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Dissolved inorganic carbon sourcing using δ 13 C DIC from a karst influenced river system
Author(s) -
McClanahan Kegan,
Polk Jason,
Groves Chris,
Osterhoudt Laura,
Grubbs Scott
Publication year - 2015
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3856
Subject(s) - carbonate , carbon cycle , geology , total inorganic carbon , dissolved organic carbon , carbonate rock , carbonate minerals , drainage basin , isotopes of carbon , karst , lithology , siliciclastic , hydrology (agriculture) , geochemistry , carbon dioxide , total organic carbon , dolomite , structural basin , environmental chemistry , geomorphology , facies , sedimentary rock , oceanography , ecosystem , chemistry , paleontology , ecology , biology , cartography , geotechnical engineering , organic chemistry , geography
Rivers, representing the primary conduits of dissolved inorganic carbon (DIC) from the continents to the oceans, are important components to the global carbon cycle. To better understand the complex carbon cycling dynamics within two nested, mixed lithology watersheds, two sites were studied along the karst influenced upper Green River in south‐central Kentucky, USA. Weekly samples were collected from June 2013 through May 2014 and analyzed for δ 13 C DIC . The mixing model IsoSource was employed to better understand source partitioning differences over seasonal time spans and across the two nested basins. In both the lithologically mixed upstream basin (53% carbonate rocks, 47% siliciclastic) and carbonate rock dominated downstream basin (96% carbonate rocks in the drainage area between Greensburg and Munfordville, 78% in the total area upstream from Munfordville), DIC was primarily derived from soil respiration. The proportion of DIC from dissolved carbonate minerals derived from the downstream carbonate rock dominated basin was similar to the upstream basin, due to carbonate mineral dissolution having such a consistent effect on the overall DIC content of the river. Seasonally, soil respiration provided the most DIC from fall to winter. Early spring precipitation, combined with limited seasonal photosynthesis, shifted groundwater to be the primary source of DIC, bringing in a flush of carbonate mineral‐rich water during higher flows. This study provides insight into carbon dynamics across multiple lithologies and the important influence of seasonality using carbon isotope sourcing to determine carbonate mineral dissolution variability and aid in understanding its contribution to global carbon flux quantification. Copyright © 2015 John Wiley & Sons, Ltd.