铬铜复合污染下铬形态分布及与土壤酶活性的关系

采用土培盆栽实验和室内分析相结合的方法,研究了Cr单一和Cu-Cr复合污染条件下,外源施加的Cr在土壤中的形态变化及其对土壤酶活性的影响。结果表明:随外源Cr浓度的增加,土壤交换态Cr含量增多,残渣态占总量的百分比减少,铁锰氧化物结合态与有机结合态变化不大(碳酸盐结合态未检出)。Cu-Cr复合污染条件下,≤400mg·kg-1Cu能促进Cr从有机结合态向交换态及铁锰氧化物结合态转化(P<0.05),而高浓度Cu(800mg·kg-1)却抑制了这种转化的发生。与对照(CK)相比,重金属Cu、Cr单一及复合污染均对土壤脲酶、碱性磷酸酶和过氧化氢酶活性产生一定的抑制作用,且酶活性抑制率随外源金属浓度的增加而增大;3种供试酶相比较,Cr、Cu对土壤脲酶和碱性磷酸酶活性影响较大,对除C(r5mg·kg-1)处理的过氧化氢酶活性影响较小;低浓度C(r5mg·kg-1)对土壤过氧化氢酶活性有一定激活作用。土壤脲酶活性受土壤交换态Cr含量的影响较大;碱性磷酸酶活性与铁锰氧化物结合态Cr含量有关;铁锰氧化物结合态和有机物结合态Cr对土壤过氧化氢酶活性产生一定的影响。残渣态Cr含量与3种供试的土壤酶活性间无显著相关。

The Effect of Differential Fractions of Chromium on Soil Enzyme Activities Under Chromium and Copper Joint Contamination

A pot experiment and laboratory analysis were carried out to study the speciation transformation of added chromium in soil and its effects on soil enzyme activity. The results showed that exchangeable chromium content increased with the added content of chromium raise, while the percentage of residual chromium content and total decreased relatively, and content of chromium bound to Fe-Mn oxides or organic matters had no significant change(chromium bound to carbonate was below detection limit). Lower concentration of copper(≤400 mg·kg-1) significantly stimulated the transformation of chromium from relatively stable organic form to exchangeable or Fe-Mn oxides form (P<0.05). While high concentration of coppe(r800 mg·kg-1)could inhibite this transformation. Compared with the control, Cu and Cr singly or combined had inhibited effects on activity of urease , alkaline phosphatase, catalase. And inhibition rates of enzyme activities increased with the heavy metal concentration raise. Comparing with three tested enzymes, chromium and copper had larger effects on activity of urease , alkaline phos- phatase, and catalase was the least sensitive enzyme to Cu-Cr contamination. While in the 5 mg·kg-1 Cr treatment, the activity of catalase was promoted. Exchangeable chromium played an dominate role in the variation of unease activity, chromium bound to Fe-Mn oxides in the alka- line phosphatase activity, and chromium bound to Fe-Mn oxides or organic matters in the catalase activity. Residual chromium had no signif- icant correlation with the three kind soil enzemy activity.