The application of tert-butanol as an OH scavenger in aqueous, oxygenated solutions was studied by pulse radiolysis and computer simulation of the entire reaction mechanism. In such systems, the initially produced tert-butanol radical (. Rib) reacts with O2 with a rate constant ofk = 1.4. IO9.M-' s-'. The UV absorption-spectrum of the resulting tert-butanol peroxy-radical, . OORlb, was determined. The rate constant for its dimerization, 2 . OOR,,+ R,b04R,b, is k = 1.8. lo8 M-' s-'. The formation of H 0 2 from the decay of RlbO4RLb has often been neglected in earlier studies. Our reinvestigation showed a yield of 5 f 2%.In deoxygenated systems we confirmed the rate constant for . Rtb dimerization to be k = 6. lo8 M-' s-'.The UV spectrum o f . Rlb was determined to be slightly different from literature data.

Atmospheric Chemistry / Chemical Kinetics / Pulse Radiolysis / Thansition Metals IonsThe catalytic decay of 0; radicals due to Cu+ and Cu2+ ions in 0, saturated solutions of low ionic strength was studied by pulse radiolysis and computer simulation of the entire reaction mechanism. Phosphate was used as buffer and formate was used to convert OH radicals into 0;. At pH = 6, the very low solubility products of Cu2+ with OH-and PO:-limited the copper concentration to the order of wM. In experiments with [Cu*+]>[O,], the rate constant k(Cu2+ +OF) = (8.0rt0.5).109M-'s-1 was determined. In systems with[O?] * [CuItot, steady state for the copper ions is attained with apparent first-order kinetics, which correlates k(Cu2+ +OF) with k(Cu+ +OF). The 0, decay rate decreased with increasing pH due to Cu2+ complexation with HPOZ-. Correspondingly the pK(CuHP04) was found to be -4.Ok0.2 under the assumption that k(CuHP04+O;)S0.01 *k(Cu2+ +O;). With this value, k(Cu+ +O;) could be determined as (9.4k0.8).lo9 M -' s-' by an iterative procedure. The consequences for the chemistry of atmospheric waters are discussed.

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