Thallium Distribution in Sediments from the Pearl River Basin, China

Thallium (Tl) is a rare element of high toxicity Sediments sampled in three representative locations near industries utilizing Tl containing raw materials from the Pearl River Basin China were analyzed for then total Tl contents and the Tl contents in four sequentially extracted fractions (i e weak acid exchangeable reducible oxidizable and residual fraction) The results reveal that the total Tl contents (1 25-19 1 mu g/g) in the studied sediments were slightly high to quite high compared with those in the Chinese background sediments This indicates the apparent Tl contamination of the investigated sediments However with respect to the chemical fractions Tl is mainly associated with the residual fraction (>60%) of the sediments especially of those from the mining area of Tl bearing pyrite minerals indicating the relatively low mobility and low bioavailability of Tl in these sediments This obviously contrasts with the previous findings that Tl is mainly entrapped in the first three labile fractions of the contaminated samples Possible reasons were given for the dominating association of Tl with the residual fraction (>95%) of the mining area sediments The significant role of certain K-containing silicates or minerals of these sediments on retaining Tl in the residual fraction discovered by this study provides a special field of research opportunity for the Tl containing wastewater treatment