研究土壤中汞(Hg)元素积累的空间变异和迁移转化规律对土壤利用、环境评价和污染修复具有重要参考价值.本研究选择经济发展迅速的苏南某地为研究区域,对土壤、水稻和大气降尘中的Hg进行了详细分析.结果表明,该区域土壤全汞平均含量达1345μg kg-1,有效汞(HCl-Hg)平均含量51 μg kg-1,水稻Hg平均含量20 μg kg-1,大气Hg沉降量为5.13 g km-230 d-1.土壤和水稻高含量Hg主要积聚于城镇周边,随着与城镇距离的增加其含量逐渐减少.大气Hg沉降量在空间上变化不大.进入土壤中的Hg主要在土壤表层0～20 cm范围内富集,但直至60 cm深处依然存在积累现象,整个剖面土壤活性态汞和半活性态汞含量占全汞的比例变化不大.研究区土壤出现了明显Hg积累,导致水稻Hg吸收明显增加,不少样点超过了国家土壤环境质量二级标准(300μg kg-1)和国家食品污染物限量标准(20 μg kg-1),可能对环境和人体健康产生危害.较低的大气Hg沉降量和土壤积累的Hg已与土壤条件达到平衡的事实表明,目前Hg的积累已明显减少.今后应采取措施修复污染土壤或者通过改变作物种类来减少土壤Hg含量或抑制作物对Hg的吸收,达到环境治理的目的.%The research on spatial variability, accumulation and transfer of soil mercury (Hg) has great reference values to soil utilization, environmental assessment and polluted soil remediation. Mercury in the soil, rice and atmospheric deposition in an area with fast developing economy in the South Jiangsu was analyzed. It was found that on average, the soil total Hg was 1345 μg kg-1, available (HCl-extractable or HCl-Hg) 51 μg kg-1, Hg in rice 20 μg kg-1 and Hg in atmospheric deposition 5.13 g km-2 30 d-1. Spatially, high Hg concentrations in soil and rice were found mainly in places closely around the town, and the concentration decreased exponentially with the distance of the sampling site from the town. Atmospheric Hg deposition was found low in variability within the whole study area. Mercury in the soil accumulated mainly in the 0～20 cm soil horizon, however, Hg accumulation could still be found at 60 cm in depth. The percentages of soil Hg in mobile and semi-mobile state to total Hg did not vary much in the whole soil profile. Obvious soil Hg accumulation observed in the studied area led to higher Hg concentrations in rice. The concentration in quite a number of sampling sites already exceeded the second grade criterion of the National Standard for Soil Environmental Quality ( 300 μg kg - 1 ) and the National Food Safety Standard (20 μg kg - 1 ), and would bring about hazard to the environment quality and human health. The fact that balance is maintained between the soil conditions and Hg accumulation in soil and that the low atmospheric Hg deposition indicate that the ongoing accumulation is not as significant. Measures such as remediation of the polluted soil or rotation of low-Hg-uptake crop species should be taken to reduce soil Hg or to inhibit Hg uptake by crops, and hence to achieve the target of environmental management.
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