Emerging Pollutants in Groundwater: The Origin, Transport Pathways, Remediation, and Challenges

Emerging pollutants (EPs) constitute a diverse group of novel or evolving chemicals and compounds, which usually have concentrations ranging from nanograms (ng) to micrograms (μg) per liter in aquatic environments. As the human population and activities continue to escalate, EPs are increasingly released into the groundwater. Due to their physical characteristics, the EPs would be transferred into groundwater through natural water cycling, leaching, and direct disposal, potentially threatening living organisms. The lack of comprehensive understanding of EPs makes it challenging to establish relevant legislation or effectively remediate EPs in groundwater. The absence of policies and regulations addressing EPs can lead to widespread repercussions, impacting groundwater quality and the health, economy, and social fabric of communities reliant on this vital resource. This review specifically identifies and analyzes four EPs: per- and polyfluoroalkyl substances (PFAS), nano- and micro-plastics (MNPs), pharmaceuticals and personal care products (PPCPs), and microorganisms. The transport pathways, global distribution, and remediation strategies of such four EPs are discussed. Additionally, we examine the challenges encountered and propose avenues for future research. This review article aims to address the substantial knowledge gap faced worldwide, and it will help establish and enforce effective regulations crucial to safeguarding groundwater quality and ensuring a sustainable and healthy environment for present and future generations.