Metal Removal, Distribution, and Bioavailability in a Constructed Wetland

Metal removal, distribution, and bioavailability in the H-02 constructed wetland located on the Savannah River Site, SC, USA were evaluated to validate operational efficiency of the wetland. The presented study is a detailed mechanistic investigation conducted over three months in the summer of 2023, marking 15 years of wetland operation. Results complement and help explain long-term performance data from other studies. The study not only evaluated the efficiency of copper (Cu) and zinc (Zn) removal from the Tritium Extraction Facility’s effluent and stormwater runoff but also delved into the specific binding characteristics of these metals to organic matter and mineral surfaces. Advanced factorial ANOVA was employed to evaluate spatial differences and interactions affecting metal retention. Utilizing diffusive gradient thin films (DGT) in both water and sediment probes, this study found substantial reductions in bioavailable Cu and Zn concentrations along the wetland flow path. The bioavailability and potential toxicity of the metals were analyzed thoroughly, revealing that the majority of retained Cu and Zn were immobilized and not bioavailable. Total metal concentrations in the effluent were lower than the regulatory discharge limit with an average removal efficiency of 62.0% for Cu and 76.9% for Zn. These findings underscore the wetland’s effectiveness in enhancing metal retention, reducing bioavailability, and maintaining compliance with environmental regulations over several years.