Microplastics in soil and groundwater: occurrence and transport through environmental matrices

Microplastics (MPs) have been found in various environmental compartments. However, their transport in soils and groundwater remains poorly understood. This study assessed the presence of MPs at different soil depths and in the Bauru Aquifer System, São Paulo, Brazil. Two samples were collected in the unsaturated zone (depths: 1.0 and 5.5 meters) and two in the saturated zone (depths: 6.5 and 10.5 meters) by hand auger drilling. The points were positioned in an urban area. After installing a monitoring well, five liters of groundwater were sampled using a stainless-steel bailer. The samples underwent sieving through a 63μm mesh stainlesssteel sieve, flotation, and filtration on mixed cellulose ester membrane filters. The samples were analyzed under a stereomicroscope for the identification and morphological characterization of particles (size, shape, and color). MPs were identified in all samples. In the soil, only fibers in transparent, blue, black, and red colors were observed, while in the groundwater, blue fragments were also identified. In the soil samples, the concentrations ranged from 1279 particles/100 g soil dw soil at 1 m depth, to 1658 particles/100 g soil dw at 5.5 m, to 2578 particles/100g soil dw at 6.5 m and 11616 particles/100 g soil dw at 10.5 m depth. In the groundwater sample, 255 particles/L were identified. The higher concentration of MPs in the saturated zone may be associated with sewage contamination from distant sources and transport through the aquifer, given the high vulnerability of the Bauru Aquifer System to contamination, as evidenced by nitrate levels above potability limits. All samples predominantly contained particles Also see: https://micro2024.sciencesconf.org/559510/document