Aquatic Ecosystem Protection Research Division, Water Science & Technology Directorate, Environment Canada, Canada Centre for Inland Waters, 867 Lakeshore Road, PO Box 5050, Burlington, Ontario, Canada L7R 4A6.
Sci Total Environ. 2012 Feb 15;417-418:189-203. doi: 10.1016/j.scitotenv.2011.12.040. Epub 2012 Jan 20.
A dated sediment core from a lake polluted with mercury (Hg), other heavy metals, and arsenic (As) from coal-burning power plants was analysed to test the hypothesis that power plant emissions have distinctive Hg isotope signatures which may be preserved in sediments but are altered by natural processes. Coal and fly ash were also analysed. The research yielded evidence for mass-dependent and mass-independent fractionation of Hg isotopes (MDF and MIF, respectively) by combustion and flue gas reactions in the power plants and natural processes in the lake. Power plant pollution and earlier pollution attributable to domestic coal burning produced a characteristic isotope signature indicative of depletion in lighter isotopes by MDF and enrichment in (199)Hg and (201)Hg by MIF, suggesting loss of isotopically light gaseous Hg(0) and reactions of Hg with free radicals at the sources of pollution; but coal and fly ash data showed that combustion imparted a different signature to the ash, corroborating chemical evidence that reactive gaseous Hg(II), not particulate Hg(II), was the principal Hg fraction deposited in the lake. Moreover, the core data imply alteration of the anthropogenic isotope signature by microbially mediated MDF and MIF, with alteration of the microbial activities themselves by toxic effects of As and metals from the emissions. Effects of metals on isotope fractionation increased with the stability constants and ligand field stabilisation energies of metal complexes, suggesting inhibition of microbial enzymes and metal binding by microbial carrier molecules. The importance of fractionation by natural (possibly microbial) processes is also indicated by depletion in (199)Hg and (201)Hg owing to MIF in sediments predating local pollution. In brief, the isotope signature of the polluted sediment is probably the net result of abiotic reactions at the sources of pollution, microbial activities in the lake, and effects of toxic pollutants on the microflora.
从一个受燃煤电厂汞（Hg）、其他重金属和砷（As）污染的湖泊中采集了一个年代久远的沉积物岩芯，以验证这样一个假设，即电厂排放的汞具有独特的同位素特征，这些特征可能在沉积物中得以保留，但会被自然过程改变。同时也对煤和飞灰进行了分析。研究结果为在电厂燃烧和烟道气反应以及湖泊中的自然过程中汞同位素的质量依赖和质量独立分馏（分别为 MDF 和 MIF）提供了证据。电厂污染以及更早的归因于家庭燃煤的污染产生了一个特征性的同位素特征，表明 MDF 导致较轻同位素的消耗，以及 MIF 导致（199）Hg 和（201）Hg 的富集，这表明同位素较轻的气态 Hg(0)的损失以及 Hg 与污染源处自由基的反应；但煤和飞灰数据表明，燃烧给灰烬赋予了一个不同的特征，这与化学证据相符，即反应性气态 Hg(II)，而不是颗粒状 Hg(II)，是主要的 Hg 部分沉积在湖泊中。此外，岩芯数据暗示人为同位素特征受到微生物介导的 MDF 和 MIF 的改变，以及排放物中的 As 和金属对微生物活性本身的毒性影响导致的改变。金属对同位素分馏的影响随着金属配合物的稳定常数和配体场稳定化能的增加而增加，这表明微生物酶的抑制和微生物载体分子对金属的结合。自然（可能是微生物）过程的分馏的重要性也由沉积物中由于 MIF 导致的（199）Hg 和（201）Hg 的消耗所表明，这些 MIF 发生在当地污染之前。简而言之，污染沉积物的同位素特征可能是污染源处的非生物反应、湖泊中的微生物活动以及有毒污染物对微生物区系的影响的综合结果。
