Effect of overlying water pH, temperature, and hydraulic disturbance on heavy metal and nutrient release from drinking water reservoir sediments

How environmental factors impact the release of pollutants from sediment is critical to ensure the safety of drinking water, especially when the seasons change. Here, we investigated the effect of water pH, temperature, and hydraulic disturbance on the release of heavy metals and nutrients from the sediment of drinking water reservoir. The results show that lower initial water pH promoted the Zn release, while low temperature enhanced the Mn flux after 15 days. Meanwhile, continuous disturbance caused more metals releasing from sediment than intermittent disturbance due to greater shear stress and turbulence effect. However, intermittent high-speed disturbance greatly altered the dynamic release of Zn from L-shaped curve to U-shape in water column. Moreover, lower water pH caused higher ammonium in water but lower nitrate since H+ restrained the nitrification. Yet, higher temperature inhibited the release of ammonium from sediment, which might relate to the accelerated mineralization of organic nitrogen and elevated dissolved oxygen caused by the algae growth. Notably, hydraulic disturbance with various intensity and duration greatly influenced the fluxes of various species of nitrogen and soluble phosphate in water column, because the disturbance facilitated the nitrogen and phosphorus exchanges between sediment-water and water-air interfaces. Practitioner points Lower water pH induced Zn release, while low temperature gradually enhanced Mn level. More metals were released from sediment under continuous disturbance than intermittent disturbance. Lower water pH caused higher ammonium nitrogen in water but lower nitrate nitrogen. Higher temperature inhibited the release of ammonium nitrogen from sediment. Hydraulic disturbance greatly changed the release of different species of nitrogen and soluble phosphate from sediment.

Automated summary

The investigation revealed that water pH, temperature, and hydraulic disturbance significantly impact the release of pollutants from sediment in drinking water reservoir. Lower water pH promoted zinc release, while low temperature enhanced manganese flux. Continuous disturbance caused more metal release, while high-speed disturbance altered the dynamic release pattern of zinc. Ammonium and nitrate levels in water were influenced by water pH and temperature. Hydraulic disturbance affected the release of various nitrogen and phosphorus species.