Investigation of the sorption behavior of atrazine in new and aged microplastic and evaluation of its phytotoxic potential

The increasing presence of microplastics in aquatic environments and their interaction with emerging organic pollutants, such as atrazine, a widely used herbicide in agriculture, have raised concerns about ecological impacts. Atrazine can adsorb onto the surface of microplastics, increasing its persistence in the environment and elevating the risk of toxicity to aquatic organisms. This study investigated the sorption of atrazine onto new and aged polyethylene microplastics under two distinct conditions: distilled water (DW) and nutrient-enriched water for hydroponics (NE), simulating a eutrophic environment, assessing the adsorption capacity and phytotoxicological impacts on the germination of Lactuca sativa. The results revealed that aged microplastics (AMP) showed a higher adsorption capacity for atrazine under both conditions: 0.6460 mg/g (14.4917%) in DW and 0.7419 mg/g (15.8671%) in NE, compared to 0.4047 mg/g (9.0793%) and 0.5042 mg/g (10.7845%) for new microplastics (NMP), respectively. This greater adsorption capacity of AMP is likely due to surface modifications caused by photodegradation, such as increased roughness and the formation of oxygenated functional groups. Phytotoxicity assays demonstrated that atrazine adsorbed to AMP exerted an inhibitory effect on seed germination, with a maximum inhibition of 34% in the treatment with aged microplastic sorbed with atrazine at 2 mg/L, classifying the effluent as moderately toxic. This study highlights that the aging of microplastics increases their capacity to adsorb atrazine, amplifying the risks of toxicity in aquatic environments, especially under eutrophic conditions, and reinforces the need for further research on the impacts of the interaction between microplastics and pollutants in different aquatic ecosystems.