沿海碱性农田土壤pH、重金属分布及污染分析

Analysis of Soil pH, Heavy Metal Distribution and Pollution in Coastal Alkaline Farmland

摘要: 对上海市沿海某地块农田土壤中pH、As、Cd、Cu、Pb、Hg、Ni的分布及污染特征进行研究。结果表明，土壤pH值范围为8.36~9.89，偏碱性，As、Cd、Cu、Hg和Ni 5项重金属最大浓度高于国家和上海的土壤背景值，Pb最大浓度和平均浓度均低于国家和上海市土壤背景值。重金属变异系数Hg > As > Cu > Cd > Pb = Ni。以国家土壤背景值为基准时，Cd、Cu、Ni、Hg呈现污染；以上海市土壤背景值为基准时，As、Cu、Hg呈现污染；以GB 15618-2018的风险筛选值为基准时，土壤的环境质量为清洁。pH与Cd、Cu、As、Ni、Pb等5种重金属存在显著负相关性，Cd、Cu、As、Ni、Pb重金属间存在显著正相关性，且同源性较强，Cu-Cd相关性系数最高(0.81)。Hg与大部分重金属不存在相关性，Hg受人为源影响比较大。

Abstract: The distribution and pollution characteristics of pH, As, Cd, Cu, Pb, Hg and Ni in the farmland soil of a coastal area in Shanghai were studied. The results showed that the pH value of the soil ranged from 8.36 to 9.89, which was slightly alkaline. The maximum concentrations of As, Cd, Cu, Hg and Ni exceeded the national and Shanghai soil background values. The maximum and average concentrations of Pb were lower than the national and Shanghai soil background values. The coefficient of variation of heavy metals followed the order: Hg > As > Cu > Cd > Pb = Ni. When the national soil background value was used as the benchmark, Cd, Cu, Ni and Hg were polluted. When the Shanghai soil background value was used as the benchmark, As, Cu and Hg were polluted; when the risk screening value of GB 15618-2018 was used as the benchmark, the soil environmental quality was found to be clean. pH was significantly negatively correlated with the five heavy metals of Cd, Cu, As, Ni and Pb, and there was a significant positive correlation among Cd, Cu, As, Ni and Pb, with strong homology. The correlation coefficient between Cu and Cd was the highest (0.81). Hg showed no significant correlation with most of the heavy metals, indicating that Hg was more strongly influenced by anthropogenic sources.