Dissolved organic matter (DOM) is a complex and heterogeneous mixture of chemical compounds ubiquitous in aquatic ecosystems. The DOM has acid-base properties (i.e., proton binding) that are essential in controlling the biogeochemical cycles of carbon and nutrients. For example, interactions between metals and DOM are conditioned by environmental factors such as pH, ionic strength, and temperature, and the competition with other cations, including protons, for the binding sites of the DOM. Here we investigate the proton binding properties of DOM extracted from two distinct points along the Ebro River (NNE of Spain), the second longest and fastest flowing of the Iberian Peninsula. The first sample was collected at the source of the river, and the second one after an area under great demographic and agricultural pressure. We used the non-ideal competitive adsorption (NICA) model to describe heterogeneity and biding at equilibrium and account for the impact of ionic strength via the Donnan electrostatic interaction model. We identify potential changes in DOM composition according to variations in 1) the number of chemical groups available for cation binding; 2) the intrinsic proton affinity constants; 3) the chemical heterogeneity. The obtained intrinsic binding parameters can provide insight into DOM reactivity, source, fate, and bioavailability, and better predict potential changes under future environmental stressors in terms of temperature and pH.

Primary Presenter: Joao Alves Macedo, University of Lleida (joaocarlosalvesmacedo@hotmail.com)

Authors:

Joao Alves Macedo, University of Lleida  (joaocarlos.alves@udl.cat)

Pablo Lodeiro, University of Lleida  ()

Carlos Rey-Castro, University of Lleida  ()

Calin David, University of Lleida  ()

Jaume Puy, University of Lleida  ()