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CONCENTRATIONS AND LOADS OF NITRATE IN THE ATCHAFALAYA RIVER, LOUISIANA, USING CONTINUOUS MONITORING
Impact/Purpose:
USGS will use the information generated to predict hypoxic zone size in the Gulf of Mexico.
The tasks are as follows:
Task 1. Instrumentation for the continuous (hourly) measurement of nitrate concentrations will be installed at the Atchafalaya River at Butte La Rose, Louisiana. This instrumentation utilizes fluorometry-based, cadmium-reduction methodology. This method, although commonly used in laboratories, is relatively new for field-deployed instruments.
Task 2. Data will be collected for one year, although the USGS plans to develop this study into a long-term cooperative network. The site will be visited weekly by USGS personnel for the first two months of operation. The site will then be visited bi-weekly or monthly.
Task 3. Water samples will be collected for the first two months during each site visit for analysis at the USGS National Water Quality Laboratory for calibration, verification, and QA/QC purposes. Additional water samples will be collected and analyzed during a rapid rise in river stage to verify the monitor,s ability to track rapidly-changing nitrate concentrations. The ability to accurately document nutrient changes during rapid hydrologic changes is considered critical to the success of the project.
This project will directly address the Gulf of Mexico Program,s Sub-Objective4(A)(1): Implement coordinated federal/state program to develop eutrophication model for the northern Gulf hypoxic zone.
Description:
Specific Results/Outcomes Expected: Deliverables of each Tasks include: Task 1. Several field studies by USGS personnel have shown that iono-selective nitrate probes currently marketed do not meet performance minimum criteria for accurately measuring nitrate concentrations. The new technology allows the USGS to gather this information. Task 2. Nitrate concentration data will be collected along with water samples, water temperature, and specific conductance. Measuring in-stream nitrate concentrations combined with stream-discharge information will allow researchers and data managers to better quantify the nitrate yield, and ultimately predict the size of the hypoxic zone in the Gulf of Mexico. Task 3. Information from the water samples will aid in the interpretation of nitrate information from this site. Data produced by this project will be made available to other researchers.