Binding of Calcium and Magnesium Ions to Terrestrial Chromophoric Dissolved Organic Matter (CDOM): A Combination of Steady-State and Time-Resolved Fluorescence Study

Revealing the binding properties of calcium ion (Ca2+) and magnesium (Mg2+) to terrestrial chromophoric dissolved organic matter (CDOM) facilities understanding effect natural water components on photophysics matter. Steady-state time-resolved fluorescence spectrometry, dynamic light scattering were applied investigate quenching process CDOM by Ca2+ Mg2+. Due a remarkable decrease steady-state intensity slight lifetime, cations mainly occurred through static process. The was profound under longer excitation emission wavelengths. constant (K, L/mol) for ranged from 4.29 5.09 (lgK), which approximately one order magnitude higher than that Mg2+ (3.86 4.56). Nevertheless, efficiency Ca2+, much lower Cu2+. Fluorescence decay became faster in presence high concentration (>20 mg/L) (>50 mg/L). In these two metal ions, particularly lifetime excited states shifted relatively small value side, indicating interaction Ca2+/Mg2+ with long-lived fluorophores.