Document Type : Original Article
Authors
- Ali Mehrabinejad 1
- Nasrollah Kalantari 2
- Farshad Alijani 3
- Seyede Fatemeh Mousavi 4
- Hadi Mohammadi 1
1 Department of Geology, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz, Ahvaz, Iran
2 Professor, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz, Iran
3 Department of Mineral and Ground Water Resources, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran
4 Consultant Engineers of Kamyab Gostar Jonoub, Ahvaz, Iran
Abstract
This research was conducted to assess the hydrochemical status and nitrate contamination of the urban aquifer in Izeh. Given the lack of a sewage collection system and the infiltration of urban wastewater through absorption wells, coupled with agricultural activities, the study primarily aimed to determine water quality and health risks associated with nitrate. Water samples were collected from nine operational water wells during six sampling periods (December 2023 to November 2024), analyzing physicochemical parameters including electrical conductivity, major ions, nitrate, nitrite, ammonium, COD, BOD, and pH. Hydrochemical controls were evaluated using Durov and Gibbs diagrams and the chloro-alkaline index. The Water Quality Index (CCMEWQI) assessed suitability for various uses, the Health Risk Index (HQ) determined nitrate exposure risks for different age groups (infants, children, adolescents, adults), and the Nitrate Pollution Index (NPI) evaluated contamination severity and spatial distribution. Results revealed that groundwater was predominantly calcium-magnesium bicarbonate type, with reverse sodium-calcium ion exchange. The WQI indicated "good to excellent" quality for drinking and agricultural uses, though reduced quality was observed in southern areas. The mean nitrate concentration (53.35 mg/L) exceeded the permissible limit (50 mg/L), with 39% of samples contaminated (NPI>1.5) and 20% at critical levels (NPI=0.75–1.5). Nitrate plumes were concentrated near the southern karst aquifer and expanded seasonally with rainfall. Health risks (HQ>1) were identified in 54% of samples for infants, 46% for children, and 39% for adults. Mitigation strategies were proposed to reduce groundwater nitrate levels, emphasizing pollutant infiltration prevention as essential for aquifer protection.
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