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1.
The Norwegian Monitoring Programme for Long-Range Transported Air Pollutants started in 1980. The biological part of this programme includes besides invertebrate studies in streams, (i) fish community status in lakes by means of interviews, test-fishing in lakes by using standard gill-net series, recruitment studies of brown trout in inland streams, and juvenile stock assess and monitoring of fish kills in salmon rivers. Damaged fish stocks are recognized within a land area of 51,500 km2 in southern Norway and 30 km2 in northern Norway. At least 6,000 lake-dwelling fish stocks have either been lost or are at various stages of reduction. Brown trout (Salmo trutta) is the most widespread and abundant species of fish in Norwegian watersheds, and is also most severe affected by acidification. More recently, there are some indications of an increase in the abundance of brown trout in some areas. However, analysis of age structure in lakes, and fry densities in streams in such areas revealed large annual variations in recruitment rate, which indicates unstable water chemical conditions. Atlantic salmon (Salmo salar) is virtually extinct in 25 rivers in southernmost, southwestern and western Norway.  相似文献   

2.
In this paper we document the effects of acidification on fish populations in lakes in Sør-Varanger near the Russian border in northern Norway. We used questionnaires in order to assess the current status and distribution of different fish species, and conducted test-fishing to determine relative abundance (CPUE-T) and age structure. Acidification of surface waters in this area is due to emissions of SO2 from smelters on the Kola Peninsula in Russia (Nikel and Zapoljarnij) between 10 and 30 km from the Norwegian border. Sulphur deposition in Sør-Varanger ranges from 0.6 to 2.0 g S m-2 yr-1, which is similar to levels in the most acidified areas in southern Norway. However, a dominant fraction of the acidic deposition reaches the ground in particulate form during summer and autumn. Coastal areas in Sør-Varanger receive small amounts of precipitation; the annual mean is 580 mm. We obtained fish status from 401 lakes, about 40% of all lakes larger than 3 ha, which were inhabited by 236 and 293 populations of Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta), respectively. The extent of fish damage was small as only three populations of Arctic charr were lost, while three populations of Arctic charr and eight populations of brown trout were at various stages of reduction. Damaged and lost fish populations were identified in smaller lakes at relatively high elevations (172–349 m) in six areas in the Jarfjord Mountains, covering a land area of 30.0 km2. Most of the damage probably occurred during the 1970s and 1980s. In lakes that supported or had supported Arctic charr and brown trout, we found a significant relationship between CPUE-T, and acid neutralizing capacity (ANC) and pH, and also between alkalinity and the concentration of inorganic Al for brown trout. In both species, the catch of fish in age groups 1+ and 2+ (CPUE-R) increased significantly with CPUE-T. Affected populations typically exhibited irregular age composition, and age-classes were missing, indicating that reductions in fish populations were due to recruitment failure. The limited fish damage is related to relatively good catchment resistance to acidic inputs, small amounts of wet deposition as well as precipitation. These conditions result in low accumulation of acidic compounds, producing less acidic run-off waters and few episodes of unfavourable water quality.  相似文献   

3.
The joint research project, ‘Acid Precipitation — Effects on Forest and Fish‘ (the SNSF-project) of the Agricultural Research Council of Norway and the Norwegian Council for Scientific and Industrial Research was started in 1972. The objectives of the project are to: (1) establish as precisely as possible the effects of acid precipitation on forest and freshwater fish; and (2) investigate the effects of air pollutants on soil, vegetation, and water, required to satisfy point 1. Research activities on the project are organized and carried out mainly at four institutes. Within and between these institutes groups are formed carrying out investigations in fields including atmospheric transport and chemistry, dry deposition and leaching of foliage, forest growth, soil biology and soil chemistry, hydrological relationships of peatland, hydrobiology with special stress on fish, and hydrochemistry including snow chemistry.  相似文献   

