Nitrogen sourcing in groundwater (2014)
This project quantitatively examined wastewater signatures in groundwater emanating from two coastal aquifers on O'ahu, Hawai'i, using N and O stable isotopes and a recharge model. We found that cesspools contribute only ~4% of recharge in the Waialae West Aquifer, but account for 54 to 95% of total N and P loads in the aquifer. Read more here
Submarine groundwater discharge and reef biogeochemistry (2015)
We investigated the relationship between coastal groundwater discharge and reef biogeochemistry to better understand how differences in groundwater geochemistry may drive changes in proximal marine carbonate chemistry. Overall, sites closest to groundwater inputs showed reduced calcification and elevated dissolution rates relative to sites further from the groundwater discharge points at both reefs. Read more here
Lateral carbon loss in drained peatlands (2016 to present)
This project will provide a broader understanding of the hydrologic and biogeochemical processes that influence aqueous C exports from peat-rich islands in the Sacramento-San Joaquin Delta in central California. This work is relevant to the management of the Delta ecosystem as dissolved C losses may contribute to island subsidence, and the delivery of dissolved C from Delta islands to surrounding waterways can create water quality issues both in the Delta and in water exported to other areas of California.
Biogeochemical controls on agricultural drainage geochemistry (2016 to present)
This project examines the dominant sources and biogeochemical processes that influence macronutrient, major dissolved ion, and trace element concentrations in agricultural drainage in the Sacramento-San Joaquin Delta using a suite of stable isotope tracers and geochemical parameters. This project will establish a baseline understanding of the geochemistry of a poorly-characterized anthropogenic input to the larger Delta environment.
Nitrogen sourcing in rivers
(2017 to present)
This project examines how water and nitrate sources to the San Lorenzo River in central coastal California shift during annual streamflow transitions to baseflow. This work combines a commonly used endmember mixing analysis with stable isotope data, a relatively novel approach to nitrate sourcing in watersheds. These results will be useful to both local and state agencies who are interested in locating nitrate sources in rivers for more targeted management approaches.
Historical changes in river nitrate concentrations in relation to land use metrics (2018 to present)
Long-term records of discharge and nitrate concentrations from select central coastal California rivers are being analyzed to evaluate the evolution of nitrate inputs in these systems and their possible relation to land use metrics. This information is critical to our understanding of nitrate dynamics in ecologically-important rivers and allows for the evaluation of management success in different watersheds.