Geology Seminar Series - Jamie Schmidt, MSc student - The geochemical controls on mercury methylation and sulphur cycling in Prairie Pothole Region wetland complexes

Wed., Jan. 25, 2023 4:00 p.m. - Wed., Jan. 25, 2023 5:00 p.m.

Location: College West Room 237.1

We are excited to invite you to our very first seminar this winter semester as apart of the Geocience Seminar Series. Note this seminar will be offered in person only.

Topic: The geochemical controls on mercury methylation and sulphur cycling in Prairie Pothole Region wetland complexes

Date and Time: Wednesday, January 25, 2023 at 4:00 PM

Location: College West Room 237.1 (Note a new location)

Speaker: Jamie Schmidt - Master Student, Dept. of Geology, University of Regina

Abstract:

Fossil fuel combustion and industrial emissions have contributed to increased levels of atmospheric mercury (Hg) globally. Deposition of atmospheric Hg in aquatic ecosystems can lead to the generation of methylmercury (MeHg), a neurotoxin that may bioaccumulate in food webs. Methylmercury in wetland ecosystems is formed as a by-product of various anaerobic metabolic processes, including bacterial sulphate reduction (BSR). Yet, the formation of MeHg in the Prairie Pothole Region (PPR) wetland complexes remains poorly understood due to variability in hydrology and biogeochemistry.

This thesis project explores the geological and geochemical controls and influence of sulphur cycling on MeHg production at the St. Denise National Wildlife Area (SDNWA) within the PPR. Dependant on the hydrologic position and prevailing water and sediment geochemistry, the wetland ponds of the SDNWA produce varying MeHg levels. Trace metal sediment geochemistry and stable sulphate isotope signatures for sediment pore water for three representative ponds indicate that there are distinct differences in metal cycling and the microbial processing of Hg in high and low MeHg ponds. In addition, contrary to other sulphate rich systems, the wetlands of the PPR appear host an active community of bacterial sulphate reducers capable of ongoing Hg methylation in sulphate rich porewaters. It has been determined that the topographic position and the prevailing bottom water and sediment redox conditions of the wetlands fundamentally influence both sulphur and metal cycling in the ponds.