Total dissolved inorganic carbon

Almgren et aL (1982) have reported a precision of 0.2 % for this method, but differences as high as 1 % between repeat determinations. As with the potentimnetric titration methods, accuracy will depend to a large degree on the accurate of the volume measurements and of the hydrochloric acid concentration. 

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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. 

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). 

There may, however, be some cancellation of errors. For example, the concentration of atmospheric C02 ([ref], in Eq. (T)) depends in a nonlinear fashion on the amount of total dissolved inorganic carbon in the ocean surface layer because of the equilibria with water (see Chapter 8.B) so that relatively less atmospheric C02 can be taken up by the oceans as its atmospheric concentrations increase. This would leave relatively more C02 in the atmosphere, increasing its greenhouse effect. On the other hand, since the strongest infrared absorption bands of C02 are already saturated (vide supra), the radiative forcing (at-(), in Eq. (T)) decreases as its concentrations increase. 

Polesello, S., G. Tartari, P. Giacomotti, R. Mosello, and S. Cavalli. 2006. Determination of total dissolved inorganic carbon in freshwaters by reagent-free ion chromatography. J. Chromatogr. A 1118, 56-61. 

The major disadvantage of solid phase extraction is that it provides a chemically biased view of the DOM reservoir, and seems to preferentially extract compounds with relatively low amounts of N. Other problems include sample contamination by various resins and incomplete elution of adsorbed DOM. SoHd phase extraction remains, however, the only technique capable of reproducibly isolating DOM compounds within the entire range of MWs. Furthermore, the radiocarbon content (A " C) of DOC isolated by XAD resins is depleted relative to the total dissolved inorganic carbon (DIG) reservoir values for XAD isolates are between —300... 

Figure 4 Vertical profiles of total dissolved inorganic carbon (TIC) in the ocean. Curve A corresponds to a theoretical profile that would have been obtained prior to the Industrial Revolution with an atmospheric CO2 concentration of 280 ixmol mol The curve is derived from the solubility coefficients for CO2 in seawater, using a typical thermal and salinity profile from the central Pacific Ocean, and assumes that when surface water cools and sinks to become deep water it has equilibrated with atmospheric CO2. Curve B corresponds to the same calculated solubility profile of TIC, but in the year 1995, with an atmospheric CO2 concentration of 360 xmol moPk The difference between these two curves is the integrated oceanic uptake of CO2 from anthropogenic emissions since the beginning of the Industrial Revolution, with the assumption that biological processes have been in steady state (and hence have not materially affected the net influx of CO2). Curve C is a representative profile of measured TIC from the central Pacific Ocean. The difference between curve C and B is the contribution of biological processes to the uptake of CO2 in the steady state (i.e. the contribution of the biological pump to the TIC pool.) (courtesy of Doug Wallace and the World Ocean Circulation Experiment).

Fig. 5.5 Relationship between the total dissolved inorganic carbon species (TDIC i.e. H2C03 + HCOj + COj ) and pH. Most natural waters have pH between 7 and 9 where the HC03 anion is abundant (>80% of the TDIC). In highly alkaline waters (pH > 10.3) the COf anion becomes dominant, while in acidic waters (pH <6.4) the undissociated acid (H2C03) is the dominant TDIC species.

Figure 10.5. Concentration profiles showing downgradient propagation of the reaction fronts and pH-buffered geochemical zones during tailings fluid intrusion. Groundwater flows from left to right. DIC denotes total dissolved inorganic carbon. All concentration units are in molL-1, except for pH. Solid, dashed, and dotted lines represent concentration profiles at 0 (initial conditions), 2.5, and 5 years from the start of the simulation, respectively.

Samples of the culture system water were collected bi-weekly for determination of total alkalinity and total dissolved inorganic carbon (DIG) concentrations, the carbon isotopic composition of DIG (8 G(DIG)), and the oxygen isotopic composition... 

The rate of total neritic carbonate production in the modern ocean is roughly 25-10 mol yr from which 60 % (15 10 molyr ) accumulate as shallow-water carbonates. The difference, 10-10 molyr, is the contribution of the neritic environment to the pelagic environment, either in the form of flux of total dissolved inorganic carbon or particulate accumulation on continental slopes and in the deep sea. 

Fig. 10.4 Schematic diagram showing the effect of biofractionation and thermodynamic effects on the carbon isotopic composition of total dissolved inorganic carbon (according to Zahn and Keir 1994).

Robinson C and Williams PJ, leB, (1991) Development and assessment of an analytical system for the accurate and continual measurements of total dissolved inorganic carbon. Marine Chemistry 34 157-175. 

Revelle factor A dimensionless number that expresses the relative sensitivity of the partial pressure of CO2 and total dissolved inorganic carbon in a solution to the incremental additional or removal of CO2, bicarbonate or carbonate ions. 

V. Martinotti, M. Balordi, G. Ciceri, A flow injection analyser conductometric coupled system for the field analysis of free dissolved CO2 and total dissolved inorganic carbon in natural waters. Anal. Bioanal. Chem. 403 (2012) 1083-1093. 

Determination of total alkalinity and total dissolved inorganic carbon... 

The aim of this chapter is to describe both the high precision methods for the determination of total alkalinity At (potentiometric titration) and total dissolved inorganic carbon Ct (coulometry) that are the methods of choice today, and also a simpler method for total alkalinity (back titration) which does not require sophisticated computerised equipment. Thermodynamic calculations of carbonate speciation are also covered. 

The accuracy of the sophisticated methods is such that it is possible to follow shifts in alkalinity (Ax) and total dissolved inorganic carbon (Cx) caused by the following processes. Uptake of CO2 or HCO3", formation of carbohydrates ... 

Total dissolved inorganic carbon can also be evaluated from the potentiometric titration method described in Section 8.4.1, if it is performed in a closed cell. However, this technique does not give the highest precision possible and thus the coulometiic method first described by Johnson et al. (1985) and outlined here is nowadays the method of choice. Nevertheless, Ct can be evaluated from the potentiomettic titration curve, either Gran function linearization (Section 8.4.2.3 Gran evaliiation ) or by a curve fitting procedure (Section 8.4.2.3 Non-linear curve-fitting ). 

The total dissolved inorganic carbon concentration Cr /jmol/(kg-seawater) is calculated as... 

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