Methyl-mercury affects microbial activity and biomass,bacterial community structure but rarely the fungal community structure

Monomethyl-mercury is one of the most toxic compounds. Methylation of Hg usually appears under anoxic conditions. In Swiss forest soils, methyl-Hg concentrations of up to 3 μg kg⁻¹ soil dw have been observed, but the impact of methyl-Hg on soil microorganisms have rarely been examined so far. In this study, we investigated the effect of increasing concentrations of methyl-Hg (0, 5, 20, 90 μg kg⁻¹ soil dw) on the microbial communities in various forest soils differing in their physico-chemical properties. Experiments were conducted in microcosms under controlled conditions and the basal respiration (BR), the microbial biomass carbon (MBC) and the bacterial and fungal community structures using T-RFLP-profiling were investigated. BR was significantly affected by methyl-Hg. In general, the BR increased with increasing methyl-Hg concentrations, whereas the MBC was significantly reduced. Bacterial communities were more sensitive to methyl-Hg than fungal communities. In five out of seven soils, the bacterial community structures differed significantly between the treatments whereas the fungal communities did not. The impact of methyl-Hg on the soil bacterial communities was site specific. In one soil, a methyl-Hg concentration of already 5 μg kg⁻¹ soil dw significantly affected the relative abundance of 13% bacterial operational taxonomic units (OTU), whereas in other soils concentrations of even 90 μg kg⁻¹ soil dw rarely affected the abundance of OTUs. In this study, for the first time, the impact of methyl-Hg on soil bacterial and fungal communities in forest soils was assessed. We showed that its impact strongly depends on the physico-chemical conditions of the soil and that bacterial communities were more sensitive to methyl-Hg than fungi.     

宝鸡燃煤电厂周围土壤环境Hg污染及其评价

通过对宝鸡燃煤电厂周围土壤环境的调查、采样,研究了土壤汞的污染状况。结果表明,电厂周围土壤中Hg的含量为0.137~2.105mg kg-1,平均值为0.606mg kg-1,高于陕西、全国和世界土壤中Hg的平均含量。单因子污染指数、地质累积指数和潜在生态危害系数评价结果表明,电厂周围土壤出现不同程度汞的污染。     

土壤矿物对汞的吸持特性研究

吸附热力学与动力学试验研究结果表明 ,5种土壤矿物对Hg的吸附容量与吸附强度均表现为MnO2 >Fe2 O3 >膨润土 >高岭土 >CaCO3 。MnO2 对Hg吸附容量大且固持能力强 ,CaCO3 则与之相反。各土壤矿物结合汞的形态分布特征表明各土壤矿物结合汞在不同环境的稳定性及相应数量比例。挥发试验结果表明各土壤矿物结合汞的环境活性 (挥发活性 )大小受土壤矿物对Hg吸附容量与吸附强度制约 ,并与矿物结合汞的形态分布特征相关 ,水溶交换态和酸溶态比例越高则土壤矿物结合汞挥发活性越强 ,碱溶态和残渣态比例越高则土壤矿物结合汞挥发活性相应越弱     

黄河上游青川甘段表层沉积物重金属分布特征及风险评价

为揭示黄河上游青川甘段表层沉积物重金属分布特征和生态风险,选取青川甘段内黄河干流以及主要支流（白河、黑河、洮河、湟水）18个位点,采集表层沉积物样品,分析铬(Cr)、砷(As)、汞(Hg)、镍(Ni)、铜(Cu)、锌(Zn)、镉(Cd)、铅(Pb)等8种重金属元素含量的空间分布特征和来源,采用内梅罗综合污染指数法、地累积指数法和潜在生态危害指数法进行风险评价。结果显示,沉积物中As和Hg平均含量分别为11.74 mg/kg和0.034 mg/kg,分别富集1.3倍和1.0倍,其他6种重金属含量均低于中国水系沉积物背景值。As富集程度最高,内梅罗综合污染指数最高,为中度污染,但潜在生态风险远低于Hg和Cd。Hg的潜在生态风险值最高,为40.29,中等级别,其次为Cd,仅在黑河Cd为中等生态风险。根据主成分分析法和相关性分析结果推测,部分断面较高的As、Hg和Cd污染程度和生态风险主要受人类活动影响,如干流的龙羊峡库区出水口（G5）、支流洮河的西寨大桥（T1）、黑河的大水(H2),应加强监控。     

