Constants of mercury methylation and demethylation rates in sediments and comparison of tracer and ambient mercury availability
Constants of mercury methylation and demethylation rates in sediments and comparison of tracer and ambient mercury availability
复制标题
DOI：
10.1002/etc.5620190909
复制
发表时间：
2000-09
影响因子：
4.1
通讯作者：
H. Hintelmann;Katherine Keppel‐Jones;R. D. Evans
中科院分区：
文献类型：
--
作者：
H. Hintelmann;Katherine Keppel‐Jones;R. D. Evans
建立了一种同时测定水样中汞甲基化和去甲基化速率常数的方法。将含有稳定同位素示踪剂199Hg2+和CH3202Hg+的溶液以亚环境浓度注入湖泊沉积物中。采用气相色谱分离法和电感耦合等离子体质谱法同时测定了CH3199Hg+的形成和CH3202Hg+的减少。计算了这两个过程的特定速率常数，并将其与通过监测同一样品中环境甲基汞浓度变化获得的速率常数进行了比较。无机汞示踪剂199Hg2+的甲基化速率高于环境无机汞示踪剂Hg2+，说明添加的示踪剂Hg2+比环境汞示踪剂Hg2+更容易发生转化反应。示踪剂和环境甲基汞的降解速度相似，添加的示踪剂和环境甲基汞之间没有显着差异。沉积物中甲基汞的半衰期为1.7 d，表明湖泊沉积物中甲基汞的周转迅速，持久性较低。研究了不同种类的汞在甲基化反应中的可用性。与Hg(NO3)2相比，Hg‐fulvate的可用性降低，新沉淀的HgS几乎无法获得。
A method was developed to measure mercury methylation and demethylation rate constants simultaneously in aquatic samples. Solutions containing stable isotope tracers of 199Hg2+ and CH3202Hg+ were spiked into lake sediments at subambient concentrations. The formation of CH3199Hg+ and the decrease in CH3202Hg+ were measured simultaneously in time series experiments using gas chromatographic separation and isotope‐specific detection by inductively coupled plasma mass spectrometry. Specific rate constants for the two processes were calculated and compared to rate constants obtained by monitoring changes in concentration of the ambient methylmercury in the same sample. The inorganic mercury tracer 199Hg2+ was methylated at a faster rate compared with the ambient inorganic Hg2+, which indicates that the added tracer Hg2+ is more available for transformation reaction than the ambient Hg2+. The degradation of tracer and ambient methylmercury proceeded at a similar rate, showing no significant differences between added tracer and ambient methylmercury. The calculated half‐life for methylmercury in sediments was 1.7 d, suggesting a rapid turnover and low persistence of methylmercury in lake sediments. Different Hg species were investigated regarding their availability for methylation reactions. Compared to Hg(NO3)2, Hg‐fulvate showed reduced availability and freshly precipitated HgS was hardly available.