Modeling the acid-base chemistry of organic solutes in Adirondack, New York, lakes

C. T. Driscoll, M. D. Lehtinen, T. J. Sullivan

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Abstract

Organic acid analog models were calibrated to observations of pH, dissolved organic carbon (DOC), and organic anion (An-) concentrations from a reduced data set representing 1128 individual lake samples, expressed as 41 observations of mean pH, in intervals of 0.1pH units from pH 3.9 to 7.0. Of the four organic analog approaches examined, including the Oliver et al. model, as well as monoprotic, diprotic, and triprotic representations, the triprotic analog model yielded the best fit (r2=0.92) to the observed data. Moreover, the triprotic model was qualitatively consistent with observed patterns of change in organic solute charge density as a function of pH. A low calibrated value for the first H+ dissociation constant (pKa1=2.62) and the observation that organic anion concentrations were significant even at very low pH (<4) indicate that naturally occurring organic solutes in these waters have strongly acidic functional groups. Inclusion of organic acidity in model calculations resulted in good agreement between measured and predicted values of lake water pH and acid neutralizing capacity. -from Authors

Original languageEnglish (US)
Pages (from-to)297-306
Number of pages10
JournalWater Resources Research
Volume30
Issue number2
DOIs
StatePublished - 1994

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ASJC Scopus subject areas

  • Aquatic Science
  • Environmental Science(all)
  • Environmental Chemistry
  • Water Science and Technology

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