The effects of agricultural activities and atmospheric acid deposition on carbonate weathering in a small karstic agricultural catchment, Southwest China

In order to quantify the sources and fluxes of DIC, the effects of the use of N-fertilizers and acid deposition on carbonate weathering have been quantified by hydrochemistry and δ13CDIC of groundwater in Qingmuguan underground river system (QURS) – a small karstic agricultural catchment of Southwes...

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Bibliographic Details
Published in:Acta Carsologica
Main Authors: Chen, Yu, Jiang, Yongjun
Format: Article in Journal/Newspaper
Language:English
Published: ZRC SAZU, Založba ZRC 2016
Subjects:
Online Access:https://ojs.zrc-sazu.si/carsologica/article/view/4507/4395
https://ojs.zrc-sazu.si/carsologica/article/view/4507
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Summary:In order to quantify the sources and fluxes of DIC, the effects of the use of N-fertilizers and acid deposition on carbonate weathering have been quantified by hydrochemistry and δ13CDIC of groundwater in Qingmuguan underground river system (QURS) – a small karstic agricultural catchment of Southwest China. The results show that: (1) the significant temporal variations for major element concentrations and δ13CDIC of groundwater in different months were observed, especially, of which the groundwater showed significant high concentrations of DIC, Ca2+, Mg2+, NO3−, SO42− and δ13CDIC in rainy season and fertilizing period in the QURS; (2) the contributions of carbonate dissolution by carbonic acid to total concentrations of (Ca2++Mg2+) and HCO3− of groundwater in different months averaged 68.5 % and 81.0 %, respectively. While the contributions of carbonate dissolution by nitric acid originated from the use of N-fertilizers and atmospheric acid deposition to total concentrations of (Ca2++Mg2+) and HCO3− of groundwater in different months averaged 11.1 % and 6.7 %, respectively, and the contributions of carbonate dissolution by sulphuric acid originated from the atmospheric acid deposition to total concentrations of (Ca2++Mg2+) and HCO3− of groundwater in different months averaged 20.4 % and 12.3 %, respectively; (3) the δ13CDIC increased obviously with (Ca2++Mg2+)/HCO3− of groundwater in the rainy season and fertilizing period indicated that the use of N-fertilizers and atmospheric acid deposition should be responsible for the elevated the δ13CDIC and the molar ratio of (Ca2++Mg2+)/HCO3− of groundwater in the QURS.Key words: carbonate weathering, karst groundwater, agricultural activities, atmospheric acid deposition, Qingmuguan, Southwest China.