Dynamics of reactive sulfide and its control on metal bioavailability and toxicity in metal-polluted sediments from Lake Taihu, China.

This study was conducted to elucidate the vertical and seasonal distribution of acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) in sediment cores of metal-polluted areas of Lake Taihu, China. The concentrations of AVS in sediments were more dynamic than the SEM values, which were higher in warmer seasons. Two types of AVS profiles were identified in the studied area. Generally, the AVS levels increased at a certain depth (6-18 cm), below which they decreased, except for two sites during summer. Very high concentrations of AVS were observed at these two sites during summer, and its concentrations decreased almost exponentially with increased depth. The higher content of AVS near surface sediments in summer at these two sites was attributed to a high input of organic matter resulting from dead algal deposits. The SEM contents decreased with depth and remained almost constant with season. Metal toxicity in the sediment cores was assessed on the basis of three models: ΣSEM - AVS, ΣSEM/AVS, and ΣSEM - AVS/f(OC), and the results showed that toxicity occurred in the surface sediment interval (0-1 cm) at one site during winter.