中文摘要：

华南酸性森林土壤分别在pH值为3．46、4．24和4．84条件下用含不同浓度盐基离子（Ca^2＋）的酸性浸提液浸提，以查明降水中盐基离子对土壤水中Al和H^＋的影响。实验结果表明：随着Ca^2＋浓度的增加，土壤浸出液中H^＋和Al都有增加的趋势。随着Ca^2＋浓度的变化，H^＋和Al有不同的来源：当Ca^2＋〈0．5mmol L^-1，土壤主要通过Ca—H交换机制释放H^＋，浸出液中Al主要来源于土壤活性铝的溶解；当Ca^2＋〉0．5mmolL^-1时，由于Ca—Al交换反应，浸出液中Al随Ca^2＋浓度增加而显著增加，此时H^＋主要来源于Al的水解反应。浸出液中pH—pAl关系也随pH值（或Ca^2＋浓度）的变化有显著不同：当浸出液pH〉3．7（Ca^2＋〈0．5mmolL^-1）时，浸出液中Al^3＋活度随pH的变化幅度较小，这可能是酸性土壤中活性铝已显著流失的缘故；当pH〈3．7（Ca^2＋〉0．5mmol L^-1）时H^＋对于Al浓度具有较强的依赖性，故pH随Al^3＋活度增加而显著降低。因此，降水中盐基离子的增加能够引起土壤水乃至地表水中酸性阳离子（特别是Al）的迅速增加，可能造成对水生生物的突发性影响。

英文摘要：

Ca-H-Al exchanges and aluminium mobility were studied to investigate the influence of base cations on Al and H^＋ in acid soil solution. The study was based on a batch experiment using extractant solutions different in base cation （calcium） concentration and pH. Experimental data showed increased Ca^2＋ concentration led to increases in both Al and H^＋ through different mechanisms dependent on Ca^2＋ concentration. With Ca^2＋ concentration lower than 0.5 mmol L^-1, H^＋ was the dominant acidic cation in the extracts due to Ca-H exchange. Al in these extracts originated mainly from dissolution of active aluminium pools. With Ca^2＋ concentration higher than 0.5 mmol L^-1, Ca-Al exchange was the main contributor of aqueous aluminum in such extracts, while hydrolysis of aluminum was the one to H^＋ variation. Geochemical calculation also indicated that pH-pAl relationship that strongly deviated from equilibrium of gibbsite minerals varied with pH or Ca^2＋ concentration. With pH higher than 3.7 （Ca^2＋ 〈 0.5 mmol L^- 1 ）, the Al^3＋ activity did not vary significantly with pH, which was likely attributed to high leaching of easily soluble aluminium pools in such acidic soils. With pH lower than 3.7 （ Ca^2＋ 〉 0.5 mmol L^- 1 ） , hydrolysis of aqueous Al resulted in a much steeper slope between pAl and pH. Therefore, an increase in base cation deposition would enhance release of hydrogen and aluminum ions from mature acidic soils, which may pose episodic threats to aquatic biota.