小浪底水库鱼体和沉积物中汞稳定同位素组成特征

Characteristics of stable mercury isotopic compositions in fish and sediments from Xiaolangdi Reservoir

使用多接收器电感耦合等离子体质谱仪(MC-ICP-MS)测定了小浪底水库鱼体和沉积物中汞同位素的组成.结果显示,小浪底水库鱼体具有偏负的δ^(202)Hg和偏正的Δ^(199)Hg(δ^(202)Hg:-0.26‰±0.30‰;Δ^(199)Hg:0.79‰±0.08‰),而沉积物比鱼体具有更加偏负的δ^(202)Hg和趋近于0值的Δ^(199)Hg(δ^(202)Hg:-1.48‰±0.38‰;Δ^(199)Hg:0.01‰±0.02‰).与以往的研究相比,小浪底水库鱼体内汞同位素特征与淡水水库区域鱼体中类似,而Δ^(199)Hg/Δ^(201)Hg的比值为1.22,表明小浪底水库鱼体内汞的非质量分馏主要是甲基汞的光化学降解产生的;沉积物的同位素特征表明其受到了人为源排放的影响.鱼体内δ15N数据表明在营养转移的过程中会发生质量分馏,但不会发生非质量分馏.

The isotopic compositions of mercury（Hg） in fish and sediment samples collected from the Xiaolangdi Reservoir, Henan province, were determined using multi-collector inductively coupled plasma mass spectrometry（MC-ICP-MS）. Negative δ^（202）Hg（-0.26‰±0.30‰） and positiveΔ^（199）Hg（0. 79‰ ± 0. 08‰） observed in fish samples are similar to those in fish species from freshwater reservoirs reported in previous studies. The slope of Δ^（199）Hg / Δ^（201）Hg in fish was 1. 22,indicating the mass independent fractionation in fish from the Xiaolangdi Reservoir subject to the photodegradation of monomethylmercury. Negative δ^（202）Hg（-1.48‰±0.38‰） and near-zero Δ^（199）Hg（0.01‰±0.02‰） in sediments indicate the influence of anthropogenic emission. The relationships between mercury isotopic compositions and δ15N in fish indicate that the mass-dependent fractionation occured during trophic transfer,while mass-independent fractionation was absent during this process.