Heavy metal contamination and risk in soils irrigated with treated wastewater: a case study of Zabol

Sargolzaee, Fatemeh; Einollahi Peer, Fatemeh; Dahmardeh Behrooz, Reza; Okati, Narjes

doi:10.22111/jneh.2026.54284.2150

Heavy metal contamination and risk in soils irrigated with treated wastewater: a case study of Zabol

Articles in Press

Document Type : Research Article

Authors

¹ Master's degree in Environmental Pollution, Faculty of Natural Resources, University of Zabol, Zabol, Sistan and Baluchestan, Iran

² Associated Prof., Department of Environment, Faculty of Natural Resources, University of Zabol, Zabol, Sistan and Baluchestan, Iran

10.22111/jneh.2026.54284.2150

Abstract

Freshwater scarcity in arid and semi‑arid regions has led to the use of treated wastewater for irrigation. However, the continued practice may result in the accumulation of heavy metals in soil, thereby threatening human health and food security. This study is the first in the Zabol region to evaluate the quality of treated wastewater using the Canadian Water Quality Index (CWQI) combined with a comprehensive soil health risk assessment. In this study, the physicochemical parameters and heavy metal concentrations in the influent and effluent of the Zabol wastewater treatment plant were measured, and the suitability of the effluent was assessed using the CWQI. Additionally, heavy metal concentrations were determined in soil samples (0–20 cm depth), and the contamination factor (CF), geo‑accumulation index (Igeo), pollution load index (PLI), as well as the average daily dose (ADD) and hazard quotient (HQ) were calculated for health risk assessment; dried sludge was also examined. The CWQI results indicated that the quality of the effluent fell into the poor category, making it suitable only for recreational uses and, with caution, for irrigation. In the soil, mercury showed the highest CF (CF ≥6), while all other metals had CF values below 1. The PLI was zero for all elements. According to the Igeo index, the contamination intensity followed the order: Hg < Co < Ni < Cr < Cu < Zn < V < Mn. Human health risk assessment revealed that HQ values for all metals were below the critical limit, indicating minimal adverse effects. Nevertheless, heavy metal concentrations in the dried sludge exceeded standard limits, representing a potential contamination source if mismanaged. Thus, with its novel approach (CWQI and risk assessment), this study goes beyond mere heavy metal concentration measurements. Overall, the use of treated wastewater (except for Hg) poses no significant risk to soil; however, under current conditions, non‑agricultural uses and non‑fruit‑bearing tree planting are recommended, and improving treatment processes is essential to provide safer water during drought periods in Zabol.

Keywords

Main Subjects

Environmental Contamination

References

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