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1.
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   

2.
This study was carried out to evaluate acid depositions and to understand their effect. Wet precipitation has been collected at twenty-four sites in Korea for one year of 1999. The ion concentrations such as H+, Na+, K+, Mg2+, NH4 +, Ca2+, Cl?, NO3 ? and SO4 2? were chemically analyzed and determined. Precipitation had wide range of pH(3.5～8.5), and volume-weighted average was 5.2. The contribution amounts of Cl?, SO4 2? and NO3 ? in anion were shown to be 54%, 32%, and 14%, respectively and those of Na+ and NH4 + in cation were 32% and 25%. The ratios of Cl? and Mg2+ to Na+ in precipitation were similar to those of seawater, which imply that great amount of Cl? and Mg2+ in precipitation could be originated from seawater. The concentration of H+ is little related with SO4 2?, NO3 ? and Cl? ions, whereas nss?SO4 2? and NO3 ? are highly correlated with NH4 +, which could suggest that great amount of SO4 2? and NO3 ? exist in the form of ammonium associated salt. The annual wet deposition amounts (g m?2year?1) of SO4 2?, NO3 ?, Cl?, H+, NH4 +, Na+, K+, Ca2+ and Mg2+ were estimated as 0.88～4.89, 0.49～4.37, 0.30～9.80, 0.001～0.031, 0.06～2.15, 0.27～4.27, 0.10～3.81, 0.23～1.59 and 0.03～0.63.  相似文献   

3.
Runoff and atmospheric chemistry in the Krusne hory Mts. have changed significantly from 1978 to 1994. Forest die-back related deforestation resulted in decreased dry deposition of SO2 and changes in streamwater chemical composition. Atmospheric sulphur (S) deposition decreased from extremely high values of 66.6 kg S ha?1 year?1, in the early 1980s to 35.5 kg S ha?1 year?1 in 1994. Decreasing S input is reflected in decrease of streamwater sulphate (SO4 2?) concentrations, which decreased from 1560 μeq l?1 to 1164 μeq l?1. Runoff export of S was 53 kg S ha?1 year?1 in 1993, S is not retained in the catchments. Nitrogen (N) budget indicates accumulation in the catchment, which is attributed to forest regrowth.  相似文献   

4.
Precipitation chemistry was discussed from the viewpoint of potential sources for four rural sites where wet-only daily-basis measurement data sets were available during the period from April 1996 to March 1997 in Japan. Annual volume-weighted mean concentrations of nss-SO4 2? and NO3 ? ranged from 18.0 to 34.6 µeq L?1, and from 9.3 to 23.1 µeq L?1, respectively. The degree of neutralization of input acidity in terms of the concentration ratio, [H+] / ([nss-SO4 2?] + [NO3 ?]), ranged from 0.46 to 0.63. This suggests that about half of the input acidity due to H2SO4 and HNO3 was neutralized by NH4 + and nss-Ca2+ to produce the pH values of 4.46 to 4.82 for these sites. Maximum likelihood factor analysis was then performed on the logarithmically transformed daily wet deposition of major ions. Two factors successfully explained a total of about 80% of the variance in the data for each site. Interpreting varimax rotated factor loadings, we could identify two source types: (1) acid source with large loadings on ln(H+), ln(nss-SO4 2?), ln(NO3 ?) and ln(NH4 +), (2) sea-salt source with large loadings on ln(Na+), ln(Cl?), ln(Mg2+) and ln(K+). The rural wet deposition over Japan appears to have a similar structure in terms of the kinds of sources and their relative location.  相似文献   

5.
Discharge to concentration relationships for eight streams studied by the U.S. Geological Survey (USGS) as part of the U.S. Environmental Protection Agency's (U.S. EPA) Long-Term Monitoring Project (1983–89) indicate acidification of some streams by H2SO4 and HNO3 in atmospheric deposition and by organic acids in soils. Concentrations of major ions in precipitation were similar to those reported at other sites in the northeastern United States. Average concentrations of SO4 2? and NO3 ? were similar among streams, but base cation concentrations differed widely, and these differences paralleled the differences in acid neutralizing capacity (ANC). Baseflow ANC is not a reliable predictor of stream acidity at high flow; some streams with high baseflow ANC (>150 Μeq L?1) declined to near zero ANC at high flow, and one stream with low baseflow ANC (<50 Μeq L?1) did not approach zero ANC as flow increased. Episodic decreases in ANC and pH during peak flows were associated with increased concentrations of NO3 ? and dissolved organic carbon (DOC). Aluminum concentrations exceeding 300 Μg L?1 were observed during peak flows in headwater streams of the Neversink River and Rondout Creek. Seasonal Kendall Tau tests for temporal trends indicate that SO4 2? concentrations in streamwater generally decreased and NO3 ? concentrations increased during the period 1983–1989. Combined acid anion concentrations (SO4 2? + NO3 ?) were generally unchanged throughout the period of record, indicating both that the status of these streams with respect to acidic deposition is unchanged, and that NO3 ? is gradually replacing SO4 2? as the dominant acid anion in the Catskill streams.  相似文献   

