improved its predictions, particularly at large electrical conductivities. This equation can be reliably used in conjunction with chemical speciation software to assess EC₂₅ from the ion composition of soil solutions.     

Study of wet and dry atmospheric deposition at two altitudes in central Switzerland

The analysis of various ions in atmospheric deposition at two altitudes (515 m and 950 m a.s.l.) in Switzerland during 1983/84 revealed that dry deposition depends more on altitude than wet deposition. During autumn and winter, when vertical air exchange is limited, dry deposition of substances from anthropogenic sources (e.g. SO₄-S) was higher at the lower site. In the course of the year, the pattern of wet deposition was independent of altitude and showed highest rates for S, N and Ca in summertime. A comparison between rates of wet, particulate and gaseous S and N deposition suggested that during the growing season wet deposition is the dominant flux. Total (wet + dry) deposition of S, N and Cl was lower than in other parts of Europe, but a substantial increase of NO₃-N deposition during the past 25 years must have occured.     

Relationship of ambient atmospheric hydrocarbon (C12–C32) concentrations to deposition

Anthropogenic and biogenic high molecular weight (C₁₂–C₃₂) hydrocarbons (HC) were deposited from the atmosphere in association with both wet and dry deposition. Wet deposition generally removes HC at a faster rate (22 to 670 μg m^?2 day^?1) than dry deposition (4 to 189 μg m^?2 day^?1). However, due to longer periods during which dry deposition occurred, the removal of atmospheric HC by wet and dry deposition is almost equal during this sampling period. Atmospheric HC concentrations ranged from 0.8 to 4.1 μg m^?3 and show no simple relationship to wet or dry deposition rates. Large variabilities in deposition rates for individual events were found, but long-term average deposition was relatively constant.     

Evaluation of the land reclamation project at the As Pontes Mine (NW Spain) in relation to the suitability of the soil for plant growth

The reclamation and monitoring methodologies implemented at the mining waste dump at the As Pontes Lignite Mine in Galicia (NW Spain) are briefly described. In addition the factors affecting achievement of reclamation objectives and an evaluation of the factors limiting plant growth on the constructed soils are outlined. The most serious limitations were found in the oldest mine soils constructed from sulphide-bearing spoils; high acidity, toxicity, nutrient deficiency, seasonal waterlogging due to their impermeability, and compaction. The youngest soils were constructed using sulphide-free spoils as topsoil substitutes and had fewer limitations for plant development. The results show that proper handling of spoils, and paying special attention to selective placement of sulphide bearing materials, are the most important factors in providing a suitable medium for plant growth. © 1998 John Wiley & Sons, Ltd.     

Estimation of wet and dry deposition of pollutant sulfur in eastern Canada as a function of major source regions

The contributions of major anthropogenic source regions to wet and dry deposition of total S in eastern Canada are estimated for a winter month and a summer month with the ASTRAP model. Results indicate that the U.S. and Canada contribute approximately equal amounts to total S deposition in Canada; Canadian sources contribute more than one half of dry deposition and less than one half of wet deposition.     

PCB concentrations in stream sunfish (Lepomis Auritus and L. Macrocmirus) in relation to proximity to chronic point sources

Sunfish (Lepomis auritus and L. macrochirus) were used to monitor polychlorinated biphenyl (PCB) contamination in a group of small streams flowing into a larger stream/reservoir system. Mean PCB concentrations in sunfish appeared to reflect exposure conditions at the site of capture. Fish from uncontaminated sites 1 to 2 km distant from PCB-contaminated sites did not exhibit PCB contamination, and PCB concentrations in fish downstream from a discrete source decreased at a rate greater than or equal to downstream dilution of the point source. Mean PCB concentrations in fish near the source exhibited relatively large (-40%) fluctuations between semi-annual sampling periods, suggesting that PCB concentrations in sunfish populations may respond rapidly to changes in exposure. Sunfish were not sensitive enough indicators of contamination to use in assessing whether or not problematic levels of contamination may occur in other species. Although the presence of PCB contamination in sunfish can be used to infer that PCBs are elevated in other species, the absence of PCB contamination in sunfish cannot be used to infer that older, fattier fish higher up the food chain are uncontaminated.     

