Measurement of the Apparent Dissociation Constants of Carbonic Acid in Seawater at Atmospheric Pressure1

Mehrbach, C.; Culberson, Charles H.; Hawley, J. E.; Pytkowicx, Ricardo M.

doi:10.4319/lo.1973.18.6.0897

Cited by 3,109 publications

(2,021 citation statements)

References 14 publications

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“…The pCO 2 were determined using both the direct method (equilibrator) and the indirect one. The later, less accurate than the direct method, is based on experimental determination of pH (NBS scale) and total alkalinity (Gran electrotitration on GFC filtered samples), with appropriate constants for carbonic acid (Mehrbach et al, 1973). Results were obtained while sailing across the whole salinity gradient, from the river mouth to the city of Bordeaux.…”

Section: Performance Tests and Resultsmentioning

confidence: 99%

A new design of equilibrator to monitor carbon dioxide in highly dynamic and turbid environments

2001

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Abstract}A new design of equilibrator for carbon dioxide monitoring in natural waters is described. It consists in a vertical tube filled with marbles through which water is flowing while equilibrating with a closed air circuit. It offers several advantages compared with classical equilibrators, among which is a fast response time (half-life constant % 30 s) and the potential to work in very turbid water. The proposed equilibrator is of particular interest to monitor carbon dioxide in coastal ecosystems, such as estuaries, which are known to be turbid and highly dynamic. Two performance tests and some field results are presented to illustrate the efficiency of the proposed system. #

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Section: Performance Tests and Resultsmentioning

confidence: 99%

A new design of equilibrator to monitor carbon dioxide in highly dynamic and turbid environments

2001

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“…Most geochemists and their models use the NBS pH scale for freshwaters. Third, the difference between the most recently measured K, and K2 values and those of Mehrbach et al (1973) are small when converted to the same scale (Miller0 1995). Fourth, the signal change during the mixing reported here is so large that our conclusions are not affected by the choice of either set of constants.…”

Section: Resultsmentioning

confidence: 99%

“…Fourth, the signal change during the mixing reported here is so large that our conclusions are not affected by the choice of either set of constants. For the NBS scale, the determined dissociation constants of carbonic acid of Mehrbach et al (1973), as given in Plath et al (1980), are not meant to be extrapolated to low-salinity water. The original data were determined for salinities of 26-43, and pure water constants were not used in the fitting of Plath et al (1980).…”

Section: Resultsmentioning

confidence: 99%

The chemistry, fluxes, and sources of carbon dioxide in the estuarine waters of the Satilla and Altamaha Rivers, Georgia

Cai

Wang

1998

Limnology & Oceanography

492

325

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The pH, alkalinity (Alk), and dissolved inorganic carbon (DIC) in estuarine waters of several rivers of Georgia in the southeastern United States are reported. Although they discharge into a narrow area in the South Atlantic Bight, the rivers along the coast of Georgia differ significantly in their drainage area (Piedmont rivers vs. coastal plain rivers), chemical composition (contents of carbonate and humics), and discharge rates. Large differences in pH, DIC, and Alk between these rivers clearly reflect the differences of material inputs to the rivers. Dramatic pH increases in the early stage of mixing (more obvious for the coastal plain rivers) reflect the low buffering capacity of the river waters despite the high content of humic substances. Flux of riverine DIC to the South Atlantic Bight is estimated to be 52.5 X lo9 mol yr-*. We suggest that the presently available world total riverine DIC flux to the ocean could have much uncertainty if the small river fluxes are important. Calculated pC0, values from the pH and DIC measurements are extremely high in low-salinity areas (1,000 to >6,000 patm at salinity < 10) as are the corresponding CO, fluxes to the atmosphere (20 to >250 mol m-* yr-I at salinity

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“…Duplicate measurements were made for TA and triplicate measurements for DIC. Carbonate system parameter values for media and treatment samples were calculated from TA and DIC measurements using the programme CO 2 sys (Pierrot et al, 2006) with dissociation constants of carbonic acid of Mehrbach et al (1973) refitted by Dickson and Millero (Dickson and Millero, 1987).…”

Section: Carbonate Systemmentioning

confidence: 99%

Effects of elevated CO2 on phytoplankton community biomass and species composition during a spring Phaeocystis spp. bloom in the western English Channel

et al. 2017

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A 21-year time series of phytoplankton community structure was analysed in relation to Phaeocystis spp. to elucidate its contribution to the annual carbon budget at station L4 in the western English Channel (WEC).Between 1993-2014 Phaeocystis spp. contributed $4.6% of the annual phytoplankton carbon and during the March À May spring bloom, the mean Phaeocystis spp. biomass constituted 17% with a maximal contribution of 47% in 2001. Upper maximal weekly values above the time series mean ranged from 63 to 82% of the total phytoplankton carbon ($42-137 mg carbon (C) m À3 ) with significant interannual variability in Phaeocystis spp. Maximal biomass usually occurred by the end of April, although in some cases as early as mid-April (2007) and as late as late May (2013).The effects of elevated pCO 2 on the Phaeocystis spp. spring bloom were investigated during a fifteenday semi-continuous microcosm experiment. The phytoplankton community biomass was estimated at $160 mg C m À3 and was dominated by nanophytoplankton (40%, excluding Phaeocystis spp.), Phaeocystis spp. (30%) and cryptophytes (12%). The smaller fraction of the community biomass comprised picophytoplankton (9%), coccolithophores (3%), Synechococcus (3%), dinoflagellates (1.5%), ciliates (1%) and diatoms (0.5%). Over the experimental period, total biomass increased significantly by 90% to $305 mg C m À3 in the high CO 2 treatment while the ambient pCO 2 control showed no net gains. Phaeocystis spp. exhibited the greatest response to the high CO 2 treatment, increasing by 330%, from $50 mg C m À3 to over 200 mg C m À3 and contributing $70% of the total biomass.Taken together, the results of our microcosm experiment and analysis of the time series suggest that a future high CO 2 scenario may favour dominance of Phaeocystis spp. during the spring bloom. This has significant implications for the formation of hypoxic zones and the alteration of food web structure including inhibitory feeding effects and lowered fecundity in many copepod species.Crown

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Measurement of the Apparent Dissociation Constants of Carbonic Acid in Seawater at Atmospheric Pressure1

Cited by 3,109 publications

References 14 publications

A new design of equilibrator to monitor carbon dioxide in highly dynamic and turbid environments

A new design of equilibrator to monitor carbon dioxide in highly dynamic and turbid environments

The chemistry, fluxes, and sources of carbon dioxide in the estuarine waters of the Satilla and Altamaha Rivers, Georgia

Effects of elevated CO2 on phytoplankton community biomass and species composition during a spring Phaeocystis spp. bloom in the western English Channel

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