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1.
Depth profiles of total S, organic S, soluble SO 4 2? -S, FeS, and FeS2 were characterized for Sphagnum-derived peat cores collected from 9 sites. Marcell S-2 Bog (MN), Tamarack Swamp (PA), Cranesville Swamp (MD/WV), and Big Run Bog (WV) receive water from precipitation and upland runoff; atmospheric S deposition is 13, 47, 54, and 114 mmol m?2, yr?1, respectively. McDonald's Branch Swamp (NJ) is predominantly groundwater fed. Tub Run Bog (WV) and Allegheny Mining Bog (MD) receive augmented SO 4 2? inputs through acid coal mine drainage. Jezerní slat' and Bo?í Dar Bog in Czechoslovakia receive atmospheric S inputs of 33 and 243 mmol m?2 yr?1, respectively. In the peat from all sites except Allegheny Mining Bog, where the substantially augmented SO 4 2? input was reflected in an unusually high dissolved SO 4 2? pool in the surface peat, organic S (probably mostly carbon bonded S) was the dominant S fraction; FeS2 was generally the dominant inorganic S fraction. Subsurface peaks in total S, organic S and FeS2-S in peat from the runoff water fed sites were interpreted as indicative of depth-dependent patterns in S reduction/oxidation and in S immobilization/mineralization. Unless SO 4 2? inputs to a site are tremendously augmented (e.g., Allegheny Mining Bog), the rapid turnover of the dissolved SO 4 2? pool combined with the relative stability of the other inorganic and organic S pools, apparently functions as an effective buffer against site differences in S inputs, leading to a general similarity in vertical S profiles in the peat deposits.  相似文献   

2.
About 90% of total S in a peat profile from a valley mire was associated with organic matter, and in the anaerobic zone, most of the remaining S could be distilled as H2S (steam-volatile H2S). [35S]SO2?4 was rapidly incorporated into both organic and steam-volatile H2S pools, with preferential labelling of organic matter at the surface of the peat (? 10 cm depth) and of steam-volatile H2S at greater depth (? 10 cm depth). Less than 2% of the steam-volatile H2S could be accounted for as H2S in solution in the pore water, and evidence suggesting FeS as the source of this fraction is presented. Less than 2% of the total S in the profile was present as FeS2 or S°, and S2O2?3 and S4O2?6 could not be detected. Measurements of total S content of the peat and estimates of the age of the deposit indicate a rate of S accumulation of 4.76–6.06 g S m?2yr?1. The results are discussed in the context of the mechanisms of S transformations and uptake by other mire systems.  相似文献   

3.
Although water chemistry of precipitation and lakes in Nova Scotia is dominated by C1 from sea salt, correction for marine influence reveals that the dominant anion in acidified lakes is SO4. Atmospheric deposition of non-marine SO4 (SO4) and NO3- for the period 1977–1980 at 4 stations in southwest Nova Scotia averaged 47 meq SO4 * m?2 yr?1 and 21 meq NI3-m?2 yr?1 compared with 38 and 13 meq, respectively, for the average of 3 stations in the northeastern third of the province. Precipitation pH increased from 4.5 to 4.8 along the same axis. Almost 50% of the SO4 deposition occurred when storms came from the southwest, indicating low pressure tracks which pass south of major Canadian sources of S. SO4 * deposition in metropolitan Halifax (1982 bulk data) was 87 meq m?2 yr?1, due to local emissions of ca. 28 300 tonne S in the area, as well as LRTAP. Concurrent deposition of NO3-N was 15 meq m?2 yr?1 (2.1 kg ha?1 yr ?1). Loadings from SO4 deposition in the Halifax area amount to 42 kg ha?1 yr?1 and clearly exceed the federal guideline (M.O.I., 1983) of 20 kg ha?1 yr?1. Water chemistry of southwest, northeast, and Halifax area lakes show the same general SOI trends as observed for atmospheric deposition. In addition we find a positive relationship between SOI concentrations in the urban lakes and proximity to the center of the urban area.  相似文献   