Wet-only and bulk deposition studies at New Delhi (India)

Water, Air, & Soil Pollution - Rain water samples were collected at New Delhi during the monsoon of 1994 at a height of 30 m above the ground level using a wet-only collector. Simultaneously,...     

The effects of wet deposition chemistry on reproductive processes in two pine species: Apparent pollination effectiveness in relation to species pollen sensitivity

A field investigation was carried out to compare the effects of simulated wet deposition of varying chemistry on reproduction in clones of an eastern white pine (Pinus strobus L.) and those of a red pine (Pinus resinosa Ait.). The simulants had a pH of 2.6, 3.6, 4.6, and 5.6 and contained additional concentrations of Pb or Cu (0, 0.05 or 0.01 mg 1^?1, respectively). They were applied to the receptive conelets after controlled pollination. Simulated wet deposition significantly affected (P < 0.05) seed set per bract. However, the trends were in different directions for the two species. Acidity increased apparent pollination effectiveness in red pine but was inhibitory in white pine. This difference apparent in response was also related to the pH sensitivity of the pollen in the two species. Previous experiments have shown that red pine pollen has a substantially lower pH threshold for germination inhibition than white pine. The effects of Cu and Pb were generally not significant; however, they did appear antagonistic to the effect of pH. The direct effects of wet deposition and its chemistry on pollination effectiveness has implications in terms of fertility selection, gametic selection, and the possible manipulation of the pollination mechanism in pines.     

Sulfur dioxide inhibition of photosynthesis at different CO2 and O2 concentrations in relation to photorespiration

The mechanism of SO₂ inhibition of photosynthesis in intact leaves of tomato and maze was studied to evaluate SO₂ inhibition of photorespiration. Leaf tissues were fumigated with SO₂ under photorespiratory (low CO, and/or high O, concentrations) and non-photo-respiratory conditions. When tomato leaf disks were fumigated with 10 ppm SO₂ at 2, 21 and 100° o O., SO₂ inhibited photosynthesis at 2% O₂ in the same degrees as at 21% O₂. SO₂ inhibition of photosynthesis was depressed at higher CO₂ concentrations when the disks were fumigated with SO₂ at different CO₂ concentrations. High CO₂ concentrations also reduced the photosynthesis inhibition of maize leaf disks. These results suggest that SO₂ inhibits photosynthesis through other mechanisms than photorespiration inhibition and confirm the view that SO₂ competes with CO₂ for the carboxylating enzymes in photosynthesis     

A comparison between wet and bulk deposition at an urban site in the U.K.

As a part of an ongoing investigation into urban acidic deposition in Greater Manchester, a wet-only collector was collocated with a bulk collector in the city centre of Manchester, one of 18 sites of an urban precipitation monitoring network. A comparison of data from these collocated bulk and wet-only collectors allowed estimates of the contribution of dry deposition to the bulk collector to be made. Dry deposition was found to contribute between 15 and 17% to elevated deposition and concentrations of non marine sulphate, nitrate and ammonium in the bulk collector. By a statistical analysis between ion concentrations with gas concentrations and an evaluation of the available literature, the form of the dry deposited material was inferred. The contribution of dry deposited Ca²⁺ to concentration and deposition in the bulk collector was found to be 46%. Calcium species are suggested as being those which reduce acidity most. Statistical analyses revealed significant differences between concentrations of ions found in the bulk and wet-only collectors. An evaluation of the data from the collocated collectors has identified possible sampling artifacts introduced by the use of bulk collectors in urban areas.     

