Biomethylation of arsenic in an arsenic-rich freshwater environment

Arsenic circulation in an arsenic-rich freshwater ecosystem was elucidated to detect arsenic species in the river water and in biological samples living in the freshwater environment, Water-soluble arsenic compounds in biological samples were extracted with 70% methanol, Samples containing arsenic compounds in the extracts were treated with 2 mol dm(-3) of sodium hydroxide and reduced,vith sodium borohydride, The detection of arsenic species was accomplished using a hydride generation/cold trap/cryofocus/gas chromatography-mass spectrometry (HG/CT/CF/GC-MS) system, The major arsenic species in the river water, freshwater algae and fish are inorganic arsenic, dimethylarsenic and trimethylarsenic compounds, respectively. Trimethylarsenic compounds are also detected in aquatic macro-invertebrates, The freshwater unicellular alga Chlorella vulgaris, in a growth medium containing arsenate, accumulated arsenic and converted it to a dimethylarsenic compound, The water flea Daphnia magna, which was fed on arsenic-containing algae, converted it to a trimethylarsenic species. (C) 1997 by John Wiley & Sons, Ltd.