Source, dynamics, and risks of microplastics and nanoplastics in agricultural groundwater systems

Micro- and nanoplastics (MNPs) are emerging contaminants increasingly recognized for their environmental and health implications. While surface water systems have been extensively studied, the presence, behavior, and impacts of MNPs in groundwater remain underexplored, despite its critical role as water source worldwide. The findings in this review highlight that agricultural activities, particularly plastic mulches, pesticides containers, fertilizer bags, greenhouses, are major sources of MNP. Nanoplastics, predominant in groundwater due to their enhanced mobility in the vadose zone, exhibit a higher sorption capacity, facilitating the transport and accumulation of toxic substances such as hydrophobic organic pollutants and trace metals to/in groundwater. The review also discusses the hydrogeological and environmental factors influencing micro(nano)plastics distribution. In complement, synergistic and antagonistic effects arising from MNP interactions with other contaminants were reviewed, emphasizing the interactions with contaminants derived from agricultural practices (nitrate, herbicides, pesticides, and salts). Despite the generally low concentrations of MNPs in groundwater, their seasonal variability, combined with the aging of particles, underscores the need for long-term monitoring and risk assessments specific to groundwater systems. These findings reinforce the importance of research that addresses the unique challenges posed by micro- and nanoplastics in groundwater systems, ensuring their environmental protection.