改性当地土壤技术修复富营养化水体综合效果研究:Ⅰ.水质改善的应急与长期效果与机制

摘要

The effect of algal bloom control and water quality improvement using modified local soil/sand induced ecological restoration technology ( MTS-IER) was studied in an enclosure in Meiliang Bay in the northern Lake Taihu from October 2010 to September 2011. Lab experiments were used to study the mechanism of long-term water quality improvement including resuspension and internal loads control at water-sediment interfaces. Field monitoring results indicated that, TN, NO3- -N, NH4+ -N, TP and PO43- -P were reduced by 66% , 57% , 60% , 93% , 92% and 98% , respectively, 30 min after treatment using MLS; and the average concentrations were reduced by 39. 83% ,48.53% ,52.30% , 18.75% and 60. 00% , respectively, within the following 11 months compared to the control area. The resuspension experiment showed that the anti-resuspension ability of modified soil and sand increased by a factor of 3 and 5 compared to unmodified soil. The sediment-water incubation experiment showed that algae flocculation followed by capping with MLS remarkably increased the ORP and DO at the sediment-water interface, which reversed the source of sediment-water flux of TP and TN into a sink and remarkably reduced the flux of PO43- -P and NH4+ -N from sediment to water column. The results suggested that, after nutrients were quickly removed from the waler by flocculating the algal blooms, it is possible to physically reduce the resuspension of the algae floes and chemically block the release of nutrients from the sediment by MLS capping. The sustainable water quality improvement and reduction of algal bloom recruitment can be achieved when the buried algae banks arc decomposed and absorbed by the restoration of submerged vegetal ions in shallow waters, which is triggered by the MLS-IER technology.%2010年10月-2011年9月在太湖梅梁湾围隔内研究了改性当地土壤絮凝除藻及其对水质改善的应急和长期效果,并结合室内实验研究了该技术防控底泥再悬浮和减少底泥二次污染的长效机制.现场围隔实验结果表明,改性当地土壤除藻30 min后,TN、NO3--N、NH4+-N、TP、PO43--P和Chl.a的去除率分别为66％、57％、60％、93％、92％和98％；长期监测结果表明,与对照区域相比,围隔内的TN、NH4+-N、NO3--N、TP和PO43--P在处理后11个月内的平均值分别降低了39.83％、52.30％、48.53％、18.75％和60.00％.室内再悬浮实验结果表明,改性土壤和沙子抗再悬浮能力较未改性土壤分别提高了3和5倍.室内柱培养结果表明改性土壤絮凝除藻和沙土覆盖相结合可有效提高表层沉积物-水界面的氧化还原电位和溶解氧,使沉积物向水体的TP和TN通量从源逆转成汇,PO43--P和NH3+-N通量大幅度降低.改性土壤技术在利用絮凝除藻快速改善水质后,可通过改性沙/土分层底泥调控分别达到对藻絮体再悬浮的物理控制和营养盐再释放的化学控制,通过将亚表层底泥中的藻细胞分解并被沉水植物根系吸收,可实现对底泥中水华蓝藻复苏和水体富营养化的长效生态控制.