Binding interactions of algal-derived dissolved organic matter with metal ions

The nature and composition of dissolved organic matter (DOM) strongly influences its binding properties to heavy metals and thus their fate, mobility and toxicity in aquatic environments. Fluorescence spectroscopy with parallel factor analysis (PARAFAC) was used to characterize DOM exuded by the cosmopolitan freshwater green algae Scenedesmus acutus during early exponential growth phase. One protein-like (peak T; C2) and two humic-like components (peaks A + C and A + M, C1 and C3, respectively) were split half validated on 122 emission-excitation matrices (EEMs). Our data show that both humic-like could be associated with biological activities. Unlike Cd, Pb and Zn, Cu strongly binds to algogenic DOM with conditional stability constants (log K) averaging 5.26 ± 0.29 (from 4.85 to 5.36). Significant differences in log K values were found between humic-like PARAFAC components, indicating clear differences in the binding properties of humic-like components with copper.

► One protein- and two humic-like components are found in Scenedesmus acutus exudates. ► Biological activities can produced peaks C and M. ► Visible photodegradation and microbial degradation affect algal exudate composition. ► Unlike Cd, Pb and Zn, Cu strongly binds to algogenic DOM. ► Significant differences in log K values are found between humic-like components.