甲基汞的大气-水-土壤界面交换通量

通过模拟实验和野外实测,对甲基汞在大气－水和大气－土壤的界面交换进行了初步研究．结果表明,甲基汞释放通量与水中的甲基汞浓度有关,水－气体系中甲基汞释放通量大于水－土－气体系中甲基汞释放通量;甲基汞在大气－土壤界面的释放通量为０．２１～３．０９ｎｇ·ｍ^-2·ｈ^-1;在大气－水界面的释放通量为０．１４～０．７９ｎｇ·ｍ^-2·ｈ^-1．     

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.     

春季胶州湾海水汞的形态研究

于2010-04对胶州湾进行定点连续采样,采用现场和室内分离测定的方法,分析了海水中汞的形态及其日变化特征,以进一步认识汞在近海环境中的归宿和环境效应.结果表明,胶州湾表层海水中溶解态元素汞(DEM)浓度为97.5 pg.L-1(38.2～156 pg.L-1),最高值和最低值分别出现在13:00和17:30,主要受潮汐和光照的影响.DEM含量随深度的增加而下降,表层海水DEM主要来源于Hg(Ⅱ)的光致还原.活性汞(RHg)、溶解态汞(DHg)浓度分别为7.94 ng.L-1(4.39～19.3 ng.L-1)和13.9 ng.L-1(7.32～49.1 ng.L-1),均在13:00出现最大值,主要是受潮汐带来污染较重的海水的影响.活性汞和溶解态汞浓度随水深变化的趋势相似,受到光照和水温的影响,表层海水活性汞占溶解态汞的比例最大.海水中活性汞平均占溶解态汞的62%,具有相对较高的活性和生物可利用性,为DEM的形成提供了条件.甲基汞(MeHg)浓度较低,平均为0.30 ng.L-1,部分未检出.     

低温热解技术修复不同类型汞污染土壤中甲基汞变化的研究

低温热解技术是修复汞污染土壤的有效方法之一,对高浓度汞污染土壤除汞效率可达90%以上,但对甲基汞(MeHg)的去除效果目前还缺少研究。本研究以化工汞污染和汞矿污染类型土壤为研究对象,研究低温热解修复前后土壤性质、总汞(THg)、汞的形态分布和MeHg等的变化及其影响情况。研究表明,化工污染区和汞矿污染区土壤MeHg去除率分别在99. 65%和90. 96%左右,THg去除率分别在94. 35%和95. 40%左右;高浓度汞污染土壤中汞的形态分布以残渣态汞和有机结合态汞为主,经低温热解修复后化工污染区和汞矿污染区土壤中有机结合态汞分别降低96. 62%和92. 05%,残渣态汞分别降低93. 08%和96. 79%;有机质含量高的稻田土壤具有较强的汞甲基化能力,其土壤MeHg含量化工污染区(56. 47±2. 65μg/kg)>汞矿污染区(3. 98±0. 42μg/kg)。     

三峡库区典型农田小流域水体汞的时空分布特征

以三峡库区典型农田小流域——重庆涪陵王家沟为对象,分别于2012年11月~2013年9月对流域内不同类型水体总汞(THg)和总甲基汞(TMeHg)含量进行为期1 a的监测,探讨汞在农田流域水体中的时空分布特征.结果表明,流域内水体THg、TMeHg浓度范围分别为1.12~64.04 ng·L-1、0(未检出)~4.24 ng·L-1,均值分别为(13.54±10.55)ng·L-1、(0.22±0.42)ng·L-1,各类型水体THg均以颗粒态为主,雨水和池塘水TMeHg以颗粒态为主,井水和沟渠水则相反.在空间分布上,THg表现为雨水最高,池塘次之,井水最低,W2井相较于其他井THg浓度最高,各沟渠点水体THg浓度差异不大;TMeHg表现为沟渠水最高,池塘次之,井水最低,井水TMeHg浓度下游大于上游,各沟渠点水体TMeHg浓度差异大,甲基化率为沟渠水>池塘水>井水>雨水.在时间变化上,各类型水体THg浓度均表现为冷季高于暖季,TMeHg浓度则因水体类型而异.综合分析发现雨水是流域内汞的重要来源;农田流域颗粒物的迁移是汞、甲基汞迁移的主要途径,地表径流是影响流域对水库汞负荷贡献量的重要因素.     

