The total (or titration) alkalinity of a natural water sample can be regarded as a measure of the proton deficit of the solution relative to an arbitrarily defined zero level of protons. The problem of unambiguously incorporating any particular acid-base system into the definition of alkalinity is thus the one of deciding which form to specify as the zero level of protons, and it is proposed that it be defined so that acids with a dissociation constant K > 10−4·5 (at 25°C and zero ionic strength) are considered as proton donors, whilst those bases formed from weak acids with K ⪕ 10−4·5 are cosidered proton acceptors. A non-linear least squares procedure is suggested in order to estimate the total alkalinity (AT) and total inorganic carbon (CT) of a seawater sample from potentiometric titration data. The approach offers a significant conceptual improvement over the currently used refined Gran functions. In addition, an estimate of the statistical uncertainty of the estimated values of AT and CT is available. As it unnecessary to titrate beyond the alkalinity equivalence point, it may also be possible to speed up the titrations.

An exact definition of total alkalinity and a procedure for the estimation of alkalinity and total inorganic carbon from titration data

Reference materials for oceanic CO2 analysis: a method for the certification of total alkalinity

The carbon isotopic fractionation accompanying formation of biomass by alkenone-producing algae in natural marine environments varies systematically with the concentration of dissolved phosphate Specifically, if the fractionation is expressed by epsilon p approximately delta e - delta p, where delta e and delta p are the delta 13C values for dissolved CO2 and for algal biomass (determined by isotopic analysis of C37 alkadienones), respectively, and if Ce is the concentration of dissolved CO2, micromole kg-1, then b = 38 + 160*[PO4], where [PO4] is the concentration of dissolved phosphate, microM, and b = (25 - epsilon p)Ce The correlation found between b and [PO4] is due to effects linking nutrient levels to growth rates and cellular carbon budgets for alkenone-containing algae, most likely by trace-metal limitations on algal growth The relationship reported here is characteristic of 39 samples (r2 = 095) from the Santa Monica Basin (six different times during the annual cycle), the equatorial Pacific (boreal spring and fall cruises as well as during an iron-enrichment experiment), and the Peru upwelling zone Points representative of samples from the Sargasso Sea ([PO4] < or = 01 microM) fall above the b = f[PO4] line Analysis of correlations expected between mu (growth rate), epsilon p, and Ce shows that, for our entire data set, most variations in epsilon p result from variations in mu rather than Ce Accordingly, before concentrations of dissolved CO2 can be estimated from isotopic fractionations, some means of accounting for variations in growth rate must be found, perhaps by drawing on relationships between [PO4] and Cd/Ca ratios in shells of planktonic foraminifera

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96GB03939

Consistent fractionation of 13C in nature and in the laboratory: growth-rate effects in some haptophyte algae.

Distribution of alkalinity in the surface waters of the major oceans.

The apparent dissociation constants of carbonic acid (K1∗, K2∗) were determined at atmospheric pressure by potentiometric titrations in artificial seawater. Constants (K1∗, K2∗) were extracted from the experimental titration curves both by a non-linear curve-fitting procedure, and by using the Gran functions. There is good agreement between the two mathematical calculations for both constants. Throughout the salinity range of 10 < S < 50 and the temperature range of −1°C < T < 40°C this new data set agrees closely with the previous set of Hansson (1972). His results, combined with ours and fitted as a function of temperature and salinity, satisfy the following relationships: 
pK1∗=812.27T+3.356−0.00171 x S x ln(T)+0.000091 x S2

pK1∗=1450.87T+4.604−0.00385 x S x ln(T)+0.000182 x S2
where the constants K1∗ are expressed in moles per kilogram of solution.

Ingemar Hansson

Papers

Evaluation of the accuracy of gran plots by means of computer calculations