Spatial and temporal variations of base cation release from chemical weathering on a hillslope scale

Research output: Contribution to journalArticle

Abstract

Cation release rates to catchment runoff from chemical weathering were assessed using an integrated catchment model that included the soil's unsaturated, saturated and riparian zones. In-situ mineral dissolution rates were calculated in these zones as a function of pH, aluminum and dissolved organic carbon (DOC) concentrations along a hillslope in Northern Sweden where soil water was monitored over nine years. Three independent sets of mineral dissolution equations of varying complexity were used: PROFILE, Transition-State Theory (TST), and the Palandri & Kharaka database. Normalization of the rate-coefficients was necessary to compare the equations, as published rate-coefficients gave base cation release rates differing by several orders of magnitude. After normalizing the TST- and Palandri & Kharaka-rate coefficients to match the base cation release rates calculated from the PROFILE-equations, calculated Ca2 + and Mg2 + release rates are consistent with mass balance calculations, whereas those of Na+ and K+ are overestimated. Our calculations further indicate that a significant proportion of base cations are released from the organic soils in the near-stream zone, in part due to its finer texture. Of the three sets of rate equations, the base cation release rates calculated from the normalized TST-equations were more variable than those calculated using the other two sets of equations, both spatially and temporally, due to its higher sensitivity to pH. In contrast, the normalized Palandri & Kharaka-equations were more sensitive to variations in soil temperature.

Details

Authors
  • M. Erlandsson
  • E. H. Oelkers
  • K. Bishop
  • H. Sverdrup
  • S. Belyazid
  • J. L J Ledesma
  • S. J. Köhler
Organisations
External organisations
  • Uppsala University
  • University of Iceland
  • University College London
  • Swedish University of Agricultural Sciences
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Geochemistry

Keywords

  • Acidification, Mineral dissolution kinetics, PHREEQC, PROFILE, Riparian zone, Transition-State-Theory
Original languageEnglish
Pages (from-to)1-13
Number of pages13
JournalChemical Geology
Volume441
Publication statusPublished - 2016 Nov 21
Publication categoryResearch
Peer-reviewedYes