Effects of sediment capping to eliminate simulated alage-caused black bloom in eutrophic lakes

Abstract

湖泛的发生与湖泊底部氧化还原条件和致黑致臭物充足供给直接相关.利用黄土和细沙对太湖湖泛易发区(月亮湾)底泥进行覆盖,模拟在湖泛可形成条件下,底泥-水体系及其界面主要物化性质与感官变化过程.结果表明:0.5cm黄土和1.0cm细沙的覆盖,从水色和嗅味半定量角度达到了对湖泛黑臭的控制,与对照组相比,覆盖组底泥间隙水中主要致黑物Fe²⁺浓度仅为对照组的1/3,主要致臭物甲硫醇和二甲基三硫醚等浓度则不到50%.进一步分析底部水体和底泥性质发现:经覆盖处理底部水体的溶解氧浓度提高近1倍,氧化还原电位基本处于250 mV以上水平,覆盖层1cm左右表层氧化还原电位和pH均远高于对照底泥.以黄土为主的底泥覆盖,主要因阻隔了下层底泥中物质迁移供给和对厌氧微生物参与的控制,以及黄土本身性质对湖底物化环境的影响等,在藻体大量聚集和死亡的水柱环境中,较好地阻止了致黑致臭物的形成,从而较有效控制湖泛的发生.;The occurrence of black bloom is directly related to adequate supply of odor and black substance and redox conditions at the bottom of lakes. Capping with losses and sand was conducted with the sediment from Yueliang Bay, which was heavily polluted and suffered from black blooms in the past years, to investigate the efficiency of black bloom control. The main characteristics of sediment-water system and sensory change process were analyzed. The results shows that capping with losses (0.5cm) and sand (1cm) control the formation of black bloom, from the perspective of visual and olfactory results (semi-quantitative). The main black substance (Fe²⁺) and odor substance (methanethiol and dimethyl trisulfide), in the pore-water of capping sediments was only 1/3 and 1/2 of the control cores, DO concentration and Eh of the bottom water was enhanced up to 100% and to 250 mV, respectively. Eh and pH of the surface capping sediment was also higher than uncapping control cores. Overall, the integrated capping system could eliminate the diffusion of nutrients from sediment and anaerobic microorganisms in the water, block the formation of taste and odors in the water, and prevent the occurrence of black bloom.