Source identification and screening of safe utilization methods of farmland soil heavy metals:Taking parts of Junlian county of Yibin as an example
[Objective]Based on the main input source of soil heavy metals pollution idenfitication and screening the most efficient immobili-zing agent and low accumulation varieties of vegetable and rice for Cd contaminated soil,the study aimed to provide a reference for farmland soil heavy mtal pollution preventing and control.[Method]The expreriment was conducted to monitor heavy metals concentrations in atmos-pheric deposition,fertilizer,irrigation water and sediment and further calculated soil heavy metals input flux by these different pathways to find out the pollution source of soil heavy metals in some towns in Junlian county of Yibin,which was in the south of Sichuan province.Fur-ther field experiments were conducted to screen vegetables and rice varieties with lowest accumulation of Cd and the most efficient immobili-zing agents in JL town.[Result]Hg,As,Pb and Zn in soil mainly came from atmospheric deposition,accounting for 99.99％,75.88％,90.57％and 84.82％,respectively.While Cd,Cr and Ni mainly came from fertilizer use,all accounting for 100％.Cu was mainly from irrigation water in the study area during 2019 to 2020,accounting for 93.66％.The application of iron manganese fertilizer(FeSO4 750 kg/hm2+MnSO4 75 kg/hm2)had the best effect on reducing the Cd content in rice grains,mainly attributed to the improvement of soil microel-ement supplement on fertility,while the passivation material compounding(3000 kg/hm2)had the highest Cd content in rice grains.The screening results of low Cd accumulation of vegetables and rice varieties showed that Jiujing radish and Chuankangyou 6276 were the most suitable vegetable and rice varieties for planting in the Cd polluted soil in JL town with the Cd content in edible parts after harvest met the na-tional food safety standard.[Conclusion]To ensure the quality and safety of crops,selecting fertilizers that meet national standards and con-trolling atmospheric decomposition are primary step.Besides the iron manganese fertilizer,humic acid and phosphorus fertilizer passivation agents are suggested to be used,and Jiujing radish and Chuankangyou 6276 varieties are recommended to be planted in the study area.
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