High-frequency monitoring reveals how hydrochemistry and dissolved carbon respond to rainstorms at a karstic critical zone, Southwestern China

Qin, C., Li, S.-L., Waldron, S. , Yue, F.-J. , Wang, Z., Zhong, J., Ding, H. and Liu, C.-Q. (2020) High-frequency monitoring reveals how hydrochemistry and dissolved carbon respond to rainstorms at a karstic critical zone, Southwestern China. Science of the Total Environment, 714, 136833. (doi: 10.1016/j.scitotenv.2020.136833) (PMID:32018977)

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Hydrochemical behavior and dissolved carbon dynamics are highly-sensitive to hydrological variations in the monsoon-influenced karstic critical zone which has high chemical weathering rates and experiences strong anthropogenic impact. Continuous high-frequency monitoring in the spring outlet of a karstic catchment in Southwestern China revealed that most hydrochemical variables changed distinctively in response to hydrologic variations, influenced by mixing of different sources and miscellaneous biogeochemical processes. Na+, K+ and SO42− varied significantly with hydrology, showing weak chemostatic behavior controlled by dilution. The flushing effect and random behavior of NO3− and Cl− likely reflect agricultural inputs from high throughflow. Soil CO2 in infiltrated water supports carbonate weathering, enabling DIC (dissolved inorganic carbon) and weathering products (e.g., Ca2+ and Mg2+) to maintain chemostatic behavior. Biogenic DIC exhibited a stronger chemostatic response than carbonate sources and was the foremost control in DIC behavior. Carbon exchange between DIC and DOC (dissolved organic carbon) did not significantly influence DIC concentration and δ13C due to very low DOC concentration. More DOC was exported by flushing from increasing discharge. Hysteretic analysis indicated that the transport processes were controlled by proximal sources mixing and diverse mobilization in various periods responding to rainstorms. NO3− and Cl− presented different hysteresis behavior as sourced from agricultural activities. DOC increased on the hydrograph rising limb and was controlled by a transport-limited regime. However, the hysteresis behavior of most weathering products and DIC were regulated by a process-limited regime in the karstic critical zone. Overall, biogeochemical processes, hydrogeological properties, storm intensity/magnitude and the timing of storms (antecedent conditions) are main factors influencing the response of hydrochemical variables and dissolved carbon to storm events.

Item Type:Articles
Additional Information:This study was jointly funded by the National Natural Science Foundation of China [grant numbers 41571130072, 41861144026], the National Key Research and Development Program of China [grant number 2016YFA0601002]; and the UK Natural Environment Research Council [grant number NE/N002806/1].
Glasgow Author(s) Enlighten ID:Waldron, Professor Susan and Yue, Dr Fu-Jun and Ding, Dr Hu
Authors: Qin, C., Li, S.-L., Waldron, S., Yue, F.-J., Wang, Z., Zhong, J., Ding, H., and Liu, C.-Q.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Science of the Total Environment
ISSN (Online):1879-1026
Published Online:21 January 2020
Copyright Holders:Copyright © 2020 Elsevier B.V.
First Published:First published in Science of the Total Environment 714:136833
Publisher Policy:Reproduced under a Creative Commons license

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172190Addressing a significant knowledge gap in fluvial system atmospheric CO2 efflux: the contribution from karst landscapesSusan WaldronNatural Environment Research Council (NERC)NE/N002806/1GES - Geography