Please use this identifier to cite or link to this item:
Scopus Web of Science® Altmetric
Type: Journal article
Title: Constraining the carbonate system in soils via testing the internal consistency of pH, pCO₂ and alkalinity measurements
Other Titles: Constraining the carbonate system in soils via testing the internal consistency of pH, pCO(2) and alkalinity measurements
Author: Bargrizan, S.
Smernik, R.J.
Mosley, L.M.
Citation: Geochemical Transactions, 2020; 21(1):4
Publisher: BioMed Central
Issue Date: 2020
ISSN: 1467-4866
Statement of
Sima Bargrizan, Ronald J. Smernik and Luke M. Mosley
Abstract: Inorganic carbon exists in various dissolved, gaseous and solid phase forms in natural waters and soils. It is important to accurately measure and model these forms to understand system responses to global climate change. The carbonate system can, in theory, be fully constrained and modelled by measuring at least two of out of the following four parameters: partial pressure (pCO2), total alkalinity (TA), pH and dissolved inorganic carbon (DIC) but this has not been demonstrated in soils. In this study, this "internal consistency" of the soil carbonate system was examined by predicting pH of soil extracts from laboratory measurement of TA through alkalinity titration for solutions in which pCO2 was fixed through equilibrating the soil solution with air with a known pCO2. This predicted pH (pHCO2) was compared with pH measured on the same soil extracts using spectrophotometric and glass electrode methods (pHspec and pHelec). Discrepancy between measured and calculated pH was within 0.00-0.1 pH unit for most samples. However, more deviation was observed for those sample with low alkalinity (≤ 0.5 meq L-1). This is likely attributable to an effect of dissolved organic matter, which can contribute alkalinity not considered in the thermodynamic carbonate model calculations; further research is required to resolve this problem. The effects of increasing soil pCO2 was modelled to illustrate how internally consistent models can be used to predict risks of pH declines and carbonate mineral dissolution in some soils.
Keywords: Internal consistency; Soil carbonate system; Spectrophotometric method; Total alkalinity
Rights: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.
RMID: 1000018236
DOI: 10.1186/s12932-020-00069-5
Appears in Collections:Geology & Geophysics publications

Files in This Item:
File Description SizeFormat 
hdl_124688.pdf836.87 kBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.