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1.
Daily measurements of the concentrations of major ions in ambient air and in precipitation at Kejimkujik National Park, Nova Scotia, Canada over the period May 1979 to December 1987 are used to estimate the wet, dry and total deposition to the watershed. Variations on three time-scales are apparent. The strongest variation, of up to two orders of magnitude occurs on a day to day basis resulting in a coefficient of variation in the range of 110 to 140%. Deposition is highly episodic with the highest 20% of the daily events accounting for 55 to 60% of the long-term deposition. The most systematic variation is the annual cycle observed for many of the species. The air concentration of SO2 has the most pronounced cycle with a winter maximum and a summer minimum. The SO inf4 sup= air concentrations show a smaller amplitude and are out-of-phase with SO2, showing a summer maximum. Air concentrations of HNO3 and particulate N0 inf3 sup- also have an out-of-phase annual cycle, with a summer maximum and summer minimum respectively. Wet deposition of SO inf4 sup= shows a broad maximum through the summer months, but for NO inf3 sup- no systematic cycle is evident. On an ion equivalent basis, NO inf3 sup- contributes as much as SO inf4 sup= to the acidity of winter precipitation, but only one-third as much in the summer months. Although 8.7 yr is too short a time-scale to establish long term variations with any certainty, there does appear to be an overall downward trend in S concentrations and deposition, but not for N. This is not inconsistent with the trends in the emissions of SO2 and NOX in the regions upwind of Nova Scotia. The fraction of the S input to the watershed as dry deposition is estimated to average 22% of the total.  相似文献   

2.
Sulfate concentrations in rainwater and in air measured on four summer days at St. Louis were highly variable, both spatially or temporally. Maximum/minimum ratios of aerosol SO inf4 sup? varied by up to a factor of 9, and those in rainwater by a factor of 3 on the average. Generally, SO inf4 sup? concentration patterns in air and rainwater were similar, and consistent with wind direction and the location of sources. Direct relationships between SO inf4 sup? in air and in water were evident on two of the individual days, but not for all days together. The non-uniformity of the SO inf4 sup? pattern plus consideration of possible sources of SO inf4 sup? suggests that nucleation of SO inf4 sup? particles must be a major cause of S scavenging, with some possible influence from sub-cloud impaction.  相似文献   

3.
Data from two national precipitation chemistry monitoring networks, and several regional air and precipitation chemistry networks are used to describe some broad-scale features of acidic deposition in eastern North America. In northeastern North America, the coefficient of variation is shown to increase from 10–16% for annual averages to nearly 100% for daily values. There is a strong annual cycle in H+, SO inf4 sup= and NH inf4 sup+ deposition and some of the other ions although these cycles are not all in phase. The wet NO inf3 sup? deposition contributes relatively more than SO inf4 sup= to the acidity of snow as compared to rain. Wet deposition is highly “episodic” with about 50% to 70% of the total annual deposition of SO inf4 sup= and NO inf3 sup? accumulating in the highest 20% of the days. Estimates made in various ways indicate that, over eastern North America as a whole, dry deposition is approximately equal to wet for both SO inf4 sup= and NO inf3 sup? . Dry may exceed wet in the high emissions zone but drops to about 20% of the total deposition in more remote areas. Deposition via fog or low cloud impaction is an important input to high elevation forests, but more data are required to quantify the magnitude and regional extent of this.  相似文献   

4.
More than 1400 precipitation samples were collected weekly from 5 sites in Nova Scotia between 1978 and 1987. High concentrations of H+, non-marine SO inf4 sup= (*SO4) and NO inf3 sup- were observed in 1978 and 1986. In 1983, concentrations of all three parameters were the lowest in the data record. Fluctuations in emissions for SO2 are insufficient to account for the variability observed in concentration and deposition values. Mean annual concentrations in 1983 were 13, 16, and 6 ueq L-1 for H+, *SO4, and NO inf3 sup- , respectively. In 1986 the values were 35, 28, and 13 ueq L-1. Concentrations in 1978 were 31, 38, and 16 ueq L-1. Average pH of precipitation was 4.61 during the 10 yr study. The two most acidic years were 1979 (4.47) and 1986 (4.46). In 1983, the average pH was 4.89. The ratio (equivalents) of NO inf3 sup- to *SO4 was 0.41, so most acidity in the precipitation results from H2SO4 However, multiple regression analysis revealed that H+ is more sensitive to changes in NO3-concentrations than *SO4. Ratios of summer (JJA) vs winter (JFM) average concentrations were examined. During summer months, *SO4 and H+ were 1.8 times winter values. Summer to winter ratios for NO inf3 sup- and NH inf4 sup+ were 1.4 and 2.5, respectively.  相似文献   

