Co-occurrence of microplastics, PFASs, antibiotics, and antibiotic resistance genes in groundwater and their composite impacts on indigenous microbial communities: A field study

There is a major gap in the occurrence of mixed emerging contaminants, which hinders our efforts in exploring their behaviors and transport in environmental media, as well as their toxicity to human and ecosystem. This study assessed the occurrence and their correlations of mixed contamination by microplastics (MPs), per- and polyfluoroalkyl substances (PFASs), antibiotics, and antibiotic resistance genes (ARGs) in groundwater collected from a pharmaceutical and chemical industrial park. MPs, PFASs, antibiotics and ARGs were detected at all monitoring wells. The total concentration range of MPs and 20 PFASs were 693-1032 pieces/L and 577.47-2982.45 ng/L, respectively, with perfluorooctanoic acid (PFOA) being the most prevalent compound among PFASs in groundwater. The abundance of detected target antibiotics and ARGs ranged from 1.97 to 30.65 ng/L and from 2.65 × 10² to 7.53 × 10⁵ copies/mL, respectively. MPs and PFASs have a significant positive correlation, yet interestingly, no correlation was found between antibiotics and ARGs. In addition, the relatively high abundance of integron intI1 detected in the study area illustrated the potential horizontal transfer risk of ARGs in the subsurface. Furthermore, the effects of these mixed emerging contaminants on the indigenous microbial communities were elucidated. The coexistence of MPs, PFASs, antibiotics, and ARGs led to the enrichment of species that were tolerant to pollutants. Specifically, MPs, PFASs and ARGs were found to be positively correlated with Acinetobacter, unclassified_f__Comamonadaceae, Pseudomonas, Simplicispira and Proteiniphilum, while antibiotics were positively associated with Paenisporosarcina and Arthrobacter. Moreover, geochemical parameters such as oxidation-reduction potential and nitrate also played a key role in shaping the microbial community structure. The co-occurrence of mixed emerging contaminants highlighted in this study underscores the urgent need for comprehensive environmental monitoring, systematic toxicity assessments, and stricter regulatory frameworks. In addition, it offers insights in the development of effective bioremediation strategies to mitigate their impacts on both ecosystems and public health.