The influence of organic acidity on the acid-base chemistry of surface waters in Maine, USA

Kahl, Jeffrey S.; Norton, Stephen A.; MacRae, Russell K.; Haines, Terry A.; Davis, Ronald B.

doi:10.1007/bf00192859

Cited by 29 publications

(1 citation statement)

References 45 publications

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“…Cations (Ca, Mg, and Na) and anions (Cl) were analyzed using a Dionex model ICS 2000 ion chromatography system and AS40 autosampler. Samples with cation:anion ratios greater than 15% from unity after adjustment for the ionic contributions of DOC and Al (23) were reanalyzed. The same analytical methods were used in 1984, except that base cations were analyzed by flame AAS.…”

Section: Approach and Methodsmentioning

confidence: 99%

Anthropogenically Driven Changes in Chloride Complicate Interpretation of Base Cation Trends in Lakes Recovering from Acidic Deposition

Rosfjord

Webster

Kahl

et al. 2007

Environ. Sci. Technol.

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Declines in Ca and Mg in low ANC lakes recovering from acidic deposition are widespread across the northern hemisphere. We report overall increases between 1984 and 2004 in the concentrations of Ca + Mg and Cl in lakes representing the statistical population of nearly 4000 low ANC lakes in the northeast U.S. Increases in Cl occurred in nearly all lakes in urbanized southern New England, but only 18% of lakes in more remote Maine had Cl increases. This spatial pattern implicates road salt application as the major source of the increased Cl salts. Among the 48% of the lake population classified as salt-affected, the median changes in Cl (+133 microeq/L) and Ca + Mg (+47 microeq/ L) were large and positive in direction over the 20 years. However, in the unaffected lakes, Cl remained stable and Ca + Mg decreased (-3 microeq/L), consistent with reported long-term trends in base cations of acid-sensitive lakes. This discrepancy between the Cl groups suggests that changes in ion exchange processes in salt-affected watersheds have altered the geochemical cycling of Ca and Mg. One policy-relevant implication is that waters influenced by Cl salts complicate regional assessments of surface water recovery from "acid rain" related to the passage of the Clean Air Act.

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Section: Approach and Methodsmentioning

confidence: 99%

Anthropogenically Driven Changes in Chloride Complicate Interpretation of Base Cation Trends in Lakes Recovering from Acidic Deposition

Rosfjord

Webster

Kahl

et al. 2007

Environ. Sci. Technol.

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Effects of Soil Warming on Carbon and Nitrogen Cycling

Rustad¹,

Melillo²,

Mitchell³

et al. 2000

Ecological Studies

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Chemical character and origin of organic acids in streams and seepage lakes of central Maine

David

Vance

1991

Biogeochemistry

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Abstract. Organic acids and inorganic chemistry were examined in seventeen seepage lakes, seven streams, and one seep in central Maine. The objectives of this analysis were to determine the quantity and quality of dissolved organic carbon (DOC), and to assess the relationship between organic and inorganic surface water chemistry. Lakes and streams sampled were dilute (average conductivity of 20.3 pScm-') with a wide range of DOC (125-2593 pmol C L-'). Organic acids in DOC were evaluated by:-DOC fractionation (hydrophobic acids and neutrals, and hydrophilic acids, bases, and neutrals); -DOC isolation followed by FT-IR, base titration, and chemical analyses; -adsorption on solid phase extraction columns; and charge balance studies.All lakes and streams were dominated by hydrophobic and hydrophilic acids (60 to 92% of DOC). Lakes and streams with low DOC had low hydrophobic to hydrophilic acid ratios (ca 1.2-1.3), regardless of pH and acid neutralizing capacities (ANC), compared to lakes and streams with moderate to high DOC concentrations (ca 1.9-2.4). Based on FT-IR spectroscopy and chemical analysis, organic acids were found to be dominated by a strong carboxylic character. Titration data of isolated DOC allowed accurate prediction of organic anions, which were strongly pH dependent (organic anions ranged from 14 to 198peq L-' ). Exchange acidity averaged 11.3, 13.6, and 8.7 peq mg C-' for lake hydrophobic acids, lake hydrophilic acids, and stream hydrophobic acids, respectively.Overall evidence suggested that DOC and organic acid characteristics were related to their carboxylic functional group content and that the nature of these constituents was similar despite the source of origin (upland soils, wetlands, or Sphagnum deposits). Also, contact of soil leachates with B horizons seemed to be a controlling factor in DOC quantity and quality in the lakes and streams studied.

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The influence of organic acidity on the acid-base chemistry of surface waters in Maine, USA

Cited by 29 publications

References 45 publications

Anthropogenically Driven Changes in Chloride Complicate Interpretation of Base Cation Trends in Lakes Recovering from Acidic Deposition

Anthropogenically Driven Changes in Chloride Complicate Interpretation of Base Cation Trends in Lakes Recovering from Acidic Deposition

Effects of Soil Warming on Carbon and Nitrogen Cycling

Chemical character and origin of organic acids in streams and seepage lakes of central Maine

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