Water Resources Research Act Program

Details for Project ID 2019LA117B

Quantifying fluxes of dissolved carbon and CO2 outgassing from the Lower Mississippi River before entering the Gulf of Mexico

Institute: Louisiana
Year Established: 2019 Start Date: 2019-02-28 End Date: 2020-02-28
Total Federal Funds: $16,800 Total Non-Federal Funds: $38,265

Principal Investigators: Y. Jun Xu

Project Summary: Draining approximately 48% of the continental US land surface, the Mississippi River flows through Louisiana before entering the Gulf of Mexico. The river annually discharges about 680 cubic kilometers of water with a tremendous quantity of dissolved and particulate materials, strongly affecting chemical, physical and biological domains in Coastal Louisiana. Understanding organic carbon dynamics in and delivery from the Lower Mississippi River to the Gulf of Mexico is important to the management and conservation practices of estuarine, coastal and marine ecosystems in coastal Louisiana. This proposed research will investigate dissolved carbon transport and transformation in the Lower Mississippi River from Baton Rouge at River Mile (or RM) 228 to Belle Chasse at RM 76. The research will conduct instream measurements on partial pressure of dissolved carbon Dioxide (pCO2) and ambient water quality parameters, and will collect water samples for chemical analysis of dissolved inorganic carbon (DIC) dissolved organic carbon (DOC), as well as their carbon-13 isotopes(). DIC and DOC fluxes at these two locations will be quantified and their fluctuation under different seasons and varying flow conditions will be analyzed. Carbon Dioxide (CO2) outgassing from the river surface water will be calculated using field pCO2 measurements, and the total outgassing rate from the 152-mile river reach between Baton Rouge and Belle Chasse will be estimated. Findings from this proposed research will provide much needed updates on the latest dissolved carbon transport from North America's largest river and will fill in a critical knowledge gap in dissolved carbon emission from the river. Such information is not only scientifically interesting but also practically relevant to resource managers and policymakers seeking to improve and protect coastal resources in Louisiana. The Mississippi River Basin represents an excellent example of a nature-human coupled terrestrial-riverine system. The processes of generation, transport and transformation of organic carbon in such a coupled system should be climate-sensitive, yet their functioning is rarely considered in hydrological prediction and their response to climate change is still largely unknown. With the data that we gain from this proposed research, we will make a first step contributing to predicting future riverine carbon fluxes from the Mississippi River Basin to Louisiana's waters, aquatic life, and wetlands, as well as to reducing the large uncertainty in current global estimates of riverine carbon.