蓟运河水中甲基汞形态分布研究

以受汞污染的蓟运河水为对象,用化学平衡模拟方法研究了甲基汞不同形态的分布规律,运用IECWDI计算水体系化学平衡程序,收集蓟运河水九种金属离子、十种配体数据,考虑了72种络合物物种,25种可能生成的固体和两个氧化还原体系,计算中需用的甲基汞与黄腐酸络合物常数,建立了溶剂萃取法进行测定。最后计算了盐度、pH、pE等对形态分布的影响。     

三峡水库消落带植物汞的分布特征

以三峡库区重庆段忠县石宝寨、涪陵珍溪和开县汉丰湖消落带为主要研究地点,调查并采集了植物样品,分析样品总汞和甲基汞,探讨三峡水库消落带植物汞的分布特征及植物汞库存量.结果表明,调查区域消落带植物总汞含量在(1.62±0.57)~(49.42±3.93)μg·kg-1范围,植物各部位总汞的含量呈根叶茎的趋势分布;植物甲基汞含量在(15.27±7.09)~(1 974.67±946.10)ng·kg-1范围,植物根部甲基汞含量高于茎和叶.同类植物中,开县汉丰湖消落带植物总汞和甲基汞含量均较忠县石宝寨、涪陵珍溪镇消落带植物略高;不同高程植物总汞及甲基汞储存量存在差异,145~150、150~160、160~170和170~175 m高程的植物总汞储存量分别为145.3、166.4、124.3和88.2 mg·hm-2,甲基汞储存量分别为1.9、2.7、3.6和3.2 mg·hm-2.消落带优势种植物对总汞的富集能力相对较弱(BAF1),而对甲基汞的富集能力相对较强(BAF1).     

甲基汞和腐殖质在污泥堆肥过程中的变化特征及其相互关系

好氧堆肥-土地利用是实现污泥资源化处置的主要方式,但污泥中重金属的环境健康风险是限制污泥土地利用的重要因素。通过观测北方某工程规模的污泥好氧堆肥过程汞、甲基汞的变化,并基于三维荧光光谱区域积分分析,研究好氧堆肥过程甲基汞的变化特征及其与有机物中腐殖质变化关系。结果表明,堆肥前后,汞与甲基汞质量分数未发生明显变化,但通过质量衡算发现,堆肥结束后堆体中汞总量从(272.56±25.71) g下降到(211.10±12.97) g,出现22.5%的汞散失,而甲基汞质量从0.37 g下降至0.28 g,24.3%的甲基汞可能发生去甲基化而形态转变。在堆肥过程中,甲基汞质量与荧光区域Ⅲ（富里酸）体积积分呈显著负相关(r=−0.897,p<0.05),与荧光区域Ⅳ（微生物代谢副产物）体积积分呈显著正相关(r=0.933,p<0.01)。基于堆肥过程甲基汞和汞质量的动态变化,在堆肥前10 d的有机物快速腐熟化阶段发生了甲基汞的去甲基化,而后随好氧堆肥过程翻堆、曝气发生了汞的蒸发散失。本研究结果可为评价污泥好氧堆肥后对汞、甲基汞健康风险提供参考。     

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.     

Response of Mercury Contamination in Fish to Decreased Aqueous Concentrations and Loading of Inorganic Mercury in a Small Stream

Approximately 250 000 kg of mercury was lost towater and soils at the U.S. Dept. of Energy Y-12 Plantin Oak Ridge, Tennessee in the 1950s and early 1960s. A creek originating within the plant receivedcontinuous inputs of waterborne mercury, predominantlyas dissolved inorganic mercury, from groundwater,streambed contamination, and sump and process waterdischarges to the contaminated storm sewer network.These produce aqueous total mercury concentrations of1–2 g L^-1 in the upper reaches of the stream,decreasing to about 0.1–0.2 g L^-1 in its lowerreaches. A program to reduce mercury concentrationsin the creek identified specific sources (buildingsumps, contaminated springwater seeps, foundationdrains, and contaminated piping) and rerouted wateraround contaminated portions of the drain system orcollected and treated mercury-contaminated waterbefore discharging it. As a result, waterbornemercury concentrations in the creek and total mercuryloading were reduced from 1.8 g L^-1 to0.6 g L^-1 and 100 to 20 g d^-1, respectively, in the last 5 yr.Mean mercury concentrations in fish nearest sourceareas in the creek headwaters decreased at roughly thesame rate as waterborne total mercury concentrationsover the past five years, but at the facility boundarydownstream the decline in mercury bioaccumulation wasmuch less. At sites 5–15 km farther downstream, nodecrease was evident. Dissolved methylmercury tendedto increase with distance downstream in a patterninverse to that noted for its dissolved inorganicmercury precursor.Improvements in water quality and modification ofweirs to allow the passage of fish have resulted inthe establishment of large populations of fish inmercury-contaminated headwater areas previously devoidof fish. It may be that the accumulation, retention,and eventual downstream transport of this reservoir ofbiologically incorporated methylmercury has acted tobuffer against expected reductions in mercury in fishat downstream sites.