Application of surface complexation modeling to trace metals uptake by biochar-amended agricultural soils

Md Samrat Alam, Logan Swaren, Konstantin von Gunten, Manuel Cossio, Brendan Bishop, Leslie J. Robbins, Deyi Hou, Shannon L. Flynn, Yong Sik Ok, Kurt O. Konhauser, Daniel S. Alessi

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)


Biochar has emerged as a useful amendment to release nutrients into agricultural soil, to increase crop productivity, and as a sorbent to remediate metals and organics contamination. Since soils have heterogeneous physical properties across a given crop field, and even over a growing season, it is imperative to select the most appropriate biochar for the intended purpose and in defining the amendment level. In this study, we investigate the adsorption of Cd(II) and Se(VI) as model pollutant cations and anions, respectively, to two agricultural soils amended with a wood pin chip biochar (WPC). The proton reactivity of each sorbent was determined by potentiometric titration, and single-metal, single-sorbent experiments were conducted as a function of pH. The resulting data were modeled using a non-electrostatic surface complexation modeling (SCM) approach to determine the proton and metal binding constants and surface functional group concentrations of each soil and WPC. The SCM approach is a considerable advance over empirical modeling approaches because SCM models can account for changes in pH, ionic strength, temperature, and metal-to-sorbent ratio that may happen over the course of a growing season. The constants derived from the single-metal, single-sorbent experiments were then used to predict the extent of metal adsorption in more complex mixtures of Cd, Se, soil and WPC. Overall the SCM approach was successful in predicting metal distribution in multi-component mixtures. In cases where the predictions were poorer than expected, we identify reasons and discuss future experiments needed to further the application of SCM to sorbent mixtures containing biochar.

Original languageEnglish
Pages (from-to)103-112
Number of pages10
JournalApplied Geochemistry
Publication statusPublished - 2018 Jan

Bibliographical note

Funding Information:
This work was supported by NSERC Discovery Grants and an NSERC RTI award to DSA and KOK. LJR gratefully acknowledges support from a Vanier CGS .

Publisher Copyright:
© 2017 Elsevier Ltd

ASJC Scopus subject areas

  • Environmental Chemistry
  • Pollution
  • Geochemistry and Petrology


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