白洋淀沉水植物机械收割对淀区水质影响分析

Analysis on the effects of submerged plant mechanical harvesting on water quality in Baiyangdian Lake

为了解决白洋淀内源污染问题,对淀区沉水植物进行适时收割十分有必要,因此,考察了沉水植物机械收割对淀区水质及富营养化状态的影响,并定量分析了沉水植物收割对淀区水体所贡献的氮、磷削减量,为白洋淀水草收割提供理论指导与数据支持。结果表明,植物机械收割会对淀区水体造成一定程度的扰动,致使水体浊度增加,并且水体溶解氧浓度平均降低1.78~3.61 mg·L~(-1)。但是,与处于植物生长期和衰亡期的淀区水域相比,经过植物生长末期收割的水域其有机物、总氮、氨氮、总磷平均浓度分别减少了28.0%~35.3%、55.8%~69.1%、25.0%~33.3%、50.0%~90.9%,说明通过收割将植物残体带出水体,可有效避免植物衰亡腐解向水体中释放有机物和氮磷等污染物,以叶绿素a、总磷、总氮为代表的营养状态指数也分别下降了81.8%~87.3%、17.3%~31.4%、17.6%~42.6%,水体富营养化程度从轻度/中度富营养降到贫/中营养,且每收割1 t沉水植物所贡献的淀区氮削减量为39.4~49.6 kg、磷削减量为2.30~3.18 kg。

In order to solve the endogenous pollution in Baiyang Lake,it is necessary to timely harvest submerged plants.Therefore,the effects of mechanical harvesting of submerged plants on the water quality and eutrophication status of Baiyang Lake were investigated,and the reduction of nitrogen and phosphorus resulted from submerged plants harvest-ing was quantitatively analyzed,to provide theoretical guidance and data support for the plants harvesting.The results showed that mechanical harvesting of plants caused disturbance to the water body of Baiyang Lake by a certain degree,re-sulting in an increase in the water turbidity,and the DO concentration decreased by 1.78~3.61 mg·L-1 on average.Howev-er,compared with the waters in the growth and decay periods of plants,the average concentrations of organics,total nitro-gen,ammonia,and total phosphorus in the waters where plants were harvested at the end stage of growth decreased by 28.0%~35.3%,55.8%~69.1%,25.0%~33.3%,and 50.0%~90.9%,respectively.This has indicated that taking the plant residues out of the waters through harvesting can effectively prevent the decomposition of plants from releasing organics,nitrogen and phosphorus into the water body.The nutritional status index,Chlorophyll a,total phosphorus and total nitro-gen,dropped by 81.8%~87.3%,17.3%~31.4%and 17.6%~42.6%,respectively,and the eutrophication of the waters de-creased from mild/medium eutrophication to poor/medium nutrition.The reduction of nitrogen and phosphorus resulting from harvesting 1 ton submerged plants was 39.4~49.6 kg and 2.30~3.18 kg,respectively.