外源铜和镍在土壤中的化学形态及其老化研究

Chemical forms of exogenous copper and nickel in field soils and the effect of aging

采用连续提取法测定了外源铜和镍进入田间土壤后的化学形态分布,比较研究了这2种重金属在3种不同类型土壤（红壤,水稻土和潮土）中随老化时间的形态转化和分布。结果表明,外源铜以残留态（40%-60%）和EDTA可提取态（40%）为主;随老化时间,EDTA可提取态、易还原锰结合态及铁铝氧化态向残留态转化;外源镍在酸性红壤中以可交换态（40%）和残留态（30%-50%）为主,在中性水稻土中以EDTA可提取态（30%）和残留态（30%-50%）为主,在碱性潮土中以铁铝氧化态（20%）和残留态（40%）为主。随老化时间,水溶态、可交换态、EDTA可提取态等向残留态转化。土壤pH较低时水溶态和可交换态含量较高,但是同时随老化时间的降低量也明显;pH较高时有利于易还原锰结合态和有机质结合态的转化。

The sequential extraction procedure was used to measure the different chemical forms of copper and nickel added to the three kinds of field soils. Aging effect and transformation of the two metals were studied. The results showed that the EDTA extractable and residual fractions were dominant fractions in the three soils. With aging, the EDTA extractable, easily reducible Mn, and Fe（A1） oxides fractions were transformed into residual fraction. Lower pH soils and higher concentration of the metal could accelerate the transformation. While the exchangeable and residual fractions were the major fractions for nickel in acidic soil, EDTA extractable and residual fractions in the neutral soil, and Fe（A1） oxides and residual fractions in alkaline soil. With aging, other fractions were transformed into residual fraction in a certain extent. Low pH soils accelerated transformation of soil solution and exchangeable forms, while high pH was in favor of easily reducible Mn and organic matter forms.