松花江甲基汞污染危害的环境流行病学研究

调查了从第二松花江饮马河口至第一松花江同江全长1271km沿江重点人群受甲基汞污染危害的情况。查出慢性中毒2人,观察对象18人,甲基汞吸收120人。受害者症状轻微,基本稳定,无明显自觉症状。发汞和甲基汞较汞污染治理前有显著下降,说明治理取得了显著的健康效益。但少数人体内仍有过量的汞和甲基汞蓄积,为防止敏感者受害,每周食松花江鱼量不应超过2kg。文中还对诊断、受害者的年龄、性别和发病江段作了讨论。     

Understanding the excretion rates of methylmercury and inorganic mercury from human body via hair and fingernails

Effective biomarkers are necessary to better understand the human mercury (Hg) exposure levels. However, mismatched biomarker sampling method causes extra uncertainty in assessing the risk of Hg exposure. To compare the differences between hair and fingernail, and further understand the excretion rates of methylmercury (MeHg) and inorganic mercury (IHg) via hair and fingernails, the total mercury (THg), MeHg, and IHg concentrations in paired hair and fingernail samples were investigated through paired samples collected from two typical mining areas, Wanshan mercury mine area (WMMA) and Hezhang zinc smelting area (HZSA). The positive correlation in THg, MeHg, and IHg concentrations (p <0.01) between hair and fingernail samples indicated that those two biomarkers can be corrected in application of assessing human Hg exposure. Compared to fingernails, the hair was suggested to be a more sensitive biomarker as the concentration of THg, MeHg and IHg were 2 ∼ 4 times higher than those in fingernails. Furthermore, the amounts of THg, MeHg, and IHg excreted via hair were 70 ∼ 226 times higher than that excreted via fingernails, and the hair plays a more important role than fingernails in the excretion of Hg from human bodies. Present study therefore provides some new insights to better understand the fate of human assimilated Hg.     

Biochar affects methylmercury production and bioaccumulation in paddy soils: Insights from soil-derived dissolved organic matter

Biochar has been used increasingly as a soil additive to control mercury (Hg) pollution in paddy rice fields. As the most active component of soil organic matter, soil dissolved organic matter (DOM) plays a vital role in the environmental fate of contaminants. However, there are very few studies to determine the impact of biochar on the Hg cycle in rice paddies using insights from DOM. This study used original and modified biochar to investigate their effect on DOM dynamics and their potential impact on methylmercury (MeHg) production and bioaccumulation in rice plants. Porewater DOM was collected to analyze the variations in soil-derived DOM in paddy soils. The results showed that the addition of biochar, whether in original or modified form, significantly reduced the bioaccumulation of MeHg in rice plants, especially in hulls and grains (p<0.05). However, MeHg production in soils was only inhibited by the modified biochar. Biochar addition induced a significant increase in DOM's aromaticity and molecular weight (p<0.05), which decreased Hg bioavailability. Furthermore, enhanced microbial activity was also observed in DOM (p<0.05), further increasing MeHg production in the soil. Thus, the effect of biochar on the fate of Hg cycle involves competition between the two different roles of DOM. This study identified a specific mechanism by which biochar affects Hg behavior in rice paddy soil and contributes to understanding the more general influence of biochar in agriculture and contaminant remediation.     

Assessing pre/post-weaning neurobehavioral development for perinatal exposure to low doses of methylmercury

Fetuses and neonates are known to be high-risk groups for Methylmercury(MeHg)exposure.MeHg can be transferred to the fetus through the placenta and to newborn offspring through breast milk.The aim of the present study was to investigate the neurotoxic effects of low doses of MeHg(1 and 5 μg/m L in drinking water) administration,from gestational day 1 to postnatal day(PND) 21,on the neurobehavioral development of rats.The results showed that the no-observed-effect level of MeHg is somewhere in the range of 1–4 μg/mL.Neurobehavioral development analysis revealed a delayed appearance of cliff drop and negative geotaxis reflexes in the 5 μg/mL MeHg exposure group.Developmental exposure to MeHg affected locomotor activity functions for the females,but not for the males,implying that the female pups were more vulnerable than the male pups.All pups exposed to 5 μg/mL of MeHg showed a significant deficit in motor coordination in the rotarod test compared with controls,and the highest accumulated concentrations of Hg were found in the cerebellum,followed by the hippocampus and cerebral cortex,indicating that the cerebellum is a possible target for MeHg toxicity.We demonstrated adverse effects of developmental exposure to MeHg associated with tissue concentrations very close to the current human body burden of this persistent and bioaccumulative compound.     

