贵州省典型铅锌矿区居民血液总汞和甲基汞暴露及健康风险模型预测评估

汞是铅锌矿石的常见伴生元素,铅锌冶炼活动会给当地居民带来潜在汞暴露风险.为了解铅锌矿区居民血液汞暴露及健康风险,选择贵州省赫章县为研究区域,以贵阳市为对照区,分别采集居民血液样品418和118份,利用冷原子荧光法测定其总汞和甲基汞含量,结合年龄和性别分析血液总汞与甲基汞含量特征,估算育龄期妇女头发甲基汞含量并进行甲基汞暴露致新生儿IQ（智商）损失评估,利用单区室PBPK（生理药代动力学）模型预测居民甲基汞ADI（日均摄入量）.结果表明:①铅锌矿区（赫章县）和对照区居民血液总汞含量几何均值分别为（3.11±5.05）和（1.83±1.19）μg/L,范围分别为0.63~54.26和0.46~11.88 μg/L,分别有21.5%和0.85%的血液样本总汞含量超过人体血液总汞安全限值（5.8 μg/L）.②铅锌矿区成年居民和0~6岁儿童血液总汞含量分别为（2.80±3.85）和（2.49±2.08）μg/L,分别有77和7人血液总汞含量超过5.8 μg/L,超标率分别为24.37%和10.61%,存在潜在总汞暴露风险.③斯皮尔曼相关性分析显示,铅锌矿区居民血液总汞和甲基汞含量分别与年龄（R=0.108,P < 0.05）和性别（R=-0.185,P < 0.05）相关,老年人较其他年龄段人群总汞暴露的风险更高,其血液总汞含量达（5.29±5.03）μg/L;男性血液甲基汞含量〔（0.24±0.32）μg/L〕高于女性〔（0.18±0.22）μg/L〕.④蒙特卡洛模型模拟结果显示,铅锌矿区和对照区育龄妇女头发甲基汞平均含量分别为（0.07±0.11）和（0.11±0.13）mg/kg,范围分别为0~11.81和0~5.74 mg/kg,其中铅锌矿区2.27%的育龄期妇女头发甲基汞含量超过发汞临界值（0.58 mg/kg）,导致IQ评分为70~70.18分范围内的约0.05%的婴儿从IQ正常转变为MMR（轻度智力低下）.⑤单区室PBPK模型预测表明,铅锌矿区和对照区居民甲基汞日均摄入量分别为（0.005±0.006）和（0.007±0.008）μg/kg,分别有0.082%和0.013%的居民甲基汞日均摄入量超过RfD（参考剂量值,0.1 μg/kg）.研究显示:铅锌矿区成年居民和0~6岁儿童血液总汞含量高于国内其他地区,男性血液甲基汞含量明显高于女性;铅锌矿区约2.27%的育龄期妇女头发甲基汞含量超过发汞临界值,可致IQ评分在70~70.18分范围内的约0.05%的婴儿从智力正常转变为MMR;铅锌矿区居民甲基汞非致癌风险高于对照区.      

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）.      

贵州省万山汞矿区地表水中不同形态汞的空间分布特点

利用两次金汞齐-冷原子荧光光谱法,对贵州省废弃汞矿山万山矿区地表水不同形态汞(活性态、溶解态、颗粒态)的含量进行测定。样品活性态汞为1.04~402 ng／L;溶解态汞为12.5~426 ng／L;颗粒态汞变化很大,最低只有1.38 ng／L,最高达4 427 ng／L。研究表明:(1)直接与矿山冶炼活动排放物炉渣接触的溪流水污染程度最高,总汞高达4.46μg／L;(2)与矿山开采活动排放的废石或贫矿石接触的溪流水污染程度较低;(3)远离汞矿开采、冶炼活动区的地表水总汞接近汞矿化带背景参考值。     