4.
To gain insight into the effects of drying and rewetting events on anaerobic respiration in ombrotrophic peat soils, we investigated bacterial sulfate (SO4) reduction and methane (CH4) production in anaerobic incubations of intact peat microcores from 30 to 40 cm depth of Mer Bleue bog, Ontario/Canada. Concentrations of dissolved SO4, carbon dioxide (CO2), CH4, acetate, and hydrogen (H2) were recorded and net turnover rates calculated from regression. Gross rates of bacterial sulfate reduction were determined by 35SO4 tracer incubation. After incubation, the peat was dried and rewetted, with saturated peat serving as control. CO2 production was initially rapid (up to <360 nmol cm?3 d?1) and slowed towards an endpoint of 2–3 mmol l?1, which was only partly related to thresholds of Gibbs free energies of the involved processes. Acetate rapidly accumulated to levels of 600–800 μmol l?1 and remained constant thereafter. CH4 production (0–2.8 nmol cm?3 d?1) was small and delayed, even after SO4 was depleted, by about 30–40 d. Hydrogenotrophic methanogenesis was endergonic and the process thus likely followed an acetotrophic pathway. Drying and rewetting replenished the SO4 pool, enhanced SO4 reduction rates and suppressed methanogenesis. The overall contribution of net SO4 reduction and methanogenesis to the CO2 production rate was small (0.5–22%) and only enhanced in replicates subjected to drying (35–62%). The major fraction of respiration in the incubated peat cores thus followed yet unidentified pathways.  相似文献   

5.
A mixed provenance Sitka spruce plantation, planted in 1986 on a drained deep peat, has been exposed to 6 different simulated mist treatments in 4 replicated blocks since 1996. Treatments provided N and/or S at a concentration of 1.6 mol m?3, supplying ca. 50 kg S and/or N ha?1 yr?1 as N (NH4NO3), S (Na2SO4), NS Acid (NH4NO3 + H2SO4 at pH 2.5), 2NS Acid (double dose by application at twice frequency), a control treatment supplied with additional rainwater only and a 'no treatment' set of plots. Throughfall, preserved with thymol in the field, was collected using gutters with a surface area of 1 m2 in all the replicate plots, and was analysed for all major ions. Prior to treatment in 1999, S deposition in throughfall exceeded that in rain because of dry deposition of SO2 and SO4 2? to the canopy; NH4 + and NO3 ? ions were both retained in the canopy. During treatment, only 20–40% of the applied N in the high-N treatments was retained in the canopy. Acidity in the applied mist was partly neutralised by the canopy, but not primarily through exchange of base cations, leading to the conclusion that weak organic acids, in solution or in situ in the canopy, contributed to the buffering of the H+ ion deposition in the acid treatments.  相似文献   

6.
From a level of 1 kg ha?1yr?1 in north central Minnesota, emission-related wet SO4 deposition increases across northern Wisconsin and northern Michigan to about 18 kg ha?1yr?1 in south central Michigan. Samples taken from 82 clearwater (low color) lakes across this region in the summer of 1984 showed a pattern of acidification in proportion to deposition. We found a linear increase in the difference between alkalinity and Ca+Mg and in lake SO4 concentration with increasing deposition. We developed a simple equation to predict the emission-related SO4 deposition levels that will cause the alkalinity of sensitive clear-water lakes to go to zero.  相似文献   

7.
Variations in sulphate (SO4 2-) concentration of porewater and net SO4 2- mobilization were related to differences in water level fluctuations during wet and dry summers in two conifer swamps located in catchments which differed in till depth and seasonality of groundwater flow. Sulphate depletion at the surface and in 20 cm porewater coincided with anoxia and occurred mainly during the summer when water levels were near the peat surface and water flow rates were low in both catchments. There was an inverse relationship between net SO4 2- mobilization and water level elevation relative to the peat surface, explaining variation in SO4 2- dynamics between the swamps during summer drought periods. Aeration of peat to 40 cm and a large net SO4 2- mobilization (10–70 mg SO4 2- m-2 d-1) occurred during a dry summer in which the water level dropped to 60 cm below the surface in the swamp receiving ephemeral groundwater inputs from shallow tills within the catchment. This resulted in high SO4 2- concentrations in the surface water and porewater (30–50 mg L-1), and elevated SO4 2- concentrations remained through the fall and winter. In contrast, within the swamp located in the catchment with greater till depth (> 1 m), continuous groundwater inputs maintained surface saturation during the dry summer, and SO4 2- mobilization and concentrations of SO4 2- in the pore water during the following fall did not increase. Susceptibility to large water table drawdown and mobilization of accumulated SO4 2- is influenced by the occurrence of ephemeral vs. continuous groundwater inputs to valley swamps during dry summer periods in the Canadian Shield landscape. This study reveals that extrapolation of results of SO4 2- cycling from one wetland to another requires knowledge of the hydrogeology of the catchment in which the wetlands are located.  相似文献   

