产甲烷菌中汞甲基化研究进展与展望

微生物作用是无机汞转化为甲基汞最主要的方式.其中,硫酸盐还原菌和铁还原菌被认为是主要的汞甲基化微生物,近年来的研究表明,产甲烷菌在汞甲基化过程中同样发挥重要作用.产甲烷菌参与沉积物、水体和土壤等多种环境中的汞甲基化过程,并在部分环境中主导甲基汞的生成;在实验室纯培养体系中,多个产甲烷菌能将10%以上的无机汞转化为甲基汞.产甲烷菌对于甲基汞的生成至关重要,然而目前缺乏对产甲烷菌汞甲基化作用的系统总结.本文分别从原位环境、纯培养和共培养的角度,详细阐述了产甲烷菌在汞甲基化中的作用.在此基础上,对产甲烷菌可能的汞甲基化途径进行探讨,提出汞甲基化过程与一碳代谢极大可能存在功能上的关联性,并展望了后续研究的方向和重点.

不同粒径生物质炭对水稻甲基汞富集的影响

【目的】研究生物质炭粒径的改变对其理化性质以及汞污染稻田土壤中修复能力的影响,以期为减少汞污染地区水稻Oryza sativa甲基汞富集量、保障粮食安全提供科学依据。【方法】以水稻秸秆为制备生物质炭的原料,通过筛分法制备不同粒径(<0.5、0.5~1.0、1.0~2.0 mm)的水稻秸秆生物质炭,利用元素分析仪、比表面分析仪、傅里叶红外光谱仪和扫描电镜仪分析不同生物质炭的结构特征变化,并结合盆栽试验研究施用不同粒径生物质炭对水稻甲基汞富集的影响。【结果】(1)随着粒径的减小,生物质炭的表面形貌变化明显,生物质炭比表面积增大,孔隙增多,C—O、—OH和—COO含氧官能团强度增加。(2)与对照相比,3种粒径生物质炭的施入均降低了土壤中甲基汞的生物有效性,水稻各组织中甲基汞富集量减少,其中小粒径生物质炭的降低效果最佳,添加粒径<0.5 mm的生物质炭组精米中的甲基汞质量分数降低了47.01%。(3)生物质炭的施入增大了水稻根际土壤甲基汞质量分数,且这种正向促进作用随着生物质炭粒径的减小而更加明显。【结论】生物质炭粒径的减小能够增强其在汞污染稻田土壤中的修复能力,减少水稻对甲基汞的积累,降低甲基汞暴露风险。

液相色谱—原子荧光光谱联用法测定海鱼粉中甲基汞含量的不确定度评定

本文评估了用液相色谱法—原子荧光光谱法测定海鱼粉中甲基汞的不确定度。对测试过程中不确定度的来源进行分析,并对各组分的不确定度进行计算。结果表明,当海鱼粉中甲基汞的含量为0.670 mg/kg,扩展不确定度为0.034 mg/kg(k=2)。

海洋汞同位素的研究范式及最新进展

汞(Hg)是一种具有生物毒性且能够全球传输的重金属元素,在海洋环境中易转化为神经毒素甲基汞并沿食物网进行富集和放大,危害生态系统和人类健康。准确约束海洋汞的来源、迁移与转化是理解海洋汞循环的关键,对更新现有海洋汞循环模型和制定相关环境政策具有重要价值。近十多年发展起来的汞稳定同位素技术为研究环境中的汞循环以及生态环境效应开辟了新视野。汞同位素独特的“三维”分馏模式,特别是非质量分馏(MIF),为研究海洋汞循环带来了科学范式的改变,取得了一系列重要发现。本文从海洋汞的来源以及甲基汞的生成、迁移与转化两大方面的应用系统阐述了近十多年来汞同位素体系在示踪海洋汞循环方面的主要进展,重点剖析了汞同位素在远洋大气汞沉降途径以及甲基汞循环方面的应用等近期研究热点。未来需结合更精细的汞同位素测试手段以及汞同位素分馏控制实验进一步明确海洋汞同位素分馏的主要控制因素,拓展汞同位素的应用空间。

水产品中甲基汞标准物质的研制

研制水产品中甲基汞标准物质。选用大鱿鱼脚作为候选物,经过洗涤、冻干、粉碎过筛、混样、装瓶等制样过程,每瓶按10 g分装,共制备300瓶。采用液相色谱-原子荧光法测定制备的标准物质中甲基汞含量,并进行均匀性和稳定性检验,由6家实验室采用同一检测方法协作定值,对定值结果的不确定度进行评定。研制的水产品中甲基汞参考标准物质中甲基汞的质量分数为0.164 mg/kg(以Hg计),扩展不确定度0.014 mg/kg(k=2),均匀性和稳定性良好,有效期为6个月。