武汉城市湖泊表层底泥汞分布、风险评价及影响因素

底泥作为汞重要的"汇"及二次"源"，在湖泊系统汞生物地球化学循环中起到了重要作用。本文以武汉主要城市湖泊为研究对象，探究了表层底泥中总汞（THg）和甲基汞（MeHg）的分布特征、潜在生态风险及主要影响因素。结果表明，武汉15个城市湖泊表层底泥THg平均浓度为152±170 ng/g （24~611 ng/g），与国内其它湖泊系统相比处于较高水平；MeHg浓度为52.0±46.8 pg/g （ND~161.0 pg/g），低于其它湖泊系统。空间分布上，底泥THg浓度呈现由武汉市中心向外逐渐递减的趋势，MeHg含量并未呈现类似THg的分布趋势。潜在生态风险评价（PERI）结果显示，所有采样点位中汞潜在生态风险极高和高风险等级占比均为5.7%，且主要分布在市中心附近，说明武汉市中心附近湖泊底泥汞污染程度较重，而市中心外围湖泊底泥汞生态风险较低。相关性分析结果显示，有机质可能是影响武汉城市湖泊底泥THg分布的重要因素之一，而MeHg主要受控于无机汞的原位甲基化过程。底泥THg浓度-湖泊距市中心距离间显著的负相关关系、THg浓度-湖泊所在区GDP/人均GDP间的显著正相关关系均表明人为活动对武汉城市湖泊汞分布影响明显。     

长寿湖水库垂直剖面不同形态汞的季节变化特征及其影响因素

分别于2013年9月至2014年7月,在三峡库区长寿湖水库设置5个采样点,分季节、分层次对水样和沉积物间隙水进行了采集和分析,考察了水库水体和沉积物间隙水不同形态汞浓度及垂向分布特征,并研究了沉积物中汞向上覆水的扩散通量.结果表明,长寿湖水库水体总汞浓度平均值为(14.77±12.24)ng·L-1,总甲基汞浓度平均值为(0.41±0.47)ng·L-1.夏秋季采样点溶解态甲基汞浓度在表层下4~8 m出现峰值,随之其值降低近湖底部再次跃增.颗粒态甲基汞浓度峰值出现在表层下8~20 m而非在沉积物-水体界面处,主要与上层水体颗粒物吸附甲基汞的沉降有关.长寿湖水库垂直剖面间隙水甲基汞峰值出现在表层下16 cm和28 cm,可能硫酸盐还原细菌活动扩展到更深的区域,从而导致了沉积物深处甲基化率的提高.间隙水溶解态甲基汞在秋季和夏季向上覆水体扩散通量分别为28.2 ng·(m2·d)-1和30.0 ng·(m2·d)-1,远高于冬季3.8ng·(m2·d)-1,这与夏秋两季水温较高有关.夏季、春季水体DMe Hg浓度与DO相关关系(r=-0.482**,P0.05;r=-0.339*,P0.01),秋季和冬季不具有相关性.     

Ant colonization increased total mercury but reduced methylmercury contents in boreal mires, Northeast China

Soil macroinvertebrates as ecosystem engineers play significant, but largely ignored, roles in affecting mercury (Hg) cycle by altering soil physical-chemical properties. Ant is likely expanded into boreal mires with climate warming, however, its impacts on Hg cycle remained poorly understood. We compared total Hg (THg) and methylmercury (MeHg) contents in soils from antmounds (Lasius flavus) and the nearby ambient in a boreal mire in Northeast China. The present work seeks to unravel factors that controlling MeHg levels in case of ant appearance or absence. The average THg was 179 µg/kg in the ant mound and was 106.1 µg/kg in nearby soils, respectively. The average MeHg was 10.9 µg/kg in the ant mound and was 12.9 µg/kg in nearby soils, respectively. The ratios of MeHg to THg (%MeHg) were 7.61% in ant mounds and 16.75% in nearby soils, respectively. Ant colonization caused THg enrichment and MeHg depletion, and this change was obvious in the 10-20 cm depth soil layer where ants mainly inhabited. Spectrometry characteristics of soil dissolved organic matter (DOM) exert a stronger control than microorganisms on MeHg variation in soils. A structural equation model revealed that the molecular weight of DOM inhibited MeHg irrespective of ant presence or absence, while humification conducive to MeHg significantly in ant mound soils. Microorganisms mainly affected Hg methylation by altering the molecular weight and humification of DOM. We propose that the effects of ant colonization on MeHg rested on DOM feature variations caused by microorganisms in boreal mires.     

