Absolute second-order rate constants for hydroxyl radical (HO^●) reaction with four organophosphorus pesticides, malathion, parathion, fenthion and ethion, and a suite of model compounds of structure (EtO)₂P(S)-X (where X = Cl, F, SH, SEt, OCH₂CF₃, OEt, NH₂, and CH₃) were measured using electron pulse radiolysis and transient absorption techniques. Specific values were determined for these four pesticides as k = (3.89 ± 0.28) x 10⁹, (2.20 ± 0.15) x 10⁹, (2.02 ± 0.15) x 10⁹ and (2.93 ± 0.10) x 10⁹ M^-1 s^-1, respectively, at 20 ± 2^oC. The corresponding Brönsted plot for all these compounds demonstrated that the HO^● oxidation reaction mechanism for the pesticides was consistent with the model compounds, attributed to initial HO^●-adduct formation at the P(S) moiety. For malathion, steady-state ⁶⁰Co radiolysis and ³¹P NMR analyses showed that hydroxyl radical-induced oxidation produces the far more potent isomalathion, but only with an efficiency of 4.9 ± 0.3%. Analogous kinetic measurements for the hydrated electron induced reduction of these pesticides gave specific rate constants of k = (3.38 ± 0.14) x 10⁹, (1.38 ± 0.10) x 10⁹, (1.19 ± 0.12) x 10⁹ and (1.20 ± 0.06) x 10⁹ M^-1 s^-1, respectively, for malathion, parathion, fenthion and ethion. Model compound measurements again supported a single reduction reaction mechanism, proposed to be electron addition at the P=S bond to form the radical anion. These results demonstrate, for the first time, that the radical-based treatment of organophosphorus contaminated waters may present a potential toxicological risk if advanced oxidative processes are used.

绝对二阶速率常数的羟基自由基（HO ^●）有四个有机磷农药，马拉硫磷，对硫磷，倍硫磷和乙硫磷，和一个套结构的模型化合物（ETO）反应₂ P（S）-X（其中X = Cl ，F，SH，SEt，OCH ₂ CF ₃，OEt，NH ₂和CH ₃）的测定采用电子脉冲辐射分解和瞬态吸收技术。确定了这四种农药的特定值，分别为k =（3.89±0.28）x 10 ⁹，（2.20±0.15）x 10 ⁹，（2.02±0.15）x 10 ⁹和（2.93±0.10）x 10 ⁹ M ^-1 s ^-1分别在20±2^ø C.相应的布朗斯台德情节对所有这些化合物证明，HO ^●对于杀虫剂的氧化反应机制是与模型化合物，归因于初始HO一致^●在P（S）部分-adduct形成。对于马拉硫磷，稳态⁶⁰ Co辐射分解和³¹ P NMR分析表明，羟基自由基诱导的氧化作用产生的异马拉硫磷作用要强得多，但效率仅为4.9±0.3％。通过水合电子诱导的这些农药还原反应的类似动力学测量得出比速率常数k =（3.38±0.14）x 10 ⁹，（1.38±0.10）x 10 ⁹，（1.19±0.12）x 10 ⁹和（1.20±0.06） ）x 10马拉硫磷，对硫磷，倍硫磷和乙硫磷分别为⁹ M ^-1 s ^-1。模型化合物的测量再次支持单一的还原反应机理，该机理被认为是在P = S键处加成电子以形成自由基阴离子。这些结果首次证明，如果使用高级氧化工艺，有机磷污染水基的自由基处理可能会带来潜在的毒理学风险。