BIOCONCENTRATION OF INORGANIC AND ORGANIC THALLIUM BY FRESHWATER PHYTOPLANKTON

摘要

Uptake of inorganic Tl(Ⅰ) and dimethylthallium, (CH_3)_2Tl~+, by Chlorella spp. (Chlorophyta) and the diatom Stephan-odiscus hantzschii (Heterokontophyta) were measured using radio-tracer techniques in water from Lakes Erie and Superior (North America). Uptake of both Tl(Ⅰ) and dimethylthallium was bioactive. Uptake of [~(204)Tl]-Tl(Ⅰ) was greater in Lake Superior water than in Lake Erie water due to the. greater K content in Lake Erie that inhibits Tl(Ⅰ) uptake by phytoplankton but not that of [~(204)Tl]-dimethylthallium. Volume-based bioconcentration factors for Tl(Ⅰ) after 72 h of exposure were 5 x 10~4 and 1.1 x 10~4 for Chlorella sp. and S. hantzschii; for dimethylthallium they were 7.8 x 10~2 and 8.3 x 10~3. Both Tl(Ⅰ) and Tl(Ⅲ) were concentrated similarly by Chlorella spp. These results suggest that chlorophytes, but not diatoms, accumulate Tl(Ⅰ) to a greater extent than dimethylthallium. Greater bioaccumulation factors of inorganic Tl are possible in waters containing low amounts of K~+; water quality guidelines seeking to protect biota from deleterious effects of Tl should consider the role of K.