[Characteristics of Stable Mercury Isotopic Compositions in the Food Web of the Caohai Lake].

Caohai Plateau Wetland is a National Nature Reserve. The characteristics of stable mercury isotopic compositions in the food web were studied by comprehensively analyzing the concentrations of Hg species (MeHg, THg), C, and N, and the isotopic compositions of Hg in different aquatic organisms. The main results are as follows:all samples of the food web show mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) and a negative Hg(-0.93‰±1.32‰, =14)and positive △ Hg(0.79‰±0.76‰, =14). The Hg values are significantly positively correlated with N (=0.65, <0.05) and the Hg values also exhibit a positive correlation with N, except for (N=-1.88‰), indicating that the bioaccumulation of mercury leads to an enrichment with heavier isotopes. The △ Hg values increase with N(=0.67, <0.05). Nevertheless, the △ Hg values correlate with% MeHg (=0.58, <0.05), indicating that the increase of the MIF level in the samples with the food web might be related to% MeHg.