POSTER: Application of Radium Isotopes to Study the Transport of Dissolved Inorganic Carbon from the Caloosahatchee River to the Gulf of Mexico
Research Mentor: Dr. Puspa Adhikari
Additional Authors:
Abstract:
Dissolved Inorganic Carbon (DIC) is an important indicator of climate change and global warming. The four major species of DIC in the marine carbonate system (CO2, H2CO3, HCO3- and CO32-) act as major buffers in the ocean, making them integral in the study of ocean acidification. The short-lived radium isotopes (223Ra and 224Ra) can be used to track the residence times, mixing rates, and transport fluxes of water and associated DIC as well as nutrients in the coastal marine environments. In this study, we used radium isotopes to track the transport of DIC and nutrients (nitrate, nitrite, nitrogen, ammonia, and orthophosphate) from the Caloosahatchee to the Gulf of Mexico. Due to the lack of research in Southwest Florida, it is important to identify whether the influx of nutrients and DIC from the river plume affects the Gulf. Moreover, the utilization of radium isotopes aids in the development of river-gulf mixing models. We collected water samples for DIC, alkalinity, and nutrients from 20 sites along two transects throughout the Caloosahatchee and the Gulf of Mexico. For radium isotope analysis at each site, 40 liters of water samples were collected and then gravity filtered through manganese fibers. The Mn fibers were analyzed using a Radium Delayed Coincidence Counter (Radecc) for 223Ra and 224Ra. The activities of 223Ra and 224Ra varied respectively from 3.2 to 40.70 dpm/100L, and 8.35 to 126.25 dpm/100L. Similarly, the concentrations of total nitrogen, total phosphorous, and DIC varied from 1.60 to 0.25 µg/L, 94.90 to 18.05 µg/L, and 23.28 to 26.70 mg/L, respectively. While we are still working on further lab analyses, the preliminary results show that this region is a very spatially and temporally dynamic system. The radioisotopes showed mixed results by location, indicating that both groundwater influx and river discharge play important role in DIC and nutrients loading in this region. Upon completion, the results from this study will help determine the importance of freshwater plume discharge in tr ansporting DIC.