大连湾表层沉积物中总汞和甲基汞的分布及影响因素

为研究大连湾表层沉积物中THg（总汞）和MeHg（甲基汞）的分布及影响因素,于2016年7月对大连湾12个采样点表层沉积物进行了调查,分析了沉积物中w（THg）和w（MeHg）及其与环境因子的关系.结果表明:①大连湾表层沉积物中w（THg）和w（MeHg）的平均值分别为（79.5±47.1）和（0.53±0.26）ng/g,MeHg%（甲基化比率）范围为0.39%~1.46%,平均值为0.74%.②沉积物中w（THg）和w（MeHg）均表现出由湾内向湾外降低的趋势,而MeHg%的空间分布特征与w（THg）和w（MeHg）相反,并且水产养殖活动的外源输入也可对MeHg%产生影响.③w（MeHg）与各环境因子均呈显著相关关系,表明沉积物中w（MeHg）主要受w（THg）和氧化还原条件的影响;MeHg%与Hg/C（THg与TOC摩尔比,下同）呈显著负相关,可能主要与沉积物中生物可利用Hg的比例影响有关,而MeHg%虽然与w（TOC）、w（TS）的相关性均不显著,但也体现出有机质和硫对Hg的生物可利用性的影响.研究显示,沉积物中生物可利用Hg在MeHg的产生过程中具有重要作用,而减少大连湾内汞和有机质的输入将有助于降低沉积物中w（MeHg）.      

Evaluation of mercury methylation in fresh and pre dried sediments using ~(203)Hg radioisotope

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｏｇｎｉｔｉｏｎｏｆｍｅｒｃｕｒｙａｓａｔｒａｎｓ ｎａｔｉｏｎａｌｂｏｕｎｄａｒｙｐｏｌｌｕｔａｎｔａｎｄｔｈｅｄｉｓｃｏｖｅｒｙｏｆｔｈｅｎｅｇａｔｉｖｅｃｏｒｒｅｌａｔｉｏｎｂｅｔｗｅｅｎｆｉｓｈｍｅｒｃｕｒｙｌｅｖｅｌｓａｎｄｗａｔｅｒｐＨａｎｄｉｔｓｉｍｐｌｉｃａｔｉｏｎｗｉｔｈｒｅｇａｒｄｔｏａｃｉｄｒａｉｎｈａｖｅｇｅｎｅｒａｔｅｄａｌｏｔｏｆｉｎｔｅｒｅｓｔｉｎｓｃｉｅｎｔｉｆｉｃｒｅｓｅａｒｃｈｏｎｅｎｖｉｒｏｎｍｅｎｔａｌｍｅｒｃｕｒｙｃｏｎｔａ…     

Exposure of aboriginal people to methylmercury due to gold mining in the Amazon, Brazil

ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｃｅｔｈｅｅａｒｌｙ 1980’ｓ,ｒａｐｉｄｉｎｃｒｅａｓｅｓｉｎｇｏｌｄｍｉｎｉｎｇａｃｔｉｖｉｔｉｅｓｕｓｉｎｇｍｅｒｃｕｒｙａｍａｌｇａｍａｔｉｏｎｔｅｃｈｎｉｑｕｅｉｎｍａｎｙｄｅｖｅｌｏｐｉｎｇｃｏｕｎｔｒｉｅｓｈａｓｂｅｅｎｏｎｅｏｆｔｈｅｍａｉｎｓｏｕｒｃｅｓｏｆｍｅｒｃｕｒｙｐｏｌｌｕｔｉｏｎ ,ｐａｒｔｉｃｕｌａｒｌｙｉｎｔｈｅＡｍａｚｏｎａｎｄｏｔｈｅｒｔｒｏｐｉｃａｌｒｅｇｉｏｎｓ(Ｍａｌｍ ,1990 ;Ｒａｍｅｌ,1996;Ｉｋｉｎｇｕｒａ,1996;Ｌａｃｅｒｄａ,…     

汞在酸性紫色水稻土的转化与水稻汞富集特征

采用盆栽模拟试验,对汞(Hg)及甲基汞(MeHg)在酸性紫色水稻土中不同水稻生长期的动态变化进行了研究,并分析对比了总汞(THg)和MeHg在水稻体中的富集特征.结果表明:在水稻生长期间,土壤总汞含量变化较小,MeHg含量随时间增加而增加,土壤MeHg/THg值的变化趋势和土壤中MeHg含量变化一致.完熟期THg在水稻中植株的分布状况为:根籽粒茎叶穗壳,MeHg的分布为:籽粒根茎叶穗壳.水稻植株中MeHg/THg均值为24.03%,大于土壤均值3.05%,说明水稻植株中具有较强的MeHg累积能力.在水稻生长周期内,水稻体内MeHg富集系数均值为8.16,远大于THg富集系数的均值2.31,且籽粒中的MeHg富集系数大于根、茎、叶,说明水稻对MeHg的富集能力强于THg,且籽粒更易于富集MeHg.水稻体内的MeHg的转移系数大于THg,且籽粒中MeHg的转移系数大于1,进一步说明MeHg比THg更易在水稻体内转移.     

