IDENTIFYING THE SOURCES OF ORGANIC CARBON IN SEDIMENT DEPOSITED BY THE MISSISSIPPI RIVER FLOOD OF 2019

Large volumes of mineral and organic sediment as well as anthropogenic pollutants, for instance windblown coal dust from a nearby terminal, are mobilized during floods of the Mississippi River. Sediment carried by floodwaters constitutes the raw material that nourishes the rapidly disappearing wetlands of coastal Louisiana. In this study, we analyze the sediment deposited in the Bonnet Carre Spillway during the Mississippi River flood of 2019 to quantify and characterize organic carbon in the deposit. These measurements will inform estimates of the burial rates of organic carbon in river diversions like the Bonnet Carre Spillway. Buried organic carbon contributes to the overall volume of carbon sequestered in wetland development schemes. Funding for these initiatives could be offset through the sale of carbon credits to industries responsible for emitting large volumes of green-house gases.

We will present preliminary progress towards the project goals of: (1) quantifying the ratio of organic carbon to mineral sediment in the suspended load and bedload deposits within the Bonnet Carre Spillway, (2) separating the detrital organic fraction from the fraction of contaminant coal in the deposits using Wavelength-Dispersive X-Ray Spectroscopy, and (3) placing the organic carbon fraction sequestered in the spillway deposits from the 2019 flood within the context of organic carbon fractions in sediment deposited in the upstream portions of the Mississippi River network. By estimating carbon burial rates, and characterizing the sources of organic carbon present, we are building a data-set of carbon burial rates that will inform models for future diversion projects on the Mississippi Delta.