HR: 0800h
AN: B41B-07    [Abstracts]
TI: A Simple, Buoy Deployable Instrument for Accurate Dissolved Carbon Dioxide and Dissolved Inorganic Carbon Measurements in Freshwater and Marine Ecosystems
AU: * Browne, B A
EM: bbrowne@uwsp.edu
AF: University of Wisconsin - Stevens Point, College of Natural Resources 800 Reserve Street, Stevens Point, WI 54481, United States
AU: Wyss, J R
EM: jwyss@uwsp.edu
AF: University of Wisconsin - Stevens Point, College of Natural Resources 800 Reserve Street, Stevens Point, WI 54481, United States
AU: Bowling, J M
EM: jbowling@uwsp.edu
AF: University of Wisconsin - Stevens Point, College of Natural Resources 800 Reserve Street, Stevens Point, WI 54481, United States
AU: Schueller, D J
EM: dschu502@uwsp.edu
AF: University of Wisconsin - Stevens Point, College of Natural Resources 800 Reserve Street, Stevens Point, WI 54481, United States
AU: Sherman, J F
EM: jsherman@uwsp.edu
AF: University of Wisconsin - Stevens Point, College of Natural Resources 800 Reserve Street, Stevens Point, WI 54481, United States
AB: The need for better knowledge of (1) the oceanic sink for anthropogenic CO₂, (2) the impact of anthropogenic CO₂ on the oceanic CaCO₃ system and (3) lake and stream metabolism in freshwater ecosystems is driving growing interest in real-time technologies to measure pCO₂ and dissolved inorganic carbon (DIC). To be useful, these technologies must meet stringent data quality requirements of marine and freshwater biogeochemical research initiatives such as the Joint Global Ocean Flux Study, the Coral Reef Environmental Observatory Network, the National Ecological Observatory Network, and the Global Lake Ecological Observatory Network. In this presentation, we introduce new methodology and a device for unaccompanied measurement of pCO₂ and DIC on research buoys or ocean/freshwater vessels. This small-scale, essentially "plug and play" device (shoe box size) has limited power requirements (≤1.8 amps) for continuous or discontinuous (e.g., one reading per hour) measurements and does not bio-foul. DIC and pCO₂ can be measured in sequence using one infrared detector or in parallel using two. The accuracy and precision (<0.15% coefficient of variation) for pCO₂ and DIC meet or approximate the data quality requirements for large-scale biogeochemical research initiatives. Training requirements are minimal, providing flexibility for deployments on multiple vessel types. The device works by induction of ebullition. A hydrostatic pressure drop upstream of a pump causes a temporary condition of gas oversaturation. The collection cell downstream of the pump then acts like an overpressurized soda bottle. As pressure is released within the collection cell, the dissolved gas streams passively and reliably into the infrared detector(s), at a nominal rate of 7 mL per minute, carrying CO₂ into the cell essentially at its in-situ partial pressure. To measure DIC, a valve allows for the addition of acid to the sampling line upstream of the pump converting all DIC to CO₂ prior to reaching the collection cell. With the acid valve on, DIC is measured. With the acid valve off, pCO₂ is measured. We will present data illustrating the accuracy and precision of this device in both laboratory and field circumstances. We will also show the unique possibility of coupling not only pCO₂ and DIC in one device, but dissolved organic carbon as well.
DE: 0428 Carbon cycling (4806)
DE: 1806 Chemistry of fresh water
DE: 1895 Instruments and techniques: monitoring
DE: 4806 Carbon cycling (0428)
DE: 4894 Instruments, sensors, and techniques
SC: Biogeosciences [B]
MN: 2007 Joint Assembly