8.
Atmospheric deposition of N and S on terrestrial and aquatic ecosystems causes effects induced by eutrophication and acidification. Effects of eutrophication include forest damage, NO3 pollution of groundwater and vegetation changes in forests, heathlands and surface waters due to an excess of N. Effects of acidification include forest damage, groundwater pollution, and loss of fish populations due to Al mobilization. Critical loads (deposition levels) for N and S on terrestrial and aquatic ecosystems in the Netherlands related to these effects have been derived by empirical data and steady-state acidification models. Critical loads of N generally vary between 500 and 1500 mol c ha?1 yr?1 for forests, heathlands and surface waters and between 1500 and 3600 for phreatic groundwaters. Critical loads of total acid (S and N) vary between 300 to 500 mol c ha?1 yr?1 for phreatic groundwaters and surface waters and between 1100 to 1700 mol ha?1 yr?1 for forests. On the basis of the various critical loads a deposition target for total acid of 1400 mol c ha?1 yr?1 has been set in the Netherlands from which the N input should be less than 1000 mol c ha?1 yr?1. This level, to be reached in the year 2010, implies an emission reduction of 80–90% in SO2, NO x and NH3 in the Netherlands and of about 30% in neighboring countries compared to 1980 emissions.  相似文献   

9.
Ion mass and H+ budgets were calculated for three pristine forested catchments using bulk deposition, throughfall and runoff data. The catchments have different soil and forest type characteristics. A forest canopy filtering factor for each catchment was estimated for base cations, H+, Cl? and SO 4 2? by taking into account the specific filtering abilities of different stands based on the throughfall quality and the distribution of forest types. Output fluxes from the catchments were calculated from the quality and quantity of the runoff water. Deposition, weathering, ion exchange, retention and biological accumulation processes were taken into account to calculate catchment H+ budgets, and the ratio between external (anthropogenic) and internal H+ sources. In general, output exceeded input for Na+, K+, Ca2+, Mg2+, HCO 3 ? (if present) and A? (organic anions), whereas retention was observed in the case of H+, NH 4 + , NO 3 ? and SO 4 2? . The range in the annual input of H+ was 22.8–26.3 meq m?2 yr?1, and in the annual output, 0.3–3.9 meq m?2 yr?1. Compared with some forested sites located in high acid deposition areas in southern Scandinavia, Scotland and Canada, the catchments receive rather moderate loads of acidic deposition. The consumption of H+ was dominated by base cation exchange plus weathering reactions (41–79 %), and by the retention of SO 4 2? (17–49 %). The maximum net retention of SO 4 2? was 87% in the HietajÄrvi 2 catchment, having the highest proportion of peatlands. Nitrogen transformations played a rather minor role in the H+ budgets. The ratio between external and internal H+ sources (excluding net base cation uptake by forests) varied between 0.74 and 2.62, depending on catchment characteristics and acidic deposition loads. The impact of the acidic deposition was most evident for the southern Valkeakotinen catchment, where the anthropogenic acidification has been documented also by palaeolimnological methods.  相似文献   

10.
Year-to-year variation in acidic deposition within a mature sugar maple-dominated forest and in leaching of ions from the associated podzolic soil were examined at the Turkey Lakes Watershed between 1981 and 1986. Below-canopy inputs to the soil of SO4 2? and NO3 ? in throughfall averaged 640 and 295 eq. ha?1 yr?1; the corresponding ranges were 493–917 and 261–443 eq. ha?1 yr?1. The contribution of atmospheric deposition to SO4 2? NO3 ? and Ca2+ leaching decreased over the six years. During the study period, the mean annual volume-weighted NO3 ? concentration decreased in throughfall and forest-floor percolate and increased in the mineral-soil solution collected below the effective rooting zone. A substantial shift in the balance between SO4 2? and NO3 ?leaching from the mineral soil was observed; leaching of SO4 2?decreased and NO3 ? leaching increased with time. Leaching of Ca2+ and Mg2+ from the soil was increased as a result of excess NO3 ? production in the soil. The calculated output of NO3 ? from the soil, which averaged 1505 eq. ha?1 yr?1, considerably exceeded the atmospheric deposition of NO3 ?, whereas SO4 2? outputs were only moderately greater than inputs.  相似文献   

