Monochlorophenols (CP) and hydroxybenzoic acids (HBA) have been used to model poorly-adsorbing and strongly-adsorbing pollutants in aqueous slurries containing TiO2(P25). Profiles are presented and compared for the manner in which initial rates for TiO2-photocatalysed depletions of those pollutants under low, moderate and high fluxs of 365 nm photons varied as a function of various initial aqueous-phase concentrations attained after adsorption-desorption equilibration in the dark. Marked intensity-related differences are, thus, observed, especially for well-adsorbing 3-chloro 4-hydroxy benzoic acid (CHBA). Differences stem in part from a major rate-determining role for primary photooxidation events in the surface solution monolayer under low intensity, whereas under high intensity that role is filled by desorption of strongly adsorbed products and/or by activated diffusion along surfaces within TiO2 aggregates which is altered under high photon flux.