施用河塘底泥对农田土壤性状的影响及果蔬的重金属风险评价

Effects of Adding Ponds Sediments to Field on Soil Characters and Risk Assessment of Heavy Metals of Fruits and Vegetables

河塘底泥含有丰富的有机质、氮、磷、钾等营养元素,但底泥中重金属的释放易对土壤—植物造成污染,成为底泥资源化利用的限制因素。本研究以南渡江下游塘柳塘底泥为材料,按容积比10%,20%,30%施入沿岸河滩沙地（0--30 cm土层）,种植空心菜、苦瓜、丝瓜,探讨不同底泥施用量对土壤性状以及果蔬食品安全的影响。结果表明：（1）施用底泥可以改良土壤结构、提高土壤肥力,但存在中低水平重金属污染风险。（2）除施用20%,30%河塘底泥的样地土壤重金属Cd含量超过国家的限值外,其余样地土壤重金属均在国家限值以内。（3）丝瓜、苦瓜等瓜果类农产品重金属含量小,安全性高;空心菜有可能存在污染风险,而其根茎重金属Cr、As污染风险较大。在底泥重金属污染风险评价基础上,通过果蔬品种选择,可降低风险,确保农产品安全,实现底泥资源化利用。

The ponds sediments were rich in N, P, K and organic matter, but the release of heavy metal in sediments had potential risk for soil and plants, and it was the main limiting factor that restricts the resource utilization of pond sediments. In this study, the sediments in Tangliutang River, a typical pond in the lower Nandujiang River, were taken as the experimental material. In order to investigate the effect of pond sediment application on soil properties and food safety of fruits and vegetables, the volume ratios of 10%, 20%and 30% in 0~30 cm depth soil were designed to rebuild soil tillage layer by adding ponds sediments, and Ipomoea aquatica Forsk,balsam pear and Luffa acutangula were planted. The results showed that：（1） The ponds sediments could improve the soil structure and the soil fertility, but it also had the risk of heavy metal pollution in lower-middle level.（2） The contents of heavy metals were lower than the national limits in all experiment plots except that the contents of heavy metal Cd exceeded the national limits in the experiment plots adding 20% and 30% ponds sediment to the soil layer.（3） The heavy metal contents in balsam pear, Luffa acutangula were lower, and the agricultural products were safety. Ipomoea aquatica Forsk had less contamination risk, but its roots had a high risk of heavy metal Cr and As contamination. Based on the risk assessment of heavy metal pollution of river sediments, and through the variety selection of fruits and vegetables, it was possible to reduce risk and ensure the safety of agricultural products, and achieve utilization of sediment.