6.
We evaluated the element budgets in a forested watershed in Jiulianshan, southern China. The element input in bulk precipitation was characterized by high depositions of H+, NH4 +, Ca2+, and SO4 2?, i.e., 400, 351, 299, and 876 eq/ha/yr, respectively. The outputs of H+, NH4 +, and SO4 2? from the watershed were very low, while those of Ca2+ and Mg2+ were high, 712 and 960 eq/ha/yr, respectively. The element budgets suggested that i) the net retentions of H+, NH4 +, and SO4 2? in this watershed were high, and ii) the net release of Mg2+ from this watershed was high mainly due to weathering. The net release of Ca2+ was not so high because of the high atmospheric deposition, while atmospheric deposition of Mg2+ was not so high (130 eq/ha/yr). Decrease of acid neutralizing capacity in the soil, i.e., net soil acidification, was caused mainly by the net release of Mg2+. Moreover, the net retention of SO4 2? also contributed to soil acidification.  相似文献   

7.
To clarify nitrogen (N) sources, the overall N budget in a forested watershed in Kanagawa Prefecture, Central Japan was estimated by measuring dissolved inorganic N (DIN; NH4 + + NO3 – + NO2 –) from Nov 2004 through Oct 2005. The estimated N budget (–1.43 kg N ha–1 year–1) showed that the N output rate (stream water N) was higher than the N input rate (bulk deposition N) in the watershed. The annual NO2 – and NO3 – input rates were 0.02 and 1.99 kg N ha–1 year–1, respectively. NH4 + was the predominant source in this forested watershed, accounting for 71% (4.99 kg N ha–1 year–1) of DIN input rate. In addition, this study estimated rainfall pH, air temperature, and wind direction, which were considered as controlling factors related to the atmospheric deposition rate of NH4 +. This study showed that the rainfall NH4 + was inversely proportional to the initial pH of the rainfall, which was calculated by adding the amount of H+ consumed by the dissociation process of NH3(aq) to the measured rainfall pH. This result implies that acid rain can elevate the solubility of NH3(g) and the dissociation capacity of NH4 + throughout the process of precipitation. Also, this study provides strong evidence that the high NH4 + deposition rate is mainly derived from NH3(g) emitted from livestock wastes under the NH3 transport condition of warm summer and favorable wind direction.  相似文献   

8.
Longitudinal and temporal variations in water chemistry were measured in several low-order, high-elevation streams in the Great Smoky Mountains to evaluate the processes responsible for the acid-base chemistry. The streams ranged in average base flow ANC from ?30 to 28 μeq L?1 and in pH from 4.54 to 6.40. Low-ANC streams had lower base cation concentrations and higher acid anion concentrations than did the high-ANC streams. NO3 ? and SO4 2? were the dominant acid anions. NO3 ? was derived from a combination of high leaching of nitrogen from old-growth forests and from high rates of atmospheric deposition. Streamwater SO4 2? was attributed to atmospheric deposition and an internal bedrock source of sulfur (pyrite). Although dissolved Al concentrations increased with decreasing pH in the study streams, the concentrations of inorganic monomeric Al did not follow the pattern expected from equilibrium with aluminum trihydroxide or aluminum silicate phases. During storm events, pH and ANC declined by as much as 0.5 units and 15 μeq L?1, respectively, at the downstream sites. The causes of the episodic acidification were increases in SO4 2? and DOC.  相似文献   

9.
A simple mass flux model was developed to simulate the response of SO4 2- concentrations in surface waters to past and anticipated future changes in atmospheric deposition of SO4 2-. Values of bulk (or wet) SO4 2- deposition and dry deposition of S determined from measured air concentrations and a deposition velocity were insufficient to balance watershed SO4 2- export at the Hubbard Brook Experimental Forest, NH and for a regional survey of watersheds in the northeastern U.S. We propose two explanations for the unmeasured S source: 1) a significant underestimation of dry S deposition, and/or 2) internal watershed S sources, such as weathering and/or mineralization of soil organic S. Model simulations based on these two mechanisms agreed closely with measured stream SO4 2- concentrations at Hubbard Brook. Close agreement between measured and model predicted results precluded identification of which of the two mechanisms controlled long-term trends in stream SO4 2-. Model simulations indicated that soil adsorption reactions significantly delayed the response of stream water to declines in SO4 2- inputs since 1970, but could not explain the discrepancy in watershed S budgets. Extrapolation of model predictions into the future demonstrates that uncertainty in the source of the S imbalance in watersheds has important implications for assessments of the recovery of surface water acid neutralizing capacity in response to anticipated future reductions in SO2 emissions.  相似文献   

