Naslov
Daily resolution electrical conductivity of drip water measured in slow-drip sites - implementation in Stara Jametina Cave (Croatia)

Autori
Krklec, Kristina ; Švob, Mirna ; Šušnjar, Josip ; Zgorelec, Željka ; Domínguez-Villar, David

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Climate Change: The Karst Record IX (KR9), Programme and Abstracts / Moseley, G. et al. - Innsbruck : University of Innsbruck, 2022, 78-79

Skup
Climate Change: The Karst Record IX (KR9)

Mjesto i datum
Innsbruck, Austrija, 17.07.2022. - 20.07.2022

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
electrical conductivity, drip rate, cave, karst, prior calcite precipitation

Sažetak
Paleoclimate studies for long-term records are often obtained from speleothems fed with very slow drips that have a diffusional flow and consequently a limited amount of water available for monitoring studies. Using a HOBO U24-001 data logger, we have implemented a methodology for measuring electrical conductivity (EC) in drip water samples with volume <2 ml. After applying a filter, we provide daily resolution drip water EC data during the period 2019-2020 in a 60 m deep hall within the cave Stara Jametina (Croatia). EC data was calibrated with data obtained from aggregated samples measured monthly using a Myron L Ultrameter 6P that is calibrated with standard solution prior to every use. Both datasets show same variability, allowing us to correct the continuous dataset and obtain accurate daily values of drip water EC and to record high- frequency events that were not observed during monthly monitoring campaigns. The cave of Stara Jametina is characterized by Mediterranean climate (Csa) with dry and hot summers. Here, the mean annual temperature recorded during the 2019-2020 period was 14.7 °C, while the mean annual amount of precipitation was 1050 mm. Together with EC measurements, temperature, drip rate, concentration of cave air CO2 and drip water hydrochemistry were monitored. Results show that Ca2+ and dissolved inorganic carbon are major chemical species affecting EC of drip water. The outstanding seasonal variability of drip water hydrochemistry is the result of prior calcite precipitation (PCP), a process driven by enhanced cave ventilation. PCP occurs mostly during the “winter season”, when cave air temperature is higher than the external temperature, resulting in low values of cave air CO2 concentration. Furthermore, saturation index in relation to calcite and the Mg/Ca ratio of the drip waters are highly dependent of the ventilation mode of the cave, favouring seasonal variability of calcite precipitation. The hydrochemistry shows that drip water is mostly controlled by well mixed vadose water, although the high-resolution EC record shows the existence of rare high-frequency events with no clear connection to any of the parameters measured. Those occasional events represent only 1% of the studied period and could be attributed to occasional preferential water flows. Due to their short duration, these events are unlikely to leave a significant fingerprint in the speleothem record. Thus, the studied speleothem is potentially a very good archive of long-term paleoclimate in the region with an outstanding seasonal character on the calcite precipitation that could result in annual laminations.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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