长期秸秆还田对污染农田土壤与农产品重金属的影响

Effects of Long-term Straw Returning on Heavy Metals of Soil and Agricultural Products in the Polluted Farmland

在浙东某地选择一污染农田,布设了秸秆还田、秸秆不还田、秸秆还田+石灰及秸秆不还田+石灰4个处理试验,进行了为期9年的土壤、秸秆、谷物、蔬菜等农产品中重金属动态监测。结果表明,污染农田中施用石灰可明显降低水稻秸秆和谷物及蔬菜中重金属的积累,但对土壤重金属含量影响不明显;施用石灰对水稻秸秆和谷物及蔬菜中重金属降低作用随试验时间逐渐减弱。与秸秆不还田比较,秸秆还田在短期内对土壤、水稻秸秆和蔬菜重金属积累的影响较小,但4~5年后秸秆不还田农田土壤镉、汞积累及水稻秸秆和蔬菜中镉、铅、汞积累明显低于秸秆还田农田,对土壤中铅积累的影响较小;随着试验时间的增加,秸秆还田与秸秆不还田农田之间土壤、水稻谷物及蔬菜中重金属积累的差异逐渐加大。秸秆还田农田土壤有机质和速效钾含量高于秸秆不还田农田。研究结果表明,在镉、汞污染农田中长期推行秸秆还田不利于农产品质量的提高,应控制重污染水稻秸秆还田。

In this study,a polluted farmland in eastern Zhejiang province was selected.Four treatments,including straw returning,straw non-returned,straw returning+lime,and straw non-returned+lime were set up.The dynamic monitoring of heavy metals in soil,straw,cereals,and vegetables was carried out for nine years.The results showed that the accumulation of heavy metals in rice straw,grain,and vegetable was significantly reduced by applying lime in polluted farmland,but the effect of applying lime on the content of total heavy metals in soil was not obvious.The effect of applying lime on the reduction of heavy metals in rice straw,grain,and vegetable was gradually weakened with the experimental time.Compared with straw non-returned,straw returning had less effect on the accumulation of heavy metals in soil,rice straw,and vegetable in a short time.However,the accumulation of cadmium and mercury in soil and the accumulation of cadmium,lead,and mercury in rice straw and vegetable after 4~5 years were significantly lower in straw non-returned farmland than that in straw returning farmland,and the effect on the accumulation of lead in soil was less.With the increase of test time,the difference of heavy metal accumulation in soil,rice grain,and vegetable between straw returning farmland and straw non-returned farmland gradually increased.The content of soil organic matter and available potassium in straw returning farmland was higher than that in straw non-returned farmland.It was concluded that long-term application of straw returning in cadmium and mercury polluted farmland was not conducive to the improvement of agricultural product quality,and the heavy-polluted rice straw returning should be controlled.