10.
We examined long-term changes in soil solution chemistry associated with experimental, whole watershed-acidification at the Bear Brook Watershed in Maine (BBWM). At BBWM, the West Bear (WB) watershed has been treated with bimonthly additions of ((NH4)2 SO4) since 1989. The adjacent East Bear (EB) watershed serves as a biogeochemical reference. Soil solution chemistry in the EB watershed was relatively stable from 1989?C2007, with the exception of declining SO4?CS concentrations associated with a progressive decline in SO4?CS deposition during this period. Soil solution chemistry in WB reflected a progressive change in acid-neutralization mechanisms from base cation buffering to Al buffering associated with treatment during this period. Total dissolved Al concentrations progressively increased over time and were ~4× higher in 2007 than in 1989. Treatment of WB was also associated with long-term increases in soil solution H+, SO4?CS, and NO3?CN, whereas soil solution dissolved organic carbon (DOC) was unresponsive to treatment. For solutes such as Ca, H+, and SO4?CS, changes in stream chemistry were generally parallel to changes in soil solution chemistry, indicating a close coupling of terrestrial and aquatic processes that regulate the chemistry of solutions in this first-order stream watershed. For other solutes such as Al and DOC, solute concentrations were higher in soil solutions compared with streams, suggesting that sorption and transformation processes along hydrologic flow-paths were important in regulating the chemistry of solutions and the transport of these solutes.  相似文献   

11.
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   

12.
A statistically significant decrease in sulfate was observed in high elevation Cascade lakes during 1983 through 1988. The total decrease averaged 2.2 μeq L?1 in two slow-flush lakes and 4.2 μeq L?1 in three fast-flush lakes for 1983–1985 vs 1986–1988, respectively. Coincident with these changes in sulfate concentrations were a sharp decrease of SO2 emissions from the ASARCO smelter (100 km SE of the lakes), from 87 to 70 kt yr?1 during 1983–1984 to 12 in 1985, the year of its closure, and a gradual change in SO2 emissions from Mt. St. Helens, from 39 to 27 during 1983–1984 to 5 in 1988. The sharpest decreases occurred in non-marine sulfate in fast-flush lakes from 1984 to 1985 (about 2 μeq L?1) and in slow-flush lakes from 1985 to 1986 (1 μeq L?1, which point to the ASARCO closure as the sole cause. However, some of the more gradual decline in non-marine sulfate observed during 1983 through the 1988 sampling periods may have been due to a slow washout of sulfate enriched ash from the 1980 Mt. St. Helens' eruption. Sulfate concentrations in precipitation also declined significantly by about 2 μeq L?1, but changes in volume-weighted sulfate content were not significant. Lake alkalinity did not show a consistent increase in response to decreased sulfate. This was probably due to either watershed neutralization of acidic deposition or the greater variability in alkalinity measurements caused by small changes in acidic deposition making it difficult to detect changes.  相似文献   

13.
Twenty-four low acid neutralizing capacity (ANC) lakes in Vermont have been monitored since 1980 to characterize their chemical variability, and to determine if they exhibit temporal trends in acid/base chemistry. Many of the lakes exhibit significant decreasing trends in SO4 2? and base cation (CB) concentrations, but few exhibit significant changes in pH or ANC. An examination of all trend results (significant and insignificant) suggests a tendency for ANC and pH values in these lakes to be increasing, but either the changes are too small, or the number of observations too small, for these trends to be significant. Data from these lakes suggest that the primary responses of surface waters in this region to declining rates of SO4 2? deposition are decreases in SO4 2? concentrations and rates of cation leaching from watershed soils. Decreasing rates of cb deposition may combine with lower rates of cation leaching to produce declines in cB that are very similar to measured declines in SO4 2? concentration. Vermont lakes exhibit their lowest ANC values in spring, attributable, for the most part, to dilution of cB concentrations during spring snow melt. Concentrations of SO4 2? are also more dilute in the spring, but cB decreases are greater, and the net effect is a lowering of ANC. One quarter of the Vermont lakes monitored exhibit strong seasonality in NO3 ? concentrations, with peak concentrations near 70 Μeq L?1. In these lakes, spring increases in NO3 ? concentrations are more important than CB dilution in producing minimal spring ANC values.  相似文献   