4.
Concentrations of sulphate in precipitation in southern Norway have decreased by 50–60% from 1980–1999. This has caused a decrease in sulphate concentrations in lakes of 30–40% from 1986–1999. Nitrogen in precipitation has decreased slightly over the last 10-years. In lakewater there has also been a significant but slight decrease. Concentrations of non-marine base cations in precipitation have decreased by 40% from 1980–1999. In lakewater, non-marine base cation concentrations have been at about the same level the last 10 years. This indicates that acid deposition has decreased sufficiently such that the pool of exchangeable base cations in the soil is now being replenished. The acidification situation in lakes in Norway has thus shown a clear improvement over the last 8–10 years. pH, alkalinity and ANC (acid neutralising capacity) have all increased. Concentrations of inorganic (toxic) aluminium species have decreased. The trends in H+ and Aln+ do not follow the relation expected if Aln+ concentrations were governed solely by a single solid phase of Al(OH)3.  相似文献   

5.
We have measured the input and output rates of substances to and from both lakes and watersheds in the Sudbury and Muskoka-Haliburton areas of Ontario. At the former location, we have conducted mass balance studies on 5 lakes and their watersheds for 2½ yrs. At the latter site, we have measured mass balances for 6 lakes and about 30 individual watersheds for the past 5 yrs. Substances studied included SO4 2?, NO3 ?, NH4 +, H+, major cations (Ca2+, Mg2+, Na+, K+) and HCO3 ?. During the course of the investigation at Sudbury we have made several observations that indicate that the inputs of some substances, specifically SO4 2? or SO4 2?-precursors and strong acids, to lakes and watersheds are underestimated when measured as bulk deposition (i.e. by collection in a continuously open container): (a) The output of SO4 2? from the calibrated watersheds was substantially greater than the input measured as bulk deposition. (b) The SO4 2? concentrations of the lakes could not be explained on the basis of the measured inputs. An additional input directly to the lake surface was needed to obtain a mass balance. (c) The net input of acids measured as bulk deposition to the watersheds was much less than the acid consumed, which was estimated by the net output of Ca2+, Mg2+, Na+, K+, Al3+, and the net retention of NO3 ?. (d) The major cation content of the study lakes could be explained on the basis of weathering reactions in the lakes' watersheds only if the input of strong acid had been underestimated. When these observations were quantified, they indicated a major portion of the total input of SO4 2?-precursors and of strong acid was not included in our bulk deposition measurements. Deposition of SO2 is the most likely explanation for these observations.  相似文献   

6.
Acid deposition has led to acidification and loss of fish populations in thousands of lakes and streams in Norway. Since the peak in the late 1970s, acid deposition has been greatly reduced and acidified surface waters have shown chemical recovery. Biological recovery, in particular fish populations, however, has lagged behind. Long-term monitoring of water chemistry and fish populations in Lake Langtjern, south-eastern Norway, shows that around 2008, chemical recovery had progressed to the point at which natural reproduction of brown trout (Salmo trutta) reoccurred. The stocked brown trout reproduced in the period 2008–2014, probably for the first time since the 1960s, but reproduction and/or early life stage survival was very low. The results indicate that chemical thresholds for reproduction in this lake are approximately pH?=?5.1, Ali?=?26 μg l?1, ANC?=?47 μeq l?1, and ANCoaa?=?10 μeq l?1 as annual mean values. These thresholds agree largely with the few other cases of documented recovery of brown trout in sites in Norway, Sweden, and the UK. Occurrence and duration of acidic episodes have decreased considerably since the 1980s but still occur and probably limit reproduction success.  相似文献   

7.
Estimating the atmospheric input of ions to a watershed has traditionally been accomplished through either the extrapolation of point measurements of deposition or the integration of model estimated deposition. This paper examines the characteristics of precipitation chemistry on the eastern seaboard of the United States where precipitation quality could conceivably affect fish habitats in estuaries. The measured values presented here have been extracted from the data base of the Utility Acid Precipitation Sampling Program (UAPSP) precipitation chemistry network. These data illustrate the nature of ionic deposition at four points on the eastern seabord. The deposition of H' (acidity) is shown to be dependent upon the amount of sulfate and, to a lesser degree, nitrate in the precipitation. It is also shown that the quantity of ionic deposition on a storm-by-storm basis was influenced by the amount of water deposition but the relationship was not very strong. Thus the use of water deposition as a surrogate for ionic deposition is not justified in these watersheds. Finally, it is shown that the deposition of H+, SO4 2?, NO3 ?, and NH4 + were not clearly seasonal. While a large percentage of total ionic deposition occurred in a small number of precipitation events, these exceptional events were not confined to a particular season.  相似文献   