浙江地区中华绒螯蟹中甲基汞分布特征与食用风险

为了研究浙江地区中华绒螯蟹中甲基汞的分布特征与食用风险,在浙江主要养殖地区的养殖场设点抽样,利用LC-AFS6000液相色谱原子荧光联用仪检测样品可食部分中的甲基汞含量。结果表明,中华绒螯蟹的蟹肉中甲基汞含量明显高于蟹黄中的甲基汞含量,蟹肉中的甲基汞含量远小于0.5 mg/kg,吴兴乔溇采样点的蟹肉中甲基汞含量最高达到0.043 mg/kg。综上所述,浙江地区中华绒螯蟹符合国家相关要求,可以放心食用,同时建议对甲壳类动物中重金属甲基汞限量作更细的区分和说明。

Effect of methylmercury on some neurotransmitters and oxidative damage of rats

In order to study the molecular mechanism of injury in rat organs induced by methylmercury, and the relationship between neurotransmitter and oxidative damage in the toxicity process of rat injury by methylmercury was studied. The control group was physiological saline of 0.9%, the concentration of exposure groups were 5 mg/(kg5d) and 10 mg/(kg5d) respectively. The content of AChE, ACh, NOS, NO, MDA, SOD, GSH-Px and GSH in different organs of rats were determined with conventional methods. The results showed that after exposure to methylmercury for 7 d, the mercury content in brain of exposure groups increased clearly and had significant difference compared with the control group(P<0.01). In rat's brain, serum, liver and kidney, the content of ACh and AChE were all decreased; the content of NOS and NO were all increased; the content of MDA was increased compared with the control group, the exposure groups had significant difference (P<0.01); the content of SOD, GSH and GSH-Px was decreased compared with the control group, the exposure groups had significant difference(P<0.01). It could be concluded that methylmercury did effect the change of neurotransmitter and free radical. They participated in the toxicity process of injury by methylmercury. The damage of neurotransmitter maybe cause the chaos of free radical and the chaos of free radical may also do more damage to neurotransmitter vice versa.

Distribution characteristics of total mercury and methylmercury in the topsoil and dust of Xiamen, China

The levels and distribution of mercury （Hg） species, including total mercury （THg） and methylmercury （MeHg） in the topsoil and dust collected from twenty sampling stations located in different land function areas of Xiamen, China, were investigated. The THg concentrations in topsoil ranged from 0.071 to 1.2 mg/kg, and in dust ranged from of 0.034 to 1.4 mg/kg. For stations where the THg of dust was less than 0.31 mg/kg, THg concentrations in the topsoil were significantly correlated to those in the corresponding dust （r = 0.597, n = 16, P = 0.014）. The MeHg concentrations in topsoil were varied between 0.14 and 5.7 μg/kg. The ratios of MeHg/THg in the topsoil ranged from 0.069% to 0.74%. The range of MeHg concentration in the dust were 0.092-2.3 μg/kg. The ratios of MeHg/THg in the dust were at the same level as those in the topsoil. The MeHg concentrations in both topsoil and dust were linked to corresponding THg concentrations and soil organic matter. Neither THg nor MeHg concentration in the topsoil and dust was obviously linked to the land function.

Effect of methylmercury on LPO levels, SH groups and activities of GSH-Px, SOD, XOD in liver of rats

In recent years, lipid peroxidation has been considered as the initial step for foreign toxic substances to damage cells. In this paper, the effects of methylmercury (MeHg) on LPO (lipid peroxide) levels, SH (sulfhydryl) groups and activities of GSH\|Px (glutathione peroxidase), SOD (superoxide dismutase), XOD (xanthine oxidase) in liver of rats treated with doses of MeHg at different intervals were studied by TBA, Ellman Reagent, NBT colorimetric methods and chemilluminescence. Meanwhile, the contents of FR (free radical)and MeHg in the liver of female rats were measured by ESR and GC. Results showed that the LPO levels in the experimental group increased significantly over those of the control group ( p<0.05— p<0.001) , reaching maximum point on the first poisoning day. Both male and female rats showed marked positive dose\|effect relations (Male: Y=261.4±49.4X, r=0.94, p<0.02; Female : Y=255.0±73.0X, r=0.99, p<0.001 ). N-SH (nonprotein sulfhydryl), P\|SH (protein sulfhydryl), T-SH (total sulfhydryl) contents and GSH\|Px activities decreased significantly (p<0.05-p<0.001). For GSH\|Px, both groups reached minimum value on the first poisoning day. In female rats, activities of SOD and XOD increased markedly ( p<0.02-p<0.01 ) although the contents of FR showed no significant changes. The contents of MeHg was determined by GC, and it ranged from 0.0081—0.0191 ppm.

