NOAA's recent field testing of coastal water quality monitoring systems - quantifying impacts of biofouling and investigating chloride measurement techniques

The National Oceanic and Atmospheric Administration (NOAA) Center for Operational Oceanographic Products and Services (CO-OPS) maintains and continues to develop over 300 hundred coastal observatories throughout the United States, which make up the National Water Level Observation Network (NWLON), and 22 integrated Physical Oceanographic Real-Time Systems (PORTS). In-situ, real-time observations of various water quality parameters, including dissolved oxygen, pH, turbidity, chloride, conductivity and temperature, have been identified as measurements of critical interest in many coastal regions where CO-OPS' real-time infrastructure exists. Of these parameters, only conductivity and temperature are collected at a limited number of CO-OPS' existing stations. CO-OPS has recently begun development and testing of real-time water quality systems that could be integrated with existing NWLON and PORTS stations, thereby leveraging infrastructure and enhancing the data available at locations with rich records of historical oceanographic and meteorological data. Field tests of multiple real-time water quality measurement systems were conducted at sites collocated with existing operational water quality sondes maintained by the Chesapeake Bay National Estuarine Research Reserve in Virginia (CBNERR-VA). One site was located in a polyhaline environment, a salinity regime typical of most CO-OPS observatories, and a separate freshwater site was chosen in order to test the performance of in-situ chloride probes. In addition to evaluating instrument performance and demonstrating system integration, these tests focused on two unique aspects of particular interest to CO-OPS: 1) assessing calibration and maintenance requirements through the side by side comparison of three multi-sonde water quality systems, one with a rigorous and routine maintenance program, and two others with sensors intentionally unmaintained; and 2) a comparison of chloride measurements obtained using three different methods: laboratory analysis, derivation from conductivity, and direct, automated measurement from an ion-selective electrode (ISE) sensor. This paper includes a brief description of test system design, a summary of system integration efforts, results of test data analysis, and plans for continuing work driven by the results of this study.