Aluminum chemistry of nonallophanic Andosols

这项研究的目的是通过研究铝在以铝腐殖质复合体为主的土壤中的溶解度和释放速率来扩展以前关于铝化学的研究。在30天的平衡研究中，确定了pH值为3-5的铝的溶解度关系。用搅拌流通式反应容器测量了焦磷酸钠、酸性草酸盐和KCl溶液处理过的土壤样品的铝释放速率，其中醋酸盐缓冲液的pH值分别为3.5、4.0和4.5。非透光性安多索样品的PAL斜率为2.0-2.4，溶解度明显低于普通Al(OH)3相。土壤样品表现出非常快的铝释放速率。铝的释放率与萃取液的pH值和离子强度有很大关系。焦磷酸盐处理使铝的释放速率降低到很低的水平，表明铝腐殖质复合体是溶解铝的主要来源。一些非透磷土壤的铝释放速率和铝的释放总量都大于或接近于未处理的土壤样品。因此，在以腐殖质复合体为主的土壤中，1MKCl可提取铝的量并不总是反映可交换性铝的量。这些数据表明，铝离子与腐殖质的交换在很大程度上影响了铝在非透湿安多沙土中的动态变化。

The aim of this study is to expand upon previous investigations about aluminum chemistry by examining aluminum solubility and release rates in soils dominated by Alhumus complexes. Aluminum solubility relationships over the pH range 3-5 were determined in a 30-d equilibration study. Aluminum release rates were measured using a stirred, flow-through reaction vessel with 10^<-3> M acetate buffer adjusted to pH 3.5, 4.0 and 4.5 for pretreated soil samples with Na-pyrophosphate, acid oxalate and KCl solutions.The nonallophanic Andosol samples displayed pAl versus pH slopes of 2.0-2.4 and solubilities considerably lower than those of common Al(OH)_3 phases. The soil samples showed very rapid Al release rates. The Al release rates were greatly dependent on the pH and ion strength of extracting solution. Pyrophosphate treatment reduced Al release rates to very low levels indicating that Al-humus complexes were the primary source of dissolved Al.Some non-allophanic soils showed that the aluminum release rates and the total amount of Al released from KCl-treated residues were greater than or nearly identical with those of non-treated soil samples. Thus, the amount of 1M KCl-extractable Al does not always reflect the amount of exchangeable Al in soils dominated by Al-humus complexes.This study and the literature showed that the amount of KCl-extractable Al is closely related to the amount of organically complexed Al. These data indicates that the dynamics of aluminum in nonallophanic Andosols is largely influenced by the exchange of Al ions with humic substances.