This proof-of-concept project focuses on determining the behavior of co-occurring nanoplastics (NP) and associated per- and polyfluoroalkyl substances (PFAS) during environmental transit within a novel type of constructed wetland that holds promising efficacy for the treatment of a wide variety of chemicals of concern, when contrasted with traditional vegetated wetlands. However, the implications of this nature-based design on NP and PFAS in isolation or as a collective are not understood. The controlled nature of the laboratory-scale approach, and its demonstrated applicability to query field-scale mechanism, could further provide insights into the environmental fate and transport of these co-occurring chemicals in other surface water systems such as wetlands, streams and estuaries.

Specific project objectives are designed to:

1. Establish a standardized protocol for NP quantification during wetland transit.
2. Model the sorption behavior of select PFAS onto NP for influent water conditions.
3. Determine the transport parameters of different types of NP through the lab-scale treatment wetland.
4. Leverage these learnings to quantify the impact of this treatment wetland on NP-PFAS interactions, fate, and transport.

The colloidal nature of NP, coupled with their propensity to self-aggregate in the presence of dissolved organic matter (DOM), poses challenges for their quantification. Furthermore, when evaluating the sorption behavior of PFAS onto NP, the extent to which this association is influenced by NP characteristics (composition, reactive surface area, age), or various aqueous environmental factors such as pH, salinity, DOM, and redox conditions can be highly variable. To address these challenges, a novel NP tagging and tracking technology developed by the project team will be enhanced, where a small quantity of exogenous metal dopants (e.g., Ta, Sn) are used to calibrate particle number. This tracer technique will enable precise measurement of NP amidst natural background particles like cells and clays and hence track NP transit through laboratory-scale systems. Subsequently, the project team will establish a targeted subset of NP-PFAS sorption isotherms for different plastic states (weathered versus virgin), two polymer compositions, and PFAS classes (anionic versus cationic). In complement, the project team will assess NP transport dynamics in model flow-through wetland systems. Insights will inform targeted applications in culminating experiments to better understand the interconnected fate and transport of NP and associated PFAS during wetland transit. The demonstrated scalability of the laboratory infrastructure will provide a foundation for future field-scale research in an operational treatment wetland where the project team could optimize wetland design and operation to manage the fate and transport of emerging chemicals.

Expected benefits include: 1) closing data gaps regarding the intricate interactions between NP and PFAS in aquatic systems, allowing for better decision-making regarding treatment of impacted sites; 2) improved analytical detection of nanoplastics and associated COC; and 3) wetland-based treatment of NP and PFAS could help meet regulatory requirements related to water quality. Ultimately, the results of this study will contribute to the DoD's ability to manage PFAS-impacted sites, ultimately improving implementation of cost-effective solutions that support critical defense infrastructure and the workforce. (Anticipated Completion Date - 2026)