Wildfire is a prominent global ecosystem disturbance that is expected to increase in size and intensity with projected changes in future climate. Wildfire ash materials are highly susceptible to fluvial transport by rainfall-runoff processes thereby impacting downstream aquatic ecosystems. Upon deposition in aquatic environments, dissolved organic matter (DOM) can be released from the ash (as DOMash) and interact with ambient dissolved metals, such as mercury (Hg). However, DOMash derived from ash materials can be markedly different from DOMnom released from natural organic matter (NOM) sources such as decomposing litter and soils. Thus, Hg interactions with DOMash may reveal unique reactions that have unknown consequence for this global pollutant. In particular, DOMash have been found to be enriched in condensed aromatic hydrocarbon but less lignin-type compounds. Therefore, the abundance of functional moieties in chelating Hg in DOMash could be different from DOMnom. Our laboratory incubations of wildfire ash materials showed a very low bioavailability of Hg to methylating microbes when associated with DOMash. To gain a better mechanistic understanding, we used Fourier Transform Ion Cyclotron Resonance mass spectrometry (FTICR-MS) to examine the molecular interactions between Hg and DOMash. These new insights characterizing Hg-DOMash interactions from wildfire ash provide important information for assessing the impacts of wildfire on DOM transformations and Hg biogeochemistry in aquatic ecosystems.

Biogeochemical interactions of mercury with wildfire ash derived-dissolved organic matter

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.