连续施用污泥堆肥土壤剖面中重金属积累迁移特征及对小麦吸收重金属的影响

通过大田试验,定量研究连续施用污泥堆肥后土壤剖面中不同重金属积累迁移和对小麦吸收重金属的影响,为科学确定农田土壤重金属环境容量和农田土壤重金属污染防控提供依据.结果表明,连续4 a施用污泥堆肥农田耕层土壤(0~15cm)中Cu、Zn含量随污泥施用时间和施用量增加而显著增加,污泥施用带入的Cu、Zn在耕层土壤中积累率最高分别可达到75.3%和85.9%;污泥施用量较高时,Cu、Zn向土壤深层迁移,本试验条件下Cu可迁移至15~30 cm土层,Zn可迁移至60~90 cm土层;连续施用污泥堆肥4 a后,0~15 cm土层中Cd、Pb含量显著增加,与对照相比增幅分别是57.2%~165.2%、13%~34%,60~90 cm土层中Cr、As、Pb含量也显著高于对照;连续施用污泥堆肥小麦籽粒中Zn含量显著增加,增幅为13.3%~47.9%.部分污泥处理小麦籽粒中的Cr、Pb含量超出国家食品卫生标准(GB 2762-2012);4 a小麦收获对各重金属累计携出率均低于10%,小麦籽粒对Cu、Zn的累计携出量大于秸秆,而对Cr、As、Cd、Pb的累计携出量小于秸秆.随污泥施用量的增加,小麦收获对各重金属累计携出率降低.确定农田土壤重金属环境容量时要考虑重金属在土壤剖面中的向下迁移量.

Effects of Continuous Application of Sewage Sludge Compost on Heavy Metals Accumulation and Mobility Characteristics in Soil Profile and on Heavy Metals Uptake of Wheat

The use of sewage sludge compost(SSC)as fertilizer may cause increased leaching due to its high content of heavy metals and thus pose a threat to groundwater quality. The effect of SSC application on heavy metals leaching in calcareous soils has been studied in field trials, which provides basis for determining heavy metals environmental capacity and preventing metal pollution in farmland soil scientifically. The results indicated that the contents of Cu, Zn elevated obviously with the increase of the age and the dosage of SSC utilization in the topsoil(0-15 cm) under 4-year continuous application of SSC. Under higher levels of the compost treatment, the heavy metals Cu and Zn were found to migrate into the 15-30 cm soil and 60-90 cm soil under the experimental condition. Nevertheless, the majority of Cu and Zn from SSC accumulated in topsoil and the highest accumulation rates could reach 75.3% for Cu and 85.9% for Zn. The contents of Cd, Pb increased significantly in topsoil after 4-year continuous application of SSC, and their increases could reach 57.2%-165.2% for Cd and 13%-34% for Pb compared with CK. At 60-90 cm soil, the contents of Cr, As and Pb were also significantly higher than those in CK treatment. Application of SSC not only caused accumulation of some heavy metals in topsoil but also leached heavy metals located in the subsurface soil down in this experiment. Continuous utilization of SSC increased Zn concentration of wheat grain, and the increase could reach 13.3%-47.9%. For the concentrations of Cr and Pb in wheat grain, the values exceeded the national food and healthy standards value (GB 2762-2012) in part of compost treatments. The cumulative ratio of heavy metals carried out by wheat were all below 10% after 4-year experiment, wheat grain carried much more Cu, Zn out than wheat straw, but it was opposite for Cr, As, Cd, Pb. The cumulative ratio of heavy metals carried by wheat decreased with the increasing level of SSC utilization. The amounts of heavy metals migrated to deeper soil should be considered when determining the environmental capacity of heavy metals in farmland soil.