Assessing the source of the photochemical formation of hydroxylating species from dissolved organic matter using model sensitizers.

Dissolved organic matter (DOM) is ubiquitous in natural waters and can facilitate the chemical transformation of many contaminants through the photochemical production of reactive intermediates, such as singlet oxygen (O), excited triplet state DOM (DOM*), and hydroxylating species (˙OH and other intermediates of similar reaction chemistry). The formation mechanism of most reactive intermediates is well understood, but this is not the case for the formation of hydroxylating species from DOM. To investigate this chemistry, DOM model sensitizers were irradiated with two different probe compounds (benzene and benzoic acid) at two irradiation wavelengths (254 and 320 nm).

Investigation of the Coupled Effects of Molecular Weight and Charge-Transfer Interactions on the Optical and Photochemical Properties of Dissolved Organic Matter.

We studied the formation of photochemically produced reactive intermediates (RI) from dissolved organic matter (DOM). Specifically, we focused on the effects of variable molecular weight and chemical reduction on the optical properties of DOM (absorbance and fluorescence) and the formation of singlet oxygen ((1)O2), DOM triplet excited states ((3)DOM*), and the hydroxyl radical ((•)OH). The data are largely evaluated in terms of a charge-transfer (CT) model, but deficiencies in the model to explain the data are pointed out when evident.