Water chemistry and water quality pollution indices of heavy metals: a case study of Chahnimeh Water Reservoirs, Southeast of Iran

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Chahnimeh reservoirs are the main drinking water sources for the big cities of Sistan and Baluchestan Province (Zabol, Zahak and Zahedan) and their water quality of may have a great influence on public health. Therefore, the aims of this study are to assess hydrogeochemical characteristics, and heavy metal(loid)s pollution in four Chahnimeh reservoirs using water quality pollution indices and principal component analysis. The concentrations of Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, U, and Zn in 84 water samples were measured for two periods. Hydrogeochemical analyses, Piper and Gibbs diagrams, show a change in the water type from Na–HCO3 and Na–SO4 to Na–Cl, and a bit tendency of water–rock interaction to evaporation, from September 2017 to April 2018. Based on the heavy metal pollution index, heavy metal evaluation index, and contamination index, water quality of Chahnimeh reservoirs is decreased in order: reservoirs 2 > 3 > 4 > 1. The result of statistical analysis reveals that Mo content is affected by a geogenic origin, while Se and U indicate a quasi-independent behavior within the groups reflecting contribution of both geogenic and anthropogenic sources. HCO3 plays a significant role in distribution of Se and U. Also, Fe, Mn and Al oxy-hydroxides can control concentrations of Cu, Pb and Ni. Overall the obtained results indicated that the variation of water quality in the study area was related to climatic conditions, high evaporation, water–rock interaction, different land uses, drying Hamoun Lakes and anthropogenic effects in the Hirmand watershed. The current study reveals that the use of integrated methods such as statistical methods and heavy metal pollution indices to determine the water quality is very suitable.