水稻甲基汞富集对大气气态单质汞浓度升高的响应研究

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,p0.05),与大气汞含量无线性关系(p0.05),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,p0.05;下部茎:r=0.9178~0.9484,p0.05),与大气汞含量没有相关性(p0.05),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,p0.01),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,p0.05),与大气汞含量无明显的线性关系(p0.05),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.     

中国大米汞含量研究

从中国9个省、市或地区的市场采集了303个大米样品,测定了其总汞和甲基汞的含量,评估了我国居民食用大米导致汞暴露的健康风险。大米总汞采用混合酸消解后CVAFS测定,甲基汞采用萃取-反萃取-水相乙基化结合GC-CVAFS测定。结果显示：各地区大米总汞的平均含量为3.6～17μg·kg-1,低于我国食品汞限量标准20μg·...     

甲基汞对未分化型PC12细胞的毒性机制

应用未分化型PC12细胞为体外模型,研究甲基汞对多巴胺能神经元的毒性作用机制.利用MTT法检测甲基汞的细胞毒性,Hoechst33258荧光染色观察细胞形态变化,流式细胞术定量分析细胞周期分布和凋亡比率,并进一步通过比色法评价各项氧化应激指标.结果显示,甲基汞以剂量依赖性方式降低了细胞存活率,干扰细胞周期,造成S期细胞阻滞,细胞出现典型的凋亡性死亡特征.另外,甲基汞暴露导致PC12细胞内O-.2、H2O2和·OH等活性氧含量急剧增加,脂质过氧化程度升高,且SOD、CAT和GSH-Px等抗氧化酶活性降低.因此,甲基汞对多巴胺能神经元具有强烈的毒性,毒性作用机制涉及到干扰细胞周期、诱导细胞凋亡和引发严重的氧化损伤.     

Plausibility of toxicological interaction between lead and methylmercury

Humans are exposed to both lead (Pb) and methylmercury (MeHg), two chemicals known to affect the developing nervous system. It is therefore important to know whether these chemicals interact toxicologically to develop reliable estimates of human health risks. The nature of the potential interaction and how it may change with dose are also critical factors which need to be understood and considered in risk assessment. The available toxicological literature was reviewed and yielded five animal studies which involved combined exposure to both metals. None of these studies examined developmental neurotoxicity, the key endpoint of interest. Doses in these studies were also in the range of 1–100?mg?kg^?1?day^?1, which is far above average exposure levels for Pb and MeHg in the U.S. population. The combined exposure literature is therefore uninformative concerning the potential for Pb–MeHg interaction. A subsequent evaluation of the available mechanistic data was conducted, looking for similarities in proposed modes of action relevant at low doses. Shared biological targets suggesting a potential for low dose interaction include protein kinase C, calcium homeostasis, and apoptosis. Whether interaction actually occurs, and the form the interaction might take, remains to be studied. A phased research program is proposed that may provide data needed to address this significant data gap and permit more robust Pb and MeHg risk assessment.     

Effects of phosphorus on uptake and translocation of methylmercury in rice

The aim of this study was to determine uptake and translocation of MeHg in the absence or presence of P in three rice cultivars, named Tianyou196 (TY196), NanJing35 (NJ35), and ZiXiangnuo (ZX). Rice seedlings from each cultivar were divided into two groups. One group was grown in normal P (+P) nutrient solution and the other in absence of P or starvation (?P) nutrient solution for 2 weeks. Both groups were subsequently exposed to 200 mg/L MeHg chloride culture solution and maintained in a greenhouse for 4 weeks. The results showed that the amount of reddish Fe plaque outside rice root was significantly increased by P starvation treatment, but in the +P treatments, rice roots remained white. It is proposed that Fe plaque formed sequestered MeHg and consequently reduced translocation of MeHg from roots to shoots. It is of interest that MeHg content in roots and shoots of TY196 and NJ35 was 11.1%–18.8% and 28.9%–32.3% lower than in ZX, respectively. Therefore, in practice, depletion of P to enhance Fe plaque formation in rice growing area is effective in preventing MeHg translocation from roots to shoots and ensures food safety in mine locations.