乌梁素海水体富营养化原位生态修复实验及效果分析

为探讨原位生态修复技术对乌梁素海水体富营养化的治理效果，在乌梁素海农田排水入湖口作业区用双层防水围隔建立了实验示范区，测定了水体中氮磷质量浓度和底泥中氮磷质量分数；在室内进行模拟实验，研究了溶解氧(DO)和pH值变化下柱状底泥营养盐的静态释放规律。室外实验结果表明：示范区水体中总氮(TN) 和总磷(TP)质量浓度显著低于对照区(P<0.001)，削减率分别为66%和68%，水体平均TN质量浓度为0.99 mg·L⁻¹，TP质量浓度为0.11 mg·L⁻¹；就水质年度变化而言，5月份水体TN和TP质量浓度相对较高，随着水生植物生长，其质量浓度显著降低，11月达到最低值，翌年1月，其值有所回升；实验示范区底泥中的平均TN和TP质量分数分别为1.43 g·kg⁻¹和0.43 g·kg⁻¹，显著低于对照区的数值(P<0.01)，削减率分别为16% 和28%。室内模拟实验结果表明：当DO质量浓度低于2.0 mg·L⁻¹时，底泥中磷的释放速度较快；当DO质量浓度高于2.0 mg·L⁻¹时，随着pH值的增加，底泥中磷的释放速率显著增加(P<0.01)；在厌氧状态下，pH值对底泥氮释放影响较小；在好氧和缺氧状态下，底泥中氮的释放速率显著增加后又下降；DO和pH值对底泥氮磷释放有很强的协同作用。综上所述，原位生态修复技术可显著降低水体和底泥中氮磷营养盐质量浓度，达到净化水质，减缓内源污染的目的，有望成为治理乌梁素海富营养化的一种有效措施。

Experiment study and effect analysis of in situ ecological restoration for eutrophication in Wuliangsu Lake,China

In order to explore the effect of in situ ecological restoration technology on the eutrophication control of Wuliangsu Lake, an experimental demonstration area and a double-layer waterproof enclosure were established in the operation area of farmland drainage into the entrance of Wuliangsu Lake, and the mass concentrations of nitrogen and phosphorus in the water body and sediment were measured. A simulation experiment was set up in the laboratory to study the static release law of nutrients in columnar sediments with the changes of dissolved oxygen (DO) and pH. The outdoor experiment results showed that the mass concentrations of total nitrogen (TN) and total phosphorus (TP) in the water body of the demonstration area were significantly lower than those of the control area (P<0.001), their reduction rates were 66% and 68%, respectively, and their average mass concentrations were 0.99 mg·L−1 and 0.11 mg·L−1, respectively; In terms of annual change in water quality, the mass concentrations of TN and TP in the water body were relatively high in May, then decreased significantly with the growth of aquatic plants, reached the lowest values in November, and rose again the following January. the average mass fractions of TN and TP in the sediments of the experimental demonstration area were 1.43 g·kg−1 and 0.43 g·kg−1, respectively, which were significantly lower than the values in the control area (P<0.01), their reduction rates were 16% and 28%, respectively. The results of laboratory simulation experiments showed that: when the DO concentration was lower than 2.0 mg·L−1, the release rate of phosphorus in the sediment was faster; when DO concentration was higher than 2.0 mg·L−1, the release rate of phosphorus in the sediment increased significantly with the increase of pH value (P<0.01). Under anaerobic conditions, pH value had slight effect on nitrogen release from sediment. Under aerobic and anoxic conditions, the release rate of nitrogen in the sediment increased significantly at first, and then decreased. DO and pH had a strong synergistic effect on the release of nitrogen and phosphorus in the sediment. To sum up, in situ ecological restoration technology can significantly reduce the concentrations of nitrogen and phosphorus nutrients in water and sediment, achieve the purpose of purifying water quality and slowing down endogenous pollution, and is expected to become an effective measure to control the eutrophication of Wuliangsu Lake, China.