The MAGIC simulation of surface water acidification at, and first year results from, the Bear Brook Watershed Manipulation, Maine, USA

The catchments of East and West Bear Brooks, Maine, USA, have been hydrologically and chemically monitored for 3.5 years. Stream chemistries and hydrographs are similar. These clear water streams are low in ANC (0-70 microeq litre(-1)), with variations caused by changing concentrations of base cations, SO4, NO3 and Cl. The latter range between 90-120, 0-40 and 65-75 microeq litre(-1), respectively. The West Bear catchment is being treated with six applications per year of dry (NH4)2SO4 at 1800 eq ha(-1) year(-1). After one year of treatment, the response of the stream chemistry and the response modelled by MAGIC are similar. Retentions of NH4 and SO4 are nearly 100% and greater than 80%, respectively. The additional flux of SO4 is compensated principally by an increased Ca concentration. Episodes of high discharge in the treated catchment are now characterized by lower ANC and pH, and higher Al than prior to the manipulation. Concentrations of NO3 have increased about 10 microeq litre(-1) during the dormant season, presumably due to additional nitrification of N from NH4. Discharge-chemistry relationships indicate that changes in stream chemistry, except for NO3, are dominated by ion exchange reactions in the upper part of the soil profile.     

Artificial acidification of a non-acidic and an acidic headwater stream in Maine, USA

Two headwater streams with low DOC and different pHs (4.5-4.8 and 5-6.5) were acidified with H2SO4 to pH 4.1 and 4.5, respectively, for 24-h periods. Neutralization of the added acid occurred by protonation of ANC (HCO3-dominated in the higher pH stream), desorption of Ca (< 15 microeq litre(-1)) and Mg (<6 microeq litre(-1)), and desorption and dissolution of AL (<250 microg litre(-1)) from the stream bed. The concentrations of dissolved organic carbon (DOC) remained constant within the experimental reaches. The concentrations of Na, K an H4SiO4 also remained constant, indicating no detectable increase in the rate of chemical weathering in the stream bed. After acid addition was stopped, concentrations of Ca, Mg and Al decreased to below background, indicating reversible ion exchange as the principal mechanism for the mobility of Ca and Mg and to a lesser extent for Al. Repeated acidifications indicated that significant regeneration of cations on the exchange surfaces of the stream substrate occurs rapidly.     

Chemical composition of fogwater in an urban area: Strasbourg (France)

To investigate the acidity and to identify the predominant compounds, this work presents the chemical analysis of 18 fogwater samples collected during the year 1991 in Strasbourg, in the east of France. For each fog event, two droplet size categories (2-6 microm and 5-8 microm) have been separately collected and 16 ionic components have been analysed. These two fraction sizes were chosen because they correspond approximately to the size range that can penetrate the human lung and they may have possible health effects. The dominant species were NH4+, NO3-, SO4(2-) and Cl-, with a maximum level of 12,640, 17,270, 21,620 and 13,540 microeq litre(-1), respectively. For most of the fog events the highest concentrations of all analysed species were observed in the 2-6 microm droplets. pH values ranged between 2.79 and 5.70 and the fogwater acidity was governed by three strong acids, H2SO4, HNO3 and HCl and was partially neutralised by NH3 and probably by the presence of CaCO3 in the 'loess', which is the major constituent of soils in the upper Rhine valley. In other respects the acetate/formate ratio (methanoate/ethanoate), generally lower than 1, indicates an important pollution due to automobile exhaust, although the Pb concentrations are moderate due to the general use of unleaded gasoline in France since 1989.     

Contemporary (1979-1988) and inferred historical status of headwater lakes in North Central Ontario, Canada