11.
SO4 2?, NO3 ? and H+ depositions are estimated in the Brazilian territory based on the existing rainfall chemical data and on annual rainfall distribution over the whole territory. Local and regional depositions are estimated. Rainfall chemical data over the Braziliian territory shows that the average pH values are usually low (between 4.0 and 5.5). These values are observed in the tropical Amazon forest as well as in urban areas. However, the rainwater acidity in the tropical forests are due to organic acids naturally produced by the vegetation while in urban areas the acidity is mainly due to acidic anion deposition (NO3 ? and SO4 2?). In some Amazonian areas, the average input values through rainfall for NO3 ? is about 0.06 keq.ha.yr?1 and for SO4 2? is between 0.23 and 0.54 keq.ha?1.yr?1. On the other hand, in some urban centers, such as São Paulo, values of .072 keq.ha?1.yr?1 for NO3 ? and 1.16 keq.ha?1.yr?1 of SO4 2? are found and in sites where sulfate sources (coal mining) are present, as for the area of Florianópolis, values as high as 5.59 keq.ha?1.yr?1 for SO4 2? are found.  相似文献   

12.
Emissions of SO2 in the Sudbury area declined from an estimated average of 1.41 × 106 tonne yr?1 in 1973–78 to 0.68 × 106 tonne yr?1 in 1979–85. As a result, SO4 concentrations of lakes in the area have decreased, and the pH of each of the acidic lakes that was studied has increased. Aluminum, Cu, Ni and Zn concentrations have also decreased; however, the latter three metals have probably declined because of reductions in emissions of metals from the smelters rather than because of the pH changes in the lakes.  相似文献   

13.
Blanket‐bog peats, mapped as the Winter Hill and Crowdy associations by the Soil Survey of England and Wales, are an oceanic manifestation of the ombrotrophic ‘raised‐bog’ (Hochmoor) peats that cover large tracts in the boreal zone of the northern hemisphere. This paper examines monthly analyses from 1992 to 1997 of major ions and other variables from an upland blanket bog in southwest England in relation to seasonality, rainfall, and the chemical composition of rainwater. Average ionic composition of surface water (and peat) integrates variable atmospheric solute inputs over the years. The dominant ions in the surface water, Na+ and Cl–, showed only weak seasonality, but divalent cations a stronger seasonal pattern with a summer maximum. Mean pH ranged from c. 4.4 in February to c. 4.2 in August. Changes in concentration of different cations were closely interlinked by cation exchange. The anion deficit, accounted for by anionic groups on the dissolved organic matter, was strongly seasonal with a summer maximum, as was optical absorbance at 320 nm. Nitrate and NH4+ were both at much smaller concentrations than in rain. Nitrate exceeded 1 μmol l?1 only during cold periods in winter, mainly following drought in the summer of 1995; NH4+ reached a few μmol l?1 only in summer. There was evidence of net retention of S by the peat in wet sites and during wet periods, and of net release of SO42– (and acidity) under dry conditions. The 1995 summer drought and ensuing dry year in 1996 had marked and persistent effects on pH, apparent ion deficit (DEF), SO42–, the divalent cations and Fe.  相似文献   

14.
Cores of podzolic soil (monolith lysimeters) were treated for 4.8 yr with 1500 mm yr?1 of either 0.5 mM H2SO4 at pH 3, equivalent to 24 g S m?2 yr?1 (acid treated) or distilled water (controls). The acid treatment was about 37 times greater than the average annual input of H3O+ from rain at the site from which the monoliths were taken. Acid treatment acidified the litter (from pH(CaCl2)3.4 to pH(CaCl2)2.6) and the mineral soil to a depth of 80 cm (mean pH(CaCl2) decrease of 0.2 unit). In the litter and upper A horizon, ion-exchange reactions provided the main neutralizing mechanism, resulting in a decrease in the reserves of extractable (in 2.5 % acetic acid) Ca, Mg, and Mn of about 70 to 80 %. Dissolution of solid phase Al from hydrous oxides provided most neutralization below this depth. Al3+ was the principal soluble Al species throughout the profile. In the litter and upper A horizon, some of the mobilized Al3+ was retained on cation exchange sites resulting in an increase in exchangeable Al. Deeper in the profile, where the exchange sites were effectively saturated with Al3+, no increase in exchangeable Al occurred, and Al3+ was, therefore, available for leaching. Some reversible adsorption of SO4 2?, associated with hydrous Al oxides, occurred in the Bs and C horizons. The results are discussed in relation to possible effects of acid deposition over regions of Europe and N. America.  相似文献   

