ECOLOGICAL EFFECTS AND ENVIRONMENTAL FATE OF SILVER NANOPARTICLES IN SOIL AND IN THE WATER ECOSYSTEM: A REVIEW

Silver nanoparticles, which are appreciated due to their increased antibacterial, catalytic and conductive functions, are commonly employed in medical kits, cloths, cosmetics, and water filters, but their release through wastewater, biosolids, and runoff is highly dangerous as there is no regulation of their emission and transformation, such as sulfidation, aggregation, and dissolution. In soil ecosystems, AgNPs react with pH, redox conditions, organic matter, and clay, and sulfidation to Ag2S causes short-term bioavailability to decrease but increases persistence; they disrupt microbial communities, inhibit nitrogen-fixing bacteria (e.g., Rhizobium), mycorrhizal fungi, and enzyme activities, decrease soil fertility, nutrient cycling, and plant-microbe symbiosis and cause oxidative stress in earthworms. Aquatic systems facilitate AgNP disaggregation, sedimentation, and ion release driven by organic matter and ions and cause toxicity at all trophic levels: algae experience the inhibition of photosynthesis and ROS damage, zooplankton feeding problems, and fish experience bioaccumulation, neurotoxicity and reproductive problems. Ag+ ion release leading to protein/DNA damage, Oxidative stress due to ROS, membrane peroxidation, quorum sensing disruption and systemic changes in stress, detoxification and metabolism pathways confirmed by omics is a subset of the toxicity mechanisms. Though the water body information is plentiful, soil research is still very limited; gaps still exist in long-term low dose field effects and co-contamination. The research in the future recommends mesocosm/field testing, model dynamic transformation, and the safer design of nanoparticles to guide the risk analysis and sustainable management