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1.
The effects of artificial acid rain on soil leachate composition were studied in a lysimeter experiment. Cambic Arenosol (Typic Udipsamment) in monolith lysimeters was treated for 6 1/2 yr with 125 mm yr?1 artificial rain in addition to natural precipitation. Artificial acid rain was produced from groundwater with H2SO4 added. pH levels of 6.1, 4 and 3 were used. Increasing content of H2SO4 in the artificial rain increased the concentration of Ca2+ and Mg2+ in the leachate significantly. The pH of the leachate was slightly reduced only by the most acidic treatment (pH 3). The H+? retention was not accompanied by a proportionate increase in the Al ion concentration. A slight increase in the Al ion concentration was only observed in the leachate from the pH 3-treated lysimeter. We conclud that cation exchange and/or weathering were the main buffer mechanisms in the soil. The study supports conclusions from other acidification studies, that acidic precipitation is likely to increase the leaching of Ca2+ and Mg2+ from soils.  相似文献   

2.
This study focuses on fluxes of elements from, and changes in the soil properties of shallow organic material rich soil as a result of changes in precipitation acidity. Intact soil columns including natural vegetation from two areas (one exposed to acidic precipitation and one unpolluted) were used in a lysimeter experiment. The lysimeters were watered with simulated normal rain (pH 5.3) or simulated acidic rain (pH 4.3) for four years. Sulphuric acid and ammonium nitrate were used to regulate the quality of the simulated rain. Significantly more SO4 2? was leached from lysimeters receiving acid rain. Rain acidity had no significant effect on NO3 ? leaching. Significantly more Mg2+ was leached from lysimeters receiving acid rain, but this only applied for the soils from the unpolluted area. Four years of treatment did not cause any significant effect on the soil acidity and the amounts of base cations in the soil. The more acidic rain did, however, cause a significant lower cation exchange capacity. For the soils from the polluted area the acid precipitation did cause a lowering of the exchangeable K+ in the upper 5 cm of the soil. Different quality of the soil organic material indicated by different vegetation types appeared to cause significant differences in the amount of components leached from the soil, but did not cause any difference in response to the different rain qualities.  相似文献   

3.
Rain water at two forested sites in Guangzhou (south China) show high concentrations of SO4 2?, NO3 ? and Ca2+ and display a remarkable seasonal variation, with acid rain being more important during the spring and summer than during the autumn and winter. The amount of acid rain represents about 95% of total precipitation. The sources of pollutants from which acid rain developed includes both locally derived and long-middle distance transferred atmosphere pollutants. The seasonal variation in precipitation chemistry was largely related to the increasing neutralizing capacity of base cations in rainwater in winter. Soil acidification is highlighted by high H+ and Al3+ concentrations in soil solutions. The variation in elemental concentration in soil solution was related to nitrification (H+, NH4 + and NO3 ?) and cation exchange reaction (H+, Al3+) in soil. The negative effect of soil acidification is partly dampened by substantial deposition of base cations (Ca2+, Mg2+ and K+) in this area.  相似文献   

4.
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   

5.
Ion leaching in 3 sandy spruce forest soils of different origin and pH was investigated in the laboratory. Zero-tension lysimeters containing undisturbed soil columns of varying soil depth were subjected to H2SO4 loadings for a period of 9 weeks. The analysis of the resulting leachate supports the hypothesis that Al-sulphate minerals may form in acidic soils when exposed to acid (H2SO4) deposition. In the B horizon of a glaciofluvial sandy soil (pH 4.2), both H+ and sulphate ions were retained to maintain 2pH + PSO4 = 11.9 in the leachate solutions. This relation between H+ and sulphate activity may be due to an adsorption mechanism or a precipitation mechanism. The precipitation mechanism is favored by the good fit of leachate composition to the conditions for jurbanite [AlOHSO4] formation from gibbsite [Al(OH)3]. In the B horizon of a sandy till at pH 3.7, the Al in soil solution (0.5 mmol L?1) was leached with sulphate. As the sulphate load was increased, some sulphate was retained. This may also be due to the dissolution and precipitation of an Al-sulphate mineral. The ion activity products of leachate solutions from the B horizon of this soil were close to the pKs reported for jurbanite. The conditions for the possible existence and/or formation of Al-sulphate minerals in acidic soils are discussed.  相似文献   