5.
Natural mats of C. stellaris growing in the subarctic lichen woodlands of northern Québec were treated in a randomized complete block design with solutions of simulated rain at pH 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 and 5.6. These solutions were acidified by addition of mixtures of sulfuric and nitric acids to give both 2 : 1 and 6 : 1 μequivalent ratios of SO inf4 sup= : NO inf3 sup? . After two years of acidification there was no significant effect of either pH or SO inf4 sup= : NO inf3 sup? ratio on the growth of C. stellaris, but thallus discoloration was evident below pH 3.5. After three years of acidification marginally significant (p = 0.05) but erratic depression of growth occurred under the 6 : 1 but not the 2 : 1 acidification regime, especially at pH 4.5 or less. Acid precipitation therefore only very gradually impairs the growth of C. stellaris, and the deleterious effects of acidification may be partially offset by nitrogen enrichment when precipitation is relatively rich in nitrate compared to sulfate ions.  相似文献   

6.
Bulk precipitation, throughfall, and soil water chemistry were studied from November 1983 to November 1984 at two ridge-top Appalachian deciduous forest sites to isolate causes of differing episodic stream acidification. The Fork Mountain site in West Virginia, which exhibited little episodic stream acidification, had lower deposition of H+ and SO inf4 sup2? and greater reductions of H+ in the water circulating through the forest canopy, forest floor, and mineral soil than the Peavine Hill site in Pennsylvania. Greater neutralization at Fork Mountain was linked to higher Ca and Mg carbonate contents in the sandstone and shale soil parent materials. Fork Mountain had greater amounts of exchangeable bases in the organic and mineral soil horizons. Neither site appeared to be accumulating SO inf4 sup2? in the soil, with Peavine Hill losing 56% more than was received in bulk deposition. Anions in soil leachate at Fork Mountain were largely balanced by Ca2+ and Mg2+, while at the Peavine Hill site A1" was the dominant cation. Results suggest that the typically-low carbonate content of sandstone and shale soil parent materials commonly found in Appalachian forests may be a key parameter controlling soil and stream acidification. Data for the one-year period also suggest bulk deposition of H+ was 63% greater at Peavine Hill than Fork Mountain.  相似文献   

7.
Precipitation samples in Alberta were collected and analyzed monthly from six Alberta Environment stations. Samples were collected with Sangamo samplers and analyzed for the major ions, pH and acidity. The data were tabulated and analyzed for spatial distribution, seasonal variation, temporal trends, ionic character and wet sulphate deposition. The major ionic species in Alberta precipitation are Ca2+, SO inf4 sup2? , NH inf4 sup+ and N0 inf3 sup? . The spatial distribution shows a slight decrease in pH from southern Alberta (pH 6.0) to northern Alberta (pH 5.4). The seasonal variation shows higher hydrogen ion content in the summer months (pH 5.4 in summer and pH 5.8 in winter). Temporal trends are not apparent over the five year period investigated. The five year average wet sulphate deposition rate in Alberta is 9.1 kg ha?1 yr?1.  相似文献   

8.
Over 3 yr of particulate measurements were made at two high elevation sites in the southern Appalachian Mountains of Tennessee and Virginia. Both dichotomous samplers and filter packs were used to obtain day and night, week-long samples for subsequent elemental and ionic analysis. Total No inf3 sup? (HNO3 + No in3 sup? ) and SO inf4 sup2? averaged, respectively, 1.1 and 5.0 µg m?3 at Look Rock, Tennessee and 2.0 and 6.4 µg m?3 at Whitetop Mountain, Virginia. At Whitetop Mountain, the spring and summer seasons had the highest average SO inf4 sup2? concentrations. Seasonally, total N03 varied little. The diurnal variation of elements and SO inf4 sup2? was small. Only total NO inf3 sup? varied substantially with highest values during the day. The fine fraction (particle diameter < 2.5 µm) accounted for about 67% of the total mass. Fine mass and elemental concentrations were generally higher at Look Rock. The elements comprising the principal mass fraction of the coarse samples (2.5 gm < particle diameter < 10 to 15 µm) were of crustal origin (e.g., Al, Si, Ca, Fe) while the element comprising the principal mass fraction of the fine samples (i.e., S) was of manmade origin. Cluster analysis identified two groups of elements at Whitetop Mountain. These groups, in both the coarse and fine fraction, were associate with a soil and an automobile emission component. At Look Rock, only a soil component was obvious.  相似文献   

