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The Role of Organic Acids in the Acid‐Base Status of Surface Waters at Bickford Watershed, Massachusetts
Author(s) -
Eshleman K. N.,
Hemond H. F.
Publication year - 1985
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr021i010p01503
Subject(s) - alkalinity , dissolved organic carbon , environmental chemistry , total organic carbon , surface water , groundwater , nitrate , watershed , hydrology (agriculture) , environmental science , acid neutralizing capacity , wetland , ecosystem , titration , chemistry , ecology , inorganic chemistry , soil water , soil science , environmental engineering , biology , geology , acid deposition , geotechnical engineering , organic chemistry , machine learning , computer science
An experimental field study of the alkalinity and major ion budgets of Bickford watershed in central Massachusetts indicates that organic acid production by the ecosystem contributes measurably to surface water acidification. Applying the concepts of alkalinity, electroneutrality of solutions, and mass balance, organic acids were found to comprise 20% of all strong acid sources on one subcatchment annually, a value half as large as the measured bulk mineral acid deposition. Inorganic cation to anion ratios in Provencial Brook varied between 1.0 in winter and 1.6 during summer, suggesting the presence of up to 100 μeq/L of unmeasured charge from organic anions during the growing season. Base titrations and ultraviolet photooxidation experiments confirmed the existence of low p K a (3.5–5.0) acidic functional groups. A positive linear relationship between dissolved organic carbon (DOC) and anion deficit for a group of surface and groundwater samples indicates the DOC contains about 7.5 meq carboxylic groups per gram C. Biological factors related to both upland and wetland carbon metabolism apparently control this natural acidification phenomenon, which has not been documented on other watersheds in the northeastern United States for which annual alkalinity budgets have been determined.