6.
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   

7.
Three years of N application to a Cambic arenosol (Typic Udorthent) in two lysimeter series, one with and one without young saplings of Pinus sylvestris L. have produced significant changes in soil solution and leachate chemistry. An application of 30 kg N/ha*yr?1 significantly increased NO3 ? leaching from the soil. This N load was also sufficient to significantly increase the mobility of the phyto-toxic elements Al3+ and Mn2+, likewise to increase leaching of the important plant nutrients Ca2+, Mg2+ and K+. At a N load of 90 kg N/ha*yr?1 significant increase in NH4 + leaching was observed, but total leaching of NH4 + was still very low compared to NO3 ? leaching. No significant treatment effects were found for SO4 2?, Fe2+ and Cl? in the leachate. Trees grown in the lysimeters buffered the acidifying effect of N application and increased the leachate pH by 0.2 pH units compared to lysimeters without trees.  相似文献   

8.
Rain event samples have been collected in Haifa, Israel, for nine hydrological years 1981 to 1990. Precipitation amount, pH, SO4 =, NO3 ?, Cl?, NH4 +, Na+, K+, Ca++, Mg++ and alkalinity of rainwater samples were recorded. The sampling and analysis program was based on WMO recommendations for background networks. The sampling was performed manually, and the analysis was based on wet chemistry for ions and atomic absorptions for metals. Data of 187 rain samples showed that the average pH was 5.3±1.1∶ 26% of the rain events were below pH of 5.6 and 23% above pH of 7.0. Some simple chemical mass-balance considerations indicate that natural sources, sea salt and soil carbonates are the main contributors to rain chemistry. However, the presence of low pH events observed over the years suggests that the impact of anthropogenic emissions may overwhelm the buffering capacity of the alkaline aerosol.  相似文献   

9.
A humic lake of pH 5.6 was acidified with H2SO4 to pH 4.1. Measurements of total and hollow-fiber ultrafiltered samples were made after three different times of storage, before and after the acid treatment. The nominal molecular weight cutoff of the hollow-fiber membrane was 10 kDalton. Assuming a linear molecular weight distribution of the organic complexes present in solution, the average organic molecule had an average molecular weight of 12.8?08 kDalton (n=6). Not only Ca2+ and Mg2+, but also detectable amounts of Na+ and K+ was found to be present on high molecular weight forms. No significant change in the molecular weight distribution of these elements were observed after the pH decrease. Changes in the molecular weight distribution after the acid treatment were only observed for Fe and Al. Significant amounts of SO4 2? were present on high molecular weight forms. A small, but significant increase in the relative amounts of SO4 2? present on high molecular weight forms was observed after the pH lowering. Kinetic constraints were demonstrated for dissolution of Al and Fe. To some extent, kinetic constraints in the equilibrium distribution of cation/anion exchange reactions of Al, Fe, and SO4 2? were also observed. After the acid treatment, the cation exchange capacity (CEC) of the organic pool present was estimated to be at least 18.2±1.4 (n=3) μeq of positive charges per mg C, probably because the negative sites on the organic pool are either not totally protonated or occupied by other cations at pH 4.09. This CEC is of the same order as industrially made cation exchange resins.  相似文献   

10.
The effects of artificial rain of various acidities were studied in a lysimeter experiment. Lysimeters, 29 cm in diameter, and 40 cm deep contained a Gleyed Dystric Brunisol. Natural structure, stratification and original vegetation were maintained. Artificial rain was produced from groundwater with “high” concentrations of neutral salts and from rainwater with lower concentrations. pH levels of 6, 4, 3 and 2 were established by adding H2SO4. Effects of dilution with given amounts of acid were examined by comparing the effects of 50 mm “rain” month?1 of pH 3 and pH 2 with 500 mm “rain” month?1 of pH 4 and pH 3, respectively. The study continued for 5 yr. Totals of 1250 or 12500 mm “rain” were applied in addition to a natural input of 2773 mm. Increased input of SO4 2? increased the output of SO4 2? but, as concentration increased, sorption of SO4 2? in the soil also increased. Concentrations of base cations in the leachate increased parallel to the output of SO4 2?. However, significant effects on leaching of base cations and on the content of exchangeable cations in the soil, was only found in the pH 2 treatment with 1250 mm of “rain” and in the pH 4 and pH 3 treatment with 12500 mm of “rain”.  相似文献   

