【摘要】 为探究三峡库区支流水环境的垂向分布特征及其影响因素，采用2018年2月（高水位期）和7月（汛期）对三峡水库典型一级支流——神农溪回水区水质监测数据，分析和对比了神农溪不同时期的溶解氧和叶绿素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，神农溪高水位期与汛期的溶解氧含量在0～12 m和0～6 m水体分层现象明显，其表层水体的溶解氧饱和度(S_DO)分别为104.04%和171.96%，已经达到过度饱和状态(S_DO>100%)；中层水体溶解氧浓度存在分层现象，底层水体溶解氧浓度较稳定，无分层现象。高水位期与汛期的叶绿素a含量在0～10 m水体分层现象明显，表层水体的叶绿素a浓度整体上表现为中度富营养化（5μg/L<Chl-a<20μg/L）。Pearson分析表明，神农溪高水位期与汛期水体中的溶解氧与水温、浮游植物、pH值垂向分布之间存在显著相关性，说明影响溶解氧垂向分布的部分可能因素是水温分层和浮游植物的生命活动。叶绿素a与水温和pH存在显著正相关性，与电导率和浊度存在显著负相关性，表明水温分层、水体电导率和光强对浮游植物在垂向上的分布影响较大。更多还原

【Abstract】 To provide a reference to support environmental protection and ecological restoration,we investigated the vertical distribution and environmental driving factors for dissolved oxygen(DO) and chlorophyll-a(Chl-a) in the Shennong River backwater of Three Gorges Reservoir(TGR) at different water levels.The study was based on 2018 water quality monitoring data for the Shennong River backwater collected in February(winter dry season,high water level in TGR) and July(summer flood season,low water level in TGR).A total of 6 monitoring sites were set,from the Shennong River cove(SN1) to the end of the backwater(SN6),and depth profiles of water environmental factors were obtained by taking measurements at 1 m intervals from surface to bottom.Temperature depth profiles show that the Shennong River backwater was thermally stratified,weakly in the winter and strongly in the summer.DO in the surface water was high in the photic zone,particularly in the summer,and then rapidly declined with depth as decomposition outpaced photosynthesis.This zone of highly variable DO extends from 0-12 m in winter and 0-6 m in summer.In the surface water(epilimnion),the DO saturation(SDO) was above100%(supersaturated),averaging 104.04% in winter and 171.96% in summer.The DO of the middle layer(mesolimnion) decreased with depth,and then was lower and more uniform in the bottom layer(hypolimnion).As expected,the vertical distributions of Chl-a at both high water(winter) and low water(summer) levels were similar to DO and the Chl-a concentration was consistently very low below 10 m.The average concentrations of Chl-a in the surface water were 11.4μg/L and 8.7μg/L,respectively,indicating moderate eutrophication(5μg/L<Chl-a<20μg/L).Pearson correlation analysis showed a significant correlation between the vertical distributions of DO and water temperature(WT),Chl-a and pH at both water levels.This indicates that the factors primarily affecting the vertical distribution of DO were WT(i.e.,thermal stratification) and phytoplankton production and decomposition.Phytoplankton production consumes CO2(increasing pH) and releases O2in the photic zone,while phytoplankton decomposition consumes O2and releases CO2(decreasing p H) below the photic zone.Chl-a correlated positively with WT and pH,and negatively with electrical conductivity(EC) and turbidity(Turb),indicating that WT,EC and light intensity primarily affect the vertical distribution of phytoplankton.更多还原