Mercury in forest canopy throughfall water and its relation to atmospheric deposition

A seasonal variation of both particle and gaseous Hg concentrations in the atmosphere is present in south-western Sweden. An average gaseous Hg level of 3.7 ng m⁻³ is found in winter, compared to 2.8 ng m⁻³ in summer. A weak decreasing south-north gradient for gaseous Hg in air over the Nordic countries is also present, with yearly average values from 3.2 to 2.8 ng m⁻³. A gradient for particulate Hg is less clear. An air parcel trajectory sector classification of gaseous Hg levels in air, and to some extent the particulate associated Hg, clearly demonstrates the increased concentrations in the southern sectors, especially in south-western Sweden where the gaseous Hg increase is about I ng m⁻³. These observations are consistent with an influence from the European continent. The average concentrations of Hg in precipitation at the various stations show a pronounced decreasing south-north gradient. A major portion of the total Hg present in precipitation is associated with particles. For the southern stations, a strong correlation between Hg and sulfate, or pH, is present suggesting a connection between Hg in precipitation and anthropogenic activities.     

Peatland water chemistry in Central Ontario in relation to acid deposition

Thirty-one peatlands from two areas of central Ontario were sampled to assess the influence of acid deposition on peatland water chemistry. Factor analysis differentiated peatland water chemistry along three major axes of chemical variation, interpreted as axes of organic concentration, mineral concentration, and deposition influence. Water from the surface mats had a higher organic concentration than water from open pools. Mineral influence in peatland waters was reflected by higher concentrations of Ca, Mg, Na, and silica in fen pools compared to bog pools. The influence of high acid deposition in the Wanapitei study area was indicated by high concentrations of sulphate, Ni, Mn, and Cu, and lower pH compared to an area that has received less acidic deposition (Ranger). Regression analyses indicated that H⁺ variation in bogs could be largely explained by organic C concentration, but that sulphate concentration was also positively associated with acidity, while Ca was negatively associated with acidity.     

Trends in wet and dry deposition of sulphur in the United Kingdom

UK data on sulphur deposition trends between the 1960's and 1990's are presented. Long term data sets of sulphur dioxide (SO₂) concentrations at two sites have been analysed and dry deposition determined using a resistance model. Wet deposition has been calculated from non-marine sulphate concentration and rainfall fields for 1978–80 and 1989–93. These maps have been interpolated and corrected for seeder feeder enhancement. The wet deposition of sulphur declined by about 43 % between 1979 and 1993 whereas emissions of sulphur declined by about 32 %. An indication of the trends in sulphur dry deposition is provided by data from Eskdalemuir, a site in southern Scotland where wet deposition and SO₂ concentration have been measured since 1979. Dry deposition at Eskdalemuir has decreased by 70 % and wet deposition by 48 %. Hence, while wet deposition has responded approximately linearly with the decline in UK emissions of sulphur dioxide, dry deposition has declined at twice the rate of decline in UK emissions.     

Spatial and temporal pattern of sulfate and nitrate wet deposition in Ontario

The spatial patterns of the precipitation-weighted mean concentration and total deposition of sulfate and nitrate in Ontario from 1981 to 1983 were determined using the Modified Simple Kriging method. The 3-yr averaged spatial patterns of sulfate and nitrate concentrations were similar to the sulfate and nitrate 3-yr averaged deposition patterns in Ontario. The overall spatial variability of nitrate was slightly higher than sulfate. The seasonal variation of nitrate concentrations and deposition were less regular than sulfate.     

Lichen sulphur and lead levels in relation to deposition patterns in Eastern Canada

Marked differences exist between the S and Pb concentration in Cladina ranziferina collected from eastern Canada and the Northwest Territories, Canada. These differences reflected the differing emission/deposition rates in the two regions. The spatial distribution of S and Pb in the lichen from eastern Canada is described in detail. Mean S concentrations ranged from 329 to 959 μg g^?l; Pb concentrations varied in the range 3 to 21 μg g^?l. A regional gradient in lichen S concentrations was evident with the highest concentrations being found in central and north-central Ontario and the lowest in Newfoundland. A regional gradient for Pb was apparent but was not as well defined as that for S. The regional distribution of S illustrated by the lichen agreed with another indirect measurement of S deposition. Lichen S concentrations correlated with measured wet sulphate deposition.     

