Carbonate alkalinity, calculation

The HCO amount listed in table 8.28 actually represent carbonate alkalinity, calculated neglecting CO ". The alkalinity [Aik] of a solution represents its capacity to neutralize strong acids in solution. Alkalinity can be defined as the sum of equivalents of all species whose concentrations depend on the concentration of ions in solution, minus the concentration of ions in solution. For a solution containing borates and carbonates, alkalinity can be expressed as... 

In the total inorganic carbon balance of equation 8.94, we neglected the presence of some species. Table 8.9 shows that this approximation is reasonable although, for accurate calculations, we should also have considered bicarbonates CaHC03 and MgHCO and the soluble carbonate CaCO . Note also that sulfates occur in negligible molar proportions and that carbonate alkalinity coincides with total alkalinity. 

In the following first example the liquid ozone concentration and the OH-radical concentration are calculated with semi-empirical formula from the mass balance for ozone (Laplanche et al., 1993). For ozonation in a bubble column, with or without hydrogen peroxide addition, they developed a computer program to predict the removal of micropollutants. The main influencing parameters, i. e. pH, TOC, U V absorbance at 254 nm (SAC254), inorganic carbon, alkalinity and concentration of the micropollutant M are taken into consideration. 

Detection of Alkaline Carbonates.—A colouring matter containing admixed alkali carbonate effervesces with acid the carbon dioxide may be determined and the carbonate hence calculated. 

Acidity Enter as equivalents/kg (water). This is the total hydrogen concentration, if known initially. Generally this is only known for strong acid solutions. For example, for a 1 molal H2SO4 solution, enter 2.00. Otherwise, enter 0.0. The equations used to calculate pH for the alkalinity and acidity cases are incompatible. Thus a specification of either carbonate alkalinity or acidity requires that the other variable be assigned a value of 0.00. This will channel the calculations to the proper algorithm. 

To further complicate matters in interpreting and using alkalinity measurements, apparent constants can only be used with data in which pH was measured and alkalinity calculated in exactly the same manner as that done for the samples. A classic example of the difficulties that can arise when these factors are not carefully dealt with is the GEOSECS carbonate data set (see Bradshaw et al., 1981, for discussion). Fortunately, for many open ocean water column studies of... 

Finally, models were calculated which predict the variations in chemical speciation of copper resulting from changes in the chemical parameters pH, carbonate alkalinity, concentration of dissolved organic matter, and concentration of total dissolved copper. 

Chemical Speciation Models. Using the stability constants derived by us for copper complexes with hydroxo and carbonate ligands (Table I) and for natural organic ligands (Table II), the Newport and Neuse Rivers were modeled for copper speciation as a function of pH, total copper, carbonate alkalinity and total dissolved organic matter. Speciation models were calculated from the equation ... 

Although every combination of the four carbonic acid system-analyzable variables has been used, the one pair frequently used because of its relative ease from both an analytical and calculation standpoint is pH and alkalinity. When this pair is used, the equation relating total carbonate molality to pH and carbonate alkalinity is ... 

In order to calculate the situ carbonate alkalinity, it is first necessary to calculate the situ alkalinity contribution of boric acid to the analyzed quantity, titration alkalinity. 

Some aqueous models accept only total inorganic carbon rather than titration alkalinity or carbonate alkalinity. For this reason, the sea water analysis of Table III includes total inorganic carbon which was calculated from pH, total alkalinity and salinity using the apparent sea water constants of Mehrbach et al.(82) for the dissociation of carbonic acid and the boric acid dissociation constant of Lyman (83), as expressed by Li et al. (84). 

If the 5 C values of the reacting carbonbearing species are known and the 5 C of the stream DIC determined, in theory we can calculate the relative contributions of these two sources of carbon to the production of stream DIC and carbonate alkalinity, assuming that (i) there are no other sources or sinks for carbon, and... 

Lueker T. J., Dickson A. G., and Keeling C. D. (2000) Ocean PCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for Ki and K-i. validation based on laboratory measurements of CO2 in gas and seawater at equilibrium. Mar Chem. 70, 105-119. 

Another practical consideration when dealing with the seawater carbonic acid system is that in addition to carbonate alkalinity, H and OH , a number of other components can contribute to the total alkalinity (TA). The seawater constituent that is usually most important is boric acid. Under most conditions, boric acid contributes — 0.1 mmol alkalinity it is usually taken into consideration when making calculations. Nutrient compounds, such as ammonium, phosphate, and silica, whose concentrations in seawater are highly variable, can also influence alkalinity. They must be taken into account for very precise work. In anoxic pore waters a number of compounds, such as hydrogen sulfide and dissolved organic matter, can be significant contributors to alkalinity (e.g., see Berner et al, 1970). 

