湖滨带氧化还原环境的时空变化及其环境效应

在太湖梅梁湾,沿开阔水体至湖滨带方向,对植被型湖滨带(A区)、裸露型湖滨带(B区)和开阔水体(D区)水体中DO和水/沉积物Eh进行为期1a的现场观测.结果发现,梅梁湾水体DO时空变化明显.B区和D区水体中DO常年饱和,而A区DO浓度较低(年均(5.5±1.7)mg·L-1).在植物生长季,从开阔水体至湖滨植被区溶解氧浓度从12.7 mg·L-1降到4.5 mg·L-1;在非植物生长季则从9.7 mg·L-1降到6.2mg·L-1.湖滨带水体Eh在150 mV左右波动,空间变化趋势与溶解氧变化同步.沉积物Eh也表现出明显的时空变化,在植物生长季,各区沉积物均处于较强的还原状态(-158～-101 mV);而在非植物生长季,由开阔水体向植被型湖滨带Eh逐渐升高.在沉积物的垂直剖面上,开阔水体Eh自表层沉积物向下逐渐降低,而在A区的植被覆盖区则是先降低,大概在5 cm深处开始逐渐升高,于20 cm深左右达到峰值.根据上述植被型湖滨带氧化还原环境的特点,可以推知进行湖滨带生态修复,有利于去除湖泊氮污染.

Spatio-temporal variation of redox condition in the littoral area and its environmental effects

In-situ DO and Eh in the macrophyte-covered (A) and non-macrophyte-covered (B) littoral zones and the pelagic zone (D) were measured along the gradient from the open water to the littoral area for one year. The results showed that strong spatio-temporal variation of DO occurred in Meiliang Bay. In B and D zones, DO was all-year saturated, while DO was relatively low in A zone (annually (5.5  1.7) mg  L-1 ). DO decreased in the water column from the open water to the macrophyte-covered area (12.7 mg L-1 to 4.5 mg L-1, 9.7 mg L-1 to 6.2 mg L-1, in the growing and non-growing seasons, respectively).The water-column Eh was about 150 mV and its spatial variation was similar with DO. Eh in the sediment also distinctively displayed spatio-temporal variation. In the growing season, the sediment in every zone was in a strong reductive state(-158 ~ -101 mV). In the non-growing season, Eh increased gradually from D to A zone. In the vertical section of sediment, Eh decreased gradually from the top to the bottom sediment in D zone, while in A zone, firstly, Eh decreased, at 5 cm depth, Eh increased and the maximum occurred at 20 cm depth. These results indicated restoration of littoral zones could remove large amounts of nitrogen.