Heavy metals in agroecosystems: Sources, soil contamination processes, plant uptake mechanisms and remediation approaches

The purpose behind critically analyzing the sources, pathways and ecological effects of heavy metal contamination in agroecosystems is to synthesize the available research in order to learn the important mechanisms of contamination and evaluate their effects on soil health, plant uptakes and food safety. Based on the latest scientific literature, the review discusses industrial processes as sources of cadmium, lead, arsenic, mercury, chromium, copper and nickel to the wastewater, including mining, metal and battery production and fertilizer production and also considers the contribution of municipal solid waste and sewage. With little over 30-40 % of the wastewater receiving proper treatment, there has been a massive release of untreated effluents to the natural water bodies and agricultural systems, posing persistent contamination threats. The review has placed importance on the fact that when polluted water is used in irrigation, it brings the heavy metals to soils and forms permanent complexes with the clay and organic matter, changing the soils structure, nutrient availability, microbial activity and general fertility. A thematic review of the available literature demonstrates that the bioavailability of heavy metals has been affected by the soil pH, redox potential and organic matter, which allows plants to uptake it via mass flow and diffusion and later translocation to edible tissues. This pollution of food is a great threat to human health, such as organ damage and neurological diseases. The review also assesses the existing mitigation strategies, including wastewater treatment, sustainable irrigation methods and soil remediation methods with special consideration to the potential and limitations of phytoremediation. It ends by providing research gaps and the necessity of long-term, ecosystem-level research studies to enhance plant-based remediation measures and agroecosystem resilience.