Methylated bismuth in the environment

Biomethylation of metals and metalloids of Group 14 and 15 metals such as tin, lead and arsenic takes place in the environment, but information about methylated bismuth compounds is rather limited, although bismuth compounds are used widely in alloys, cosmetics and pharmaceutical products. Cryotrapping gas chromatography and hydride generation gas chromatography coupled with an ICP–MS as a bismuth-selective detector were used to determine volatile bismuth compounds in landfill and in sewage gas, as well as non-volatile methylated compounds in water and sediment samples. One volatile bismuth compound could be determined in gaseous samples; it was identified as Me3Bi (TMB) by element-specific detection (ICP-MS, m/z 209), matching the retention time with a TMB standard. The molecular structure was recently confirmed by gas-chromatographic fractionation with MS–ion trap detection (electron impact). Among other volatile metal compounds, TMB is a major component in the gases of sewage sludge digesters: concentrations of up to 25 µg m−3 have been measured at eight sewage treatment plants. The concentration in landfill gas was approximately one order of magnitude lower. In laboratory experiments, fermentors containing an anaerobic culture from a clean pond sludge were mixed with contaminated soil from four different industrial areas. After an incubation time of two weeks at 30 °C in the dark, TMB was detected in the headspace of all the samples. The volatilization rate of bismuth did not correlate with the total amount of bismuth in the sediments or with the available fraction after acid digestion following hydride generation. Some evidence was obtained for the occurrence of methylated bismuth compounds in water samples and in sediments. Copyright © 1999 John Wiley & Sons, Ltd.