Soil geochemistry in relation to water chemistry and sensitivity to acid deposition in Finnish Lapland

Ecosystems in Finnish Lapland are threatened by heavy metal pollution and acid deposition derived from emissions of Cu-Ni smelters in Kola Peninsula and to varying extent to pollution from southern Fennoscandian and Central European sources. Extensive chemical analyses of small lake waters collected in Finnish Lapland have demonstrated that a significant number of lakes are acidified (ANC < 0μcq/l) or their buffering capacity is critical (ANC = 0–50μe/l). The relative abundance of mafic, ultramafic and carbonate rock components in the catchment were the chief factors controlling ANC and the main base cation (Ca²⁺, Mg²⁺) concentrations of lake waters. Both humic and clearwater lakes with low buffering capacity (ANC < 50μeq/l) were mainly located in the catchment areas identified as sensitive to acidification on the basis of low content of base cations (Ca²⁺ +Mg²⁺ +K⁺ < 500 meq/kg) in till. The ratio of the catchment area to the lake area was distinctly smaller for acidic lakes than for the well-buffered lakes, indicating the importance of catchment processes in determining the ANC and main base cations. The high sulphur concentrations (median 60μeq/1) of acidic lakes in northeastern Lapland, near the Finnish-Norwegian border, were strongly correlated with the highest deposition of sulphur derived from smelters of Kola Peninsula. The anomalously high concentrations of sulphur of well-buffered lakes in the western part of Lapland were due to sulphide minerals of soil and bedrock. The acidity of humic lakes in southern Lapland was in large part due to the organic acidity derived from peatlands.     

Wet deposition of mercury and ambient mercury concentrations at a site in the Lake Champlain basin

The “Great Waters” program, established in the 1990 Clean Air Act Amendments, mandated that atmospheric deposition of hazardous air pollutants to Lake Champlain (including Hg) be assessed. An assessment of the magnitude and seasonal variation of atmospheric Hg deposition in the Lake Champlain basin was initiated in December 1992 with one year of event precipitation collection, as well as collection of vapor and particle phase Hg in ambient air. Samples were collected at the Vermont Monitoring Cooperative air monitoring site at the Proctor Maple Research Center in Underhill Center, VT. The average volume-weighted concentration for Hg in precipitation was 8.3 ng/L for the sampling year and the average amount of Hg deposited with each precipitation event was 0.069 μg/m². The total amount of Hg deposited through precipitation during 1993 was 9.26 μg/m²/yr. A seasonal pattern for Hg in precipitation was evident, with increased concentrations and deposition during spring and summer months. Meteorological analysis indicated the highest levels of Hg in precipitation were associated with regional transport from the south regardless of season, and with transport from the west, southwest and northwest during spring and summer months. Concentrations of ambient vapor phase Hg were typical of rural locations and consistent across seasons. Ambient particulate Hg concentrations averaged 11 pg/m³ with highest concentrations during the winter months.     

Ambient Levels and Sources of Lower Carbonyls at Montelibretti, Rome (Italy)

Concentration levels of 11 lower carbonyls were studied at Montelibretti, a semi-rural area near Rome, Italy, over July–September 2005 and February 2006. In both periods the most abundant carbonyls were acetone and formaldehyde, followed by methylglyoxal, acetaldehyde and hexanal. Monthly variation was apparent with maximum values observed in July, when levels at least a factor two higher compared to the successive months were observed. In summer all carbonyls except acetone were reasonably well correlated among themselves and with ozone. In addition very high formaldehyde/benzene concentration ratios were measured in the summer months compared to February. These findings indicated that photochemical reactions should be the major source of carbonyls in summer. Ranking of carbonyls respect to ozone production potential emphasized the predominance of formaldehyde and methylglyoxal, followed at a distance by glyoxal and acetaldehyde.