Effect of Long-Term Use of Treated Wastewater and Clean Water Mixtures on Soil Heavy Metal Accumulation: An Assessment Using Pollution Indices

This study investigates the long-term impacts of treated wastewater (WW) irrigation on soil heavy metal accumulation under semi-arid conditions. Over four years, five irrigation regimes combining WW and clean water (CW) were tested to monitor concentrations of Cr, Ni, Cu, Zn, Cd, Fe, and Pb. Pollution indices (CF, EF, Igeo, PLI) were applied to assess environmental risks. Results showed that higher proportions of WW increased heavy metal levels, though all remained below international limits. While Pb, Fe, Zn, and Cd approached moderate contamination under 100% WW, overall enrichment and pollution indicators classified soils as unpolluted. Findings highlight that blending 25–50% WW with CW sustains soil productivity while minimizing environmental risks, underscoring its potential as a sustainable irrigation strategy.