巨牡蛎(Crassostrea sp.)对燃煤电厂脱硫海水中汞的生物累积

研究了巨牡蛎(Crassostrea sp.)对配备烟气海水脱硫装置电厂的脱硫海水中汞(Hg)的生物累积.在电厂的排水口(实验点)和参考点分别吊养牡蛎群,定期采集样品,测定海水中的Hg浓度和牡蛎的Hg含量(均以干重计).实验点和参考点海水中的总汞(THg)浓度分别为(120.6±55.5)ng.L-1(n=5)和(2.7±1.0)ng.L-1(n=5),甲基汞(MeHg)的浓度分别为(0.30±0.44)ng.L-1(n=5)和(0.28±0.31)ng.L-1(n=5).在7 d内,实验点牡蛎体内THg含量从(138.3±14.3)ng.g-1(n=6)迅速增加到(3 012±289)ng.g-1(n=6),且在后来的34 d内,一直保持在2 935～4 490 ng.g-1的高含量水平;而参考点牡蛎对THg未见明显累积,为60.7～137.5 ng.g-1之间.暴露期间实验点牡蛎体内MeHg的含量未发生显著变化,保持在55.4～73.1 ng.g-1之间.而参考点牡蛎MeHg含量呈略微下降的趋势,但变化幅度不大,在15.6～55.6 ng.g-1之间.本研究表明,燃煤电厂排放的脱硫海水中的THg可被牡蛎迅速累积至很高的含量水平,有不容忽视的潜在风险.脱硫海水中MeHg的浓度很低,其在牡蛎体内未见明显累积;在本研究的条件下,未观测到牡蛎自身合成MeHg或将无机汞转化为MeHg.     

贵州某典型汞矿区流域水稻中总汞和甲基汞含量及暴露风险

鉴于流域尺度内水稻植株不同组织中总汞和甲基汞含量及人群进食稻米的汞暴露风险研究较少,系统采集了贵州省铜仁市受万山废弃汞矿影响的瓦屋河流域内水稻植株及对应根际土壤样品,分析水稻植株不同组织中的w(总汞)、w(甲基汞)及其影响因素,以及流域内人群食用稻米的汞暴露风险.结果表明:瓦屋河流域水稻精米中w(总汞)平均值为(14.2±7.0)μg/kg(范围为4.1～34.0 μg/kg,n=24),精米中w(甲基汞)平均值为(7.229±3.957)μg/kg(范围为1.974～17.364 μg/kg,n=24).精米中w(总汞)与水稻茎、叶中w(总汞)均呈较显著正相关(R=0.531,P＜0.01;R=0.499,P＜0.05),精米中w(甲基汞)与水稻根、茎中w(甲基汞)也均呈显著正相关(R=0.525,P＜0.01;R=0.612,P＜0.01);w(总汞)、w(甲基汞)均与土壤理化参数存在一定正相关关系,并均与距污染源距离呈负相关.根据精米中w(甲基汞)平均值,并按照US EPA(美国国家环境保护局)推荐的甲基汞日暴露量(ID)和危害指数(HI)的评估方法计算的瓦屋河流域居民甲基汞日暴露量为(0.075±0.041)μg/(kg·d),低于较为严厉的US EPA推荐的甲基汞日安全摄入量(RfD),危害指数为0.75.从平均状况来看,人体摄入该地区生产的精米相对较为安全.      

三门峡水库水体中不同形态汞的分布特征

为了解三门峡水库水体中不同形态汞的分布特征,在丰水期和枯水期对三门峡水库进行采样,分别采用冷原子荧光光谱法(CVAFS)和蒸馏-乙基化衍生-气相色谱-冷原子荧光法(GC-CVAFS)测定水样中总汞、总甲基汞、溶解态总汞和溶解态甲基汞的浓度.结果表明,三门峡水库水体中总汞、溶解态汞和颗粒态汞浓度范围分别为1.65~9.65、0.80~3.16和0.70~7.81 ng·L~(-1),符合国家地表水环境质量标准(GB 3838-2002)一类水汞浓度标准限值;总甲基汞、溶解态甲基汞和颗粒态甲基汞浓度分别为0.05~0.36、0.02~0.14和ND~0.26 ng·L~(-1).三门峡水库水体总汞和甲基汞在季节和空间分布上没有呈现出明显的变化规律.总汞和甲基汞与未受污染的天然水体差别不大,水库未受到明显的汞污染.丰、枯水期沉积物中总汞浓度分别为(92.96±10.65)ng·g~(-1)和(80.06±19.14)ng·g~(-1),甲基汞浓度分别为(0.33±0.14)ng·g~(-1)和(0.50±0.19)ng·g~(-1).较低的甲基汞浓度说明在三门峡水库汞的迁移转化过程中,甲基化作用可能并非主要的过程,这可能与水体底层溶解氧浓度较高以及沉积物中有机质浓度较低有关.     

