Microplastic pollution in groundwater: a systematic review

Groundwater, a crucial freshwater source faces increasing pollution from microplastics (MPs). This study aims to comprehensively review the aquifers, sampling and analysis methods, pollution levels, polymer types, and sizes of MPs in groundwater worldwide between 2017 and 2023. Very few reports exist on the abundance, polymer type, size, and other characteristics of MPs in the field. The tools, methods, and sample collection quantities used for field sampling varied considerably among studies. However, efforts to enhance our understanding of MP analysis results through groundwater level measurements, on-site water quality parameters, ion analysis, and field blanks have been limited. The analysis results mostly indicated higher concentrations in urban and industrial areas and landfill sites, whereas lower concentrations were observed in areas with minimal human influence. MPs in groundwater are predominantly polypropylene and polyethylene. Standardized sample collection and analysis methods are needed to further promote research on MPs in groundwater and facilitate cross-comparisons.