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DOC. Amy Elizabeth Barbera. What is DOC?. Dissolved Organic Carbon Operational definition- material that passes through filter with certain pore size (0.2-0.7 µm) Most of the DOM in the CFR is DOC. The CFR is a global riverine input to Oceans
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DOC Amy Elizabeth Barbera
What is DOC? • Dissolved Organic Carbon • Operational definition- material that passes through filter with certain pore size (0.2-0.7µm) • Most of the DOM in the CFR is DOC. • The CFR is a global riverine input to Oceans • Estimated overall riverine input is 0.2 x 1015 g C yr-1 • The main source of DOC in the CFR comes from terrestrial inputs and runoff from land.
DOC Determination • Equipment • Shimadzu TOC-5050 Analyzer • ASI 5000 autosampler • High Temperature Combustion furnace (680°C) • Preconditioned Shimadzu catalyst Al2O3 with 0.5% platinum • Calibration method • Standards (125.0 – 416.6 μM) • Reagent grade KHP with ultra pure MQ-H2O • Samples and standards were acidified to pH=2 with 2M HCl • Sparged with CO2free carrier gas to remove inorganic C • 5 min at a flow rate of 125 mL/min
DOC is combusted in the HTC-chamber • The combustion products are CO2, NO., H2O, • carried by pure CO2free air into a built in Peltier cooler at 1°C to remove water vapors. • Filtered • Shimadzu particle filter • (20mm Ǿ, sub-micron membrane) • Detected • Shimadzu NDIR detector • Measure carbon dioxide gas from the combusted carbon.
Surface vs. Deep Surface DOC is higher than deep DOC for cruise 2 because of the pronounced salt wedge. This salt wedge is not apparent in cruise 1.
DOC vs. Salinity Surface only
Long Term Trends in CFREDOC vs. Salinity Surface only