Transformation of 2,4,6-trimethylphenol and furfuryl alcohol, photosensitised by Aldrich humic acids subject to different filtration procedures.

Suspended particles in a system made up of Aldrich humic acids (HAs) in water account for about 13% of the total HA mass, 10-11% of the organic carbon and 9-11% of radiation extinction in the UVA region. Extinction would be made up of radiation scattering (less than one third) and absorption (over two thirds). The contribution of particles to the degradation rates of trimethylphenol and furfuryl alcohol (FFA) (probes of triplet states and (1)O(2), respectively) was lower than 10% and possibly negligible. The results indicate that triplet states and (1)O(2) occurring in the solution bulk are mostly produced by the dissolved HA fraction. Experimental data would not exclude production of (1)O(2) in particle hydrophobic cores, unavailable for reaction with FFA. However, the limited to negligible particle fluorescence places an upper limit to particle core photoactivity.