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Acid Deposition Long-Term Trends (1986) / Chapter Skim
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Appendix D: Historical Correction Factors for Alkalinity and Acid Status of Surface Waters
Pages 471-481

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From page 471...
... This condition is not required for alkalinity because changes in Ct would not alter alkalinity. Fundamental Definitions Alkalinity (lAlk]
From page 472...
... . Thus the alkalinity endpoint is the condition in which strong acids equal strong bases with variable amounts of Cot in solution.
From page 473...
... . For example, the alkalinity endpoint pH is 5.18 for Ct = 100 peq/L (typical of a dilute unbuffered water)
From page 474...
... If the endpoint pH of the specific technique (defined as pHx) is known, the value obtained for the incorrect endpoint can be adjusted to the value for the definitions of alkalinity and CO2 acidity by the following equations: [Ark]
From page 475...
... - [correct endpoint condition] + [correct endpoint condition!
From page 476...
... The Gran function employs the more acidic titration region beyond the endpoint where [H+]
From page 477...
... , the kind of colorimetric dye needed to obtain its concentration and dissociation constant, and the respective indicator and sample volumes are known. Statistical correlations of electrometric pa and colorimetric pH have limited value because they do not incorporate the above factors.
From page 478...
... ' is the diluted difference of strong cation, [AlkC] is the alkalinity altered by dilution and reaction with the indicator, and the subscript c refers to the solution condition after addition of colorimetric pH indicator.
From page 479...
... + K1. The third means of determining actual solution pH is from [Alk]
From page 480...
... In this case the total amount of other reactive protolytes must be compared with alkalinity or acidity if we assume that the acid dissociation constant is intermediate in the titration range. The critical region then for other protolytes to have maximum effect and thus negate the carbonate assumption is when the reacting carbonates are minimal and at intermediate pH where H+ ion would have a negligible buffering effect.
From page 481...
... For the same condition, one would need about 550 ug/L total aluminum because one half of the aluminum would be in the form of the aqua ion and the other half in the form of A1OH (pK = 5 at pH of 5) , and only one half equivalent per mole contributes to alkalinity.


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