Characteristics and evaluation of mercury pollution in paddy soil of a watershed in Zhanjiang

【Objective】The potential risk of mercury in paddy soil of a watershed in Zhanjiang were investigated to provide reference for reasonable planting of farmland and ensuring the safety production of agricultural products.【Method】The mercury content in 42 soil samples of paddyfield in the upper, middle and lower reaches of the study area was determined, mainly through using the single-factor index, geo-accumulation index and potential ecological risk index.Also, the spatial distribution characteristics of mercurypollution probability were analyzed by Indicator Kriging method.【Result】The mercury content of paddy soil of a watershed in Zhanjiang ranged from 0.040 to 0.504 mg/kg, and the coefficient of variation was 68.42%, which belonged to the middle degree of variation.The average value of mercury content in the study was 0.193 mg/kg, which was generally shown as middle reaches> upper reaches> lower reaches.The average value of middle reaches was 0.343 mg/kg, which was the highest in the whole watershed.Although it did not exceed the national screening value of 0.5 mg/kg of agricultural soil pollution risk, it was as 4.3 times as the mercury content of the background value of Zhanjiang soil(0.045 mg/kg), and far higher than the background value of soil in Zhanjiang.The mercury pollution in the paddy soil of the whole watershed was obvious.The results of single factor index evaluation based on the background value of soil in Zhanjiang showed that the site of heavy accumulation of mercury in paddy soil is as high as 52.38%.The results of land accumulation index analysis showed that 33.33% of the samples belonged to medium to strong pollution.The average value of the potential ecological risk index of mercury in the whole basin was 160-320, and the risk level was IV, which was a very strong potential ecological risk.The results of Indicator Kriging method showed that, there was a high probability of mercury pollution in paddy soil of the watershed, especially in the middle reaches.【Conclusion】The content of mercury in paddy soil in this study area of Zhanjiang belongs to the safe range, but there arepotential serious ecological risks.Attention should be paid to mercury pollution in paddy soil, which is caused by the extensive use of pesticides and chemical fertilizers and automobile exhaust.