PHOTOCHEMICAL DEGRADATION RATES OF TETRAPHENYLBORATE AND DIPHENYLBORIC ACID SENSITIZED BY DISSOLVED ORGANIC-MATTER IN STREAM WATER

The photochemical degradation of tetraphenylborate (TPB) and diphenylboric acid (DPBA) was studied in stream water and humic acid solutions. The rates of indirect photolysis of TPB and DPBA were similar and directly proportional to the concentration of stream water dissolved organic matter (DOM) and humic acid for values < 10 mg/L. Direct photolysis of both organoborates was nondetectable during a 2‐h irradiation period. Indirect photolysis rates varied only slightly from pH 6.0 to 9.0, but increased markedly below pH 6.0. Removal of dissolved oxygen increased reaction rates by a factor of two, indicating that the reaction mechanism does not involve singlet oxygen oxygenation. Copyright © 1990 SETAC