Fifty-six headwater Canadian Shield lakes were repetitively sampled from 1979 to 88 to determine their response to changes in acidic deposition of the period. Annual wet sulphate loadings varied between 38 and 83 meq m(-2), with highest deposition in the late 1970s followed by somewhat lower but variable deposition in the 1980s. Median pH of the lakes increased 0.42 pH units from 1979 to 1985 and decreased by 0.15 units between 1985 and 1988. Short water renewal times (x=1.1 y) promoted rapid equilibration. Since lake were so responsive to changes in SO4(2-) inputs, they were at or near steady state at all times. Comparison of predicted original pH and ANC with 1979 data indicate a median decline of 0.45 pH units and a loss of 34 microeq litre(-1). ANC. Four of 9 lakes were found to be historically fishless, based on the continued presence of Chaoborus americanus in sediment cores. The remaining five lakes historically had fish populations, but fish were not collected in 1979 when pH ranged betwen 4.6 and 5.3. By 1987, fish species were found in five of these lakes where pH had increased on average by 0.9 pH units. Our data indicate that water quality improvements could allow for the reinvasion or resumption of recruitment for a significant number of Ontario lakes.     

Buffering processes in a boreal dissolved organic carbon-rich stream during experimental acidification

The role of organic acids on surface water acidity as well as their buffering during anthropogenic acidification and subsequent recovery was studied in a field experiment on a total organic carbon (TOC)-rich stream draining the Svartberget catchment in northern Sweden. H(2)SO(4) was added to the stream to increase SO(4)(2-) concentration by 90 microeq l(-1) for 30 h. About 60% of the added H(+) was buffered by protonation of organic acids, another 20% was buffered by base cations released from the surface of the stream channel and only ca. 20% of the added acid remained unbuffered. TOC concentrations (27 mg l(-1)), and site density of carboxylic groups--8.6 microeq (mg TOC)(-1)--remained stable during the experiment. Two models of organic acid dissociation (a triprotic model and a monoprotic pH-dependent pKa model) were fitted to the experimental results. These models explained the observed variations in organic anions, but the model parameters were quite different from those reported by studies in Northern America and Central Europe. This experiment had substantially more buffering effect of TOC between pH 4.4 and 5.3, which is an environmentally important pH range.     

Recovery from acidification in central Europe--observed and predicted changes of soil and streamwater chemistry in the Lysina catchment,Czech Republic

The geochemical model MAGIC was applied to estimate streamwater and soil chemistry between 1851 and 2030 at the Lysina catchment, an acid-sensitive granitic catchment covered by planted Norway spruce monoculture in the western Czech Republic. The total deposition of sulfur to the catchment was 164 meq m(-2) in 1991, but had declined to 52 meq m(-2) by 2000. Although SO2 emissions in the region declined by 90% compared to the 1980s, acidification recovery was small within the period 1990-2000. Stream pH increased only slightly (from 3.92 to 4.07), although SO4 concentration declined sharply from 568 microeq l(-1) (1990) to 232 microeq l(-1) (2000). Organic acids played an important role in streamwater buffering. According to the MAGIC prediction using deposition measured in 1999-2000, streamwater pH will increase to 4.3 and soil base saturation will increase to 6.2% by 2030 (from 5.7% in 2002). Pre-industrial pH was estimated to be 5.5 and soil base saturation 24.7%. The loss of base cations (Ca, Mg, Na, K) was caused predominantly by atmospheric acidity, but intensive forestry was responsible for approximately one third of the net base cation loss via accumulation in harvested biomass. Severely damaged sites, under continued pressure from forestry, will not return to a good environmental status in the near future (if ever) when the acid deposition input is only partially reduced.     

Surface water acidification in the South Pennines I. Current status and spatial variability

The South Pennines, an area of acid-sensitive geology at the centre of a major industrial region, have undergone perhaps the most severe historic exposure to sulphur and nitrogen deposition in the UK. This study addresses a lack of existing research on the region by presenting the findings of a survey of 62 surface waters sampled during a 1-week period in April 1998. Results indicate that acidification in the region is acute; 27 of the sampled surface waters had a negative acid neutralising capacity (ANC) and 28 had a pH below 5.0. Minimum recorded pH values were below 4.0. Non-marine sulphate levels were extremely high (median 222 microeq/1), and widespread high nitrate concentrations (median 41 microeq/1) suggest that soils in the region as a whole may be at an advanced stage of nitrogen saturation. A consistent relationship was identified between site acidity and the balance between the major weathering-derived cations, calcium and magnesium, and sulphate. This could in turn be linked to catchment soil type and land use, with the most acidic conditions occurring in peat-dominated catchments, where weathering is minimal and the influence of atmospheric deposition most pronounced. Percentage of peat in each catchment was the single best predictor of surface water acidity. Nitrate concentrations, although not a dominant control on acidity, varied significantly according to land use. Elevated concentrations were observed in catchments containing forestry, due to enhanced deposition inputs, and in catchments containing improved land, linked to fertiliser use. Ammonium concentrations, although low at most catchments, were a significant component of the inorganic nitrogen total in a number of surface waters draining waterlogged peat catchments.     

