Lead complexation behaviour of root exudates of salt marsh plant Salicornia europaea L.

Root exudates are considered to have an important role in mobility and bioavailability of heavy metals. High molecular weight (HMW) substances are the main components of root exudates, however, knowledge about their interactions with heavy metals is lacking. In the present study, Pb(II) complexation of the HMW fluorescent fractions in root exudates from Salicornia europaea L. was investigated using excitation emission matrix (EEM) fluorescence spectroscopy. Two protein-like fluorescence peaks were identified in the EEM spectrum of root exudates. The fluorescence of both peaks was clearly quenched by Pb(II). The values of conditional stability constants, log K-a, for these two protein-like fluorescence peaks were 4.14 and 3.79. This indicates that the fluorescent substances are strong Pb(II) complexing organic ligands.