Evaluation of Lead and Cadmium Contamination in the Zayandeh Rud River

Abstract

Despite numerous advantages, human developments have caused profound impacts on ecosystems, especially on aquatic ecosystems that represent vast development potentials. In order to monitor the health and functioning of such ecosystems, the water physicochemical characteristics have shown limited utility as contamination indicators due to their ever-changing nature (Noori et al., Desalination 2010;260(1–3):129–136). Sediments have been found to be a more reliable and valid indicator of water contamination level. Sediment contamination with heavy metals (HMs) has captured the concern and scholarly attention of many developing countries around the world such as Iran (Nafchi and Chamani, Mar Pollut Bull 2019;149:110494; Zonta et al. Estuarine, Coastal and Shelf Science, 2019; Alahabadi and Malvandi, Mar Pollut Bull 2018;133:741–749; Bagheri and Azimi, J Oceanogr 2015;6(21):27–36; Bahador et al., J Mar Sci Technol 2017;16(3):56–71; Delshab et al., Mar Pollut Bull 2017;115(1):401–411; Haghshenas et al., J Environ Health Eng 2018;5(4):359–374; Shabankareh et al., Environ Earth Sci 2018;77(3):101). Zayandeh-Rood River is the only permanent river in the central plateau of Iran. This river has been subject to an extensive discharge of wastewater and effluents from several points and nonpoint pollution sources. The objectives of the present study were to (1) investigate the Pb and Cd concentrations in surface sediments of the Zayandeh Rud River; (2) compare the resulting Pb and Cd concentrations in sediment with global standards; and (3) assess the contamination level and ecological environmental risk of HMs adopting a number of contamination indices such as bioaccumulation factor, Muller geochemical index (Muller, GeoJournal 1969;2:108–118), contamination degree (Hakanson, Water Res 1980;14(8):975–1001), modified contamination degree, and potential ecological risk index (RI) (Jafarabadi et al., Chemosphere 2017;185:1090–1111). The sediment was sampled through 3 replications at 12 stations along the Zayandeh-Rood river. The mean concentrations of Cd outweighed those of ISQG standards (0.6 mg/kg) while the mean concentration of Pb was within the acceptable ranges of ISQG standard (35 mg/kg). The results of Muller index indicated that all Cd concentrations measured in this research fell within the Moderate/Heavy pollution groups while the concentration of Pb was in the range of Unpolluted/Moderate pollution groups. Cd values showed low/moderate degree at stations 1–6 and Considerable degree at stations 7–12. mCd values showed high and very high degrees of pollution in the studied stations except 1, 2, 3 and 5. CF values of Cd has a considerable and very high degree whereas those of Pb were Moderate. The RI showed low ecological risk at stations 1 and 2, Moderate ecological risk at stations 3, 4 and 5, Considerable ecological risk at station 6 and very high ecological risk at stations 7–12. A significant rise was observed in the level of river pollutants and ecological risk in the downstream of Isfahan City, especially after the wastewater treatment plant (stations 7–12) where any water withdrawal for agricultural and livestock purposes significantly elevates the risk of food-chain contamination with HMs.