US EPA

5020556 

Journal Article 

Mercury sequestration and transformation in chemically enhanced treatment wetlands 

Bachand, PAM; Kraus, TEC; Stumpner, EB; Bachand, SM; Stern, D; Liang, YL; Horwath, WR 

2019 

Yes 

Chemosphere
ISSN: 0045-6535
EISSN: 1879-1298 

Elsevier Ltd 

217 

496-506 

English 

30439661 

10.1016/j.chemosphere.2018.10.144 

WOS:000456223500054 

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85056458173&doi=10.1016%2fj.chemosphere.2018.10.144&partnerID=40&md5=20a6e7ff567e140e0242264914d57dbb
Exit
 

Mercury (Hg) pollution is a concern to human and wildlife health worldwide, and management strategies that reduce Hg inputs to aquatic systems are of broad interest. Using a replicated field-scale study in California's Sacramento-San Joaquin Delta, we tested the effectiveness of chemically enhanced treatment wetlands (CETWs) under two coagulation treatments, polyaluminum chloride (Al treatment) and ferric sulfate (Fe treatment), in their initial removal and longer-term sequestration of Hg compared to untreated control wetlands. The primary mechanism for Hg removal by CETWs was the transfer of Hg from filtered forms to insoluble particulate forms and enhanced settling of particles. CETWs resulted in total Hg annual load removals of 63 ng m-2 yr-1 (71%) and 54 ng m-2 yr-1 (54%) for the Al and Fe treatments, respectively. Control wetlands removed significantly less at 13 ng m-2 yr-1 (14%). Load removals indicate that Fe treatment wetlands more effectively reduced filtered and total methylmercury (MeHg) exports, while Al treatment wetlands more effectively reduced particulate MeHg and total Hg exports. These differences in Hg species load reductions possibly indicate different mechanisms of Hg sequestration; current data suggest more effective floc formation and particle settling was likely responsible for the Al treatment behavior, while either preferential MeHg sequestration or methylation suppression was potentially responsible for Fe treatment behavior. Differences in Hg sequestration behavior post-coagulation between the flocs formed by different coagulants indicate the importance of in-situ studies and the need for careful selection of coagulant treatment depending on the Hg species requiring remediation. 

Agricultural drain water; Constructed wetlands; Mercury; Methylation; Sacramento-San Joaquin Delta; Water treatment