三峡水库汛后蓄水期典型支流溶解氧与叶绿素a垂向分布特征

Vertical Distribution Characteristics of Dissolved Oxygen and Chlorophyll a in Typical Tributaries During the Impoundment Period of the Three Gorges Reservoir

采用2018年9月对三峡水库典型一级支流——香溪河和神农溪回水区水质监测数据,分析和对比了香溪河和神农溪的溶解氧和叶绿素a等指标垂向分布特征,讨论了影响其垂向分布的环境因子.结果表明,香溪河与神农溪的溶解氧含量在表层0~10 m和0~12 m水体分层现象明显,且随水深增加而递减.其表层水体的溶解氧饱和度SDO分别为139.20%和107.78%,已经达到过度饱和状态(SDO>100%);中层与底层水体溶解氧浓度较稳定,无分层现象.香溪河和神农溪回水区水体中叶绿素a垂向分布与溶解氧分布的规律一致,表层水体中叶绿素a浓度整体上表现为中度富营养化(5μg·L^-1<Chl-a<20μg·L^-1).Pearson相关性分析显示,香溪河与神农溪水体中的溶解氧与水温、浮游植物垂向分布之间存在显著相关性,水温分层以及浮游植物的生命活动是影响溶解氧垂向分布的关键因素.叶绿素a与水温和pH呈现出显著的正相关性,与浊度表现为显著负相关性,表明浮游植物垂向分布主要受光照强度沿水深衰减和水温分层现象的影响.

The water quality of the backwater areas in the Xiangxi River and Shennong River,which are typical tributaries of the Three Gorges Reservoir,was monitored in September 2018.The vertical distribution characteristics of dissolved oxygen,chlorophyll a,and other indicators in the two rivers were analyzed and compared,and the environmental factors affecting their vertical distribution were discussed.The results showed that the dissolved oxygen concentration 0-10 m and 0-12 m from the surface of the Xiangxi River and Shennong River,respectively,showed significant stratification and decreased with increasing water depth.The dissolved oxygen saturation of surface water was 139.20%and 107.78%,respectively,reaching a state of supersaturation(SDO>100%).The dissolved oxygen concentration in the middle and bottom water was more stable without stratification.The vertical distribution characteristics of chlorophyll a were consistent with those of dissolved oxygen in the Xiangxi River and Shennong River,and the chlorophyll a concentration in the surface water showed moderate eutrophication(5μg·L^-1<Chl-a<20μg·L^-1).According to Pearson correlation analysis,the vertical distribution of dissolved oxygen in the Xiangxi River and Shennong River was significantly correlated with that of water temperature and phytoplankton.The stratification of water temperature and the life activities of phytoplankton were the key factors affecting the vertical distribution of dissolved oxygen.Chlorophyll a was positively correlated with water temperature and pH,and negatively correlated with turbidity,indicating that the vertical distribution of phytoplankton was mainly affected by the attenuation of light intensity along the water depth and the stratification of water temperature.