It was demonstrated in Table 4.4 how the DIG and Aj changes observed in deep waters alter the carbonate system constituents. One can predict the relative change in carbonate ion concentration resulting from solubihzation of particulate matter with an OM GaGOs molar ratio of between 10 and 1.5 by focusing on the changes in alkalinity and DIG. We use carbonate alkalinity, Ac, in this calculation for simplicity. In aU cases of Table 4.7 the composite change... 

Model geometry and parameters are compiled in Fig. 11.2. The strategy is to determine the concentrations of alkalinity and DIG in the surface ocean layer from the equations that describe the model d5mamics and the deep ocean values, and then to calculate the/coj in thermod5mamic equilibrium with these values at the mean surface water temperature and salinity. Garbonate plus borate alkalinity, Ac b. will be employed in our carbonate equilibrium calculations. (See Ghapter 6 for a discussion of the carbonate equilibrium calculations.)... 

We will now derive equations for the titration curve of carbonate alkalinity with a strong acid, HCl, first assuming the titration takes place at constant volume, then taking into account titration volume changes. To simplify our calculations the following assumptions will be made in both derivations ... 

Derive an equation for the buffer capacity of a solution due to its carbonate alkalinity at constant CO2 pressure. Base the calculation on the equation for total carbonate alkalinity (Cg), but do not convert that equation to the proton form before differentiation. This approach was suggested by van Breemen and Wielamaker (1974a 1974b). 

The carbonate solubility calculations assume that titration alkalinity is equivalent to carbonate alkalinity (Berner et al., 1970), thereby slightly overestimating carbonate activities. pS values for summer box cores (1975) were estimated from Eh measurements by use of the conversion equation of Berner (1963), which requires that the sulfide-elemental sulfur couple control Eh. These estimates are approximate, but reasonable, based on subsequent direct pS measurements at each station. pS values for FOAM and NWC gravity cores were obtained from different cores than the actual Fe " analyses (Appendix B, Part I). 

Figure 6 shows a schematic overview of the computational strategy. All quantities listed under model parameters are to be determined by the model. These parameters are combined in the vector of independent parameters p. They have to be initialized to start the calculation (see the literature for initialization strategies), and they will be varied in a systematic way in the course of the calculations. Using the initial independent parameters, the model simulates the distributions of all steady-state (temperature, salinity, oxygen, phosphate, nitrate, total inorganic carbon, alkalinity, and radiocarbon) and transient (CFCs) tracers, as in normal forward models. The simulated tracer concentrations are combined in a vector of dependent parameters p. All dependent... 

It is possible to determine experimentally the amount of acid required per liter of solution to lower the pH of a solution to pHncoa" carbonate alkalinity. This endpoint can be determined with a pH meter or by the color change of the indicator phenolphthalein so that it is often referred to as the phenolphthalein alkalinity. The amount of acid required to reach pHcoj - (the caustic alkalinity) cannot be determined readily in the laboratory because of the poorly defined endpoint, caused by the masking effect of the buffering of water (i.e., the reaction H+ + OH —> H2O). Caustic alkalinity can be determined by calculation if the carbonate and total alkalinity are known. 

A solution has a carbonate alkalinity of 1 meq/liter and a total alkalinity of 6 meq/liter. The ionic strength of the solution is 10 3 M and the temperature is 40°C. Calculate [H ], [HCO3"], and [C03 ] neglecting ionic strength effects and compare with the values obtained when corrections are made for ionic strength effects. Use the constants given in Tables 4-2 and 4-7 for your calculations. 

The nitroglycerine/nitroglycol mixture is obtained by nitration of the mixture that contains 20% ethylene glycol and 80% glycerine. The moisture content of nitroglycerine should not exceed 0.3% mass, and alkalinity calculated as sodium carbonate should not exceed 0.005%. 

Determine the total carbonate contents of the water by Part 1.4. In nearly all sea locations, except in areas of excessive land drainage, it is only necessary to know the chlorinity and pH. The assumption of a specific alkalinity of about 0.125 and a density of 1.025 is made for calculation of the total alkalinity (jeePartI.4.1.2). The pH of the sea water should be known in order to make the correction i n Table VIII but the assumption of pH 8.0 is probably adequate in most cases. If 4 is the total carbonate alkalinity in milliequivalents per liter, calculate the weight W of carbonate carbon present in the water in mg C/m by the relation ... 

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