中文摘要：

采集了华南和西南酸性森林小流域中的土壤和土壤水并分析其化学组成，利用偏最小二乘法回归（PLS）研究了土壤中铝的释放过程，以综合评价各种影响因素的相对重要性。连续3年（2000—2002）的现场监测数据表明，尽管土壤水中铝的浓度存在显著差异，但铝的形态分布在各流域之间基本相似。大多数土壤水中单体铝（Ala）主要以无机态（Ali）存在，有机铝（Alo）一般不足10％。在pH3．6—5．6范围内，土壤水中Al^3＋活度（pAl）与土壤水pH值呈显著正相关关系（P〈0．001），上层和下层土壤中pH．pAl拟合直线的斜率分别为1．28和2．00，明显偏离三水铝石（gibbsitc）的溶解平衡模式。偏最小二乘法回归分析显示，上层和下层土壤中铝具有不同的来源和主导影响因素。上层土壤中，铝主要来源于有机键合铝（Alorg），土壤水离子强度（I）是造成铝浓度差异的主导因素。与此同时，铝的释放过程明显受到离子交换反应的影响。下层土壤中，铝近乎全部来源于无机键合铝（Alinorg），土壤水H^＋浓度成为影响铝释放过程的最主要因素。与上层土壤相比，离子交换对土壤铝释放过程影响明显减小。

英文摘要：

The mechanism controlling aluminum release from Chinese acidic forest soils is still not clearly understood. To evaluate the relative contribution of possible factors, soils and soil waters from five forest catchments in southern and southwestern China were collected and analyzed for chemical parameters. Field monitoring data showed that aluminum fractions varied significantly among five catchments with similar patterns. Aqueous aluminum in these sites was dominated by inorganic aluminum （Ali） in most soil water, and organic aluminum was usually less than 10% of total monomeric aluminum （Ala）. Over the pH range of 3.6 -5.6, Al^3＋ activity （pAl） was closely and positively correlated with solution pH with regression slopes of 1.28 and 2.00 for upper and lower horizons,respectively. The variations in Al^3 ＋ activity could not be explained satisfactorily using commonly used gibbsite equilibriums, which indicated that factors other than H＋ also controlled the aluminum release process. Therefore, partial least square regression （PLS） was conducted to distinguish these possible factors and to evaluate their relative importance. PLS analysis suggested that there were different mechanisms controlling aluminum release in upper and lower soil horizons. In upper horizon, aqueous aluminum originated from both organically bound aluminum （Alorg） and inorganically bound aluminum （Alinorg）, but organically bound aluminum seemed to be more important. Ionic strength instead of H^＋ was the dominant factor controlling aluminum variation. Cation exchange reaction played an important role in regulating aluminum release from soil to soil water. In lower horizon, aqueous aluminum was dominantly of inorganic origin. Dissolution of inorganically bound aluminum by higher H^＋ was the mainly release mechanism of aluminum. At the same time, the regulating role of exchange reaction tended to be smaller in lower horizon than in upper horizon.