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

This paper outlines the results of our study aiming at evaluating the actual extent of human exposure to Hg mainly in Tapajos River Basin in central Amazonia, which is considered to be the oldest and most productive gold mining area in the Amazon. Human hair and blood as well as fish samples were collected from gold mining areas and various fishing villages located at different distances from main gold mining areas, and analyzed for total mercury(T Hg) and methylmercury (MeHg) with new methods recently being developed in our laboratory. The results to date showed the inhabitants of fishing villages particularly in the upstream Tapajos areas were constantly exposed to MeHg at abnormally high levels, with little confounding exposure to inorganic Hg. A highly significant correlation between Hg in hair and blood was observed in fishing villages, and the ratios of hair Hg to blood Hg were very close to 250g, generally established for MeHg. While, the levels of MeHg in hair and blood of gold miners and goldshop workers were low, indicating that they were mainly exposed to Hg in inorganic form. From these data, together with the levels of MeHg in fish, Hg contamination mechanisms are discussed.

Review of Risk Assessment of Methylmercury Intake from Fish and Shellfish

[Objective] To evaluate the risk of methylmercury hazards in fish and shellfsh products, and predict the possible harm and consequences, this study puts forward suggestions on the people’s intake of fish and shellfish and provides the basis for food safety regulation. [Method] Research progress in risk assessment of methylmercury intake from fish and shellfish is introduced in the study. [Result] Aquatic products are part of a healthy diet for human. However, almost all fsh and shellfish contain at least a trace amount of methylmercury. The methylmercury content in wild fsh is higher than that of cultured fsh. The methylmercury content in different aquatic products is in the order： carnivorous fsh 〉 omnivorous fsh 〉 flter-feeding fsh 〉 benthic organisms 〉 herbivorous fsh 〉 phytoplankton 〉 zooplankton, and the methylmercury content in different organs is in the order： back muscles 〉 belly muscles 〉 liver 〉 heart 〉 other organs and tissues. [Conclusion] The harm of methylmercury in fsh and shellfsh is of low risk and would not cause harm to health. However, women of childbearing age, pregnant woman, nursing woman and children should eat fsh with low mercury content and avoid some large-fsh intake.

Seasonal distribution of total mercury and methylmercury in sediments of the Wujiangdu Reservoir,Guizhou,China

The concentrations of total mercury and methylmercury in sediments were determined at the dam of the Wujiangdu Reservoir in different seasons. Total mercury (HgT) levels in the whole sediment profile were 254.2±47.0 ng/g in winter, 254.2±31.6 ng/g in spring, and 256.7±60.8 ng/g in summer, without significant variations in different seasons or at different depths. In contrast, the methylmercury (MeHg) compounds were most abundant at the sediment-water interface and decreased progressively with depth. MeHg contents of the sediments during different seasons are highly dependent on microbial activity, and seem to be higher when Hg (II)-methylating microorganisms are active. Thus, MeHg levels tend to rise in the loci where nutrient supplies and biological productivity are favorable. The percentage of HgT that is present as MeHg in the sediments increased gradually from December 2003 to April 2004 and to July 2004.

The impact of sulfate reduction on the distribution of methylmercury in reservoirs in the city of Guiyang

In this paper, the relationship between sulfate reduction potential and mercury methylation potential was studied in the Aha, Baihua and Hongfeng reservoirs from Guiyang City. The methylmercury (MeHg) concentrations of lake water in the Aha Reservoir were greatly elevated as compared to those of the Hongfeng and Baihua reservoirs, which was correlated with its distinctly high SRB abundance, SO42-, and S2- concentrations. Among the three reservoirs, however, the highest MeHg was observed in in the top several centimenters of pore water profile in the Hongfeng Reservoir where the lowest S2- in pore water occurred. The distributions of MeHg in lake water and pore water showed the highest methylation potential occurred at water-sediment surface for the Aha Reservoir and the in the top several centimenters of sediments for the Hongfeng Reservoir. It is guessed that the highest mercury methylation only occurs at the sites with certain sulfide concentrations.

