酸性条件下红壤中铝的活化及环境意义

Mobilization of aluminum from red soils under acidic conditions and its environmental implications

利用动态反复浸提模拟实验研究了4种红壤中固相铝的活化过程。结果表明,红壤酸化程度与土壤表面交换性铝呈正相关关系。当高强度外源H+输入土壤后,有机铝和无机铝均可活化。浸提初期以弱键合的有机铝活化为主,当浸提到一定程度时,弱键合有机铝亏损,无机铝活化的相对重要性显示出来。20次浸提后,宁海红壤、嵊县红壤及永春红壤的铝总活化量中无机铝占主要部分。当土壤酸化到一定程度时(如屯溪红壤),有机铝和无机铝均亏损,铝的活化量很低。酸性条件下弱键合有机铝的快速活化产生高浓度的可溶性铝以及随后的快速亏损都将对生态环境产生重要影响。

A prolonged leaching experiment is conducted to explore the mobilization process of solid phase Al of 4 red soils. The results show that the amount of exchangeable Al is directly proportional to the extent of acidification. After a large acid load from external sources, both organically bound and inorganic solid phase Al could be mobilized. At the initial time of leaching the mobilized Al is mainly from weakly organically bound solid phase Al pools. While prolonged leaching, weakly organically bound Al pool becomes depleted rapidly, and the mobilization from inorganic Al pool has much important contribution to the total released Al. After being leached 20 times, the total released Al for Ninghai, Shengxian and Yongchun red soils are mainly from mobilization of inorganic solid phase Al pool. However, once soils are acidified to such extent as Tunxi red soil, both organically bound and inorganic solid phase Al pools would become depleted and the total Al that could be mobilized would be small. The high concentration of aqueous Al after rapid mobilization of weakly organically bound Al and subsequent depletion of this Al pool might have significant ecological and environmental effect.