Rapidly increasing sulfate concentration: a hidden promoter of eutrophication in shallow lakes

[摘要] Except for excessive nutrient input and climate warming, the rapidly risingSO 4 2 - concentration is considered as a crucial contributor to theeutrophication in shallow lakes; however, the driving process and mechanismare still far from clear. In this study, we constructed a series ofmicrocosms with initial SO 4 2 - concentrations of 0, 30, 60, 90, 120,and 150 mg L −1 to simulate the rapid SO 4 2 - increase in Lake Taihu, China,subjected to cyanobacteria blooms. Results showed that the sulfate reductionrate was stimulated by the increase in initial SO 4 2 - concentrations and cyanobacteria-derived organic matter, with the maximalsulfate reduction rate of 39.68 mg (L d) −1 in the treatment of 150 mg L −1 SO 4 2 - concentration. During the sulfate reduction, theproduced maximal ∑ S 2− concentration in the overlying water andacid volatile sulfate (AVS) in the sediments were 3.15 mg L −1 and 11.11 mg kg −1 ,respectively, and both of them were positively correlated with initialSO 4 2 - concentrations ( R 2 =0.97 ; R 2 = 0.92). Theincreasing abundance of sulfate reduction bacteria (SRB) was also linearlycorrelated with initial SO 4 2 - concentrations ( R 2 =0.96 ),ranging from 6.65×10 7 to 1.97×10 8  copies g −1 .However, the Fe 2+ concentrations displayed a negative correlation withinitial SO 4 2 - concentrations, and the final Fe 2+ concentrations were 9.68, 7.07, 6.5, 5.57, 4.42, and 3.46 mg L −1 , respectively.As a result, the released total phosphorus (TP) in the overlying water, to promote theeutrophication, was up to 1.4 mg L −1 in the treatment of 150 mg L −1 SO 4 2 - concentration. Therefore, it is necessary to consider theeffect of rapidly increasing SO 4 2 - concentrations on the releaseof endogenous phosphorus and the eutrophication in lakes.

[学科分类] 大气科学