11.
Data from two Podzol O and E horizons, sampled in 1-cm layers at 13 points within 2 m × 2 m plots, were used to test the hypothesis that the composition of hydrogen ions (H) and aluminium (Al) adsorbed to the solid-phase soil organic matter (SOM) determines pH and Al solubility in organic-rich acidic forest soils. Organically adsorbed Al was extracted sequentially with 0.5 m CuCl2 and organically adsorbed H was determined as the difference between total acidity titrated to pH 8.2 and Al extracted in 0.5 m CuCl2. The quotient between fractions of SOM sites binding Al and H (NAl/NH) is shown to determine the variation in pH and Al solubility. It is furthermore shown that models in which pH and Al solubility are linked via a pH-dependent solubility of an Al hydroxide and in which cation exchange between Al3+ and Ca2+, rather than cation exchange between Al3+ and H+, is the main pH-buffering process cannot be used to simulate pH or Al solubility in O and E horizons. The fraction of SOM sites adsorbing Al increased by depth in the lower O and throughout the E horizon at the same magnitude as sites adsorbing H decreased. The fraction of sites binding the cations Ca2+ + Mg2+ + K+ + Na+ remained constant. It is suggested that a net reaction between Al silicates (proton acceptors) and protonated functional groups in SOM (proton donors) is the long-term chemical process determining the composition of organically adsorbed H and Al in the lower part of the O and in the E horizon of Podzols. Thus, in the long term, pH and Al solubility are determined by the interaction between organic acidity and Al alkalinity.  相似文献   

12.
The study aimed at evaluating whether salt-induced mobilization of acidity may be modified by the type of anion. For this purpose, the effects of different neutral salts on the solution composition of acid soils were investigated. The results were compared with those of the addition of acids. Two topsoil (E and A) and two subsoil horizons (Bs and Bw) were treated with NaCl, Na2SO4, MgCl2, MgSO4, HCl, and H2SO4 at concentrations ranging from 0 to 10 mmol dm?3. With increasing inputs of Cl? the pH of the equilibrium soil solution dropped, the concentrations of Al and Ca increased, and the molar Ca/(Al3+ + AlOH2+ + Al(OH)2+) ratios decreased. These effects were the least pronounced when NaCl was added and the most at the HCl treatments. According to the release of acidity, the topsoils were more sensitive for salt-induced soil solution acidification whereas on base of the molar Ca/(Al3+ + AlOH2+ + Al(OH)2+) ratios, the salt effect seems to be more important for the subsoils. Addition of S042? salts and H2SO4 induced higher pH and lower Al concentrations than the corresponding Cl? treatments due to the SO42? sorption, especially in the subsoils. The Ca/(Al3+ + AlOH2+ + Al(OH)2+) ratios were higher than those of the corresponding Cl? treatments. In subsoils even after H2SO4 additions these ratios were not higher than those of the NaCl treatments. The results indicate (I) that speculation about the effects of episodic salt concentrations enhancement on soil solution acidification not only need to consider the ionic strength and the cation type but also the anion type, (II) that salt-induced soil solution composition may be more crucial in subsoils than in topsoils, and (III) that in acid soils ongoing input of HNO3 due to the precipitation load may induce an even more acidic soil solution than the inputs of H2SO4 of the last decade.  相似文献   

13.
In recent years, acid rain has been a social problem all over the world. In Japan, it is also a big problem especially in the metropolitan area. Then, we have measured major ions such as H+, Na+, NH4 +, K+, Mg2+, Ca2+, Cl?, NO3 ?, and SO4 2? in precipitation and dry deposition samples which had been collected at 9 sampling sites at Hiyoshi, Mita, Kashiwa, Shiki, Fujisawa, Yokosuka, Mitaka, Hachiouji, and Ashikaga in Tokyo Metropolitan area for 10 years since 1990. The average pH of precipitation in their sites was 4.56 (n=1906). As the results of multiple regression analysis showed that pH of precipitation was determined by 5 ions such as NH4 +, nssCa2+(non sea salt calcium), nssCl?(non sea salt chloride), NO3 ?, nssSO4 2?(non sea salt sulfate) in the most of the sampling sites. Therefore, it is very important to investigate the behavior of these ions to understand the acidification of rain in Tokyo Metropolitan area. In this study, a long term trend of each ion concentration in precipitation and wet deposition was also investigated the base on the data we had observed at 7 sites for 10 years by the statistical method.  相似文献   