环境监测中汞的主要污染来源与防治对策

实验室在环境监测化学需氧量和氨氮等项目分析中会产生大量含汞废弃物。本文根据某实验室近九年来的情况分析其主要来源,并提出相应对策。     

Hg2+和Pb2+胁迫对脆江蓠生长及光合生理的影响

采用实验生态学方法研究了不同质量浓度Hg~(2+)和Pb~(2+)胁迫对脆江蓠(Gracilaria chouae)生长及光合生理的影响。实验设置Hg~(2+)质量浓度为0.01 mg/L、0.025 mg/L、0.05 mg/L、0.1 mg/L、0.25 mg/L和0.5 mg/L,Pb~(2+)质量浓度为0.05 mg/L、0.1 mg/L、0.5 mg/L、1 mg/L、2 mg/L和4 mg/L,以未添加重金属的实验组为对照,持续培养7 d,分别测定不同处理藻体的生长速率、光合放氧速率、光合色素含量、叶绿素荧光和光合碳代谢途径中关键酶活等生理生化指标。结果表明,在Hg~(2+)胁迫下,藻体特定生长率(SGR)显著下降(P0.05),质量浓度达到0.5 mg/L时藻体出现负增长;光合放氧速率降低35.48%~77.59%;叶绿素a、类胡萝卜素含量显著下降(P0.05),Hg~(2+)质量浓度高于0.1 mg/L时藻体藻蓝蛋白和藻红蛋白含量显著降低(P0.05);最大光合效率(F_v/F_m)和实际光合效率(Y(Ⅱ))随着Hg~(2+)浓度增加先降低后升高,0.05 mg/L时出现第二个峰值,丙酮酸磷酸双激酶(PPDK)也出现相似趋势。藻体对Pb~(2+)的敏感程度低于Hg~(2+),Pb~(2+)质量浓度为0.5 mg/L时,光合产氧速率显著下降(P0.05),质量浓度到达1 mg/L时,藻体SGR和叶绿素a、类胡萝卜素出现显著下降(P0.05),而叶绿素荧光参数和藻蓝蛋白含量则无显著性差异;Pb~(2+)质量浓度达到4 mg/L时1,5-二磷酸核酮糖羧化酶(RuBiSCO)出现显著下降(P0.05),PPDK酶活性则显著上升(P0.05)。实验结果证实:重金属Hg~(2+)和Pb~(2+)胁迫对脆江蓠的生长和光合作用都有不利影响,藻体对Hg~(2+)胁迫的敏感度要高于Pb~(2+),Hg~(2+)质量浓度为0.01 mg/L时,藻体出现胁迫,并随着浓度的增加而加剧,Pb~(2+)质量浓度超过1 mg/L时,藻体胁迫明显。     

饮用水中砷和汞的同时测定--氢化物发生原子荧光法

本文采用AFS-920型原子荧光光度计进行饮用水中砷和汞的同时测定。选择了最佳的仪器条件,进行了样品处理方法及酸度、干扰离子的研究,做了方法的检出限、线性范围、精密度、加标回收率等方法学的研究。结果表明：本方法准确性好,操作简便,灵敏度高。便于推广,适用于饮用水的砷、汞同测。     

Hg的土壤酶效应初步研究

采用土壤酶对汞生态毒性进行研究,在理论和实践上具有重要意义。通过室内模拟试验,针对我国几种主要类型土壤（黄褐土、风沙土、塿土和红壤）中影响土壤碳、氮、磷物质循环和微生物活性的土壤转化酶、脲酶、碱性磷酸酶、脱氢酶与Hg的关系进行了探讨。结果表明,Hg抑制土壤碱性磷酸酶、转化酶活性,但规律性不明显;土壤脲酶低浓度时激活,高浓度抑制;土壤脱氢酶和总体酶活性受到抑制。Hg浓度与脲酶、脱氢酶、总体酶活性间达显著或极显著负相关关系,揭示出其在一定程度上可表征土壤Hg污染的程度,其中尤以总体酶活性结果最优;计算Hg轻微污染时的ED10值0.0005～0.59mg·kg-1。土壤有机质和pH对二者关系具有重要影响。     

猪发酵床不同垫料中、累积规律

为研究在发酵床养猪过程中不同组成垫料的As、Hg累积规律,本文以木屑、稻壳和秸秆为原料,配制成3种垫料处理,分别为木屑（S）、木屑+稻壳（SR）和木屑+稻壳+秸秆段（SRS）,在一年半的时间里,测定了4批育肥猪养殖结束时不同层次垫料中As、Hg含量,分析了长期使用后不同发酵床垫料中As、Hg累积情况,为发酵床废弃垫料的后续农用提供理论依据。结果表明,随着猪养殖批次的延长,3种处理及其不同层次垫料As、Hg含量均存在不同程度增加。4批猪养殖结束时,As累积量最大的是SRS处理的发酵床,为1921.7 mg·栏-1,Hg累积量最大的也是SRS处理的发酵床,为21.1 mg·栏-1。S、SR、SRS处理的As、Hg含量分别为2.921、2.190、2.621 mg·kg-1和0.048、0.036、0.042 mg·kg-1,均符合《农业行业标准有机肥料》（NY 525—2012）、《食用农产品产地环境质量评价标准》（HJ/T 332—2006）的标准限值。     

Influence of Mercury on Soybean Plants (Glycine max L.) at Low pH

The influence of Hg on soybean plants under different pH conditions and Hg concentrations was studied. Growth inhibition by Hg was higher in roots than the upper part of the plant, but was highly dependant on pH condition. Growth inhibition of roots was observed when Hg concentration was higher than 1 mg Hg L⁻¹ for pH 4.0 and 5 mg Hg L⁻¹ for pH 6.0. Using ²⁰³Hg as a radioactive tracer, the amount of Hg (1 mg Hg L⁻¹) uptake in root was found to be about 1.5 times higher at pH 4.0 than that at pH 6.0; suggesting that Hg when highly accumulated at the lower pH induced inhibition of root growth. Decreased amounts of Hg due to evaporation during the plant growth were very low, but were higher at pH 6.0 than that at pH 4.0. There was hardly any translocation of Hg from roots to the upper parts through the stem within 24 h.