污灌区稻田汞污染特征及健康风险评价

选择天津北排污河灌区作为研究区域,调查了土壤和水稻总汞和甲基汞的含量及分布特征,评估污灌区稻米食用汞暴露风险,并对污灌区土壤-稻米甲基汞的影响因素进行了初步分析.结果表明,1.调查的29个污灌区稻田,土壤总汞含量为(367.04 ± 129.36) μg/kg,显著高于区域土壤Hg背景值73 μg/kg,甲基汞含量为(0.87 ± 0.77) μg/kg;水稻各部位总汞含量依次为稻叶 > 稻根 > 稻茎 > 稻米,稻米总汞含量为(12.80 ± 5.14) μg/kg,甲基汞含量依次为稻米 > 稻根 > 稻茎 > 稻叶,稻米对甲基汞具有很强的富集能力,甲基汞含量为(2.09 ± 1.20) μg/kg,甲基化率均值超过10%.污灌区稻米总汞每周摄入量为0.068~1.25μg/(kg·bw),甲基汞每周摄入量为0.0095~0.49μg/(kg·bw),污灌区稻米总汞及甲基汞暴露对居民健康风险总体仍在安全阈值内,但个别汞污染较严重地块甲基汞暴露风险值得高度关注.土壤甲基汞含量仅与土壤总汞含量及黏粒含量的相关性达到显著性水平,稻米甲基汞含量与土壤总汞含量、土壤甲基汞含量、稻米总汞含量及黏粒含量的相关性达到显著性水平.     

三峡库区消落带沉积物对鱼体富集汞的影响

水体环境中的汞（Hg）容易被鱼体富集.为了研究三峡库区消落带沉积物对鱼体Hg含量的影响,采用不同Hg含量的消落带沉积物进行了为期90 d的模拟淹水实验.结果表明沉积物淹水后,水体总汞（THg）和甲基汞（MeHg）含量显著增加,鱼体肌肉中THg和MeHg含量不断增加,而内脏和头部中THg和MeHg含量前期不断增加,后期则有轻微减小的趋势.肌肉对Hg的富集量大于内脏和头部,后两者的富集量没有显著性差异.与对照组（无沉积物）相比沉积物的存在明显增加了鱼体富集Hg的量,而且当沉积物中Hg含量较高时,鱼体对Hg的富集量也显著增加.鱼体各部位THg和MeHg含量变化曲线高度相似,各部位对MeHg的富集系数（bioaccumulation factors,BCF）在1.93×10⁵~8.89×10⁵之间,对无机Hg的BCF在1.3×10³~12.8×10³之间,表明鱼体所富集的Hg形态上主要为MeHg.鱼体各部位MeHg和THg含量均为极显著相关,线性回归方程表明,在富集Hg的量中,MeHg占THg比例分别为：肌肉80.1%、内脏79.3%、头部66.7%.消落带沉积物再淹水后会发生一定程度的净甲基化现象产生MeHg,由于扩散作用使水体MeHg浓度在一段时间内升高,这导致了鱼体对Hg的富集量增加.因此对三峡库区大面积消落带可能存在的Hg污染风险不可忽视.     

Mercury accumulation and dynamics in montane forests along an elevation gradient in Southwest China

Understanding atmospheric mercury (Hg) accumulation in remote montane forests is critical to assess the Hg ecological risk to wildlife and human health. To quantify impacts of vegetation, climatic and topographic factors on Hg accumulation in montane forests, we assessed the Hg distribution and stoichiometric relations among Hg, carbon (C), and nitrogen (N) in four forest types along the elevation of Mt. Gongga. Our results show that Hg concentration in plant tissues follows the descending order of litter > leaf, bark > root > branch > bole wood, indicating the importance of atmospheric Hg uptake by foliage for Hg accumulation in plants. The foliar Hg/C (from 237.0 ± 171.4 to 56.8 ± 27.7 µg/kg) and Hg/N (from 7.5 ± 3.9 to 2.5 ± 1.2 mg/kg) both decrease along the elevation. These elevation gradients are caused by the heterogeneity of vegetation uptake of atmospheric Hg and the variation of atmospheric Hg° concentrations at different altitudes. Organic soil Hg accumulation is controlled by forest types, topographic and climatic factors, with the highest concentration in the mixed forest (244.9 ± 55.7 µg/kg) and the lowest value in the alpine forest (151.9 ± 44.5 µg/kg). Further analysis suggests that soil Hg is positively correlated to C (r² = 0.66) and N (r² = 0.57), and Hg/C and Hg/N both increase with the soil depth. These stoichiometric relations highlight the combined effects from environmental and climatic factors which mediating legacy Hg accumulation and selective Hg absorption during processes of organic soil mineralization.     