14.
Nitrogen emissions have grown in Spain during the last 15 years. As precipitation scavenges gases and aerosols from the atmosphere, an effect on rainwater concentrations can be expected. However, time-series studies on wet N concentrations in the Iberian Peninsula are very scarce. This paper aims to fill this gap by analysing weekly rainfall N concentrations at a set of rural sites in Catalonia (NE Spain) from 1995/1996 to 2007 and a forest site monitored from 1983 to 2007. The sites encompass a range of rural environments and climate conditions, from the inland pre-Pyrenees (Sort) to the Mediterranean coast (Begur) and from north (Sort and Begur) to central (Palautordera and La Castanya) and south Catalonia (La Senia). We found a 1-year cycle for concentrations of NH 4 + and NO 3 ? whereby higher values were reached at the end of spring–early summer, except at the easternmost coastal site of Begur. Weekly NH 4 + concentrations decreased with time at all sites (except at La Senia) whilst NO 3 ? concentrations increased at all sites during the same period. Rainfall SO 4 2? concentrations decreased with time at all sites. The opposite trends in NO 3 ? and SO 4 2? concentrations determined a shift in the relative acid contribution of those anions during the 12–13-year period. To interpret the increasing trend, mean annual NO 3 ? concentrations were regressed against NO2 Spanish emissions and to some indicators of local anthropogenic activity. The increase at Sort and Palautordera showed good correlation with local anthropogenic indicators. Wet inorganic N deposition ranged between 4.2 and 6.7 kg ha?1 year?1. When including estimates of dry deposition, total annual deposition rose up to 10–20 kg ha?1 year?1, values that have been found to initiate adverse effects on Mediterranean-type forest ecosystems.  相似文献   

15.
Temporal changes in major solute concentrations in six Czech Republic lakes were monitored during the period 1984–1995. Four chronically-acidic lakes had decreasing concentrations of strong-acid anions (CSA = SO4 2- + NO3 - + Cl-), at rates of 3.0 to 9.0 μeq L-1 yr-1. Decreases in SO4 2-, NO3 -, and Cl- (at rates up to 5.1 μeq L-1 yr-1, 3.2 μeq L-1 yr-1, and 0.6 μeq L-1 yr-1, respectively) occurred. The response to the decrease in deposition of S was rapid and annual decline of SO4 2- in lake water was directly proportional to SO4 2- concentrations in the acidified lakes. Changes in NO3 - concentrations were modified by biological consumption within the lakes. The decline in CSA was accompanied in the four most acidic lakes by decreases in AlT, increases in pH at rates of 0.011 to 0.016 pH yr- 1, and decreases of Ca2+ and Mg2+ (but not Na+) in three lakes. The acid neutralizing capacity (ANC) increased significantly in all six lakes. Increases in base cation concentrations (CB = Ca2+ + Na+ + Mg2+ + K+) were the principal contributing factor to ANC increases in the two lakes with positive ANC, whereas decrease in CSA was the major factor in ANC increases in the four chronically-acidic lakes. The continued chemical recovery of these lakes depends on the uncertain trends in N deposition, the cycling of N in the lakes and their catchments, and the magnitude of the future decrease in S deposition.  相似文献   

16.
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   

17.
Rainfall, stemflow, and throughfall were collected from 1996 to 1999 at two types of forest sites: (1) forests near the traffic roads and urban areas and (2) forests away from the urban areas at Mt. Gokurakuji, Hiroshima, western Japan in order to estimatethe effects of anthropogenic activities on atmospheric deposition. Rainfall deposition for major ions showed small differences between the sites. The NO3 - and SO4 2-concentrations in stemflow were higher at the urban-facing slope than at the mountain-facing slope. Throughfall deposition of NO3 - and SO4 2- was also higher at urban-facing slopes. Net throughfall (NTF) deposition (throughfall minus rainfall) of NO3 - and SO4 2- accounted for 77 and50% of the total throughfall deposition on urban-facing slopes, respectively, while it accounted for 44 and 23% on themountain-facing slopes, respectively. These results indicated a higher contribution from dry deposition on urban-facing slopes compared to mountain-facing slopes. Atmospheric N (NO3 - +NH4 +) deposition from throughfall was estimated to be around 17–26 kg N ha-1 yr-1 on urban-facing slopes, which was greater than the threshold of N deposition that could cause nitrogen leaching in Europe and the United States. The highload of atmospheric N deposition may be one of the factors bringing about the decline of pine forests on urban-facing slopesof Mt. Gokurakuji.  相似文献   