8.
The sources and mechanisms regulating fluoride (F) in Norwegian lake waters are studied using data from regional surveys of precipitation chemistry, lake water chemistry and bedrock geology. Fluoride concentrations in Norwegian lakes range from < 5 to 560 μg L?1. Fluoride content in the bedrock is the most important factor controlling F levels in lake waters, as shown by significant differences in median value of F concentrations between lakes situated in different geological provinces. There are also weak but significant correlations between F in the lakes and components typical for weathering such as non-marine Ca, Mg, Na and K. The regional picture of F concentration in lake water shows elevated F concentrations in the acidified areas in southern and southeastern Norway compared to other regions of the country with comparable geology. There is a weak but significant correlation between F and SO4, a typical indicator of acidification in surface water. Mass balance calculations in three catchments show that F is retained in soils in pristine areas, while F output exceeds precipitation input in acidified areas. This both demonstrates the strong retention capacity for F in soils and indicates that anthropogenic F added through polluted rain is a minor source of F in surface waters. Fluoride is mobilized in acidifies areas, probably due to complexation with Al.  相似文献   

9.
A freshwater wetland at the Experimental Lakes Area in northwestern Ontario stored most of the SO4 2? received annually from precipitation, runoff and experimental additions. The S budget was determined for a small fen spray irrigated with H2SO4 and HNO3. Annual S retention was greatest during the first year of experimental addition of H2SO4 (73% of input in 1983). Retention was lowest (22%) in 1984, a year of lower than average precipitation with a long hot summer. During years with hot, dry summers, SO4 2? was produced from the reoxidation of reduced S compounds in the peat and released to surface waters. The autumn SO4 2? pulse was accompanied by the release of Ca and Mg but was not accompanied by a H+ release as has been detected in eastern Ontario and southern Norway, areas which receive more acidic precipitation.  相似文献   

10.
A total of 51 lakes in southern Quebec, Canada, were sampled between 1985 and 1993 to study changes in water chemistry following reductions in SO2 emissions (main precursor of acid precipitation). Time series analysis of precipitation chemistry revealed significant reductions in concentrations and deposition of SO4 2- from 1981 to 1992 in southern Quebec as well as reductions in concentrations and deposition of base cations (Ca2+, Mg2+), NO3 - and H+ in the western section of the study area. Reductions in atmospheric inputs of SO4 2- have resulted in decreased lakewater SO4 2- concentrations in the majority of the lakes in our study, although only a small fraction (9 of 37 lakes used in the temporal analysis) have improved significantly in terms of acidity status (pH, acid neutralizing capacity – ANC). The main response of the lakes to decreased SO4 2- is a decrease in base cations (Ca2++Mg2+), which was observed in 17 of 37 lakes. Seventeen lakes also showed significant increases in dissolved organic carbon (DOC) over the period of study. The resulting increases in organic acidity as well as the decrease in base cations could both play a role in delaying the recovery of our lakes.  相似文献   

11.
Alkalinity production in terrestrial and aquatic ecosystems of Canada, the U.S.A., Norway and Sweden is calculated from either strong acid titrations or budgets for base cations and strong acid anions, using mass-balance budgets. Where alkalinity budgets for lakes and their catchments are calculated in acid-vulnerable geological settings, in-lake processes often contribute more to lake alkalinity than yield from terrestrial catchments. Nitrate and sulfate removal, and Ca exchange with sediments are the predominant alkalinity generating mechanisms in lakes. Nitrate and sulfte removal rates increase as the concentrations of NO? 3 and SO4 2? in lake water increase, so that in-lake acid neutralizing capacity increases as acid deposition increases. Both processes occur in sediments overlain by oxic waters, at rates which seem to be controlled primarily by diffusion.  相似文献   