15.
Information on atmospheric inputs, water chemistry and hydrology were combined to evaluate elemental mass balances and assess temporal changes in elemental transport from 1983 through 1992 for the Arbutus Lake watershed. This watershed is located within a northern hardwood ecosystem at the Huntington Forest within the central Adirondack Mountains of New York (USA). Changes in water chemistry, including increasing NO3 ? concentrations (1.1 μmol c , L?1 yr-1), have been detected during this study period. Starting in 1991 hydrological flow has been measured from Arbutus Lake and these measurements were compared with predicted flow using the BROOK2 hydrological simulation model. The model adequately (r2=0.79) simulated flow from this catchment and was used to estimate drainage for earlier periods when direct hydrological measurements were not available. Modeled drainage water losses coupled with estimates of wet and dry atmospheric deposition were used to calculate solute budgets. Export of SO4 2? (831 mol c ha?1 yr?1) from the greater Arbutus Lake watershed exceeded estimates of atmospheric deposition in an adjacent hardwood stand suggesting an additional source of S. These large drainage losses of SO4 2? also contributed to the drainage fluxes of basic cations (Ca2+, Mg2+, K+ and Na+). Most of the atmospheric inputs of inorganic N were retained (average of 74% of wet precipitation and 85% total deposition) in the watershed. There were differences among years (56 to 228 mol ha?1 yr?1) in drainage water losses of N with greatest losses occurring during a warm, wet period (1989–1991).  相似文献   

16.
Abundant production of organic matter that decomposes slowly under anaerobic conditions can result in substantial accumulation of soil organic matter in wetlands. Tedious means for estimating production and decomposition of plant material, especially roots, hampers our understanding of organic matter dynamics in such systems. In this paper, I describe a study that amended typical estimates for both production and decomposition of organic matter by measuring net flux of carbon dioxide (CO2) over the peat surface within a conifer swamp, a sedge-dominated marsh, and a bog in the Appalachian Mountain region of West Virginia and western Maryland, USA. The sites are relatively productive, with net primary production (NPP) of 30 to 82.5 mol C m?2 yr?1, but peat deposits are shallow with an average depth of about 1 m. In summer, all three sites showed net CO2 flux from the atmosphere to the peat during the daytime (?20.0 to ?30.5 mmol m?2 d?1), supported by net photosynthesis, which was less than net CO2 flux from the peat into the atmosphere at nighttime (39.2 to 84.5 mmol m?2 d?1), supported by ecosystem respiration. The imbalance between these estimates suggests a net loss of carbon (C) from these ecosystems. The positive net CO2 flux seems to be so high because organic matter decomposition occurs throughout the peat deposit — and as a result concentrations of dissolved inorganic carbon (DIC) in peat pore waters reached 4,000 Μmol L?1 by late November, and concentrations of dissolved organic carbon (DOC) in peat pore waters reached 12,000 Μmol L?1. Comparing different approaches revealed several features of organic matter dynamics: (i) peat accretion in the top 30 cm of the peat deposit results in a C accumulation rate of about 15 mmol m?2 d?1; however, (ii) the entire peat deposit has a negative C balance losing about 20 mmol m?2 d?1.  相似文献   

