The influence of humic substances on the speciation and bioavailability of dissolved mercury and methylmercury, measured as uptake by Chaoborus larvae and loss by volatilization.

摘要: The influence of dissolved humic substances (HS) on the bioavailability inorganic and methyl mercury (Hg) was quantified by measuring direct uptake 203Hg in Chaoborus larvae using laboratory microcosms containing artificial freshwater. animals were exposed individually triplicate aquaria at 10 different concentrations HS covering whole range found natural freshwaters (0–110 mg C l−1). Mercury-203 monitored repeatedly same individuals their ambient water during up to days. Near-steady state Hg usually reached within 5 bioconcentration factor (BCF, only) for absence 0.55±0.09 (S.E.) ml individual−1 5.3±0.7 Hg, thus showing a 10-fold difference. Normalizing organic carbon content yields BCFOC 2.8±0.4×103 (gC)−1 2.7±0.3×104 Hg. both decreased markedly with increasing concentration HS. For decrease most pronounced below 0.2 l−1. relationship between log([HS]) sigmoid, reduction >90% when from 1 50 Similar patterns observed losses phase, mainly through volatilization. These results have implications biouptake abiotic cycling ecosystems suggest that is bound matter freshwaters, whereas only waters. Assuming free aqueous taken organisms, rather simple methodology employed here can be used estimating distribution coefficients (KOC) water. In this study, KOC values 2.5±0.7 (S.E.)×107 1.5±0.6×105 Values similar magnitude derived supporting assumption an immobilization strong negative freshwater suggests high levels often fish lakes boreal forest zone cannot explained alone phase into biota low trophic levels.