Photochemical oxidation of chrysene at the silica gel–water interface

The photolysis of chrysene at the silica–water interface proceeds more efficiently than when dissolved in solution. Loss of chrysene was apparently through self sensitized oxidation by singlet oxygen. The role of singlet oxygen in the system was probed by application of the 1O2 scavenger, 1,4-diazabicyclo[2,2,2]-octane (DABCO). The initial rate of chrysene loss exhibited a positive correlation with chrysene loading (μmol g−1) on silica gel supports. The system was subjected to model environmental conditions (simulating seawater) and the effects of halide ions on the photodegradation process were determined. Singlet oxygen steady state concentrations were measured under all experimental conditions by using 2,5-diphenylfuran as a singlet oxygen trapping agent, and varied from (3.73±0.37)×10−12 to (1.43±0.14)×10−11 M under our experimental conditions. [1O2]ss was a function of chrysene loading and salinity; high chrysene loading promoted high singlet oxygen concentrations, but high salinity suppressed it.