12.
During the period 1977–1980 we studied the effects of highly acidic precipitation (mean pH 4.1 to 4.2) on the chemistry of three Adirondack lakes: Woods Lake, Panther Lake, and Sagamore Lake. Two of these lakes (Woods and Panther) are enough like those lakes of southern Sweden and Norway studied by Henriksen that they should constitute a valid test of his ‘acidification indicator’ and ‘predictor homograph’. In our comparison we used data from weekly samples taken near the surface of the lakes during unstratified summer and fall conditions over a 3 yr period. The acidification indicator and predictor nomograph were developed using data from lake samples taken under similar conditions in Scandinavia. Our principal finding is that with regard to the empirical line of the acidification indicator (that Henriksen found separated data from lakes receiving precipitation greater or less than pH 4.6) and with the precipitation pH axis of the predictor nomograph, these two methods of evaluation are not directly applicable ‘as is’ to our lakes. The reason for this is that the chemistry of precipitation in the Adirondacks is significantly different from (and for) which the acidification indicator and predictor nomograph were developed. In the Adirondacks, acids other than H2SO4 play a much greater role in the overall acidity of the precipitation. This causes relationships between precipitation pH and lake chemistry in the two regions to be different.  相似文献   

13.
The acidification of lakes in southern Norway is largely due to sulfate. Recent data from regional surveys of lakes and from monitoring stations indicates that nitrate concentrations have increased in many lakes and rivers in southernmost Norway. The ratio of NO3 to NO3 + SO4 is still low for most areas, but is 0.54 on an equivalent basis in lakes and rivers in the area of high runoff in southwestern Norway. Here, concentrations of nitrate in the runoff are lower than for sites in Central Europe, but are higher than those in North America. The sites showing increases in NO3 also increased in Al. Further increases in nitrate as a mobile anion which may be due to decreased uptake in the watershed, will contribute to acidification in the same manner as sulfate.  相似文献   