14.
新疆伊犁察南灌区土壤盐分特征   总被引：2，自引：0，他引：2  
以察南灌区土壤为研究对象,对不同含盐量土壤进行盐化程度分级,并对该地区土壤盐分特征进行相关分析和主成分分析,以及对土壤盐分因子区域影响因素进行探讨。结果表明:察南灌区以碱性土壤为主,HCO_3~–是影响该灌区土壤p H最强的因子;对灌区0~100 cm土体土壤的分析表明,灌区盐化土面积约为总灌溉面积的1/4,盐渍化风险较大;相关性分析显示,HCO–3、Cl~–、SO_4~(2-)、Ca~(2~+)、Mg~(2~+)、Na~+、K~+为盐分主要组成离子,总盐分与各离子之间均呈正相关关系,与总盐分相关性最强的阴离子为SO_4~(2-),相关性最强的阳离子为Mg~(2~+);主成分分析显示,HCO_3~–、Cl~–、K~+为影响该灌区土壤盐分特征的主导因子;通过盐分因子区域影响因素定性分析可知,除HCO_3~–和pH是由河流以及地下水综合作用影响外,其他盐分因子均主要受河流影响。  相似文献   

15.
 The release of SO4 2–-S, K+, Ca2+ and Mg2+ from soil amended with spent mushroom compost (SMC), a byproduct of mushroom production, was measured in leachate from field lysimeters for 30 weeks. Rates of application were 0 and 80 t ha–1 moist SMC. The SMC contained 1.7% K, 6.5% Ca, 0.4% Mg and 1.2% S (of which 87% is SO4 2–-S), and has a C : S ratio of 26. The break-through curves of ion leaching were polymodal indicating the preservation of soil structure in the lysimeters and its influence on leaching. SO4 2–-S release from SMC was rapid (first-order exponential) and was very similar to the release from a laboratory incubation. The release of K+, Ca2+ and Mg2+ was described using first/zero-order models which were also used to describe their release in the laboratory. The rate and amount of Ca2+ release was similar in the field and laboratory, but the amount of K+ (and to a lesser extent Mg2+) release was less in the field than in the laboratory. Recoveries of SMC applied nutrients in leachate were 80% of S (263 kg ha–1), 3% of K (14 kg ha–1), 16% of Ca (284 kg ha–1) and 37% of Mg (40 kg ha–1). Little if any S was mineralised. Using SMC could provide plants with S, K, Ca and Mg but there is potential for SO4 2–-S losses via leaching. Received: 7 April 1999  相似文献   

16.
In order to reduce nutrient wastes to the environment the supply should be in accordance to the demand for these. Two experiments were conducted to study and quantify the effect of temperature, irradiance, and plant age on the uptake of nitrate (NO3?), ammonium (NH4+), dihydrogen phosphate ion (H2PO4?), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and sulfate (SO42). In the first experiment, various levels of temperature and irradiance were applied to plants in a growth chamber, while in the second experiment the uptake was studied along the crop season under greenhouse conditions. The uptake rates were calculated at 2-hour intervals through sampling the nutrient solution and analyzing it by inductively coupled plasma atomic emission spectrometry (ICP-AES). Increasing light and temperature enhance the uptake rates, while the rates decrease with plant age. Nitrogen absorption was similar during the day as during the night. No differences were found in the absorption of H2PO4?, K+, Ca2+, Mg2+, and SO42? between day and night. Nitrate absorption was found to have a positive correlation with the absorption of all the ions except for NH4+.  相似文献   