Aerobic dehalogenation potentials of four bacterial species isolated from soil and sewage sludge

In Polar regions subject to acid precipitation, the spring flood period is swift and can be divided into three phases. In phase one, dilution and anion substitution by SO4 controls episodic acidification. Phase two is characterized by interaction of snowmelt water with the catchment. A combination of several factors contributes to declines in pH and ANC. In forest and wetland ecosystems, organic acids greatly contribute to the pH depression in the streams. In the coastal tundra and forest-tundra zones, "salt-effect" acidification predominantes. The increase in toxic forms of trace (Ni, Cu) and rare (Fe, Al, Mn) elements during pH depressions may create stress conditions for the fauna of polar fresh waters during a flood period.     

Chemical and biological effects of acid, aluminium and lime additions to a Welsh Hill-stream

Chemical and biological responses to simultaneous additions of acid, aluminium and lime were investigated in contiguous 250m-reaches of a chronically acidic stream in Wales. Treatments were applied for 24 h, and from the upstream end were as follows: zone A-untreated, pH 5.0, 0.37 mg litre(-1) filterable Al; zone B-acidified to pH 4.5, 0.40 mg Al litre(-1) (47% of Al attributed to release from the stream bed due to acid additions); zone C-acidified to pH 4.5 and Al dosed to 0.67 mg litre(-1); zone D-dosed with limestone slurry, resulting in pH 7.2, 0.13 mg Al litre(-1). In all reaches, the chemistry of the interstitial water at depths of 0.15 and 0.3 m never fell below pH 5.5, with corresponding decreases in Al and increases in base cation concentrations. Brown trout, Salmo trutta, and crayfish, Austropotamobius pallipes, held in the stream showed decreases in plasma [Na(+)] and haemolymph [Na(+)], respectively, in all acidic zones (A, B, C): these responses were mitigated by liming (zone D). Thus both chronic and simulated episodic levels of pH and dissolved Al were sub-lethally toxic to test species of aquatic fauna. This experiment also demonstrates a stream bed source/sink of Al, and the availability of a possible refuge from acidic surface waters within the substratum.     

Heterogeneous response of central European streams to decreased acidic atmospheric deposition

We investigated the relations between mountain streamwater chemistry and atmospheric pollution in an arca of 1611 km2 of the Czech Republic by comparing concentrations of SO4. NO3, Cl, Ca and the pH at 432 localities at the time of high (1984-1986) and relatively low (1996-2000) acidic atmospheric deposition. Medians of Cl. SO4, and NO3 decreased by 17, 96 and 60 microeq l(-1), or by 23, 17 and 49%, respectively, during 12 +/- 2 years. The decreased Cl corresponds to decreased emission of industrial Cl (as HCl). The decreased stream SO4 was proportionally lower than the 71% decrease in S-emissions due to leaching of previously accumulated SO4 from soils and non-zero background concentrations. Decreases of NO3 up to 60% in streamwaters with pH < or = 6 was greater than the decrease of N emission in central Europe, about 35%. Extensive regional decrease of NO3 is surprising and is probably described for the first time. The difference in NO3 concentrations between the two periods was probably enhanced by (a) an increase of mineralisation of forest floor in the mid-1980s and (b) by higher uptake of N in the late-1990s. The median pH of the 432 streams did not change but the pH of the sub-population with pH < 6 in the mid-1980s recovered substantially. The pH of circum-neutral streams (pH > 6.5) decreased even as acidic atmospheric deposition decreased.     