14.
During the last decade a new pattern of Hg pollution has been discerned, mostly in Scandinavia and North America. Fish from low productive lakes, even in remote areas, have been found to have a high Hg content. This pollution problem cannot be connected to single Hg discharges but is due to more widespread air pollution and long-range transport of pollutants. A large number of waters are affected and the problem is of a regional character. The national limits for Hg in fish are exceeded in a large number of lakes. In Sweden alone, it has been estimated that the total number of lakes exceeding the blacklisting limit of 1 mg Hg kg-1 in 1-kg pike is about 10 000. The content of Hg in fish has markedly increased in a large part of Sweden, exceeding the estimate background level by about a factor of 2 to 6. Only in the northernmost part of the country is the content in fish close to natural values. There is, however, a large variation of Hg content in fish within the same region, which is basically due to natural conditions such as the geological and hydrological properties of the drainage area. Higher concentrations in fish are mostly found in smaller lakes and in waters with a higher content of humic matter. Since only a small percentage of the total flow of Hg through a lake basin is transferred into the biological system, the bioavailability and the accumulation pattern of Hg in the food web is of importance for the Hg concentrations in top predators like pike. Especially, the transfer of Hg to low trophic levels seems to be a very important factor in determining the concentration in the food web. The fluxes of biomass through the fish community appear to be dominated by fluxes in the pelagic food web. The Hg in the lake water is therefore probably more important as a secondary source of Hg in pike than is the sediment via the benthic food chain. Different remedy actions to reduce Hg in fish have been tested. Improvements have been obtained by measures designed to reduce the transport of Hg to the lakes from the catchment area, eg. wetland liming and drainage area liming, to reduce the Hg flow via the pelagic nutrient chains, eg. intensive fishing, and to reduce the biologically available proportion of the total lake dose of Hg, eg. lake liming with different types of lime and additions of selenium. The length of time necessary before the remedy gives result is a central question, due to the long half-time of Hg in pike. In general it has been possible to reduce the Hg content in perch by 20 to 30% two years after treatments like lake liming, wetland liming, drainage area liming and intensive fishing. Selenium treatment is also effective, but before this method can be recommended, dosing problems and questions concerning the effects of selenium on other species must be evaluated. Regardless how essential these kind of remedial measures may be in a short-term perspective, the only satisfactory long-term alternative is to minimize the Hg contamination in air, soil and water. Internationally, the major sources of Hg emissions to the atmosphere are chlor-alkali factories, waste incineration plants, coal and peat combustion units and metal smelter industries. In the combustion processes without flue gas cleaning systems, probably about 20 to 60% of the Hg is emitted in divalent forms. In Sweden, large amounts of Hg were emitted to the atmosphere during the 50s and 60s, mainly from chlor-alkali plants and from metal production. In those years, the discharges from point sources were about 20 to 30 t yr 1. Since the end of the 60s, the emission of Hg has been reduced dramatically due to better emission control legislation, improved technology, and reduction of polluting industrial production. At present, the annual emissions of Hg to air are about 3.5 t from point sources in Sweden. In air, more than 95% of Hg is present as the elemental Hg form, HgO0. The remaining non-elemental (oxidized) form is partly associated to particles with a high wash-out ratio, and therefore more easily deposited to soils and surface waters by precipitation. The total Hg concentration in air is normally in the range 1 to 4 ng m-3. In oceanic regions in the southern hemisphere, the concentration is generally about 1 ng m?3, while the corresponding figure for the northern hemisphere is about 2 ng m-3. In remote continental regions, the concentrations are mainly about 2 to 4 ng m?3. In precipitation, Hg concentrations are generally found in the range 1 to 100 ng L?1. In the Nordic countries, yearly mean values in rural areas are about 20 to 40 ng L?1 in the southern and central parts, and about 10 ng L?1 in the northern part. Accordingly, wet deposition is about 20 (10 to 35) g km?2 yr?1 in southern Scandinavia and 5 (2 to 7) in the northern part. Calculations of Hg deposition based on forest moss mapping techniques give similar values. The general pattern of atmospheric deposition of Hg with decreasing values from the southwest part of the country towards the north, strongly suggests that the deposition over Sweden is dominated by sources in other European countries. This conclusion is supported by analyses of air parcel back trajectories and findings of significant covariations between Hg and other long range transported pollutants in the precipitation. Apart from the long range transport of anthropogenic Hg, the deposition over Sweden may also be affected by an oxidation of elemental Hg in the atmosphere. Atmospheric Hg deposited on podzolic soils, the most common type of forest soil in Sweden, is effectively bound in the humus-rich upper parts of the forest soil. In the Tiveden area in southern Sweden, about 75 to 80% of the yearly deposition is retained in the humus layer, chemically bound to S or Se atoms in the humic structure. The amount of Hg found in the B horizon of the soils is probably only slightly influenced by anthropogenic emissions. In the deeper layers of the soil, hardly any accumulation of Hg takes place. The dominating horizontal flow in the soils takes place in the uppermost soil layers (0 to 20 cm) during periods of high precipitation and high groun water level in the soils. The yearly transport of Hg within the soils has been calculated to be about 5 to 6 g km?2. The specific transport of total Hg from the soil system to running waters and lakes in Sweden is about 1 to 6 g km?2 yr1. The transport of Hg is closely related to the transport of humic matter in the water. The main factors influencing the Hg content and the transport of Hg in run-off waters from soils are therefore the Hg content in soils, the transport of humic matter from the soils and the humus content of the water. Other factors, for example acidification of soils and waters, are of secondary importance. Large peatlands and major lake basins in the catchment area reduce the out-transport of Hg from such areas. About 25 to 75% of the total load of Hg of lakes in southern and central Sweden originates from run-off from the catchment area. In lakes where the total load is high, the transport from run-off is the dominating pathway. The total Hg concentrations in soil solution are usually in the range 1 to 50, in ground water 0.5 to 15 and in run-off and lake water 2 to 12 ng L?1, respectively. The variation is largely due to differences in the humus content of the waters. In deep ground water with a low content of humic substances, the Hg concentration is usually below 1 ng L?1. The present amount and concentrations of Hg in the mor layer of forest soils are affected by the total anthropogenic emissions of Hg to the atmosphere, mainly during this century. Especially in the southern part of Sweden and in the central part along the Bothnian coast, the concentrations in the mor layer are markedly high. In southern areas the anthropogenic part of the total Hg content is about 70 to 90%. Here, the increased content in these soils is mainly caused by long-range transport and emissions from other European countries, while high level areas in the central parts are markedly affected by local historical emissions, mainly from the chlor-alkali industry. When comparing the input/output fluxes to watersheds it is evident that the present atmospheric deposition is much higher than the output via run-off waters, on average about 3 to 10 times higher, with the highest ration in the southern parts of Sweden. Obviously, Hg is accumulating in forest soils in Sweden at the present atmospheric deposition rate and, accordingly, the concentrations in forest soils are still increasing despite the fact that the emissions of Hg have drastically been reduced in Sweden during the last decades. The increased content of Hg in forest soils may have an effect on the organisms and the biological processes in the soils. Hg is by far the most toxic metal to microorganisms. In some regions in Sweden, the content of Hg in soils is already today at a level that has been proposed as a critical concentration. To obtain a general decrease in the Hg content in fish and in forest soils, the atmospheric deposition of Hg has to be reduced. The critical atmospheric load of Hg can be defined as the load where the input to the forest soils is less than the output and, consequently, where the Hg content in the top soil layers and the transport of Hg to the surface waters start to decrease. A reduction by about 80% of the present atmospheric wet deposition has to be obtained to reach the critical load for Scandinavia.  相似文献   

