我国南方主要酸沉降区土壤中铝的释放与缓冲作用

RELEASING AND BUFFERING OF A13+ UNDER SIMULATED ACID RAIN IN SOUTH CHINA

本文研究了我国南方酸沉降区主要土壤类型在模拟酸雨影响下淋溶液pH值及Al离子释放特点。结果表明,石灰土和滨海盐土的阳离子淋溶量低于阳离子交换量,土壤主要处于阳离子交换缓冲范围和碳酸盐-硅酸盐缓冲范围,Al释放量一般低于0.40mmol·kg^(-1),铁铝土纲系列土壤在阳离子释放总量超过阳离子交换量后,淋溶液pH值急剧下降,此时Al淋溶量明显增加,质子缓冲转向Al缓冲范围,其释放量决定于土壤富铁铝化程度的高低和活性Al含量的多少,紫色土在低pH模拟酸雨淋溶下,由于含大量硅铝率较高的易风化原生或次生矿物,盐基释放量高于CEC,但Al释放量未明显增加,淋溶液pH也较稳定,土壤尚处于矿物风化为主的硅酸盐缓冲范围。

This paper deals with the pH value of leaching solutions and the characteristics of A13+ releasing under the treatment of simulated acid rain in main soil types collected from South China. The results showed that the amounts of base cations leached from calcareous soils and coastal solonchak were lower than the cation exchange capacity and the releasing amounts of Al3+ being lower than 0.40mmol·kg-1 all the way under the treatment of simulated acid rain with each pH value from 2.5 to 5.6,so the H+ buffering processes of these soils were still in the scope of cation exchange and carbonate-silicate dissolution. Whereas when the amounts of base cations leached from soil series of ferral-lisols exceeded the cation exchange capacity,the pH value of leaching solutions decreased sharply and the amounts of releasing A13+ increased evidently. Al dissolution was regarded as the one of the main H+ buffering reactions in these soils. In purple soil, the amounts of leached base cations went beyond the CEC highly when the pH value of simulated acid rain was lower than 3.0, but the amounts of A13+ releasing did not increase and the pH value of leaching solutions kept stable because there existed a lot of weather-able original and secondary minerals with high Sa value. That is to say, the H+ buffering of purple soil was still in the scope of the weathering of silicate.