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Photochemical, chemical, and biological transformations of dissolved organic carbon and its effect on alkalinity production in acidified lakesJi
Author(s) -
Kopáček Jiŕí,
Hejzlar Josef,
Kaňa Jiŕí,
Porcal Petr,
Klementová Šárkárka
Publication year - 2003
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2003.48.1.0106
Subject(s) - alkalinity , dissolved organic carbon , environmental chemistry , throughfall , chemistry , total organic carbon , tributary , hydrolysis , photodegradation , ecology , ecosystem , catalysis , organic chemistry , cartography , photocatalysis , geography , biology
We evaluated the significance of photochemical and biological degradation of allochthonous dissolved organic carbon (DOC) on in‐lake H + budgets by laboratory experiments and with a mass budget study for major ions in three atmospherically acidified forest lakes in the Bohemian Forest. In the experiments, photodegradation of DOC from a lake tributary resulted in (1) a liberation of organically bound Al and Fe, which consumed an equivalent amount of H + , (2) a minor decrease in concentrations of organic acid anions (A − ) despite a major decrease in DOC concentrations, and (3) the production of biologically available DOC. Biological degradation of the photochemically transformed DOC resulted in a lesser decrease in DOC concentrations than during photodegradation (28—45% of the total decline) but in a pronounced decrease in A − concentrations (64—85% of the total decline), leading to a significant pH increase. Hydrolysis of photoliberated metals under increasing pH partly reduced net H + consumption within the whole process. Watersheds of the lakes studied exported more SO 4 2− , NO 3 − , and H + than they received by throughfall, and the lakes were the dominant acidity‐consuming parts of the whole ecosystems, neutralizing 50—58% of H + input. In‐lake photochemical, biological, and chemical changes in A − fluxes consumed 56—190 meq m −2 yr −1 of H + and were the third major internal alkalinity‐producing mechanism after the biochemical reduction of NO 3 − and SO 4 2− (333—396 and 143—214 meq m −2 yr −1 , respectively). In contrast, the hydrolysis of inorganic Al was the dominant in‐lake H + ‐producing process (144—340 meq m −2 yr −1 ). The in‐lake A − removal was positively related to the DOC loading. Consequently, changes in DOC and A − fluxes should not be omitted in alkalinity budgets in lakes with low or no bicarbonate concentration and elevated DOC input.