不同种类有机物对污染农田土壤重金属活性的影响

为了解施用不同种类有机物对污染农田土壤重金属行为的影响,布设了田间小区试验,观察研究施用6种不同类型有机物对土壤水溶性重金属和农作物对重金属吸收等的影响。试验设7个处理,分别为对照(不施有机肥)、施新鲜水稻秸秆、新鲜鸡粪、鸡粪堆肥、新鲜猪粪、猪粪堆肥和商品有机肥,动态检测土壤中水溶性重金属含量、田面水中重金属浓度及收获水稻籽粒中重金属含量的变化。结果表明,与不施有机物的对照处理比较,施用各类有机物在试验前期均可明显提高土壤中水溶性重金属和田面水中重金属的含量,总体上以施用新鲜猪粪的最高,其次为新鲜鸡粪,施用商品有机肥的最低。土壤中水溶性重金属含量随试验时间增长逐渐下降。施用各类有机物对水稻籽粒中重金属的积累影响不明显。土壤中水溶性重金属及田面水中重金属含量均与相应的水溶性碳(DOC)浓度呈显著相关性,表明因有机物施用增加土壤中DOC浓度可能是土壤中水溶性重金属含量增加的主要原因;而不同有机物对土壤重金属活性影响的差异可能与有机物本身的分解程度及可释放DOC大小有关。但施用有机物引起的农田土壤水溶性重金属含量的增加是暂时的,对水稻生长后期籽粒中重金属积累的影响不明显。

Effects of Different Organic Amendments on the Activity of Heavy Metals in Contaminated Soils

In order to understand the effects of the application of organic amendments on the behavior of heavy metals in contaminated farmland soils, field plot experiment was conducted to investigate the effects of the addition of six different organic amendments on the activity of heavy metals in soils, concentration of heavy metals in surface water, and heavy metal uptake by rice plants. The tested six organic amendments were composted rice straw, fresh chicken manure, composted chicken manure, fresh pig manure, composted pig manure and commercial organic fertilizer. The results showed that application of all of the six organic fertilizers could obviously increase the contents of water soluble heavy metals in the soils and concentrations of heavy metals in the surface water at early stage of the experiment, as compared with the control without application of organic manure. The increase in the contents of water soluble heavy metals in the soils and concentrations of heavy metals in the field surface water were highest for fresh pig manure, followed by fresh chicken, and the lowest for commercial organic fertilizers. The contents of heavy metals in soils and the concentrations of heavy metals in field surface water decreased with the increase of the experimental time. The effects of applying organic fertilizer on the accumulation of heavy metals in rice grains was not obvious. Correlation analysis showed that the contents of water soluble heavy metals in soils, and concentrations of heavy metals in field surface water were all significantly correlated with the corresponding DOC concentration, suggesting that the increase of DOC could promotethe activation of heavy metals in soils. The difference in the activity of heavy metals in soils added with different organic amendments might be due to the difference in the degree of decomposition and release DOC capacity of the added organic amendments. But the research also showed that the soil DOC decreased gradually with the increasing time of organic fertilizer application. Therefore, the activation of heavy metals in farmland soils caused by organic manure was temporary, and the accumulation of heavy metals in the grain during the late rice growth was not obvious.