@article {200,
	title = {Controls on dissolved inorganic carbon and δ13C in cave waters from DeSoto Caverns: Implications for speleothem δ13C assessments},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {75},
	year = {2011},
	note = {id: 2195},
	pages = {753-768},
	abstract = {Unraveling the factors controlling the carbon chemistry and transport of carbon within extant karst systems has important implications concerning the assessment of time-series δ13C records of speleothems. Here we report the results of a 3-year study of total dissolved inorganic carbon [DIC] and δ13CDIC from cave waters at DeSoto Caverns (Southeastern USA) that offer valuable insight on carbon transport and the accompanied isotope fractionations from end-member sources to speleothems. [DIC] and δ13CDIC values of cave waters range from 0.2 to 6.0 mM and 2.7 to -12.9 ({\textperthousand} VPDB), respectively. [DIC] and δ13CDIC of {\textquotedblleft}seasonal drips{\textquotedblright} show seasonal, albeit noisy, variability and are inversely related (δ13CDIC = -2.49[DIC] + 0.64, r2 = 0.84). A shallow pool fed by multiple drips shows a bimodal δ13CDIC distribution with an isotopically heavier mode during winter (-4{\textperthousand} to -5{\textperthousand} VPDB) relative to summer months (-9{\textperthousand} to -10{\textperthousand} VPDB). A multi-year trend of decreasing water availability during the study period is not reflected in a response of cave water carbon chemistry suggesting that rainfall amount may not be a significant controlling factor of the carbon chemistry. Coupled cave air winter ventilation/summer stagnation and varying CO2 fluxes through the soil horizon and epikarst exert the strongest influence on seasonal [DIC] and δ13CDIC variability. Measured values of high [DIC] and low δ13CDIC from cave waters collected during the summer/early fall closely approximate isotopic equilibrium conditions. Conversely, low [DIC] and high δ13CDIC values during winter/early months indicate kinetically enhanced isotopic fractionations within the cave waters. The kinetically enhanced isotopic fractionation of HCO 3 - partitioned between degassed CO2 and precipitated CaCO3 ( 1000 ln α [ ( CO 2 - HCO 3 ) + ( CaCO 3 (AR) - HCO 3 ) ] / 2 ) is greater by about a factor of two (-6.7 {\textpm} 0.3{\textperthousand}) relative to the same isotopic fractionation under equilibrium conditions (-3.1{\textperthousand}).},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2010.11.006},
	url = {http://www.sciencedirect.com/science/article/pii/S0016703710006319},
	author = {Lambert, W. Joe and Aharon, Paul}
}
