污染土壤中有机质和重金属互相作用的模拟研究

Simulated study on interactions between heavy metals and organic matter in contaminated soil.

为了解污染土壤中有机质积累与重金属积累之间的相互影响,在供试土壤中添加不同等级的有机物料和重金属元素Pb与Cu,在培养条件下研究有机物对土壤重金属稳定性的影响及不同重金属添加量对土壤生物呼吸强度和有机质矿化的影响.结果表明,随着重金属添加量的增加,土壤微生物生物量和有机质矿化速率显著下降,添加的有机物料残留增加,促进了土壤有机碳的积累.同时,有机碳的积累又增加了土壤对重金属的吸附固定,增加了土壤中重金属的稳定性,降低了其淋溶性,有利于重金属在土壤中的积聚.分析结果表明,颗粒态有机质中重金属的富集是土壤有机质矿化减弱和重金属稳定性增加的主要原因.由此推断,污染土壤中重金属和有机质可通过形成重金属-颗粒态有机质复合体发生相互促进稳定或积聚的作用.

In order to understand the interactions between accumulation of organic matter and heavy metals in contaminated soil, an incubation experiment was conducted by adding different levels of organic materials, Pb and Cu to soil. The soil microbial biomass, COz-C released from incubated soil, and concentrations of heavy metals in particulate organic matter （POM） were monitored, the effect of organic matter on solubility of heavy metals （Pb, Cu） and those of heavy metal addition on respiratory intensity and mineralization of organic matter in contaminated soil were characterized. The results show that both soil microbial biomass and respiratory intensity decreased significantly with increasing addition of Pb and Cu, and thus increased accumulation of soil organic matter. Meanwhile, accumulation of organic matter declined water-extractability and mobility of the metals by formation of metal-enriched organic particles, and thus increased stabilization and sequestration of metals in the soil. It was also found that the POM has great potential to accumulate large amounts of metals by the creation of adsorption sites by microbial degradation of organic matter, with high affinities for metals thus stabilizing metal-POM. The experiments verified a mutual immobilization of metals and POM as organo-metallic complexes in contaminated soil. As a result, organic matter could be stabilized to some degree by metals due to an inhibition of microbial activity caused by toxic effects of metals and strong resistant of POM- heavy metals to biodegradation. This process would simultaneously lead to an increasing organic C and metal contents in the metal-contaminated soil.