Dissolved inorganic carbon

Dissolved inorganic carbon is present as three main species which are H2CO3, HCOs and CO. Analytically we have to approach the carbonate system through measurements of pH, total CO2 or DIC, alkalinity (Aik), and PcOj- In an open carbonate system there are six unknown species H", OH , PcOj/ H2CO3, HCOs, and CO . The four equilibrium constants connecting these species are K, Ki, Kh, and fCw. The values of these equilibrium constants vary with T, P, and S (Millero, 1995). To solve for the six rmknowns we need to measure two of the four analytical parameters (Stumm and Morgan, 1996). Direct measurement of Pco is the best approach, but if that is not possible then the most accurate and precise pair (Dickson, 1993) is Total CO2 by the coulometric method Johnson et al., 1993) and pH by the colorimetric method (Clayton et ah, 1995). 

Fig. 10-20 Observed depth profiles of (a) phosphate, (b) dissolved inorganic carbon (TC), (c) alkalinity (TA), and (d) oxygen for the Atlantic, the Indian, and the Pacific Oceans as indicated. Data are from GEOSECS stations within 5° of the Equator in each ocean. (Modified from Baes et al. (1985).)...

Fig. 11-9 (a) The vertical distributions of alkalinity (Aik) and dissolved inorganic carbon (DIC) in the world oceans. Ocean regions shown are the North Atlantic (NA), South Atlantic (SA), Antarctic (AA), South Indian (SI), North Indian (NI), South Pacific (SP), and North Pacific (NP) oceans. (Modified with permission from T. Takahashi et ah, The alkalinity and total carbon dioxide concentration in the world oceans, in B. Bolin (1981). Carbon Cycle Modelling," pp. 276-277, John Wiley, Chichester.)... 

For aerobic degradation, uptake of oxygen or the evolution of carbon dioxide is most widely used. Use of the concentration of dissolved organic carbon may present technical problems when particulate matter is present, though analysis of dissolved inorganic carbon in a closed system has been advocated (Birch and Fletcher 1991), and may simultaneously overcome problems with poorly soluble or volatile compounds. 

Birch RR, RJ Fletcher (1991) The application of dissolved inorganic carbon measurements to the study of... 

Kroopnick, P., Deuser, W. G., Craig, H., Carbon 13 Measurements on Dissolved Inorganic Carbon at the North Pacific (1969) Geosecs Station, J. Geophys. Res., 1970, 75, 7668-7671. 

The water samples were analysed for pH, electrical conductivity (EC), temperature (T), dissolved oxygen (DO), redox potential (Eh), reduced iron (Fe2+) and alkalinity (dissolved inorganic carbon, DIC, as HC03") in the field. A few special water samples were collected to determine background levels of CD4, SF6 and Kr in the headspace gas. SWL and T were recorded hourly in 3 shallow (Sites H, I, R) and 3 deep (Sites J, V, W) open bores using automatic data loggers, which were downloaded biannually. 

Previous studies addressed oceans and terrestrial vegetation as C02 sinks. Here, we describe an important C02 sink in carbonate dissolution, the global water cycle (GWC), and uptake of dissolved inorganic carbon (DIC) by aquatic. The sink is larger than previous estimates (Meybeck 1993 Gombert 2002). 

The following boxes present four case studies to illustrate how the introduction of reference materials has decreased the uncertainty of the chemical oceanographic measurement of salinity (Box 2.1), DOC (Box 2.2), and dissolved inorganic carbon (DIC) (Box 2.3). Box 2.4 illustrates the acute need for pigment reference materials, which are currently unavailable. 

Redfield (1934), who analyzed the major elemental content of many samples of mixed plankton (phytoplankton and zooplankton) caught in nets towed through the surface ocean. They compared the carbon, nitrogen, and phosphorus composition of these collections to concentration profiles of dissolved inorganic carbon (DIC), NOs, and P04 throughout the water column. This pioneering research demonstrated that these three elements are continually redistributed in the ocean by selective removal into plankton cells and their remains (i.e., fecal pellets), which are then efficiently respired as they sink through the marine water column. 

Quay, P.D., R. Sonnerup, T. Westby, J. Stutsman, and A.P. McNichol. In press. Anthropogenic changes of the 33C/32C of dissolved inorganic carbon in the ocean as a tracer of C02 uptake. Global Biogeochemical Cycles. 

Ocean C02 RMs Natural Seawater Total Dissolved Inorganic carbon, Total Alkalinty Dr. A. G. Dickson, U.C. San Diego 1 ... 

Sampling sites are also referred to as station locations. For water column work, depth profiles are constructed from seawater samples collected at representative depths. Temperature and salinity are measured in situ with sensors. Remote-closing sampling bottles deployed from a hydrowire are used to collect water for later chemical analysis, either on the ship or in a land-based laboratory. The standard chemical measurements made on the water samples include nutrients (nitrate, phosphate, and silicate), dissolved O2, and total dissolved inorganic carbon (TDIC) concentrations. 

Vertical distributions of total dissolved inorganic carbon (TDIC) in the subtropical South Atlantic (19°S 16°W) and equatorial North Pacific (9°N 135°W) oceans. These are WOCE data obtained from Java Ocean Atlas. 

Dissolved inorganic carbon (DIG) is present in seawater as the following species carbon... 

Effect of temperature, pressure, and salinity on speciation of the dissolved inorganic carbon for 2co2 = 2mmol/kg. Source After Zeebe, R.E. and D. Wolf-Gladrow (2001) Elsevier Oceanography... 

Surface water concentrations of (a) total alkalinity ( ji,mol/kg) and (b) dissolved inorganic carbon (ljumol/kg). Source After Key, R. M., et al. (2004). Global Blogeochemical Cycles 18, GB3011. (See companion website for color version.)... 

Equations 11.171.1 to 11.171.3 are, however, of limited practical application because they demand precise knowledge of the state of speciation of carbonates in aqueous solution during solid phase condensation (or late exchanges). The fact that different carbonate solute species distinctly fractionate is masterfully outlined by the experiments of Romanek et al. (1992), which indicate a marked control by solution pH of the fractionation between total dissolved inorganic carbon (DIC) and gaseous CO2 (figure 11.38). 

Fig. 2.15 Oxygen isotope fractionations between dissolved inorganic carbon (DIC) and water as a function of pH and temperatures (after Beck et al. 2005)...

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