Dissolved inorganic carbon, DIC

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.)... 

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. 

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)...

Dissolved inorganic carbon DIC C02. Quantity depending on pH, temperature, and partial pressure of C02 TIC = DIC + PIC... 

Tue-Ngeun, O., R.C. Sandford, J. Jakmunee, K. Grudpan, I.D. McKelvie, and P.J. Worsfold. 2005. Determination of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in freshwaters by sequential injection spectrophotometry with on-line UV photo-oxidation. Anal. Chim, Acta 554 17-24. 

Figure 5.3 Calculated values of partial pressure of CO2 (/>C()2), based on dissolved inorganic carbon (DIC) and pH data, versus salinity in estuarine waters of the Satilla and Altamaha Rivers (USA). (Modified from Cai and Wang, 1998.)...

Figure 9.1 Freshwater-marine mixing ratios of dissolved inorganic carbon (DIC) and isotopic composition (DI13C) across three different salinity gradients. Bottom isotopic change between — 10%e at the freshwater end-member, and +2%c at the marine end-member, both end-member values are based on concentration-weighted averages (data sources Spiker and Schemel, 1979 Spiker, 1980). (Modified from Fry, 2002.)...

Carbon is transported into the Amazon River/ocean mixing zone in numerous forms including dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and particulate organic carbon (POC). The average DIC, DOC, and POC concentrations in Amazon River water are 460, 275, and 180 pmol L-1 (Richey et al. 1991), which indicates that DOC supply exceeds POC supply and that DIC is the most abundant form of carbon in the river. Sholkovitz et al. (1978) noted that most riverine dissolved... 

Over the last several decades, the decline in alkalinity in many streams in Europe and in northeastern USA as a result of acid deposition has been a subject of much concern (Likens et al., 1979). The concentration of bicarbonate, the major anion buffering the water chemistry of surface waters and the main component of dissolved inorganic carbon (DIC) in most stream waters, is a measure of the reactivity of the watersheds and reflects the neutralization of carbonic and other acids by reactions with silicate and carbonate minerals encountered by the acidic waters during their residence in watersheds (Garrels and Mackenzie, 1971). Under favorable conditions, carbon isotopes of DIC can be valuable tools by which to understand the biogeochemical reactions controlling carbonate alkalinity in groundwater and watersheds (MUls, 1988 Kendall et al., 1992 see Chapter 5.14). 

The turnover time and fluxes of DOC into the ocean are obtained by comparing the reservoir size and radiocarbon age. The ocean inventory of DOC is —680 Gt, and nearly all of this carbon resides in the deep sea, where concentration profiles and radiocarbon values are constant with depth. DOC ages by —1,000 yr as deep seawater moves from the Atlantic to the Pacific Basin, but even in the Atlantic, DOC radiocarbon values are significantly depleted relative to dissolved inorganic carbon (DIC) (Druffel et al., 1992). DOC persists in seawater through several ocean... 

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