湖南凤凰茶田汞矿区土壤-水稻系统中汞的传输及其健康风险

通过野外系统采样和室内分析,研究了湖南凤凰县茶田汞矿区耕层土壤及水稻中Hg的含量分布以及土壤-水稻系统中Hg的传输和分配。结果表明:由于地质成因和人为采选矿活动导致矿区土壤及作物中Hg大量富集,与对照区相比,矿区耕作土壤、稻根、稻秆、稻米中Hg平均含量分别增加了267.6倍、8.6倍、5.8倍和2.3倍。土壤中的有机-硫化态Hg同稻根、稻秆、稻米中Hg含量间均呈现显著正相关性,但整体而言,Hg由土壤→稻根以及稻根→稻米的富集/迁移系数较低,移动性弱。矿区稻米Hg平均含量为0.09±0.04μg/g,与国家粮食卫生标准(GB2762–2005)的限值(0.02μg/g)相比,超标达4.5倍。当地居民终生平均每天摄入的Hg量为0.75μg/(kg.d),超过WHO推荐的可耐受剂量0.71μg/(kg.d)],面临较大的健康风险。对矿区中多种元素研究发现,稻米中Hg、Pb、Se共同富集,其复合污染机制的研究亟待开展。

Transmission and health risks of mercury in soil-paddy system in Chatian mercury mining area,Fenghuang County,Hunan Province

Mercury(Hg) in paddy soils and rice as well as its translocation and accumulation in Chatian Hg mining area of Fenghuang County,Hunan Province were studied based on field systematic sampling and laboratory analysis.The results showed that Hg concentrations in the paddy soils and rice were significantly enriched,which were primarily due to the high natural geologic background levels and anthropogenic mining activities.The average concentration of Hg in paddy soils,rice root,rice shoots and rice grain in mercury deposit area were,in average,276.6,8.6,5.8 and 2.3 folds of the corresponding parts in the control area,respectively.The concentration of Hg in paddy soils in organic-sulfide form was significant positively correlated with Hg contents in rice roots,rice shoots and rice grain.However,the transfer coefficients of Hg of paddy soils-rice roots and rice roots-rice grain were quite low.The content of Hg in rice grain in Chatian mercury mining area was 0.09±0.04 μg/g,4.5 times of the limited value(0.02 μg/g) of the National Food Sanitary Standard(GB2762-2005).Average daily intake dose(ADD) of Hg of local population ranged from 0.408 to 1.225 μg/(kg·d),mean 0.75 μg/kg body weight per day,exceeding 0.71 μg/(kg·d) of provisional tolerable daily intake(PTDI) recommended by WHO.The local inhabitants faced huge health risk due to high Hg exposure via rice consumption.In addition,Se and Pb were also found to be co-enriched in the rice grain in Chatian mining area,indicating that co-contamination of Hg and Pb may result in great risks to human health in this area.