水稻甲基汞富集对大气气态单质汞浓度升高的响应研究

Response of methylmercury accumulation in rice to the rising atmospheric gaseous elemental mercury

水稻具有很强的甲基汞（MeHg）富集能力,从而增加了汞污染地区居民甲基汞暴露的风险.本研究利用开顶气室熏蒸实验和土壤加汞培育实验探究水稻各组织中MeHg富集对大气中的气态单质汞（GEM）浓度升高的响应.结果表明：水稻根中甲基汞含量与土壤中甲基汞含量显著正相关（r=0.9462~0.9870,p〈0.05）,与大气汞含量无线性关系（p〉0.05）,表明水稻根中的MeHg主要来自土壤.水稻茎中甲基汞含量随土壤甲基汞含量的增加而线性增加（上部茎：r=0.8560,p〉0.05;下部茎：r=0.9178~0.9484,p〈0.05）,与大气汞含量没有相关性（p〉0.05）,但在气室熏蒸实验中上部茎中的甲基汞含量高于下部茎;而在土壤加汞培育实验中下部茎中的甲基汞含量高于上部茎,表明水稻茎主要受土壤汞的影响,且大气汞可能对水稻上部茎甲基汞的富集有一定的影响.水稻叶中甲基汞含量与土壤甲基汞含量显著正相关（r=0.9708,p〈0.01）,与大气汞含量无线性关系,但在气室熏蒸实验中实验组叶中甲基汞的含量高于对照组,表明水稻叶中的甲基汞可能受土壤甲基汞和大气汞的共同影响.水稻籽粒中甲基汞的含量与土壤甲基汞含量呈显著正相关（r=0.9046~0.9865,p〈0.05）,与大气汞含量无明显的线性关系（p〉0.05）,表明水稻籽粒中的甲基汞主要来自土壤,但在水稻上部茎和叶中甲基汞含量受一定程度大气汞含量影响的情况下势必会对水稻籽粒甲基汞的富集产生影响,但究竟有多大程度影响或量化其贡献还需进一步实验研究.

Studies have shown that rice has strong ability of methylmercury（ MeHg） accumulation,enhancing health risk of MeHg exposure in Hg mining areas. With open top chambers（ OTCs） fumigation experiment and soil Hg enriched experiment,this study analyzed the response of MeHg accumulation in rice to the rising atmospheric gaseous elemental mercury（ GEM）. Results indicated that MeHg levels in root were significantly correlated with soil MeHg concentrations（ r = 0. 9462 ~ 0. 9870,p〈0. 05） but insignificantly correlated with air Hg concentrations（ p〉0. 05）,indicating that MeHg in rice root was mainly from soil. The MeHg concentrations in stem increased linearly with soil MeHg concentrations（ upper stem： r = 0. 8560,p〉0. 05; bottom stem： r = 0. 9178 ~ 0. 9484,p〈0. 05）,and no obvious linear correlation with the GEM was observed. MeHg concentrations were generally higher in the upper stem in OTCs experiment,and higher in the bottom stem in soil Hg enriched experiment. This suggested that MeHg in stem was mainly from soil,and the upper stem might be affected by the GEM. MeHg concentrations in leaf were significantly correlated with soil MeHg（ r = 0. 9708,p〈0. 01）,and did not linearly correlate with air Hg（ p〉0. 05）. However,the MeHg concentrations in these experimental groups were higher than those in control group in OTCs experiment,indicating that MeHg in leaf might be influenced by both soil MeHg and air Hg. MeHg concentrations in grain were linearlycorrelated with soil MeHg concentrations（ r = 0. 9046 ~ 0. 9865,p〈0. 05）,and were not linearly correlated with air Hg（ p〉 0. 05）. GEM accumulation in upper stem and leaf would certainly impact the MeHg accumulation in rice grain. The actual degree however needs further investigation.