15.
Although the decline in fish populations due to acidicwater in Norway started as early as in the 1920's the most rapid losses appeared during the 1960–70's. Until 1978, the populations of Atlantic salmon had disappeared from the southernmost part of Norway, and in these areas, more than half of the brown trout populations had been lost. Today, in spite of no increase in acid depositions, the fishery problems seems to continue at the same speed. Data based on interviews of the local fish authority shows that lakes still holding a fish population in the late 70's, have experienced a 30% loss of brown trout populations and a 12% loss of perch in the period 1978–1983. This trend have been confirmed by testfishing in lake systems having long data series. Salmon rivers on the western coast of Norway have experienced several episodes of fish kills due to rapid changes in water quality. These fish kills have mainly affected smolts of Atlantic salmon. Spawning migrating salmon on entering their acidified home river have also been affected. In Sweden, several salmon populations along the western coast have been lost due to acidification with no positive trends so far in the 1980's. Areas in central Sweden and in some high mountain areas are still experiencing a continuous and increasing acidification with detrimental effects on invertebrates and fish. In Finland, an increase in acidic deposition during the last decades have occurred, leading to acidification in the most sensitive freshwater systems. Although some acidified freshwater lakes are reported to have lost their fish stocks, few data on fish population effects are available.  相似文献   

16.
Organochlorine residues were analyzed in brook trout (Salvelinus fontinalis) collected from six undisturbed lakes in Maine, New Hampshire and Vermont. The residues (whole body) were compared among age groups of fish and were correlated by regression analyses with water chemistry factors that might be affected by acid precipitation. There were significant differences in the organochlorine content of fish from different lakes but not among age groups of fish within each lake or among all lakes. There were no significant correlations between the water chemistry values measured and organochlorine content of the fish. Inasmuch as no organochlorine pesticides have been used within the lake watersheds, the compounds must have reached these lakes by atmospheric transport.  相似文献   

17.
A lake survey consisting of 987 randomly selected lakes was conducted in Finland in autumn 1987. The survey covered the whole country, and the water quality of the lakes can be considered as representative of the approximately 56 000 lakes larger than 0.01 km2 in Finland. The median TOC concentration is 12 mg L-1 and the median pH 6.3. The proportion of lakes with TOC concentrations > 5 mg L-1 in the whole country is 91 %. Organic anion is the main anion in the full data set (median 89 μeq L-1). The high organic matter concentrations in Finnish lakes are associated with catchment areas containing large proportions of peatlands and acid organic soils under coniferous forest. The survey demonstrated that organic matter strongly affects the acidity of lakes in Finland. The decreasing effect of organic matter on the pH values was demonstrated by both regression analysis and ion balances. At current deposition levels of *SO4 the pH of humic lakes in Finland is determined to a greater extent by high TOC concentrations than by *SO4 in most areas. In lakes with pH values lower than 5.5 the average organic anion contribution is 56 % and non-marine sulfate contribution 39 %. However, in the southern parts of the country, where the acidic deposition is highest, the minerogenic acidity commonly exceeds the catchment derived organic acidity.  相似文献   

