Abstract
Reservoirs are characterized by accumulation of sediments where micropollutants may concentrate, with potential toxic effects on downstream river ecosystems. However, sediment management such as flushing is needed to maintain storage capacity. Climate change is expected to increase sediment loads, but potential effects on their quality are scarcely known. In this context, sediment contamination by trace elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and organics (Polycyclic Aromatic Hydrocarbons PAHs, Polychlorinated Biphenyls PCBs and C > 12 hydrocarbons) was analyzed in 20 reservoirs located in Italian Central Alps. A strong As and a moderate Cd, Hg and Pb enrichment was emphasized by Igeo, with potential ecotoxicological risk according to Probable Effect Concentration quotients. Sedimentation rate, granulometry, total organic carbon (TOC) and altitude resulted as the main drivers governing pollutant concentrations in sediments. According to climate change models, expected increase of rainfall erosivity will enhance soil erosion and consequently the sediment flow to reservoirs, potentially increasing coarse grain fractions and thus potentially diluting pollutants. Conversely, increased weathering may enhance metal fluxes to reservoirs. Increased vegetation cover will potentially result in higher TOC concentrations, which may contrast contaminant bioavailability and thus toxicity. Our results may provide elements for a proper management of contaminated sediments in a climate change scenario aiming at preserving water quality and ecosystem functioning.
Highlights
Reservoirs represent a strategic resource [1] which requires careful management of hydraulic networks and dams without neglecting the protection of water quality [2,3,4]
Changes in the catchment area were considered, omitting those that could occur in the water body, such as changing in thermal stratification, increased anoxia and consequent release of nutrients or pollutants, changing in nutrients loads and consequences on water quality
These are considered minor issues in Northern Italian reservoirs since water regulation for hydropower generally determines short water residence times. In this scenario, we did not consider any variations of potential sources of anthropogenic pollution
Summary
Reservoirs represent a strategic resource [1] which requires careful management of hydraulic networks and dams without neglecting the protection of water quality [2,3,4]. Reservoirs are typical sites where sediment accumulation is favored and desiltation is needed to maintain water storage capacity, as well as proper functioning and services [5,6,7]. Different strategies are used to reduce sediment accumulation, but a common practice is flushing, i.e., the scouring out of deposited sediments using low-level outlets in dams to lower water levels, thereby increasing flow velocities in the reservoir.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
