Spatial distribution of potentially toxic elements and ecological-health risks in a wastewater-irrigated peri-urban agroecosystem: a multi-matrix assessment from Muzaffargarh, Pakistan

Abstract

Peri-urban vegetable growing areas are vital for food security but are increasingly threatened by contamination from nearby industrial sites. This study examined potentially toxic element spatial distribution, bioaccumulation, and associated ecological-health risks in vegetables cultivated with wastewater-irrigated soil for over 30 years in southern Punjab, Pakistan. A total of 540 samples of drinking water, soil, and vegetables were collected from three sectors (X, Y, and Z) for comparative analysis. Potentially toxic elements were assessed using spectrophotometry. The results of soil analyses revealed that the mean concentration of manganese in three sectors were 271.02 mg/Kg, iron were 211.67 mg/Kg as the predominant contaminant, followed by nickel 67.08 mg/Kg, lead 63.50 mg/Kg, chromium 50.83 mg/Kg, copper 30.02 mg/Kg, zinc 26.67 mg/Kg and arsenic 17.18 mg/Kg. Statistically significant (P < 0.001) differences in soil metal concentrations across the three sectors were noted. Vegetables showed elevated levels of chromium, cadmium, arsenic, and manganese with significant variations in metal uptake among sectors. Cadmium exhibited the highest ecological risk index, and the pollution load index indicated progressive soil contamination. Sector X had the highest cadmium enrichment factor. Health risk assessment revealed significantly elevated average daily doses for chromium and lead in two sectors. Soil analyses revealed iron as the predominant contaminant, followed by lead, cadmium, arsenic, nickel, zinc, manganese, and chromium. Statistically significant differences in soil metal concentrations across sectors were noted. These findings highlight the urgent need for interventions to mitigate potentially toxic element contamination in peri-urban agriculture.

Keywords: Anthropogenic contamination; Environmental monitoring; Health risk assessment; Industrial effluents; Potentially toxic elements; Soil–plant transfer; Urban agriculture sustainability.