18.
Acidic precipitation, wet or frozen precipitation with a H+ concentration greater than 2.5 μeq l?1, is a significant air pollution problem in the United States. The chief anions accounting for the H+ in rainfall are nitrate and sulfate. Agricultural systems may derive greater net nutritional benefits from increasing inputs of acidic rain than do forest systems when soils alone are considered. Agricultural soils may benefit because of the high N and S requirements of agricultural plants. Detrimental effects to forest soils may result if atmospheric H+ inputs significantly add to or exceed H+ production by soils. Acidification of fresh waters of southern Scandinavia, southwestern Scotland, southeastern Canada, and northeastern United States is caused by acid deposition. Areas of these regions in which this acidification occurs have in common, highly acidic precipitation with volume weighted mean annual H+ concentrations of 25 μeq l?1 or higher and slow weathering of granitic or precambrian bedrock with thin soils deficient in minerals which would provide buffer capacity. Biological effects of acidification of fresh waters are detectable below pH 6.0. As lake and stream pH levels decrease below pH 6.0, many species of plants, invertebrates, and vertebrates are progressively eliminated. Generally, fisheries are severely impacted below pH 5.0 and are completely destroyed below pH 4.8. At the present time studies documenting effects of acidic precipitation on terrestrial vegetation are insufficient to establish an air quality standard. It must be demonstrated that current levels of precipitation acidity alone significantly injure terrestrial vegetation. For aquatic ecosystems, current research indicates that establishing a maximum permissible value for the volume weighted annual H+ concentration of precipitation at 25 μeq l?1 may protect the most sensitive areas from permanent lake acidification. Such a standard would probably protect other systems as well.  相似文献   

19.
There is considerable interest in the recovery of surface waters from acidification by acidic deposition. The Adirondack Long-Term Monitoring (ALTM) program was established in 1982 to evaluate changes in the chemistry of 17 Adirondack lakes. The ALTM lakes exhibited relatively uniform concentrations of SO4 2?. Lake-to-lake variability in acid neutralizing capacity (ANC) was largely due to differences in the supply of basic cations (Ca2+, Mg2+, K+, Na+; CB) to drainage waters. Lakes in the western and southern Adirondacks showed elevated concentrations of NO3 ?, while lakes in the central and eastern Adirondacks had lower NO3 ? concentrations during both peak and base flow periods. The ALTM lakes exhibited seasonal variations in ANC. Lake ANC was maximum during the late summer or autumn, and lowest during spring snowmelt. In general Adirondack lakes with ANC near 100 Μeq L?1 during base flow periods may experience decreases in ANC to near or below 0 Μeq L?1 during high flow periods. The ALTM lakes have exhibited long-term temporal trends in water chemistry. Most lakes have demonstrated declining SO4 2?, consistent with decreases in SO2 emissions and SO4 2? in precipitation in the eastern U.S. Reductions in SO4 2? have not coincided with a recovery in ANC. Rather, ANC values have declined in some ALTM lakes. This pattern is most likely due to increasing concentrations of NO3 ? that occurred in most of the ALTM drainage lakes.  相似文献   

20.
Three watersheds (16.4, 544, and 83 ha) at distances of 0.5, 20, and 40 km from the Atlantic coast have been monitored for major ion chemistry of precipitation input and streamflow from May 1977 to November 1978. More than 200 precipitation and stramflow samples were analyzed for Na, K, Ca, Mg, chloride and sulphate, as well as pH, conductivity, alkalinity, and compared to similar studies at Hubbard Brook, New Hampshire, U.S.A., and Kejimkujik National Park, Nova Scotia. Major ion chemistry reflects proximity to Atlantic and Bay of Fundy coastal sources of marine aerosols. Evidence is presented implying biological reduction of H + and S04 to H2S during summer months for two consecutive growing seasons. Weighted mean annual pH values of precipitation for the three watersheds in Nova Scotia range from 4.11 to 4.63. More than 50% of the H + in precipitation is retained in the watersheds (with the exception of the ombrotrophic Fink Cove ecosystem), principally at the expense of basic cations being leached from the watersheds. Acidic deposition of Nova Scotian precipitation is predominantly as sulphuric acid, in contrast to ammonium sulphate, characteristic of continental precipitation.  相似文献   

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