17.
The contribution of atmospheric acids to cation leaching from a podzolic soil under mature maple-birch forest in central Ontario was examined during 1983. The movement of base cations was associated largely with NO3 ?, SO4 2? and organic acid anions in surface soil horizons, with SO4 2? and NO3 ? below the effective rooting zone, and SO4 2? and HCO3 ? in streamflow. Mineral soil horizons could adsorb little additional SO4 2? or associated cations at current soil solution SO4 2? concentrations. Therefore it is concluded that the soil in situ lacks a strong affinity for SO4 2?. Current annual inputs to the forest of SO4 2? and NO3 ? in bulk precipitation (26.4 and 18.2 kg ha?1, equivalent to 8.8 kg S and 4.1 kg N ha?1 , respectively) contributed significantly to cation leaching from the soil. In order to maintain exchangeable cations in soil at current levels, a rate of weathering yielding 29.6, 5.0, 4.4 and 2.2 kg ha?1 yr?1 of Ca2+, Na+, Mg2+ and K+, respectively, would be required.  相似文献   

18.
From 1986–1989, a team of scientists measured atmospheric concentrations and fluxes in precipitation and throughfall, and modeled dry and cloudwater deposition in a spruce-fir forest of the Great Smoky Mountains National Park which is located in the Southern Appalachian Region of the United States. The work was part of the Integrated Forest Study (IFS) conducted at 12 forests in N. America and Europe. The spruce-fir forest at 1740 m consistently received the highest total deposition rates (～2200, 1200, and 700 eq ha?1 yr?1 for SO4 2?, NO3 ?, and NH4 +). During the summers of 1989 and 1990 we used multiple samplers to measure hydrologie, SO4 2?, and NO3 ? fluxes in rain and throughfall events beneath spruce forests above (1940 m) and below (1720 m) cloud base. Throughfall was used to estimate total deposition using relationships determined during the IFS. Although the SO4 2? fluxes increased with elevation by a factor of ～2 due to higher cloudwater interception at 1940 m, the NO3 ? fluxes decreased with elevation by ～30%. To investigate further, we began year round measurements of fluxes of all major ions in throughfall below spruce-fir forests at 1740 m and at 1920 m in 1993–1994. The fluxes of most ions showed a 10–50% increase with elevation due to the ～70 cm yr?1 cloudwater input at 1920 m. However, total inorganic nitrogen exhibited a 40% lower flux in throughfall at 1920 m than at 1740 m suggesting either higher dry deposition to trees at 1740 m or much higher canopy uptake of nitrogen by trees at 1920 m. Differential canopy absorption of N by trees at different elevations would have significant consequences for the use of throughfall N fluxes to estimate deposition. We used artificial trees to understand the foliar interactions of N.  相似文献   

19.
Critical acid loads for Dutch forests were derived using a multi-layer steady-state model that includes canopy interactions, nutrient cycling, mineral weathering and N transformations. Values were calculated for combinations of 12 tree species and 23 soil types for a 10×10 km grid. Critical acid loads thus derived increased with decreasing soil depth. Nearly 90% of the values varied approximately between 1500 and 4000 molc ha?1 yr?1 at 10 cm soil depth and between 750 and 2000 molc ha?1 yr?1 at the bottom of the rootzone. Separate critical loads calculated for N and S at the bottom of the rootzone varied between approximately 300 and 1000 molc ha?1 yr?1 for N and between 150 and 1250 molc ha?1 yr?1 for S. Using deposition data of 1990, a median reduction of the deposition by approximately 75% was calculated to achieve the critical loads at the bottom of the rootzone. The overall uncertainty in this value was estimated to be about 10%, although it can be much larger for specific soil types such as clay and peat soils. For N a larger reduction deposition percentage was calculated than for S, especially for coniferous forests with a high present N input.  相似文献   

20.
A model has been developed that relates the cation denudation rate (CDR) of a watershed (the rate that cations derived from chemical weathering are carried off by runoff), the atmospheric load of excess SO4, and the pH of the river. Chemical and discharge data for rivers in Nova Scotia and Newfoundland were used to develop and test the model, which is based upon the common major ion chemistry of soft surface waters, and may be expressed by three statements: (1) CDR (meq m?2 yr?1) ? Excess SO4 ?? load (meq m?2 yr?1) = HCO3 ? (meq m?2 yr?1), (2) HCO3 ? (meq m?2 yr?1)/Runoff (m3 m?2 yr?1) = HCO3 ? (meq m?3), (3) pH = pK + \(pP_{CO_2 } \) ? pHCO3 ?. The model in concentration form applies well to lakes. A detailed analysis of the data for the Isle aux Morts River, Newfoundland, is presented, showing that the CDR varies throughout the year, affected by both discharge and seasonal pattern.  相似文献   

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