Zhong Huan, Wang Wen-Xiong
Department of Biology, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.
Environ Toxicol Chem. 2009 Sep;28(9):1851-7. doi: 10.1897/08-539.1.
To investigate the roles of different sulfur (S) species in controlling the partitioning and bioavailability of inorganic mercury (Hg) in anoxic sediments, we examined the differential binding of Hg with three key S species in anoxic sediment (mackinawite [FeS], pyrite [FeS2], and S(2-)) and then quantified their extraction by the gut juice of deposit-feeding sipunculans Sipunculus nudus. A sequential extraction method was simultaneously used to distinguish Hg sorption with different sediment components. All three S-containing sediment components could lead to a high binding of Hg in sediments, but most Hg was sorbed with FeS or FeS2 instead of formation of Hg sulfide despite the presence of S(2-) or humic acid. The gut juice extraction was relatively low and constant whenever FeS and FeS2 were in the sediment, indicating that both FeS and FeS2 controlled the Hg gut juice extraction and thus bioavailability. Mercury sorbed with FeS2 had higher gut juice extraction than that with FeS, while Hg sulfide was not extracted, strongly suggesting that Hg sorbed with FeS2 was more bioavailable than that with other S species. Mercury sorbed with FeS had very low bioavailability to sipunculans at a low Hg:S ratio in the sediment but was more bioavailable with increasing Hg:S ratio up to a maximum (approximately 1:10, mole based). The present study showed that different S species (FeS, FeS2) and Hg:S ratios significantly affected the binding and bioavailability of Hg in anoxic sediments.
为了研究不同硫（S）形态在控制缺氧沉积物中无机汞（Hg）的分配和生物有效性方面的作用，我们研究了缺氧沉积物中汞与三种关键硫形态（硫铁矿[FeS]、黄铁矿[FeS₂]和S²⁻）的差异结合，然后通过沉积食性星虫纲动物裸体方格星虫的肠液对其萃取量进行了定量分析。同时采用连续萃取法来区分汞与不同沉积物组分的吸附情况。所有三种含硫沉积物组分都能导致沉积物中汞的高结合，但尽管存在S²⁻或腐殖酸，大部分汞还是吸附在硫铁矿或黄铁矿上，而不是形成硫化汞。只要沉积物中存在硫铁矿和黄铁矿，肠液萃取量就相对较低且恒定，这表明硫铁矿和黄铁矿都控制着汞的肠液萃取量，进而控制着汞的生物有效性。与硫铁矿吸附的汞相比，与黄铁矿吸附的汞具有更高的肠液萃取量，而硫化汞未被萃取，这强烈表明与黄铁矿吸附的汞比与其他硫形态吸附的汞具有更高的生物有效性。在沉积物中汞与硫的比例较低时，与硫铁矿吸附的汞对星虫的生物有效性非常低，但随着汞与硫的比例增加至最大值（约1:10，摩尔比），其生物有效性会提高。本研究表明，不同的硫形态（硫铁矿、黄铁矿）和汞与硫的比例显著影响缺氧沉积物中汞的结合和生物有效性。
