The relative importance of DOM source and mineral characteristics for adsorption

Adsorption of dissolved organic matter (DOM) onto minerals plays a critical role in carbon sequestration in terrestrial and aquatic ecosystems. It remains unclear if mineral properties or DOM composition are more relevant for predicting adsorption. We tested this by quantifying the maximum adsorption capacity (Qmax) of five minerals (podzol Bs horizon, agricultural subsoil, glacial stream sediment, kaolinite-dominated clay, synthetic goethite) and five DOM sources (humic lake, peat, leaf litter, algae, and pyrogenic organic matter) using a modified Langmuir model. Three minerals were also treated with sodium hypochlorite to remove pre-existing organic matter, enabling assessment of adsorption onto bare mineral surfaces. Qmax values spanned 31–28,630 mg C kg^-1, exceeding previously reported ranges, and showing that both DOM composition and mineral properties variably control adsorption capacity. Even strongly adsorbing minerals such as goethite and clay showed a large variation across DOM sources, with highest adsorption for peat and lowest for algae. Likewise, DOM sources differed in their affinities for the mineral surfaces. Sodium hypochlorite treatment increased DOM adsorption, depending on material type and mineral characteristics, such as hydrous aluminum and iron phases. Overall, carbon adsorption onto minerals depends on both mineral and organic matter characteristics, suggesting that soil models that do not consider organic matter characteristics are limited in describing adsorption and predicting carbon sequestration potential in soils and aquatic ecosystems.

Presentation Preference: Poster

Primary Presenter: Mona Abbasi, Uppsala University (mona.abbasi@ebc.uu.se)

Authors:

Marloes Groeneveld, Department of Soil and Environment, Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden  (marloes.groeneveld@slu.se)

Klaus Kaiser, Soil Science and Soil Protection, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany  (klaus.kaiser@landw.uni-halle.de)

Karsten Kalbitz, Institute of Soil Science and Site Ecology, Technische Universität Dresden, Tharandt, Germany  (karsten.kalbitz@tu-dresden.de)

Lars Tranvik, Department of Ecology and Genetics - Limnology, Uppsala University, Uppsala, Sweden  (lars.tranvik@ebc.uu.se)

Dolly Kothawala, Department of Ecology and Genetics - Limnology, Uppsala University, Uppsala, Sweden  (dolly.kothawala@ebc.uu.se)