Mercury bioaccumulation in aquatic biota along a salinity gradient in the Saint John River estuary

Although estuaries are critical habitats for many aquatic species, the spatial trends of toxic methylmercury(MeHg) in biota from fresh to marine waters are poorly understood. Our objective was to determine if MeHg concentrations in biota changed along a salinity gradient in an estuary. Fourspine Stickleback(Apeltes quadracus), invertebrates(snails,amphipods, and chironomids), sediments, and water were collected from ten sites along the Saint John River estuary, New Brunswick, Canada in 2015 and 2016, with salinities ranging from 0.06 to 6.96. Total mercury(proxy for MeHg) was measured in whole fish and MeHg was measured in a subset of fish, pooled invertebrates, sediments, and water. Stable sulfur(δ~(34)S), carbon(δ~(13) C), and nitrogen(δ~(15)N) isotope values were measured to assess energy sources(S, C) and relative trophic level(N). There were increases in biotic δ~(13)C and δ~(34)S from fresh to more saline sites and these measures were correlated with salinity.Though aqueous MeHg was higher at the freshwater than more saline sites, only chironomid MeHg increased significantly with salinity. In the Saint John River estuary, there was little evidence that MeHg and its associated risks increased along a salinity gradient.     

Speciation of methylmercury in rice grown from a mercury mining area

Monomethylmercury (CH₃Hg⁺ and its complexes; MeHg hereafter) is a known developmental neurotoxin. Recent studies have shown that rice (Oryza sativa L.) grain grown from mercury (Hg) mining areas may contain elevated MeHg concentrations, raising concerns over the health of local residents who consume rice on a daily basis. An analytical method employing high performance liquid chromatography (HPLC) - inductively coupled plasma mass spectrometry (ICP-MS) following enzymatic hydrolysis was developed to analyze the speciation of MeHg in uncooked and cooked white rice grain grown from the vicinity of a Hg mine in China. The results revealed that the MeHg in the uncooked rice is present almost exclusively as CH₃Hg-l-cysteinate (CH₃HgCys), a complex that is thought to be responsible for the transfer of MeHg across the blood-brain and placental barriers. Although cooking does not change the total Hg or total MeHg concentration in rice, no CH₃HgCys is measurable after cooking, suggesting that most, if not all, of the CH₃HgCys is converted to other forms of MeHg, the identity and toxicity of which remain elusive.     

Methylmercury speciation in the dissolved phase of a stratified lake using the diffusive gradient in thin film technique

The diffusive gradient in thin film (DGT) technique was successfully used to monitor methylmercury (MeHg) speciation in the dissolved phase of a stratified boreal lake, Lake 658 of the Experimental Lakes Area (ELA) in Ontario, Canada. Water samples were conventionally analysed for MeHg, sulfides, and dissolved organic matter (DOM). MeHg accumulated by DGT devices was compared to MeHg concentration measured conventionally in water samples to establish MeHg speciation. In the epilimnion, MeHg was almost entirely bound to DOM. In the top of the hypolimnion an additional labile fraction was identified, and at the bottom of the lake a significant fraction of MeHg was potentially associated to colloidal material. As part of the METAALICUS project, isotope enriched inorganic mercury was applied to Lake 658 and its watershed for several years to establish the relationship between atmospheric Hg deposition and Hg in fish. Little or no difference in MeHg speciation in the dissolved phase was detected between ambient and spike MeHg.     

