Department of Chemistry and Biochemistry, California State University at Long Beach, 1250 Bellflower Blvd., Long Beach, California 90840, USA.
Environ Sci Technol. 2011 Aug 15;45(16):6932-7. doi: 10.1021/es201363j. Epub 2011 Jul 15.
The temperature-dependent bimolecular rate constants for the reaction of the hydroxyl radical (HO(•)) with organic matter (OM) (k(OM-HO(•))) have been measured for three natural organic matter (NOM) isolates and three bulk effluent organic matter (EfOM) samples using electron pulse radiolysis and thiocyanate competition kinetics. The range of values for the room temperature k(OM-HO(•)) was 1.21-9.37 × 10(8) M(C)(-1)s(-1), with NOM isolates generally reacting slower than EfOM samples. The NOM isolates had an average apparent activation energy of 19.8 kJ mol(-1), while the EfOM samples had an average value slightly lower (14.3 kJ mol(-1)), although one NOM isolate (Elliot Soil Humic Acid, 29.9 kJ mol(-1)) was a factor of 2 times greater than other samples studied. These apparent activation energies are the first determined for OM and HO(•), and the Arrhenius plots obtained for NOM isolates (lowest R(2) > 0.993) suggest that no significant structural changes are occurring over the temperature range 8-41 °C. In contrast, the greater scatter (lowest R(2) > 0.903) observed for the EfOM samples suggests that some structural changes may be occurring. These results provide a deeper fundamental understanding of the reaction between OM and HO(•) and will be useful in quantifying HO(•) reactions in natural and engineered systems.
利用电子脉冲辐射和硫氰酸盐竞争动力学，测量了三种天然有机物（NOM）分离物和三种原废水有机物（EfOM）样品中羟基自由基（HO(•)）与有机物（OM）反应的温度依赖双分子速率常数（k(OM-HO(•)))。室温下 k(OM-HO(•))的值范围为 1.21-9.37 × 10(8) M(C)(-1)s(-1)，NOM 分离物的反应速度通常比 EfOM 样品慢。NOM 分离物的表观活化能平均为 19.8 kJ mol(-1)，而 EfOM 样品的平均表观活化能略低（14.3 kJ mol(-1)），尽管有一种 NOM 分离物（埃利奥特土壤腐殖酸，29.9 kJ mol(-1)）是其他研究样品的两倍。这些表观活化能是首次为 OM 和 HO(•)确定的，并且对于 NOM 分离物获得的 Arrhenius 图（最低 R(2) > 0.993）表明，在 8-41°C 的温度范围内不会发生显着的结构变化。相比之下，对于 EfOM 样品观察到的更大分散性（最低 R(2) > 0.903）表明可能发生了一些结构变化。这些结果提供了对 OM 和 HO(•)之间反应的更深入的基本理解，并将有助于量化天然和工程系统中 HO(•)反应。
