Clay minerals as the key to the sequestration of carbon in soils

Churchman, Gordon Jock and Singh, Mandeep and Schapel, Amanda and Sarkar, Binoy and Bolan, Nanthi S (2020) Clay minerals as the key to the sequestration of carbon in soils. Clays and Clay Minerals, 68 (2). pp. 135-143. ISSN 1552-8367

Text (Churchman_CCM_preprint)
Churchman_CCM_preprint.pdf - Accepted Version
Available under License Creative Commons Attribution-NonCommercial.

Download (376kB)


Results from earlier laboratory and field experiments were interrogated for the possibilities of sequestration, or longterm accumulation, of carbon from excess greenhouse gases in the atmosphere. In the laboratory study, samples of three (top) soils dominated by kaolinite and illite (together), smectite, and allophane were examined for the adsorption and desorption of dissolved organic carbon (DOC). Adsorption and desorption of DOC were carried out on clay fractions extracted physically and after first native organic matter and then iron oxides were removed chemically. Labeled organic material was added to the soils to assess the priming effect of organic carbon (OC). In the field, changes in OC were measured in sandy soils that had been amended by additions of clay for between 3 and 17 years, both through incorporation of exogenous clay and delving of in situ clay. The laboratory experiments demonstrated that a portion of DOC was held strongly in all soils. The amount of DOC adsorbed depended on clay mineral types, including Fe oxides. Much adsorbed DOC was lost by desorption in water and a substantial amount of native OC was lost on priming with new OC. Addition of clay to soils led to increased OC. Therefore, addition of clay to soil may enhance net sequestration of C. Organic carbon close to mineral surfaces or within microaggregates is held most strongly. Carbon sequestration may occur in subsoils with unsaturated mineral surfaces. However, incorporation of carbon into macroaggregates from enhanced plant growth might be most effective in removing excess carbon from the atmosphere, albeit over the short-term.

Item Type:
Journal Article
Journal or Publication Title:
Clays and Clay Minerals
Additional Information:
The final publication is available at Springer via
Uncontrolled Keywords:
ID Code:
Deposited By:
Deposited On:
14 May 2020 16:00
Last Modified:
20 Sep 2023 01:34