Acid rain and nitrogen deposition in a sub-tropical watershed (Piracicaba): ecosystem consequences

High levels of wet N and acidic deposition were measured in southeast Brazil. In this study we addressed the sensitivity of water bodies and soils to acidification and N deposition in the Piracicaba River basin (12,400 km2). Average acid neutralization capacity (ANC) at 23 river sampling sites varied from 350 to 1800 microeq l(-1). Therefore, rivers and streams in the Piracicaba basin are well buffered, if the lower limit of 200 microeq l(-1) is assumed as an indication of poorly buffered waters. ANC is increased by untreated wastewaters discarded into rivers and streams of the region. Average NO3 concentrations varied from 20 to 70 microeq l(-1). At the most polluted river sites, NO3 concentration is not highest, however, probably due to NO3 reduction and denitrification. Most of the nitrogen in streams is also provided by wastewaters and not by wet deposition. The majority of the soils in the basin, however, are acidic with a low base cation content and high aluminum concentration. Therefore, soils in this basin are poorly buffered and, in areas of forest over sandy soils, acidification may be a problem.     

Modeling recovery of Swedish ecosystems from acidification

Dynamic models complement existing time series of observations and static critical load calculations by simulating past and future development of chemistry in forest and lake ecosystems. They are used for dynamic assessment of the acidification and to produce target load functions, that describe what combinations of nitrogen and sulfur emission reductions are needed to achieve a chemical or biological criterion in a given target year. The Swedish approach has been to apply the dynamic acidification models MAGIC, to 133 lakes unaffected by agriculture and SAFE, to 645 productive forest sites. While the long-term goal is to protect 95% of the area, implementation of the Gothenburg protocol will protect approximately 75% of forest soils in the long term. After 2030, recovery will be very slow and involve only a limited geographical area. If there had been no emission reductions after 1980, 87% of the forest area would have unwanted soil status in the long term. In 1990, approximately 17% of all Swedish lakes unaffected by agriculture received an acidifying deposition above critical load. This fraction will decrease to 10% in 2010 after implementation of the Gothenburg protocol. The acidified lakes of Sweden will recover faster than the soils. According to the MAGIC model the median pre-industrial ANC of 107 microeq L(-1) in acid sensitive lakes decreased to about 60 microeq L(-1) at the peak of the acidification (1975-1990) and increases to 80 microeq L(-1) by 2010. Further increases were small, only 2 microeq L(-1) between 2010 and 2040. Protecting 95% of the lakes will require further emission reductions below the Gothenburg protocol levels. More than 7000 lakes are limed regularly in Sweden and it is unlikely that this practice can be discontinued in the near future without adverse effects on lake chemistry and biology.     

Improvement of breeding success of the moor frog (Rana arvalis) by liming of acid moorland pools and the consequences of liming for water chemistry and diatoms

Liming experiments with powdered limestone (grain size < 3 mm) were conducted in eight acid shallow moorland pools in the Tongerense Heide heathland area from February 1988 until November 1989. The effects on water chemistry, diatoms and fungal infection of the eggs of the moor frog were studied. After an initial treatment in March 1988, the pH increased from c. 4.0 to c. 5.0 in those pools which dried out in summer and to c. 6.0 in the permanent pools. Alkalinity increased from 0 to 20-200 microeq litre(-1) in temporary pools and from 0 to 300-500 microeq litre(-1) in permanent pools. As drying out of the pools caused reacidification, after refilling the temporary pools were relimed in March 1989. No significant changes were found in concentrations of phosphate and nitrogen compounds. Eunotia paludosa, which is characteristic for ologotrophic, very acid pools and bogs with a fluctuating water table, was the dominant diatom in the untreated pools. It was replaced by eutraphentic and saprophilous taxa, particularly in the permanent pools. Species from extremely soft waters, which are very sensitive to acidification, were found only occasionally in some samples from the treated permanent pools. After liming the proportion of infected moor frog eggs decreased from c. 95% in the untreated to c. 5% in the treated pools.     