17.
[目的]通过对滨海地区盐碱土水盐动态变化规律的研究,为该地区的土壤利用以及植树造林提供科学依据。[方法]以天津大港地区刺槐林土壤为研究对象,研究不同土层的土壤水盐年份变化和盐分离子分布特征。[结果]试验地土壤全年含水量变化范围在11.9%~28.8%;含盐量变化范围在4.2%~18.4%。春(3—5月)秋(9—11月)季节土壤含水量低,含盐量高,土壤盐分含量随土层深度增加逐渐降低;夏季(6—8月),土壤含水量高,含盐量低,土壤盐分含量随土层深度的增加逐渐升高。pH值在7.37~8.39之间,土壤中K+,Na+,Ca2+,Mg2+和Cl-春季表层土壤(0—10cm)含量最高,分别为0.04,4.27,2.69,1.04和10.03g/kg。除SO2-4和HCO-3外,其他盐分离子在春季变异系数(29.99~162.98)明显大于夏秋季节(2.87~88.13)。[结论]不同土层的土壤含水量和含盐量随当地降雨量呈明显的季节性变化;试验地区土壤属于碱性土壤,随季节变化不明显;K+,Na+,Ca2+,Mg2+和Cl-与含盐量变化趋势保持一致,SO2-4和HCO-3随季节变化没有明显的规律性;春季各盐分离子在土壤中分布极为不均。  相似文献   

18.
Cation mobility in acidic soils with low organic‐matter contents depends not only on sorption intensity but also on the solubility of the species present in soil solution. In general, the following leaching gradient is observed: potassium (K+) > magnesium (Mg2+) > calcium (Ca2+) > aluminum (Al3+). To minimize nutrient losses and ameliorate the subsoil, soil solution must be changed, favoring higher mobility of M2+ (metal ions) forms. This would be theoretically possible if plant residues were kept on the soil surface. An experiment was conducted in pots containing a Distroferric Red Latosol, with soil solution extractors installed at two depths. Pearl millet, black oat, and oilseed radish residues were laid on the soil surface, and nitrogen (as ammonium nitrate) was applied at rates ranging from 0 to 150 mg kg?1. Corn was grown for 52 days. Except for K+ and ammonium (NH4 +), nitrogen rates and plant residues had little effect upon the concentrations and forms of the elements in the soil solution. Presence of cover crop residues on soil surface decreased the effect of nitrogen fertilizer on Ca leaching. More than 90% of the Ca2+, Mg2+, and K+ were found as free ions. The Al3+ was almost totally complexed as Al(OH3)0. Nitrogen application increased the concentrations of almost all the ions in soil solution, including Al3+, although there was no modification in the leaching gradient.  相似文献   

19.
Theory and experimental results have shown that neutral salts in the precipitation or supplied to the ground by other means reduce the acidification of soils by acid precipitation. This salt effect is caused by the cation exchange occurring after the entry of the rain water into the soil.The acid components of precipitation consist of H2SO4, HNO3 and HCl and of NH4+ after nitrification in the soil. The magnitude of the salt effect depends on the relative bonding energy of H3O+ and of Ca2+, Mg2+, Na+, K+, NH4+ in the soil as well as on the concentrations of H3O+ and the above cations in the precipitation. The salt effect may be considerable in very acid soils. It decreases with rising pH to become very small or negligible in neutral soils, chiefly due to the increasing bonding energy of H3O+ in this direction.The adverse effect of acid precipitation, therefore, is likely to be less in very acid soils, such as podsols, than in slightly acid and neutral soils with low buffering capacity against pH change. Soil texture and calcite content are very important factors in this respect as fine material and calcite increase the buffering.  相似文献   

20.
Chemical and Statistical Analysis of Precipitation in Singapore   总被引：1，自引：0，他引：1  
The results of chemical analyses of precipitation samples collected in Singapore between August 1997 and July 1998 are presented. Major inorganic and organic ions were determined in 169 rain samples collected using an automated wet-only sampler. The daily sample pH values ranged from 3.49 to 6.54 with a volume-weighted mean of 4.50, and about 88% of the samples had pH values less than 5.0 Nss-SO4 2? accounted for about 53 % of the sum of anions in rain, whereas chloride, nitrate, formate, and acetate accounted for the remainder. Rain chemistry data were analyzed using principal component analysis to find possible sources of the measured chemical species. Three components that accounted for 83.5% of the total variance were extracted: sea-spray (Na+, Cl? and and Mg2+) and soil particles (Ca2+ and K+), acid factor (nss-SO4 2?, NO3 ?, NH4 +, and H+), and biomass burning (HCOO? and CH3COOO?).  相似文献   

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