18.
The present study was conducted in tropical Sal forest ecosystem of the Doon valley in the Indian Himalayas to assess the critical load of sulfur and nitrogen and their exceedances. The observed pattern of throughfall ionic composition in the study are Ca2+>K+>Mg2+>Cl?>?HCO3?>?Na+>NO 3 ? >?SO 3 2? ???NH 4 + >F?. The sum of cation studied is 412.29 ??eq l?1 and that of anions is 196.98 ??eq l?1, showing cation excess of 215.31 ??eq l?1. The cations, namely Ca2+, Mg2+, K+, Na+, and NH 4 + , made a contribution of about 67% of the total ion strength, where as anion comprising of SO 4 2? , Cl?, NO 3 ? , and HCO 3 ? contributed 33%. The chief acidic components were Cl?C (12%) and HCO 3 ? (8%), while the presence of SO 4 2? (5%) and NO 3 ? (6%), respectively. Percentage contribution of bole to total aboveground biomass was ??72.38% in comparison to 2.24?C2.93% of leaf biomass, 10.34?C10.96% of branch biomass and 13.21?C17.07% of bark biomass. There was high and significant variation (P?<?0.001) in the total aboveground biomass produced at different sites. The aboveground net primary productivity (ANPP) in these sites ranged between 2.09 and 9.22 t ha?1 year?1. The base cations and nitrogen immobilization was found to be maximum in bole. The net annual uptake of the base cations varied from 306.85 to 1,311.46 eq ha?1 year?1 and of nitrogen from 68.27 to 263.51 eq ha?1 year?1. The critical appraisal of soil showed that cation exchange capacity lied between 18.37 and 10.30 Cmol (p+) kg?1. The base saturation percentage of soil was as high as 82.43% in Senkot, whereas in Kalusidh it was just 44.28%. The local temperature corrected base cation weathering rates based on soil mineralogy, parent material class, and texture class varied from 484.15 to 627.25 eq ha?1 year?1, showing a weak potentiality of the system to buffer any incoming acidity and thus providing restricted acid neutralizing capacity to keep the ecosystem stable under increased future deposition scenarios in near future. The appreciable BS of the soil indicates the presence of intense nutrient phytorecycling forces within this climate and atmospheric deposition in replenishing base cations in the soil, which includes intrinsic soil-forming processes, i.e., weathering. The highest value of critical load for acidity was 2,896.50 eq ha?1 year?1 and the lowest was 2,792.45 eq ha?1 year?1. The calculated value of the minimum critical loads for nitrogen varied from 69.77 to 265.01 eq ha?1 year?1, whereas the maximum nitrogen critical load ranged between 2,992.63 and 4,394.45 eq ha?1 year?1. The minimum and the maximum critical loads of sulfur ranged between 2,130.49 and 3,261.64 eq ha?1 year?1 and 2,250.58 and 3,381.73 eq ha?1 year?1, respectively. The values of exceedance of sulfur and nitrogen were negative, implying that in the current scenario Sal forests of the Doon valley are well protected from acidification.  相似文献   

19.
A field experiment was designed to evaluate the effects of differing forms of acidifying S and N compounds on the chemistry of soils and soil solutions in a low elevation coniferous forest in northern New England. Treatments consisted of O, 1500, 3000, and 6000 eq of SO4 2? or NO3 ? ha?1 for the 1987 growing season applied biweekly as H2SO4 or HNO3, or in a single application as dry] (NH4)2SO4. Acidifying treatments resulted in a significant increase in soil solution SO4 2? (1.2 to 2.6) or NO3 ? (12 to 80) in the upper B horizon. Excess strong acid anion leaching was associated with an accelerated loss of base cations, particularly MG2+ As solutions passed through the upper 25 cm of the soil profile, mean SO4 2? concentrations decreased by 5 to 50% of the initial values, indicating that much of the applied SO4 2? was immobilized in the upper portion of the pedon. Elevated concentrations of adsorbed and water-soluble SO4 2? indicate that abiotic adsorption of SO4 2? by soils is the dominant mechanism for the initial attenuation of SO4 2? concentrations in these solutions. Other soil properties showed only small or no change due to treatments over the single growing season of this study. These results indicate that H2SO4, HNO3, and (NH4)2SO4 can all effectively increase strong acid anion concentrations in the soil-soil solution system.  相似文献   

20.
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   

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