Mercury in alpine fish from four rivers in the Tibetan Plateau

As a global pollutant, high levels of mercury (Hg) have been found in remote ecosystem due to the long range atmospheric transport. In this study, a total of 60 fish samples were collected from four rivers across the Tibetan Plateau to study the accumulation of Hg in remote and high-altitude aquatic environment. The total Hg (THg) and methylmercury (MeHg) in fish muscles ranged from 11 to 2097 ng/g dry weight (dw) (average: 819 ng/g dw) and from 14 to 1960 ng/g dw (average: 756 ng/g dw), respectively. Significantly positive linear relationships were observed between the THg (r = 0.591, p < 0.01, n = 36) and MeHg concentrations (r = 0.473, p < 0.01, n = 36) with the trophic level of fish from Lhasa River, suggesting trophic transfer and biomagnification of Hg in this aquatic ecosystem. Moreover, the THg levels in fish had significantly positive correlations with the length (r = 0.316, p < 0.05, n = 60) and weight (r = 0.271, p < 0.05, n = 60) of fish. The high levels of Hg were attributed to the slow growth and long lifespan of the fish under this sterile and cold environment. Risk assessment revealed that the consumption of Oxygymnocypris stewartii, Schizothorax macropogon, Schizothorax waltoni, Schizopygopsis younghusbandi and Schizothorax o'connori would lead to a high exposure to MeHg.     

An experimental ecotoxicological study and its application to the behavioural study of organic mercury (CH3HgCl) in the environment: influence of temperature and pH

Laboratory experiments were carried out to study the influence of temperature (24, 28 and 30 °C) and pH (1–10) on organic mercury (CH₃HgCl) transfer and accumulation in an experimental ecotoxicological model. We followed the evolution of CH₃HgCl in a basic model (water+air) by varying temperature and pH. In a second step, we completed the model by adding sediment and fish. We added CH₃HgCl to water at the beginning of each experiment which was repeated at least three times. Results demonstrated that mercury was released from methylmercury into the air regardless of water pH and its concentration in the air increased with increasing pH. By contrast, in presence of sediment, almost all the mercury was fixed onto the sediment and no mercury was traced in air or in water. Interestingly, in the presence of sediment, the life span of fish under methylmercury exposure lasted longer despite their higher mercury body level content at their death. These results indicate that water is a bad exposure indicator for aquatic pollution. In case of chronic pollution, sediments, fish and aquatic plants are more appropriate indicators.     

乌江中上游新建水库水体甲基汞的时空分布

为了弄清新修建的水库是否造成水体甲基汞浓度升高,以贵州省乌江流域2座新建水库洪家渡水库和索风营水库为研究对象,采用蒸馏 乙基化结合（GC CVAFS）法测定了不同季节水库水体中甲基汞的浓度,最低检出限为 0.009 ng/L。探讨了水质参数对甲基汞分布的影响以及水库水体甲基汞的分布特征。结果显示:洪家渡水库总甲基汞浓度夏季平均值为 0.11 ng/L,秋季平均值为 0.08 ng/L,冬季平均值为 0.10 ng/L;索风营水库总甲基汞浓度夏季平均值为 0.11 ng/L,秋季平均值为 0.07 ng/L,冬季平均值为 0.09 ng/L。数据表明2座水库水体甲基汞含量均较低,低于目前我国环境质量标准规定的一类地表水汞含量标准限值,与世界上其他未受污染的水体基本相当。水库水体甲基汞浓度随水体深度的增加没有明显的变化规律,且夏季略高于冬季、秋季,这与夏季降雨量和温度有关,在入库处与大坝前没有明显的变化趋势。这与水库中被淹没土壤有机质含量偏低且流域内基岩为碳酸盐有关,还与其他环境因素有关(如pH值较高,DOC含量偏低等)。通过研究发现目前库区环境汞的甲基化率低,但随着水库生态系统的不断演化,内源和外源营养物的输入及水体在温度分层其间自身甲基汞的形成,导致水体甲基汞含量的逐渐增加,但仍需进一步的研究证实。