9.
Brine shrimp excystment, although highly resistant, is severely inhibited by mmolar mercuric chloride. The presence of 100 mmolar NaCl largely prevents the toxic response. The chloride effect can be explained if the toxic Hg species, neutral HgCl2, is converted into HgCl inf3 sup2? and HgCl inf4 sup2? since charged species not likely to penetrate cyst walls. Other Hg antagonists include SO in3 su2? , SeO inf3 sup2? , TeO inf3 sup2? and TeO inf4 sup2? , but not SO inf4 sup2? and SeO inf4 sup2? . The activity of both Te species can be explained by ready reduction of Te(VI) to Te(IV). Significant anti-mercurial effects were seen in mmolar thiols, ethionine and organoselenium compounds. Thiamine and methionine were both active Hg antagonists at 10 to 30 mmolar levels. The activities of S, Se and Cl? compounds show that both geochemical and physiological modes of defense against and adaptation to high Hg levels exist.  相似文献   

10.
A simple method is presented and used to estimate the portions of SO inf4 sup2? and NO inf? sup3 that contribute to the strong acidity in weekly precipitation samples collected at three NADP sites in the eastern United States. The method assumes that, in general, the difference between SO inf4 sup2? and NH inf+ sup4 represents acidic sulfate and the difference between NO inf? sup3 and soil-derived materials (the sum of Ca2+, Mg2+, and K+) represents acidic nitrate. Acidic sulfate and nitrate are considered to be the predominant source of H+ (determined from laboratory pH) in the weekly precipitation samples. Most of the acidity for all three sites was attributed to acidic sulfate. The highest fraction of acidic SO inf4 sup2? to H+ wet deposition values was for the east-central Tennessee site (0.95) and the northeastern Illinois site (0.90), and the lowest fraction occurred at the central Pennsylvania site (0.75). The Tennessee site had the greatest acidic fraction of sulfate (0.84) and the Pennsylvania site had the greatest acidic fraction of nitrate (0.59).  相似文献   

11.
Experiments were carried.out in Chongging-a city seriously damaged by acid precipitation in southwest China — to explore chemical compositions of open bulk precipitation, throughfall and stemflow in a Masson pine (Pinus massoniana) forest. The results showed that annual mean pH values of and annual ion depositions in the three types of rain water were 4.47 and 50.6 g m?2, 3.82 and 69.7 g m?2, and 2.92 and 0.215 g m?2 respectively. pH values demonstrated an obvious seasonal variation; they were lower in winter than in the rest of the year. Ca2+ and NH inf4 sup+ together made up more than 80% of the total cation, while SO in4 sup2? alone contributed over 90% to the total anion. This high level of SO in4 sup2? in rain water in Chongqing, which outran those found in other cities in China, was closely related to the combustion of locally produced coal that contains 3 to 5% sulphur. Thus, acid precipitation in Chongqing is of a typical sulphuric-acid type.  相似文献   

12.
The depletion of epilimnetic DO during fall, and the accumulation of H2S in the hypolimnion during summer, are documented for polluted hypereutrophic Onondaga Lake, NY, U.S.A. The fall epilimnetic DO depletion is so severe that in many, if not all years, the New York State standard for minimum DO of 4 mg- L?1 is violated for periods as long as 1 mo. The depletion is caused by the transport of O2 demanding species, particularly H2S, from the hypolimnion into the epilimnion. Hydrogen sulfide accumulates progressively through the summer, mostly via SO inf4 sup2? reduction, to unusually high concentrations; a maximum of 1.65 mM has been observed. These conditions are apparently manifestations of hypereutrophy, and thus may be subject to remediation through P management efforts.  相似文献   

