| Heavy metal contaminated farmland in Tielong of Shaoguan City, Guangdong Province was taken as the object in this study. In order to control the heavy metal pollution and food safety, a survey was carried out on the soil and crops in this area based on the problem of heavy metal pollution, which was from local mining activities.The characteristics of heavy metal pollution, the source of pollution and the spatial structure of heavy metal distribution in this area were evaluated and analyzed, the specific pollution parttern was divided and the appropriate Remediation strategies were made systematically. Then combined the results of farmland soil pollution and the heavy metal content in crop , put forward the safety utilization strategy of soil which is polluted by heavy metal. The results are as follows:(1) As, Cd and Pb were concentrated in the near-surface soil, they were the main pollutants in the heavy metal elements of As, Cd, Cr, Cu, Ni and Pb in Tielong. Their average value were 51.1 mg/kg, 1.60 mg/kg and 156 mg/kg, the study area was lightly polluted by As, moderately polluted by Cd and Pb. 98.5% of the sample points were heavy pollution, and the risk of potential ecological was not low.(2) It showed that they may affected by human activities as the coefficient of variation of As, Cd and Pb were 53.5%, 93.4% and 61.8%.The source of As and Pb had the commonality, the source of Cd was different from As and Pb. Analysis of heavy metal content of irrigation water, sediment and precipitation showed that the transmission routes of As and Pb may came from precipitation, and the accumulation of Cd was from the water of irrigation.(3) As and Pb were mainly concentrated in the middle of the polluted area, affected by the cement plant which was in the middle of the polluted area.The content of Cd from north to south presented a significant decrease, indicating that it was obviously influenced by upstream mining activities according to the distribution of the heavy metals.(4) The results of the classification of the study area included the Cd heavy pollution zone, the Cd moderately contaminated pollution area, the Cd-As complex pollution area and the Cd-As-Pb composite contaminated area. According to the principle of one-zone of a strategy, the technology of repairing and safe utilization of each partition was screened.The results showed that combined the stabilization technology, the content of mulberry trees in the Cd heavy pollution zone, balsam pear,pumpkin, winter melon, watermelon, peanuts in the Cd moderately contaminated pollution area, 13 kinds of low absorption varieties of maize the Cd-As complex pollution area and pumpkin, balsam pear, towel gourd, lentils and eggplant in the Cd-As-Pb composite contaminated area were all lower than the Standards for pollutant limits in crops, These crops are suitable for wide planting accordingly.(5) Micronutrient ZnS04 and MnS04 were significantly effective in inhibiting the absorption of As in spinach, with a range from 32% to 41%. and Pb in spinach, with a range from29.7% to 56.3%. Biochar, Bm and Bz can effectively inhibit the absorption of Cd and Pb in the Water spinach, and the Bm had the best effect of reducing Cd, which had 36.3% reduction compared with the control treatment. The biochar had the best inhibition of Pb in the Water spinach, the content of Pb in the Water spinach was 52.9%lower than the control. |
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