EAR-PF Short- and long-term effects of wildfire and permafrost thaw on mercury cycling and bioavailability across a major northern river delta landscape

Zolkos, Scott P, Falmouth MA

Investigators

Abstract

Dr. Scott Zolkos has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education plans at Harvard University and the Woods Hole Research Center. The proposed research will investigate the effects of wildfire and permafrost thaw on mercury and its transformation into the neurotoxicant, methylmercury, in northern high-latitude ecosystems. Northern soils represent Earth’s largest natural reservoir of mercury. The stored mercury is vulnerable to release and transformation as northern warming accelerates permafrost thaw, intensifies wildfire regimes and hydrological cycles, and strengthens land-freshwater linkages. In freshwaters like lakes and ponds, the uptake of methylmercury into food webs has potentially significant implications for ecosystem and human health. Soils and freshwaters in the Yukon-Kuskokwim (YK) Delta, Alaska, will be analyzed to better understand mercury release and methylation across gradients of wildfire and permafrost thaw. By testing the effects of ecosystem disturbance on mercury cycling in the YK Delta, this work seeks to advance understanding of rapidly changing northern contaminant cycles, from a process level to across spatial and temporal scales. Education and outreach activities include undergraduate mentoring, knowledge co-production and transfer with local northern residents, and public dissemination of findings through international early-career polar scientist networks. Among the most significant implications of northern wildfires and permafrost thaw is the release of mercury (Hg) from soils into the atmosphere and freshwaters, and the production of methylmercury (MeHg). Lakes and ponds integrate biogeochemical processes across their watersheds, providing an ideal setting to test the effects of ecosystem disturbance on Hg cycling. Working in watersheds within recent and historical burns, the proposed research will use a space-for-time substitution approach to determine wildfire and permafrost thaw effects on Hg cycling over short (sub-decadal) and long (decadal) timescales. Synoptic measurements of soil Hg will be paired with remote sensing estimates of wildfire severity and a global atmospheric Hg model to determine the magnitude and fate of Hg released from soil combustion into the atmosphere. Coupled hydrochemical measurements of Hg concentration (total and MeHg) and stable isotopes, organic matter, and nutrients will be used to constrain wildfire effects on the hydrologic transport and methylation of Hg within freshwaters during the thaw season. Models for scaling these effects across regional freshwaters will be developed by testing the relationships between Hg, spectral properties of dissolved organic matter, and remote sensing measurements of water surface reflectance. In addition to the development of the next generation of northern Hg cycle models, broader impacts include mentoring and training of undergraduate students through the Polaris Project and outreach activities with northern communities in Alaska. This project received co-funding from the Hydrological Science program in the Earth Science division. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.