Methylmercury chloride damage to the adult rat hippocampus cannot be detected by proton magnetic resonance spectroscopy

Previous studies have found that methylmercury can damage hippocampal neurons and accord- ingly cause cognitive dysfunction. However, a non-invasive, safe and accurate detection method for detecting hippocampal injury has yet to be developed. This study aimed to detect methylmercury-induced damage on hippocampal tissue using proton magnetic resonance spectroscopy. Rats were given a subcutaneous injection of 4 and 2 mg/kg methylmercury into the neck for 50 consecutive days. Water maze and pathology tests confirmed that cognitive function had been impaired and that the ultrastructure of hippocampal tissue was altered after injection. The results of proton magnetic resonance spectroscopy revealed that the nitrogen-acetyl aspartate/ creatine, choline complex/creatine and myoinositol/creatine ratio in rat hippocampal tissue were unchanged. Therefore, proton magnetic resonance spectroscopy can not be used to determine structural damage in the adult rat hippocampus caused by methylmercury chloride.

Distribution Characteristics of Methylmercury in Eriocheir sinensis Produced in Zhejiang Province and the Risk of Eating It

Based the detection of content of methylmercury in the meat and butter of Eriocheir sinensis cultured in Zhejiang Province by liquid chromatography-atomic fluorescence spectroscopy,the distribution characteristics of methylmercury were analyzed,and the exposure risk of methylmercury to consumers was evaluated. The results showed that the content of methylmercury in the crab meat was higher than that of the crab butter. According to China＇s national standard and industry standard,the content of methylmercury in the crab meat was lower than the limit and accorded with relevant regulations. According to the reference intake of methylmercury recommended by the World Health Organization（ WHO） and the United States Environmental Protection Agency（ US EPA）,the weekly intake of E. sinensis meat should not exceed 3.2 kg,and the daily intake should not exceed 200g.

Sensory Disturbance as a Characteristic Symptoms of Methylmercury Poisoning in Niigata, Japan

Fifty years have passed from the first official recognition of the methylmercury （MeHg） poisoning in Niigata （so called the second Minamata disease）, Japan in 2015. The first case of MeHg poisoning was found in January 1965, when two surveys were carried out for 20,000 inhabitants lived within 15 km from the mouth of the Agano river. From these surveys, 26 cases （including 5 cases of death） were officially recognized as MeHg poisoning. Moreover, 9 cases who had no symptoms but whose hair mercury concentration were over 200 ppm were found. Within 20 cases, 15 cases are among 26 cases officially recognized as having MeHg poisoning and 5 cases are among 9 cases who had no symptoms but whose hair mercury concentration were over 200 ppm in 1965. The distal dominant sensory disturbances of the extremities lasted for more than several decades among 20 cases. The sensory disturbance of the bilateral distal extremities could be used as the gold standard for the diagnosis of MeHg poisoning in the exposed areas. The distal dominant sensory disturbance of the extremities is a typical characteristic and important sign of the MeHg poisoning.

Fluorimetric determination of methylmercury with 2, 3-dimercaptonaphthalene

Methylmercury is the most toxic one among the mercury species. Many methods including atomic absorption spectrometry, atomic emission spectrometry, atomic fluorescence spectrometry, gas chromatography, high\|performance liquid chromatography, ion chromatography, and capillary electrophoresis, have been published for the determination of methylmercury. These methods have been reviewed (Li, 1997; 1993; Niu, 1991). These methods require expensive equipment and highly qualified analysts. Although fluorimetric method is sensitive, inexpensive, easy to operate, no data about determination of methylmercury by fluorimetry can be found in the literature. In order to obtain a better method for the determination of methylmercury by fluorimetry, several reagents such as 8\| hydroxyquinoline, 8\|aminoquinoline, 8\|mercaptoquinoline, 2,3\| diaminonaphthalene, 2, 3\|dimercaptonaphthalene were tested. The 2, 3\|dimercaptonaphthalene gave better result than the other reagents. Under the optimal conditions, the concentration of 2, 3\| dimercaptonaphthalene was 5.6×10 -5 mol/L and the pH value of the solution was adjusted to 4.0 with acetate buffer solution. The excitation and emission fluorescence wavelengths of 2,3\| dimercaptonaphthalene-methylmercury complex were 512.5 nm and 500 nm(antistokes), respectively. The linear range was 0.3—80 ng/ml and the detection limit was 0.02 ng/ml. The relative standard deviation was 2.6%. The method may be applied to determine methylmercury in environmental samples, and detailed investigation is in progress.