Organic Matter Method Development
An enduring limitation to geochemical studies aiming to link climate or land-use change for example, to dissolved organic matter (DOM) flux or reactivity in aquatic systems has been the issue of both temporal and spatial scaling. Within the lab we have directed significant effort toward utilizing optical analyses (e.g. absorbance and fluorescence) as proxies for more intensive and expensive analytical analyses (e.g. molecular-level organic biomarkers). These optical measurements can now be undertaken in-situ at high temporal resolution and allow for the development of more accurate carbon or biomarker export flux terms. Ongoing work has also shown the potential of linking such optical measurements to DOM biochemical composition and age in a host of aqueous settings from permafrost thaw streams in Siberia to major river systems such as the Mississippi and Congo. Robust development and ground truthing of optical measurements continues as a major focus of the lab with the goal of moving aquatic geochemistry from the lab to the field at high temporal resolution to improve flux estimates, and also to assess the reactivity of DOM and thus its fate at more temporally relevant timescales. Such optical measurements also hold great promise for improving spatial scaling of DOM through linkages to watershed features and via remote sensing applications. Another major theme of development in the lab is calibration of DOM source biomarkers (e.g. vascular plant, microbial) and their response to microbial and photochemical degradation using well-defined endmembers. This ongoing work aims to improve the tool-set available for quantitatively parsing source contributions to the DOM pool, which is key for getting at the role different DOM pools will play in the environment.