Dissolved organic matter affects the bioaccumulation of copper and lead in Chlorella pyrenoidosa: A case of long-term exposure.

This study evaluated the impact of dissolved organic matter (DOM) of varying molecule weights (MWs) on long-term exposure to Cu and Pb in Chlorella pyrenoidosa. Citric acid, fulvic acid, and humic acid, in the order of increasing MWs, were selected to represent DOM. The results showed that DOM with larger MWs had stronger inhibitory effects on the bioavailability of Cu to algae. However, the biosorption isotherm of Pb in the presence of DOM was different: as Pb equilibrium concentration increased, the biosorption capacity increased sharply to a maximum, then decreased. The maximum values ranged between 0.186 and 0.398 mmol g-1, as the solution DOM concentration and MW changed, exhibiting a stoichiometric relationship between DOM, Pb and algae. The ternary complex of Pb-DOM-alga formed in a limited Pb concentration range, and increased the percentage of internalized Pb. This research helps to understand the role of DOM in metal uptake in phytoplankton.