施用污泥对土壤重金属形态分布和生物有效性的影响

Effects of applying sewage sludge on chemical form distribution and bioavailability of heavy metals in soil

采用盆栽技术和BCR连续浸提法研究了污泥的添加对土壤Cd、Pb、Cu和Zn形态分布的影响及重金属在黑麦草-施污泥土壤中迁移转化规律.结果表明:污泥的添加使土壤中生物有效态的Cd和Zn含量显著增加,生物有效态Pb含量显著降低,残渣态Pb的比例较CK增加了33.3%～74.5%,而可交换态和可还原态Cu含量在污泥与土壤添加比为1:1时,仅占总量的0.7%和0.2%.污泥的添加能促进黑麦草对Cd、Cu和Zn的吸收,抑制对Pb的吸收.多元线性回归分析结果表明,黑麦草体内Cd、Zn和Cu含量分别与土壤中可还原态Cd、Zn和可氧化态Cu含量存在正相关,草体中Pb的含量则受土壤中可交换态和可氧化态Pb含量共同影响.种植黑麦草后根际土中可氧化态Cd和Cu分别向可交换态Cd和残渣态Cu转化,可交换态和可还原态Zn向可氧化态Zn转化,Pb的生物有效性基本未受影响.

A pot experiment was conducted to study the effects of applying sewage sludge on the chemical form distribution of heavy metals （Cd,Pb,Cu and Zn） in soil and the transfer and accumulation of the heavy metals in soil-plant （ryegrass） system.With the application of sewage sludge,the contents of bioavailable Cd and Zn in soil increased significantly but that of bioavailable Pb in soil had a significant decrease,and the content of residual form Pb in soil increased by 33.3%-74.5%,compared with CK.When the application rate of sewage sludge was 50% （M/M） of soil,the contents of exchangeable and reducible Cu in soil only occupied 0.7% and 0.2% of the total Cu respectively.The application of sewage sludge promoted the Cd,Cu and Zn absorption while inhibited the Pb absorption by ryegrass.Multiple linear regression analysis showed that the Cd,Zn and Cu contents in ryegrass were positively correlated with the reducible Cd and Zn and oxidizable Cu contents in soil,respectively,and Pb content in ryegrass was highly correlated with the soil exchangeable and oxidizable Pb contents.After planting ryegrass,the oxidizable Cd and Cu in rhizosphere soil were transformed into exchangeable Cd and residual form Cu,respectively,the exchangeable and reducible Zn transformed into oxidizable Zn,whereas the bioavailability of Pb was less affected.