Role of Biodegradable and Non-Biodegradable Microplastic in Modulating the toxicological Effects of Organic Pollutants in the Soil Organism Folsomia candida

The ecotoxicological efects of microplastics in soil ecosystems are complex, particularly in areas of intensive agriculture and livestock production, where plant protection products and veterinary drugs commonly coexist with plastic residues. In this study, we investigated the impact, under laboratory conditions, of 3 MP types (non-biodegradable lowdensity polyethylene (LDPE) and biodegradable polybutylene adipate terephthalate-based (PBAT-based) and a starch-based polymer) on the soil-dwelling species Folsomia candida (Willem, 1902) in soils contaminated with the anthelmintic albendazole and the fungicide pyraclostrobin. These organic pollutants (OPs) are frequently found in areas of intensive agriculture and livestock production. F. candida individuals were exposed for 28 days to soils contaminated by the OPs at 0.0001 w/w% (1 mg/kg), with and without MPs at 0.01 and 0.1 w/w% concentrations (100 and 1000 mg/kg respectively), under laboratory conditions (21±1 C°, 80%±1 RH). Adults’ survival, egg production, and juveniles’ occurrence were recorded as endpoints. Our fndings indicate that microplastics alone did not signifcantly affect the survival and reproductive outcomes of F. candida. However, in soils contaminated with albendazole and pyraclostrobin, the presence of biodegradable MPs resulted in signifcant efects compared to the control and the treatment with only microplastics. Specifcally, PBAT-based MPs signifcantly impacted adult survival, juvenile occurrence, and egg counts, while starch-based MPs primarily afected egg counts. On the contrary, co-exposure to OPs and LDPE MPs did not show signifcant efects. These results suggest that diferent MPs infuence the bioavailability and toxicity of co-occurring fungicides and veterinary drug in soil ecosystems in diferent ways, with implications for assessing the ecological risks of biodegradable and non-biodegradable plastics in contaminated soils. The potential of MPs to infuence the spatial distribution and bioavailability of organic pollutants for soil mesofauna needs further investigation.