Water chemistry and fish community responses to episodic stream acidification in Pennsylvania, USA

Five streams were studied on the Northern Appalachian Plateau of Pennsylvania from October 1988 through June 1989 to determine chemical changes that occur during episodic storm run-off and the responses of fish to these events. These second-order streams flowed through undisturbed, wooded, sandstone bedrock catchments with surface areas ranging from 500 to 1000 hectares. Median pH of precipitations was about 4.2, and among streams it ranged from 5.0 to 6.2. During storm events, pH declined by as much as 1.2 units and peak concentrations of total monomeric Al ranged from < 0.01 to 0.75 mg litre(-1). Organically bound A1 was generally a minor component of total monomeric A1. Wild brook trout (Salvelinus fontinalis) were found in all streams, although only a remnant population existed in the most acidic stream. Sculpins (Cottus bairdi or C. cognatus) were collected only in the two streams with the least severe episodes. Mortality of brook trout and sculpins in in situ bioassays ranged from 0 to about 80% among streams during acidic episodes and was positively related to concentrations of total dissolved Al. Radio-tagged brook trout moved downstream during episodes when Al reached toxic concentrations. Some displaced trout were found near groundwater seeps, where pH was higher and dissolved Al was lower than in the main channel.     

Reversal of acidification in tributaries of the River Duddon (English Lake District) between 1970 and 1998

Long-term changes in stream water chemistry in the upper Duddon catchment (southwest Lake District, UK) were investigated. Ten streams were sampled and analysed weekly during 1998, and the results compared with data for the early 1970s and 1986. The waters exhibited a range of pH, average values for 1998 being 5.04-7.04. For all the streams, the average pH in 1998 was greater than that during 1971-73. Statistical analysis was carried out, using the 1970s data to estimate the magnitude of inter-annual variation, and taking discharge into account on the basis of antecedent rainfall. The results showed that for two of the streams the pH increase was significant at the 2.5% level, while for a further three it was significant at the 10% level. Comparison of the 1998 concentrations of nitrate and non-marine sulphate with data obtained for five streams in 1973-74 showed that average nitrate concentration had increased from 11 to 20 microeq dm(-3) while that of non-marine sulphate had decreased from 94 to 50 microeq dm(-3). For four of the streams, comparisons were also made between the 1998 data and those for 1986. In three cases, pH in 1998 was generally higher, and Al generally lower, than the values for 1986, but in the fourth case little difference was evident. The present results support observations for five nearby standing waters, strengthening the evidence for a general reversal of acidification in the southwest part of Lake District, due to a decline in the deposition of pollutant sulphur.     

Chemical climatology of high elevation spruce-fir forests in the southern Appalachian mountains

The physical and chemical climatology of high elevation (> 1500 m) spruce-fir forests in the southern Appalachian mountains was studied by establishing a weather and atmospheric chemical observatory at Mt Mitchell State Park in North Carolina (35 degrees 44' 05" N, 82 degrees 17' 15"W). Data collected during the summer and autumn (May-October) of 1986, 1987, and 1988 are reported. All measurements were made on or near a 16.5 m walk-up tower extending 10 m above the forest canopy on Mt Gibbes (2006 m msl), which is located approximately 2 km SW of Mt Mitchell. The tower was equipped with standard meteorological instrumentation, a passive cloud water collector, and gas pollutant sensors for O3, SO2, NOx. The tower and nearby forest canopy were immersed in clouds 25 to 40% of the time. Non-precipitating clouds were very acidic (pH 2.5-4.5). Precipitating clouds were less acidic (pH 3.5-5.5). The dominant wind directions were WNW and ESE. Clouds from the most common wind direction (WNW) were more acidic (mean pH 3.5) than those from the next most common wind direction (ESE, mean pH 5.5). Cloud water acidity was related to the concentration of SO4(2-), and NO3- ions. Mean concentration of H+, NH4+, SO4(2-), and NO3- ions in the cloud water varied from 330-340, 150-200, 190-200 and 120-140 micromol litre(-1) respectively. The average and range of O3 were 50 (25-100) ppbv (109) in 1986, 51 (26-102) ppbv in 1987, and 66 (30-140) during the 1988 field seasons, respectively. The daily maximum, 1-h average, and 24-h average concentrations were all greatest during June through mid-August, suggesting a correlation with the seasonal temperature and solar intensity. Throughfall collectors near the tower were used to obtain a useful estimate of deposition to the forest canopy. Between 50-60% of the total deposition of SO4(2-) was due to cloud impact.     

