Dissolved organic matter inhibition of sonochemical degradation of aqueouspolycyclic aromatic hydrocarbons

Sonochemical degradation of aqueous polycyclic aromatic hydrocarbons (PAHs) was found to be rapid in the absence of other dissolved compounds (k = 0.0 06-0.015 s(-1)). In the presence of 20 mg C l(-1) fulvic acid, first-order PAH degradation rate constants decreased from 2.3- to 3.7-fold. Similar res ults were obtained with added benzoic acid, a crude analog for fulvic acid. In natural waters, PAH degradation was almost completely inhibited. Analys is of the kinetic behavior and reaction products indicates that PAHs are mo st likely degraded through a radical cation mechanism. Hydroxyl radical app eared to play an insignificant role in the degradation. Inhibited degradati on was probably the result of either altered cavitation processes or isolat ion of the PAH away from cavitation sites. (C) 1999 Elsevier Science B.V. A ll rights reserved.