稻田土壤和稻米中重金属潜在污染风险评估与来源解析

    Evaluation of potential pollution risk and source analysis of heavy metals in paddy soil and rice

    • 摘要: 该文选择贵州省典型城市(都匀市)周边水稻种植区为研究区,系统采集了稻田土壤和稻米样品各110个,测定土壤和稻米中Cd、Hg、As、Pb和Cr含量,基于多元统计分析和污染风险评价等分析方法,揭示了研究区稻田土壤重金属污染的主要来源及土壤和稻米中重金属存在的潜在风险。结果表明,与贵州土壤重金属背景值相比,稻田土壤中Cd、Hg、As、Pb和Cr超标率分别为14.55%、40.00%、16.36%、22.72%和13.64%,主要以Hg污染问题最为突出。稻米中只存在3.64% Cd超标,Hg、As、Pb和Cr平均含量均低于国家食品安全标准限定值(GB 2762-2017),说明当地居民食用稻米存在最大的潜在威胁为Cd污染稻米。稻田土壤重金属来源分析结果表明,稻田土壤中Cd、Hg、As和Pb之间呈显著正相关关系,说明土壤中Cd、Hg、As和Pb具有相同的来源,主要来源于当地铅锌矿冶炼、火电厂等污染点源排放的污染物;Cr与其他元素相关性不显著,主要来源于成土母质,为自然来源元素。

       

      Abstract: Abstract: The characterization and spatial distribution of the content and source of heavy metals in soils are necessary to assess the potential threat of heavy metals to food safety and human health. In order to investigate the origin of heavy metals in paddy soils and rice in the Duyun city, 110 sampling sites were set in this study. The soil samples in arable layer of paddy and rice were collected, the contents of Cd, Hg, As, Pb and Cr were measured, and the data were analyzed by the multivariate statistical technique. A geographic information system (GIS) was used to explore the variety of spatial distributions for 5 heavy metals. Single factor pollution index, Nemero comprehensive pollution index and potential ecological risk index were applied to evaluate the degree of soil heavy metal contamination. Our results showed that the average contents of Cd, Hg, As, Pb and Cr in soils in the Duyun were (0.45±0.48), (0.23±0.29), (11.94±10.86), (36.95±32.98) and (60.80±31.73) mg/kg, respectively. The average contents of Cd, Hg, As, Pb and Cr in rice were (38.91±86.50), (5.82±2.96), (113.26±27.18), (89.42±24.87) and (175.92±82.12) μg/kg, respectively. The proportion of Cd, Hg, As, Pb and Cr contents more than the background values of the Guizhou province were 14.55%, 40.00%, 16.36%, 22.72%, 13.64%, respectively. Anthropic activities caused the enrichment of Hg in paddy soils. Only 3.64% of all rice samples exhibited Cd content exceeding the threshold level (20 μg/kg) in the Chinese national guidelines for cereals, and the other elements were below the national limit. Distribution maps of heavy metal content were generated using the Kriging interpolation method to identify their distribution trends. The results show that the influence of smelting activities, transport services and coal combustion on the spatial distribution. These suggested that the impacts of human activities on soil heavy metals in Duyun had exceeded the impact of natural source. Multivariate and geostatistical analysis suggested that soil Cr had a lithogenic origin. The correlation analysis and principal component analysis suggested that Cd, Hg, As and Pb could be attributed to anthropogenic inputs. The accumulation of Cd, Hg and As in soils was mostly affected by lead-zinc smelting, coal combustion and agronomic practices, and the main sources of Pb were lead-zinc smelting, industrial fume, coal burning exhausts. The current study confirmed that the environmental quality could be seriously threatened by heavy metal contaminants from the smelter and industrial activity. Therefore, the use of fossil fuels (coal and oil), fertilizers and the "three wastes" emissions from the key industrial enterprises in this area should be strictly controlled.

       

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