METAL CYCLING IN A DRINKING WATER RESERVOIR: INFLUENCE OF OXYGENATION, HYDROLOGIC INPUTS AND SEDIMENTATION

Freshwater lakes and reservoirs are vital sources of public drinking water. Naturally occurring contaminants, such as Al, Ba, Cu, and Sr, can adversely affect water quality. Thus, understanding their loads and concentrations in drinking water reservoirs is critical for protecting human health and the environment. Previous studies on metal removal through artificial oxygenation and biogeochemical cycling in lakes and reservoirs have focused on metals such as Fe and Mn or toxic elements such as As. However, there has been little work conducted on other metals that can impact water quality, including the geochemical (sorption, oxidation-reduction, dissolution-precipitation, complexation) and hydrological (discharge, turbidity) processes that control their concentrations and loads.

In this study, we quantified the concentrations and loads of metals, including Al, Ba, Cu and Sr, in two seasonally stratified drinking water reservoirs in southwestern Virginia: Falling Creek Reservoir (FCR) and Beaverdam Reservoir (BVR). FCR has a hypolimnetic oxygenation (HOx) system to maintain oxic conditions in bottom waters. BVR does not have a HOx system deployed and serves as a reference reservoir. To quantify metal cycling, we utilized a dataset collected from 2018 to 2022 that includes metal removal fluxes, metal concentrations in water at multiple depths, tributary discharge measurements, and depth-continuous measurements of turbidity, DO, specific conductance and temperature in the reservoirs. Using this extensive dataset, we will examine how turbidity affects metal concentrations and fluxes, how changes in inflow to a reservoir change the turbidity, and how changes in inflow impact loading of metals seasonally and throughout the water column. This study will reveal new relationships between inflow events and metal cycling responses, which will improve filtration and treatment techniques of drinking water.