Areas of research
Hydrologic and anthropogenic controls on riverine dissolved organic matter
The chemical composition, reactivity, and fate of dissolved organic matter in inland waters is largely driven by watershed source and hydrologic conditions. Within this realm, we are investigating dissolved organic matter dynamics in local waterways. Inland waters are stressed by the cumulative impacts of local anthropogenic activity and associated climate change, the latter of which is driving increased frequency and magnitude of storm events in the northeastern United States. We are currently working to develop mechanistic relationships between the chemical properties of dissolved organic matter and seasonal hydrologic behavior in the Hudson River and lake watersheds in upstate New York. In doing so, we will lay groundwork for predicting how climate change, human impacts, and enhanced runoff will impact the quantity and quality of dissolved organic matter in these systems. Extensive connectivity exists between rivers and the landscapes they drain. Therefore, we use dissolved organic matter as a continuous indicator water quality and carbon inputs to important recreational sites and drinking water sources utilized by regional New York communities.
Inputs and spatiotemporal behavior of black carbon in fire-affected systems
Wildfire produces charcoal and fundamentally alters watershed geomorphology and hydrology. Therefore, our ongoing research seeks to reveal and refine interactions between fire, rainfall, and landscape features to better explain and predict riverine black carbon export. Given the limited water supply in the western United States and the effects of wildfire on water management, understanding the impact of wildfires on water quality in rivers used for drinking water is of critical importance. Current collaborative projects aim to capture the “first flush” of carbon and nutrients in headwater catchments that burned during the 2020 California wildfire season. Given the inherent logistical challenges of sampling recently burned areas, we are capitalizing on a rare opportunity to track and predict the temporal evolution of black carbon and nutrient export immediately post-fire through watershed recovery. We are also investigating atmospheric sources of black carbon to aquatic systems, including ash deposition to coastal waters and fossil fuel versus biomass sources of black carbon aerosols in urbanized and high altitude environments.
Thermogenic sources of condensed aromatic carbon in the environment
Using a compound-specific stable carbon isotopic method, we discovered a large isotopic discrepancy between dissolved black carbon in rivers and the open ocean. This was a major finding as it challenged the long-held assumption that condensed aromatic carbon in the ocean is exclusively terrestrial and pyrogenic in origin. High-temperature processes, such as the geologic maturation or hydrothermal alteration, have been shown to produce a suite of condensed aromatic carbon molecules from organic matter that are similar in structure and function as fire-derived black carbon. Therefore, we are currently working to identify and constrain alternative sources for these refractory, condensed aromatic compounds. We have shown that petroleum, specifically the asphaltene fraction, contains a considerable proportion of condensed aromatic carbon and that compound-specific stable carbon isotopic analysis may be used to identify and track crude oil in aquatic systems. To better understand the limitations of the methods we use to quantify black carbon, we continue to investigate other petrogenic, hydrothermal, and biological sources condensed aromatic material in the environment.