13.
Although Lake Anna, an impoundment in Central Virginia, receives acid mine drainage (AMD) from Contrary Creek, the effects of the AMD pollution on the lake are less severe than expected. Previous work at Lake Anna has shown that bacterial sulfate reduction in the lake sediments plays an important role in the recovery of the lake from the AMD inputs. Sulfate removal rates were measured in sediment microcosms under a variety of experimental conditions to determine the factors controlling the rate of sulfate and acidity removal from the lake water. Sulfate removal rates were not significantly different over the short term (3 weeks) in summer sediment microcosms incubated at 6 vs 26 °C. Winter sediment microcosms showed no significant sulfate removal during the 18 day experiment when incubated at either 6 or 28 °C. Thus there is a strong seasonal temperature effect in Lake Anna sediments but no significant short term effect. Simulated AMD, with and without Fe, was added to sediment microcosms collected from an unpolluted part of the lake. The microcosms with Fe had significantly higher rates of sulfate removal indicating that Fe plays an important role in transporting sulfate to the sediment and/or in preventing oxidation of the reduced sulfide. After 27 days, from 54 to 96% of the added sulfate in the simulated AMD was recovered as FeS or S0 in the top 4 cm of sediment. In a separate experiment, 35S-SO inf4 sup2? was found to attach to precipitating Fe oxyhydroxides (1.5 to 4.7 mol SO inf4 sup2? mol?1 Fe precipitate) upon mixing Contrary Creek (AMD) and Lake Anna waters. Results of this study suggest that sulfate removal may be more rapid in metal rich AMD systems thans in metal poor systems characteristic of those which receive acidic deposition.  相似文献   

14.
A 2 yr field study on the influence of N fertilization and rainfall on groundwater pollution was carried out in the sandy area of Belgium. The NO inf3 sup? -N and Cl? content of the groundwater at 0.5, 1.0, 1.5, and 2.0 m depths was monitored every two weeks on a field, grown with barley in 1980 and with maize in 1981. Turnips for cattle feed were grown in between the two crops. The total annual rainfall during the period under study was about 800 mm. The NO inf3 sup? -N content at all depths was at all times above 11.3 mg NO inf3 sup? -N dm?3, the WHO safe limit. Fluctuation of the NO inf3 sup? -N content occurred mainly at 0.5 and 1.0 m. The concentration at 1.5 and 2.0 m depths was higher most of the time than at 0.5 and 1.0 m. Leaching of NO inf3 sup? -N into deeper layers occurred when there was heavy rainfall. There was no important loss of NO inf3 sup? -N through denitrification at 1.5 and 2.0 m depths.  相似文献   

15.
Summary The biodegradation of litter from Festuca silvatica, Abies pectinata, Fagus silvatica, Calluna vulgaris, Picea abies associated with forest brown acid soils or with podzolic soils was studied in field lysimeters filled with granite sand. Analysis of the leachates collected during 2 years made it possible to determine NO inf3 sup- , NH inf4 sup+ , and soluble organic N production in order to investigate the specific influence of the different species of litter on the mineralization of organic N and the variations in nitrification. With Festuca silvatica (grass), active nitrification was observed after the addition of fresh litter in autumn (fall of leaves). Nitrification remained significant in winter, reached a maximum in spring until early summer, and then decreased after mineralization of the easily mineralizable organic N. Nitrification was the major N transformation process in this litter. The addition of fresh litter of Abies pectinata (fir), Fagus silvatica (beech), Calluna vulgaris (heather), and Picea abies (spruce) in autumn induced an inhibition of nitrification during winter and spring. With these litter species, nitrification started again by the end of spring and was at a maximum in summer and autumn until leaf fall. By comparison with Festuca, inhibition observed in winter and spring with the other litter species was definitely due to the chemical composition of the leaves. Simultaneously, a lower C mineralization of these plant material occured. These litter species, in particular Calluna and Picea released leachates containing significant amounts of soluble organic N that were only slightly decomposed. We conclude that NO inf3 sup- production outside of the plant growth period can definitely be involved in soil acidification and weathering processes.  相似文献   

16.
Precipitation chemistry data were collected at 8 sites in the western part of the Netherlands over a period of 151/2 yr. Using specially-designed wind direction-dependent rain collectors, it is demonstrated that levels of ion constituents in rain water vary with wind direction, which can be assigned to different sources of contamination. The strongest variation was measured for Na+. As expected, trajectories over sea contributed most. Continental sources slightly reduced the variation for Cl? and Mg2+. For both NH inf4 sup+ and excess SO inf4 sup2? , maxima were found in southeasterly rainfall. It is assumed that polluted air from the large industrial Ruhr Area crosses a region with strong NH3 emissions in the Southeast of the Netherlands. The presence of ammonium sulfate was suggested. Minor variations were measured for NO inf3 sup? (due to diffusely-spread emissions and possible sampling artefact) and for H+ and Ca2+ (dry-deposition effects). Over the period 1973–1987 excess-SO inf4 sup2? levels decreased significantly (?3.3% yr?1, p<0.01) which is consistent with reduced S emission in Western Europe. Over the last decade an upward trend in NO inf3 sup? levels has been observed (3.2% yr?1, p<0.05) which is possibly related to the increased usage of cars.  相似文献   

