衢州典型重金属污染农田镉、铅输入输出平衡分析

Assessment of Input-output Patterns of Cd and Pb of Typical Heavy Metal Polluted Agricultural Land in Quzhou

为定量评估区域农田土壤重金属输入输出平衡,以浙江省衢州市某典型镉(Cd)、铅(Pb)中、轻度复合污染农田为研究对象,对其主要输入源(大气沉降、灌溉、肥料和农药)的Cd、Pb输入通量以及输出通量(水稻秸秆与籽粒移出)开展了长期监测与定量平衡分析。结果表明,大气沉降通量无显著季节变化,由大气沉降导致的Cd、Pb年均输入量分别为3.18和54.46 g·hm-2,输入量占比分别达到34.98%和34.95%;而灌溉水Cd、Pb年均输入量分别为5.76和100.62 g·hm-2,占比分别达到63.37%和64.57%;由肥料带入的Cd、Pb年均输入量分别为0.15和0.74 g·hm-2,占比仅为1.65%和0.47%;而农药带入的Cd、Pb输入量可忽略不计。在该地区双季稻种植模式下,通过水稻秸秆和籽粒的收获和转移,Cd、Pb年输出量分别为10.69和41.74 g·hm-2。综上,调查区域农田土壤Cd的输入输出基本达到平衡,而土壤Pb仍为输入状态,建议对该地区灌溉水进行净化并开展长期监测,同时避免水稻秸秆直接还田。本研究强调了重金属污染区水稻秸秆移除的重要性,为农田土壤重金属污染风险管控提供了理论依据和数据支持。

In order to assess the input-output patterns of heavy metals of agricultural land, a typical paddy soil polluted by cadmium(Cd) and lead(Pb) in Quzhou, Zhejiang province was investigated. Four input pathways(atmospheric deposition, irrigation, fertilizer and pesticide) and two output pathways(rice straw and grain removal) were considered so as to figure out the Cd and Pb balance throughout the topsoil. Results showed that atmospheric deposition flux has no difference among seasonal, and the annual inputs of Cd and Pb were 3.18 and 54.46 g·hm-2, accounting for 34.98% and 34.95% of the total inputs, respectively. Irrigation was an important source of Cd and Pb, responsible for 5.76 and 100.62 g·hm-2, 63.37% and 64.57% of the total inputs, respectively. The average annual input of Cd and Pb by fertilizer application were 0.15 and 0.74 g·hm-2, accounting for only 1.65% and 0.47% of the total inputs, respectively. Whereas, Cd and Pb input by pesticides were negligible. Based on double-cropping rice mode in this region, the annual outputs of Cd and Pb were 10.69 and 41.74 g·hm-2 through the harvest of rice straw and grain. In brief, annual balance results demonstrated that the input of Cd was in-line with the output of Cd in this surveyed area, while soil Pb still remained input status. Control strategies were suggested such as monitoring and purification of the irrigation water, and avoiding direct returning of rice straw to the field. This work emphasizes the significance of rice straw removal for heavy metal contaminated soil, which is helpful in developing strategies to reduce heavy metal inputs into agricultural land.