基于PMF模型及地统计法的乐安河中上游地区土壤重金属来源解析

为实现较大区域范围内土壤重金属来源贡献程度的定量化,选取江西省乐安河中上游地区表层土壤为研究对象,分析污染源样品化学组分并构建本地污染源成分谱,利用PMF（正定矩阵因子分解）模型对土壤重金属进行源解析,并结合地统计空间分析法识别各源的主要影响区域.结果表明:乐安河中上游地区土壤中w（As）、w（Hg）、w（Cd）、w（Cr）、w（Zn）、w（Cu）、w（Mn）、w（Pb）的平均值分别为21.400、0.105、0.25、73.5、88.4、56.2、577.0、49.5 mg/kg,是江西省土壤背景值平均值的1.0~1.8倍,其中,w（As）、w（Cd）、w（Cu）、w（Pb）平均值超过GB 15618-1995《土壤环境质量标准》一级标准限值.土壤重金属主要受铅锌矿冶炼源、金矿选冶源、铜矿采选源、自然源、混合源的影响.铅锌矿开采冶炼活动对洎水河左岸大部分区域土壤造成了影响,源贡献率均大于30%;金矿选冶活动目前仅影响矿区附近土壤,源贡献率最高可达94%;铜矿采选活动也使德兴铜矿周边较大区域范围土壤受到影响,源贡献率处于19%~89%之间.研究显示,构建本地源成分谱可以辅助解析验证PMF源成分谱的有效性,将PMF模型与地统计空间分析法相结合,可以进一步得到源贡献率在空间上的分布状况,对于土壤污染治理决策可提供行之有效的支撑.      

Assessing the factors impacting the bioaccessibility of mercury (Hg) in rice consumption by an in-vitro method

Mercury (Hg) in rice is drawing mounting concern since methylmercury (MeHg) was found capable of accumulating in rice. In-vitro bioaccessibility is a feasible and reliable method to assess the health effects of Hg in rice and has been utilized in a number of studies. This study was done to investigate the impact of cultivar, planting location, and cooking on the total mercury (THg) and MeHg bioaccessibility of rice, for which multiple statistical analysis methods were used to analyze the significance of their effects. The THg concentrations of rice samples taken from non-Hg contaminated areas of China were all below 15 ng/g and their MeHg concentrations were below 2 ng/g. Cooking could significantly reduce the MeHg bioaccessibility of rice because the MeHg was mainly combined with protein and the protein will be denatured during the cooking process, and then the denatured MeHg is difficult to be dissolved into the liquid phase. Indica- and japonica-type rice cultivars did not show significant differentiation in either the concentration of Hg or its bioaccessibility. However, the glutinous rice type differed significantly from the above rice types, and it showed greater bioaccessibility of THg and MeHg due to its distinct protein contents and starch properties. Planting location can affect the Hg concentration in rice and THg bioaccessibility but has a limited impact on MeHg bioaccessibility. Based on these results, two macro factors (rice cultivar, planting location) are presumed to impact Hg bioaccessibility by how they affect micro factors (i.e., Hg forms).     

太湖营养状态对沉积物中总汞和甲基汞分布特征的影响

为探讨营养状态对太湖沉积物汞的分布及其甲基化的影响,以太湖不同营养水平的湖区为研究对象,采用PSA和GC-CVAFS方法,分别测定了沉积物总汞(THg)、甲基汞(MeHg)含量;另测定了沉积物有机质含量和水体总氮、总磷浓度.结果显示,太湖表层沉积物THg含量为32.30~150.28ng/g,均值为62.94ng/g,含量高低与营养化程度一致,其垂向分布主要受到人为活动和有机质的影响;MeHg含量为0.32~1.01ng/g,均值为0.51ng/g,不同营养水平的湖湾区MeHg含量差别不大,其分布受有机质的影响,高含量富集在表层,随深度的增加逐渐降低并趋于稳定;甲基化比率比较低主要是太湖水体溶解氧含量高抑制了甲基化过程.     