17.
A preliminary analysis of O3, SO2, SO inf4 sup2? , and total NO inf3 sup? deposition to the red spruce forest on the summit of Whitetop Mountain, Virginia, illustrates uncertainties in analysis methodologies, establishes the relative importance of three deposition pathways, and suggests areas for further research. Results are presented here for an analysis of the dry, wet (precipitation), and cloud water deposition pathways for the four chemical species during a 26-day period in April and May 1986. Dry and cloud water depositions are estimated using available models along with air and cloud water chemistry measurements made at the summit. For water soluble species, depositions by precipitation and cloud interception are found to be comparable in magnitude, while dry deposition appears to be about an order of magnitude less. High levels of atmospheric O3 lead to a large estimate of 03 deposition (on a mass flux basis) when compared to the estimated deposition of gaseous SO2. This is in spite of the fact that computed SO2 dry deposition velocities exceed those for O3. Model uncertainties are large for both dry deposition velocity and cloud water flux computations, and some bias in computations probably exists because of the application of the models to a complex terrain situation. Field evaluation of the cloud water deposition model is of greatest priority because of the apparent relative importance of that deposition pathway.  相似文献   

18.
Data collected during 1986 at seven widely separated sites in the eastern United States were used to estimate weekly averages of deposition velocities for SO2, O3, HNO3, and SO inf4 sup2? with both a modified version of the RADM dry deposition module and a site-specific inferential technique developed by the Atmospheric Turbulence and Diffusion Division of the National Oceanic and Atmospheric Administration's Air Resources Laboratory. The results show some systematic differences between the two techniques, even when the module uses distributions of landuse types that match as closely as possible the observed vegetation coverages used in the inferential technique. When one ignores the systematic differences that easily could be removed by minor changes in the algorithms for computing resistances to deposition, weekly averages of the deposition velocities calculated with the two methods are within approximately ±30% of each other for SO2 and O3. Overall, the relative differences in the deposition velocities for HNO3 and SO inf4 sup2? are about ±30 and ±50%, respectively. Use of the module with landuse types extrapolated to areas as large as RADM grid cells (approximately 80 km square) around the measurement stations produces weekly averages within ±20% of the site-specific estimates for SO2, O3, and SO inf4 sup2? and approximately ±30% for HNO3 if one avoids landuse types such as urban and water areas that are both nonrepresentative and have very different characteristics from the measurement sites. These estimates are not complete measures of the true uncertainty associated with the two techniques because they do not account for such effects as differences in the siting of instrumentation for collecting input data and the inability of the computational algorithms to include the many surface nonuniformities that typically exist in the areas surrounding measurement sites.  相似文献   

19.
Increased concentrations of solutes in drainage waters following forest clearcutting may affect downstream water quality. The objective of this study was to evaluate some of the processes regulating concentrations of trace metals and Fe in soil solutions and streamwater in a clearcut watershed by determining changes in metal release by soil horizon, stand vegetation and elevation. Commercial whole-tree harvesting of a watershed at the Hubbard Brook Experimental Forest, NH, U.S.A. resulted in increased loss of NO inf3 sup? from the study watershed. This N0 inf3 sup? loss resulted in acidification of soil solutions, which was associated with release of Mn and Zn from mineral soil to soil solutions and streamwater. Significant correlations of Pb and Fe with dissolved organic C (DOC) suggested that mobilization of these metals was linked to DOC transfer. However, there was little evidence of increased release of DOC, Fe, or Pb following the whole-tree harvest, except in a high elevation spruce-fir zone with shallow soils.  相似文献   

20.
The influence of NTA, EDTA, STPP, Triton X100, PO inf4 sup3 and NO inf3 sup? on the mobilization of Pb, Cd, Cu, Cr and Mn from sediments of two rivers located in Northern Greece was studied. The release caused by all examined complexing agents was higher in deionized water than either Axios or Aliakmon river water due to the lack of competition of Ca and Mg cations with the heavy metals for the studied complexing agents, and the decrease of ionic strength. From all examined agents NTA and EDTA showed the greater mobilization ability. Copper showed the greater tendency for remobilization by all examined agents, (according to the order: EDTA?NTA, Triton X1004 PO inf4 sup3? > NO inf3 sup3? ?STPP) while Cr and Mn the smallest following the orders: NTA, PO inf4 sup3? >> NO inf3 sup? , Triton X1004 EDTA, STPP and STPP > EDTA > NTA > Triton X 100 ? PO inf4 sup3? NO3, respectively. An increase in mobilization was noticed with an increase of agent concentration and time of shaking.  相似文献   

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