CARBON TRANSPORT FROM A KARST SYSTEM IN THE PADUREA CRAIULUI, ROMANIA

Geochemical and hydrological data from karst aquifers and their associated ecosystems enables the determination of sources of organic and inorganic carbon and a computation of carbon flux. This study presents results from field sampling and monitoring between October and December 2016 at Peștera Bătrânului and Vadu Crișului, a karst aquifer of Padurea Craiului in the Apuseni Mountains, Romania. Remote geochemical monitoring via a YSI EXO2 multiparameter sonde and simultaneous field chemistry measurements using a YSI ProPlus, measurements of discharge (Q), and a suite of weekly samples from both sites allow for the estimation of the source, timing, and magnitude of carbon flux within this system. Field and lab analyses included stable isotopes, DIC/DOC, SUVA, TSS, alkalinity titrations, and principal ions were conducted at Babes-Bolyai University in Cluj, Romania, Ball State University (Muncie, IN), and Indiana University – Purdue University Indianapolis.

DIC and Q are inversely related, consistent with carbonic acid dissolution of limestone. DIC has a small range of variation at both sites, between 0.38-1.16 mmol/L at Peștera Bătrânului and 4.02-4.77 mmol/L at Vadu Crișului. 𝛿¹³C_DIC ranged between -2.79 to -6.47 ‰ with samples from Vadu Crișului generally more depleted in the heavier isotope (average value of -5.68 ‰) compared to the average of -3.80 ‰ at Peștera Bătrânului. Rock samples from the study have measured 𝛿 ¹³C values of -0.31 to 0.38 ‰. Spikes in SUVA (max: 0.1322) as well as d¹⁸O and d ²H (max: -9.8 ‰, and -65.5 ‰) seen at Peștera Bătrânului are clearly precursors to the same behavior at Vadu Crișului (SUVA—max: 0.0018; d ¹⁸O and d ²H (max: -8.09 ‰, and –62.96 ‰), and exhibited the maximum measured Q during this same period.