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 di erent 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 g/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 g/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.     

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.     

Methylmercury and sulfate-reducing bacteria in mangrove sediments from Jiulong River Estuary, China

Estuaries are important sites for mercury (Hg) methylation, with sulfate-reducing bacteria (SRB) thought to be the main Hg methylators. Distributions of total mercury (THg) and methylmercury (MeHg) in mangrove sediment and sediment core from Jiulong River Estuary Provincial Mangrove Reserve, China were determined and the possible mechanisms of Hg methylation and their controlling factors in mangrove sediments were investigated. Microbiological and geochemical parameters were also determined. Results showed that SRB constitute a small fraction of total bacteria (TB) in both surface sediments and the profile of sediments. The content of THg, MeHg, TB, and SRB were (350 150) ng/g, (0.47 0.11) ng/g, (1.4 1011 4.1 109) cfu/g dry weight (dw), and (5.0 106 2.7 106) cfu/g dw in surficial sediments, respectively, and (240 24) ng/g, (0.30 0.15) ng/g, (1.9 1011 4.2 1010) cfu/g dw, and (1.3 106 2.0 106) cfu/g dw in sediment core, respectively. Results showed that THg, MeHg, TB, MeHg/THg, salinity and total sulfur (TS) increased with depth, but total organic matter (TOM), SRB, and pH decreased with depth. Concentrations of MeHg in sediments showed significant positive correlation with THg, salinity, TS, and MeHg/THg, and significant negative correlation with SRB, TOM, and pH. It was concluded that other microbes, rather than SRB, may also act as main Hg methylators in mangrove sediments.     

典型Pb/Zn矿区土壤重金属污染特征与Pb同位素源解析

以我国典型的铅锌矿区——湖南水口山铅锌矿区及其周围地区为研究对象,分析自然土壤(A层和C层)样品中不同重金属(Pb、Zn、Cr、Cu、Cd、Hg)的污染特征和Pb同位素组成.结果表明,受铅锌选矿和冶炼活动的影响,研究区域A层土壤明显受到重金属的污染,尤其是在中心区域(水口山矿区),土壤中Pb、Zn、Cr、Cu、Cd、Hg含量最高达3966.88、 2086.25、 135.31、 185.63、 56.15、 16.434 mg/kg;受原生地质环境的影响,C层土壤重金属含量虽然变化很大,但基本反映土壤背景值.土壤中不同重金属的潜在生态危害大小顺序为Cd>Hg>Pb>Cu>Zn=Cr.中心区域多重金属综合潜在生态危害明显高于周围区域,其34%、 33%、 11%、 22%的采样点分别属于轻微、中等、强和很强生态危害,而周围区域属于轻微、中等、强和很强生态危害的采样点比例分别为68%、 16%、 10%、 6%.与C层Pb同位素相比(²⁰⁶Pb/²⁰⁷Pb为1.168～1.246,²⁰⁸Pb/²⁰⁶Pb为2.014～2.130),由于人为Pb源的污染A层土壤中²⁰⁶Pb/²⁰⁷Pb值(1.166～1.226)低而²⁰⁸Pb/²⁰⁶Pb值(2.043～2.135)高.与铅锌选矿、冶炼废水和烟尘中Pb同位素比值对比表明,A层土壤铅污染主要来自于冶炼厂烟气粉尘的沉降.     

Predicted no-effect concentrations for mercury species and ecological risk assessment for mercury pollution in aquatic environment

Mercury (Hg) exists in different chemical forms presenting varied toxic potentials. It is necessary to explore an ecological risk assessment method for different mercury species in aquatic environment. The predicted no-effect concentrations (PNECs) for Hg(II) and methyl mercury (MeHg) in the aqueous phase, calculated using the species sensitivity distribution method and the assessment factor method, were 0.39 and 6.5 × 10^− 3 μg/L, respectively. The partition theory of Hg between sediment and aqueous phases was considered, along with PNECs for the aqueous phase to conduct an ecological risk assessment for Hg in the sediment phase. Two case studies, one in China and one in the Western Black Sea, were conducted using these PNECs. The toxicity of mercury is heavily dependent on their forms, and their potential ecological risk should be respectively evaluated on the basis of mercury species.