The carbon dioxide system in seawater is conventionally described by measuring two or more of four CO2 system parameters: pH, total alkalinity, total dissolved inorganic carbon, and fugacity of CO2. We present recent improvements in a method for directly determining carbonate ion concentrations in seawater using Pb(II) UV spectroscopy. The method uses the salinity dependence of lead carbonate-lead chloride equilibrium quotients and absorbance ratios to directly determine carbonate ion concentrations. Recent characterizations of Pb(II) molar absorptivity properties at shorter wavelengths should increase the method sensitivity for shipboard analyses performed at 25 �C. Using new fitting parameters, data from cruises in the Arctic Ocean and Eastern Pacific are compared with carbonate ion concentrations obtained using conventional methods. We will also present algorithms which allow in situ carbonate ion analysis over a range of temperature (5 �C� 40�C) and pressure (0 � 800 bar).

Direct carbonate ion determinations using Pb(II) UV spectroscopy for in situ analysis in seawater

245th National Meeting (2013)

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