Autonomous instrumentation for measurement of the inorganic carbon parameters pCO , pH, TCO and TA 2 2 Mike DeGrandpre Department of Chemistry The University of Montana Missoula, MT USA Motivation • pCO , pH, TCO and TA 2 2 • why autonomous sensors? Challenges • cannot be measured directly by optical methods • exceptional precision and accuracy required • more complex fluidic-based designs Alliance for Coastal Technologies (ACT) Workshop on “In situ measurement of dissolved inorganic carbon species” February 2005. Primary sensing mechanisms • pCO 2 - gas equilibration with infrared analysis - spectrophotometric (indicator) sensors • pH - spectrophotometric (indicator) sensors • TCO 2 - acidification with conductimetric detection - acidification with spectrophotometric (indicator) detection • TA - titration with spectrophotometric (indicator) detection autonomous pCO instruments 2 • infrared/equilibrator (Friederich) • spectrophotometric = membrane + indicator - CARIOCA buoy (Merlivat) - SAMI-CO (DeGrandpre) 2 autonomous pCO instruments 2 MBARI M1 Mooring in Monterey Bay CARIOCA buoys in the Southern Pacific Ocean SAMI deployment in the Labrador Sea (2004) Autonomous pH instruments spectrophotometric (indicator) based ⎛ [I− ] ⎞ pH = pK + log⎜ ⎟ ⎜ ⎟ a [HI] ⎝ ⎠ - SEAS instrument (R. Byrne) - SAMI-pH (ours) - others Autonomous pH instruments (SEAS, Byrne) Calculated Parameter System Configuration seawater pH seawater + indicator T seawater LCW from Byrne and colleagues