Distribution of arsenic between the particulate and aqueous phases in surface water from three freshwater lakes in China.

Abstract

Total arsenic (As) in suspended particulate matter (SPM) of lacustrine ecosystems has been extensively documented, but knowledge on the distribution of As between the particle and aqueous phases in freshwater lakes remains largely unknown. The present study employed a rapid method to determine the total and dissolved As and As in SPM at sites covering the entire areas of three large shallow lakes in China, e.g., Taihu, Chaohu, and Dianchi, to obtain a "representative" mean value of the As concentration in various phases. The average concentrations of total and dissolved As were below 6.0 and 3.3μg/L, respectively. Arsenic in SPM was much higher than that in waters, as ranging from 24.7 to 516μg/g. Lake Taihu exhibited extensive seasonal variation both in total and dissolved As, while little difference was observed in SPM concentration, with an average value of 54.2 and 49.3mg/L in winter and summer, respectively. Among the algae in the three lakes, Cyanophyta dominated in both cell abundance and biomass. Algae mass occupied significant parts of SPM, especially in Dianchi; the proportions of algae in the SPM fractions were measured as 10.4 and 7.1% in Taihu in winter and summer, 4.5% in Chaohu, and 53.3% in Dianchi, both in summer season. The total As in SPM had a significant positive relationship with total As in water and a high distribution coefficient (Kd) between SPM and dissolved fraction of As at all three lakes. The high proportions of Algae, especially Cyanophyta in the composition of SPM in the three large shallow lakes, might play an important role in affecting the As distribution between the aqueous and particulate phases in aquatic ecosystem.