Abstract: In order to reveal the influencing factors and sources of the temporal and spatial variation of dissolved heavy metals in karst deep-water reservoirs, this paper selected Longtan Reservoir in Pearl River Basin as the research object, and analyzed the dissolved heavy metals and hydrochemical parameters of stratified water, tributary surface water and discharged water in July 2019 and January 2020.Through piper diagram of main ions, Pearson correlation analysis among different kinds of heavy metals, cluster analysis and CCA analysis between environmental factors and dissolved heavy metals, the results show that the weathering of carbonate rocks in the basin is an important external source of dissolved heavy metals in Longtan Reservoir. The change of relative water column stability (RWCS) caused by seasonal thermal stratification of reservoir water body is the main factor affecting the spatial and temporal distribution of dissolved heavy metals in the study area. Higher RWCS usually promotes the release of Cr and Cu, while lower RWCS promotes the release of Fe and As. This study provides a theoretical basis for exploring the relationship between hydrodynamic conditions and dissolved heavy metals, and has important guiding significance for scientific utilization and protection of water resources in karst deep-water reservoirs.

Key words: Deep water reservoir, dissolved heavy metals, the relative water column stability, coupling, seasonal thermal stratification, spatio-temporal distribution