贵州高原百花湖水库湖沼学变量特征及环境效应

Limnological characteristics and environmental effects of the Baihua Reservoir in Guizhou Plateau,China

为了揭示贵州高原百花湖水库湖沼学变量特征及其与突发性水质恶化的关系,对百花湖水库的水文、营养盐及相关理化因子进行了调查.结果表明:百花湖水库表层水温在10.2～27.0℃之间,4—9月形成分层,水体分层结构为单循环混合模式;总氮(TN)、总磷(TP)、叶绿素a(Chl.a)和透明度(SD)分别为1.60mg·L-1、0.067mg·L-1、18.9μg·L-1和1.4m,指示百花湖水库为中-富营养型水体;营养盐等理化因子在河流区高于过渡区和湖泊区,且在丰水期(5—9月)显著地高于其他月份,说明水库营养盐主要来自流域地表径流的输入;氮磷质量比(N/P)在2～120之间,底层溶解氧在0.3～8.0mg·L-1之间,表明百花湖水库是一个底层滞留带季节性缺氧的高氮、磷限制水库,较高的N/P比是由贵州高原土壤中营养盐组成特点所决定,底层季节性缺氧是水体分层的结果,富营养化加剧了底层的缺氧;突发性水质恶化与水体的分层及富营养化有关,水体分层阻碍了上下层水体的交换,导致了水化学的分层,气温突降使水体分层失稳,从而发生缺氧等水质恶化事件.

In order to find out the limnological characteristics and the relationship with the paroxysmal deterioration of water quality in Baihua Reservior of Guizhou Province,China,hydrological and environmental factors were investigated from August 2008 to August 2009.From April to September,the thermal stratification was monomictic,leading to chemical stratification that affected the water quality.The mean concentrations of TN,TP,Chl.a and SD were 1.60 mg · L-1,0.067 mg · L-1,18.9 μg · L-1 and 1.4 m respectively,indicating that the reservoir was a meso-eutrophic system.Physical and chemical factors in the river zone were higher than those in the transitional and lacustrine zones.In the wet season（May to September）,all nutrient concentrations were significantly higher than those in the other periods.It was confirmed that surface runoff was the main path for nutrient loading into the reservoir.The ratios of TN/TP were from 2 to 120 in Baihua Reservior,and the dissolved oxygen was between 0.3 to 8.0 mg · L-1,meaning that the reservoir was characterized by high concentrations of nitrogen and phosphorus limitation and by seasonal anoxia in hypolimnion.The high N/P ratio was attributed to the local soil containing rich iron.Water stratificaton was responsible for seasonal anoxia at the lake bottom,which was intensified by the water eutrophication.The paroxysmal deterioration of water quality was relevant to water stratification,eutrophication,and the gravitational instability of the thermal stratification caused by surface cooling of water when the air temperature decreased abruptly in early fall,leading to a mixing of the upper and lower layer water and anoxia in the whole water body.