Potentially Toxic Metal Flux and Bioaccumulation Pathways in Buffaloes from Rural and Urban Agroecosystems: a Multi-Matrix Environmental Health Assessment

Potentially toxic metal contamination in agroecosystems poses a growing risk to environmental and food safety, particularly in arid regions where water scarcity enhances metal accumulation and increases reliance on groundwater irrigation. However, integrated assessments across environmental and biological matrices remain limited. This study quantified chromium (Cr), iron (Fe), manganese (Mn), and nickel (Ni) in irrigation water, soil, forage, milk, and hair samples collected from rural and urban buffalo-rearing systems in Bhalwal, Punjab, Pakistan. Samples were subjected to acid digestion followed by quantification using Flame Atomic Absorption Spectrophotometry (AAS). Measured concentrations in irrigation water ranged from 0.0025 to 0.047 mg/L (Cr), 1.45 to 6.70 mg/L (Fe), 0.018 to 0.097 mg/L (Mn), and 0.015 to 2.30 mg/L (Ni). While Cr and Mn remained below WHO and USEPA guideline limits (0.05-0.1 mg/L for Cr; 0.05-0.4 mg/L for Mn), Fe (limit: 0.3 mg/L) and Ni (limit: 0.07-0.1 mg/L) exceeded permissible levels at several sites, particularly in urban areas. Similar trends were observed in soil and forage, with elevated concentrations of Fe (up to 75.50 mg/kg) and Ni (up to 15.60 mg/kg). In biological matrices, milk concentrations ranged from 0.910 to 3.376 mg/L (Cr), 0.363 to 1.473 mg/L (Fe), 0.683 to 1.166 mg/L (Mn), and 0.223 to 0.915 mg/L (Ni), with several values exceeding typical background levels reported in the literature. Hair samples showed comparatively higher metal accumulation, reflecting longer-term exposure. Although concentration gradients from environmental to biological samples were observed, these findings indicate potential accumulation patterns rather than definitive trophic transfer pathways.