Description:
Except for excessive nutrient input and climate warming, the rapidly rising SO42- concentration is considered as a crucial contributor to the eutrophication in shallow lakes, however, the driving process and mechanism are still far from clear. In this study, we constructed a series of microcosms with initial SO42- concentrations of 0, 30, 60, 90, 120 and 150 mg/L to simulate the rapidly SO42- increase of Lake Taihu subjected to cyanobacteria blooms. Results showed that the sulfate reduction rate was stimulated by the increase of initial SO42- concentrations and cyanobacteria-derived organic matter, with the maximal sulfate reduction rate of 39.68 mg/L∙d in the treatment of 150 mg/L SO42- concentration. During the sulfate reduction, the produced maximal ∑S2- concentration in the overlying water and acid volatile sulfate (AVS) in the sediments were 3.15 mg/L and 11.11 mg/kg, respectively, and both of them were positively correlated with initial SO42- concentrations (R2=0.97; R2=0.92). The increasing abundance of sulfate reduction bacteria (SRB) was also linearly correlated with initial SO42- concentrations (R2=0.96), ranging from 6.65×107 to 1.97×108 copies/g. However, the Fe2+ concentrations displayed a negative correlation with initial SO42- concentrations, and the final Fe2+ concentrations were 9.68, 7.07, 6.5, 5.57, 4.42 and 3.46 mg/L, respectively. As a result, the released TP in the overlying water, to promote the eutrophication, was up to 1.4 mg/L in the treatment of 150 mg/L SO42- concentration. Therefore, it is necessary to consider the effect of rapidly increasing SO42- concentrations on the release of endogenous phosphorus and the eutrophication in lakes