Characterization, geostatistical modeling and health risk assessment of potentially toxic elements in groundwater resources of northeastern Iran

Ata Joodavi,Reza Aghlmand,Joel Podgorski,Reza Dehbandi,Ali Abbasi

doi:10.1016/j.ejrh.2021.100885

Abstract

Study regionNortheastern Iran. Study focusIn northeastern Iran, water needed for municipal and agricultural activities mainly comes from groundwater resources. However, it is subject to substantial anthropogenic and geogenic contamination. We characterize the sources of groundwater contamination by employing an integrated approach that can be applied to the identification of large-scale contamination sources in other regions. An existing dataset of georeferenced water quality parameters from 676 locations in northeast of Iran was analyzed to investigate the geochemical properties of groundwater. Gridding of the parameters graphically illustrates the areas affected by high concentrations of As, Cl−, Cr, Fe, Mg2+, Na+, NO3−, Se, and SO42-. We then identified potential anthropogenic and geogenic contamination sources by employing random forest (RF) regression modeling. New hydrological insights for the regionRandom forest (RF) models show that the major ions, As, Cr, Fe, and Se content of groundwater are mainly determined by geology in the study area. Modeling also links groundwater NO3− contamination with sewage discharge into aquifers as well as the application of nitrogenous and animal-waste fertilizers. Areas of high salinity result from evaporate deposits and irrigation return flow. Medium to high non-carcinogenic health risk is found in areas with high concentrations of geogenic As and Cr in groundwater. Our approach can be applied elsewhere to analyze regional groundwater quality and associated health risks as well as identify potential sources of contamination.

Highlights

Many parts of Iran, like other arid/semi-arid regions, rely on groundwater to satisfy its drinking, agricultural and industrial water.Journal of Hydrology: Regional Studies 37 (2021) 100885 needs (Joodavi et al, 2015; Ashraf et al, 2021)
Most hydrogeochemistry studies try to interpret geochemical reactions along groundwater flow paths in an aquifer or a watershed, this paper proposed an approach to identify the sources of salinity, nitrate and potentially toxic elements (PTEs) in groundwater in large-scale studies of broad geographical areas where there are large gaps in testing locations
Integrated approaches of statistical analysis, conventional hydrogeochemical plots, and machine learning were employed in this study to characterize the groundwater chemistry in Razavi Khorasan province and identify likely sources of contamination

Summary

Introduction

Many parts of Iran, like other arid/semi-arid regions, rely on groundwater to satisfy its drinking, agricultural and industrial water (http://creativecommons.org/licenses/by/4.0/). Journal of Hydrology: Regional Studies 37 (2021) 100885 needs (Joodavi et al, 2015; Ashraf et al, 2021). Poor groundwater quality/groundwater pollution threatens water and food security in Iran. The geochemical con ditions of an aquifer can result in high concentrations of various elements that are detrimental for human health such as As, Cd, Cr and F (Appelo and Postma, 2005). Anthropogenic activities can introduce various pollutants of ions and trace metals to groundwater, for example through agricultural and industrial activities as well as human settlements (Barbieri et al, 2019; Ricolfi et al, 2020)

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Conclusion