Seasonal and vertical distribution of nitrogen and phosphorus in the sediment under different ecological restoration measures in the West Lake Wuli,Lake Taihu

Abstract

以太湖西五里湖为研究对象,研究了生态修复工程实施两年后,疏浚区、疏浚并水生植被重建示范区、退渔还湖区及对照区沉积物中氮、磷形态的季节变化及垂直分布特征,同时分析了各区上覆水的氮磷含量.结果表明:生态修复措施的实施对沉积物中氯磷形态分布及上覆水的氮磷含量影响显著.示范区和退渔还湖区水体中氮磷含量较低;沉积物中不同磷形态的垂直分布变化较复杂;疏浚基础上进行的水生植被重建对Lab-P、Al-P、Fe-P的吸收作用显著,对Ca-P、Org-P的影响较小;退渔还湖区沉积物磷形态以Ca-P、Org-P为主,Fe-P所占比例较低,与疏浚区不同.生态修复措施对沉积物中TN的影响较小;示范区NH₄⁺-N含量在秋季突增,可能与植物残体形成的有机质的分解有关.疏浚区水体中氮磷含量与对照区差别不大,沉积物中TN的平均含量还略高于对照区,因此单一的疏浚措施对水环境改善的长期作用需要进一步研究.而示范区水体及沉积物中的TN、TP含量均比较低,水生植被恢复较好,可见在减少外来污染的前提下,对湖区底泥进行疏浚并开展水生植被恢复工程应该是控制湖泊富营养化的有效途径.;Dredging and aquatic macrophytea reestablishment were carried out in the West Lake Wuli of LakeTaihu. Total phosphorous and total nitrogen in the water, as well as different forms of phosphorus and nitrogen inthe sediment cores of different areas were investigated in different seasons to examine the effects of different restoralion measures. The results showed that, the distribution of nitrogen and phosphorus in the water and sediment underdiflferent ecological restoration were different. The content of nitrogen and phosphorus in the water in dredging onlyarea and control area was lower than other areas .Vertical distribution of different forms of phosphorus in the sediment of West Lake Wuli varied with different ecological restoration measures. Macrophytes reestablishment afterdredging affected Lab-P,AI-P}Fe-P observably, other than Ca-P and Org-P. In the former-fishery area, Ca-P andorg-P took up the largest proportion in the total phosphorus, followed by Fe-P. However, Fe-P and Ca-P took upthe largest proportion in the dredging only area.Compared with TP, the effects of ecological restoration measures onTN were not so obviously. In dredging only area,the contents of nitrogen and phosphorus in both the water andsediments were high, the long-term effects of dredging needed further study. In the area of dredging plus macro-phytes reestablishment, the content of TN and TP was the lowest, with plenty of aquatic macrophytes. It was sugested that the effective way of eutrophicated lake control may be actualizing through reestablishment of aquatic macrophytes in the dredging area by the precondition of reducing external source pollution.