A Study of Heavy Metal and Suspended Particulate Fluxes Within the Mobile River System

This project utilizes two independent approaches to evaluate the suspended sediment (SS) flux and heavy metal flux to Mobile Bay: 1) satellite remote sensing and 2) geochemistry. Using the satellite approach, in-situ suspended sediment concentration (SSC) data will be used to calibrate reflectance data obtained from the satellite imagery in order to create a remote sensing algorithm which can be applied to other images of Mobile Bay at varying dates and flow conditions to produce sediment budgets and approximate heavy metal budgets. This is possible because sediment reflects light, especially near-Infrared light, much more readily than does water resulting in reflectance values acting as proxies for SSC values (Doxaran et al. 2002). Using the second geochemical approach, I will attempt to provide a greater understanding of the origins of the suspended material whose flux will be modeled in this study. The size of this drainage basin, which spans over three states, makes determining a precise origin location difficult, and the presence of the majority of the population of Alabama, extensive fishing and recreation, and 11 superfund sites within this watershed as well as eventual outflow into the Gulf of Mexico make understanding contributions to this system a valuable consideration. To delineate the sources of SS fluxes entering into the Mobile Bay Estuary, I will determine characteristic properties of various regions, including major and trace elemental composition, radiometric analysis, mineral composition and particulate size. Two main tributaries comprise the Mobile River Watershed, the Alabama River and the Tombigbee River. The rationale is that SS from these two watersheds inherit fingerprint properties of the source rock upstream (Haddadchi et al. 2013). Then, by modifying an existing mixing model which encompasses the various fingerprinting characteristics from these two end-members as well as the mixed suspended particulate of the outflow to Mobile Bay, I will be able to determine percent contribution of each system end-member to the SS outflow into Mobile Bay. If the fingerprinting of the sources proves successful, this could also help to provide insight into the movement of other materials in the system, such as nutrients and pollutants, given that they will be carried by the same forces as the SS.