Abstract
Abstract In this study, metal concentrations in the water column and surface sediment of the Sabalan Dam Reservoir (SDR) were determined. Moreover, heavy metal pollution index (HPI), contamination index (CI), heavy metal evaluation index (HEI), enrichment factor (EF), geo-accumulation index (Igeo), sediment quality guidelines (SQGs), consensus-based SQGs (C-BSQGs), and mean probable effect concentration quotients (mPECQs) were evaluated for water and sediments of SDR. It was observed that metal concentrations in river entry sediment were lower, but those in river entry water were higher than corresponding values in the vicinity of the dam structure. The HPI values of water samples taken from 10 m depth in the center of SDR exceeded the critical limit, due to high concentrations of arsenic. However, according to CI, the reservoir water was not contaminated. The HEI values indicated contamination of SDR water with metals at 10 m depth. A comparison of water quality indices revealed that HEI was the most reliable index in water quality assessment, while CI and HPI were not sufficiently accurate. For SQGs, As and Cu concentrations in sediments were high, but mPECQ, Igeo, and EF revealed some degree of sediment pollution in SDR. The calculated EF values suggested minor anthropogenic enrichment of sediment with Fe, Co, V, and Ni; moderate anthropogenic enrichment with As and Mn; and moderate to severe anthropogenic enrichment with Cu. A comparison of SQG values revealed that the threshold effect and probable effect levels were the most reliable metrics in the assessment of sediment toxicity. Statistical analysis indicated similarities between metal concentrations in the center of the reservoir and near to the dam structure, as a result of similar sediment deposition behavior at these points, while higher flow velocity at the river entry point limited deposition of fine particles and associated metals.
Highlights
Metal contamination, toxicity, and accumulation in the aquatic environments have attracted major global attention (Purves ; Valls & Lorenzo ; Gochfeld ; Vesali Naseh et al )
It was observed that metal concentrations in river entry sediment were lower, but those in river entry water were higher than corresponding values in the vicinity of the dam structure
The Sabalan Dam Reservoir (SDR) is thermally stratified during most months of the year and only mixes in late December to early March, i.e., it was thermally mixed during the sampling period
Summary
Toxicity, and accumulation in the aquatic environments have attracted major global attention (Purves ; Valls & Lorenzo ; Gochfeld ; Vesali Naseh et al ). When metals are discharged into aquatic ecosystems, they redistribute into water and sediment strata. Metal concentrations in sediments of an aquatic ecosystem are usually three- to five-fold greater than those in the water column (Luoma ). Concentrations of metals in sediments are a good indicator of the health and contamination status of water bodies (Pekey ). Settled metals may be resuspended and released into the water column, causing ecological and health-related problems in aquatic ecosystems such as lakes and reservoirs (Saha et al ; Tiwari & De Maio ). In addition to studying metals in sediments, analyzing these pollutants in the water column provides important information for effective water quality management of aquatic environments, dams, which are usually constructed to supply drinking water
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