transport pathways and bioavailability of soil-borne heavy metals in agricultural systems

This review critically examines the mechanisms governing the transport, transformation, and bioavailability of heavy metals in soil systems, and particularly their interaction at the plant–soil interface. it integrates recent advances in the understanding of the most important physicochemical processes involving mineral dissolution, precipitation, partitioning, and complexation, as well as biological processes such as microbial mediation and root exudate interactions, which altogether determine heavy metal mobility. major transport processes such as advection, diffusion, dispersion, preferential flow, colloid-facilitated transport, and soluble metal complex migration are evaluated in relation to their contribution to leaching, runoff, and vertical movement through soil horizons. the review also discusses the influence of major soil characteristics such as ph, redox potential, texture, organic matter content, and chemical speciation on regulating metal retention and uptake behavior. agricultural management and amendments are evaluated on their potential to alter such interactions and affect long-term metal fate. field case studies are integrated to discuss practical applications. such integration constitutes a scientific basis for sustainable management practices for reduction of heavy metal pollution and enhancement of nutrient efficiency in agroecosystems.