Acidification of a Solonetzic soil by nitrogenous fertilizers

Annual applications of (NH4)2SO4, NH4NO3 and urea on a Solonetzic soil at 112 kg N/ha for 10 consecutive years reduced pH levels from 5.6 for the check to 4.4, 4.9 and 5.3, respectively for (NH4)2SO4, NH4NO3 and urea. (NH4)2SO4 generated twice as much exchange acidity as NH4NO3 and four times as much as urea. Net extractable cations leached from the Ap horizon closely approximated the amount of exchange acidity generated by (NH4)2SO4 and NH4NO3 fertilizers. The levels of soil extractable Al and Mn were greatly enhanced by (NH4)2SO4 as were plant contents. Similar acidifying effects to that produced by the (NH4)2SO4 occurred when NH4NO3 was applied at 300 kg N/ha annually for 12 consecutive years in another field experiment on the same soil. Liming samples of the field (NH4)2SO4 acidified soils in the greenhouse, significantly increased yields and lowered the Al and Mn contents of the plants to normal levels.     

广州地区酸雨状况及其影响因素探讨

对广州地区降水酸度、酸雨频率的年际变化进行了研究,发现近十几年来广州地区的酸雨污染有所减缓,但2001-2003年有恶化的趋势.为探究原因,追溯主要酸雨污染物来源,并对各酸雨污染物进行综合评价,结论表明,广州地区的大气环境已从过去的以SO2为主的煤烟型污染转变为以NOX为主的氧化型污染.还讨论了广州地区气象条件对酸雨形成的影响.     

Effects of acidic gases and mists on the reproductive capability of three fern species

The effects of exposure to 40 nl litre(-1) SO2 + 40 nl litre(-1) NO2 on the reproductive biology of Polypodium interjectum (Shivas), Dryopteris affinis (Lowe) Fraser-Jenkins and Phyllitis scolopendrium (L.) Newman were investigated after 14 weeks exposure in a closed chamber fumigation system. The numbers of sori per pinna were reduced in response to SO2 and NO2 for D. affinis but were unaffected for the other species. Numbers of sporangia in sori and spore viability were reduced in P. interjectum and P. scolopendrium but not in D. affinis in response to the SO2 and NO2 treatment. Spore size was not affected by the pollution treatment. A separate experiment tested viabilities of spores collected from the three species in response to daily spraying with simulated mists at pHs of 2.5, 3.5, 4.5 and 5.6. For all three species, there was little or no spore germination in the pH 2.5 treatment and significantly reduced germination in response to the pH 3.5 as compared to the pH 4.5 and pH 5.6 treatments.     

Systematic comparison of ILWAS, MAGIC, and ETD watershed acidification models: 3. Mass balance budgets for acid neutralizing capacity

Three watershed acidification models-ILWAS, MAGIC, and ETD-were quantitatively compared to determine model structural differences by using a combination of input mapping and ANC mass balance budgets. Input mapping is a set of rules and algorithms to ensure that consistent input values were simultaneously derived for all three models. ANC budget analysis under current SO4(2-) deposition and a 70% reduction in SO4(2-) deposition allows examination of the relative importance of biogeochemical processes in affecting predictions of ANC or predicted changes in ANC. Model inputs were based on two dissimilar watersheds having characteristics typical of watersheds in the northeastern US. After mapping inputs, the three models predicted values of outflow ANC fluxes that were similar among the models for each watershed and deposition scenario. Within each watershed, the changes in outflow ANC fluxes between the scenarios were similar for the three models. Terrestrial weathering was the major source of ANC for all three models for both watersheds and deposition scenarios. The contributions of other processes to the ANC of the two watersheds were, under certain conditions, model-specific. Cation exchange was responsible for changes in ANC when deposition decreased for the three models. Other processes responsible for changes in ANC between scenarios were SO4(2-) sorption (for MAGIC) and in-lake weathering (for ETD). The processes responsible for the change in ANC from a change in deposition (cation exchange, SO4(2-) sorption, and in-lake weathering) were different from the processes contributing to the absolute ANC for a given deposition scenario (terrestrial weathering). The budget analysis complements an earlier Monte Carlo analysis that showed that the three models are structurally different and that predictions viewed on a relative scale are more similar than absolute scale predictions.