David Gara Pedro M, Bosio Gabriela N, Arce Valeria B, Poulsen Lars, Ogilby Peter R, Giudici Reinaldo, Gonzalez Mónica C, Mártire Daniel O
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Universidad Nacional de La Plata, Argentina.
Photochem Photobiol. 2009 May-Jun;85(3):686-92. doi: 10.1111/j.1751-1097.2008.00467.x. Epub 2008 Nov 19.
The photodegradation of the herbicide clomazone in the presence of S(2)O(8) (2-) or of humic substances of different origin was investigated. A value of (9.4 +/- 0.4) x 10(8) m(-1) s(-1) was measured for the bimolecular rate constant for the reaction of sulfate radicals with clomazone in flash-photolysis experiments. Steady state photolysis of peroxydisulfate, leading to the formation of the sulfate radicals, in the presence of clomazone was shown to be an efficient photodegradation method of the herbicide. This is a relevant result regarding the in situ chemical oxidation procedures involving peroxydisulfate as the oxidant. The main reaction products are 2-chlorobenzylalcohol and 2-chlorobenzaldehyde. The degradation kinetics of clomazone was also studied under steady state conditions induced by photolysis of Aldrich humic acid or a vermicompost extract (VCE). The results indicate that singlet oxygen is the main species responsible for clomazone degradation. The quantum yield of O(2)(a(1)Delta(g)) generation (lambda = 400 nm) for the VCE in D(2)O, Phi(Delta) = (1.3 +/- 0.1) x 10(-3), was determined by measuring the O(2)(a(1)Delta(g)) phosphorescence at 1270 nm. The value of the overall quenching constant of O(2)(a(1)Delta(g)) by clomazone was found to be (5.7 +/- 0.3) x 10(7) m(-1) s(-1) in D(2)O. The bimolecular rate constant for the reaction of clomazone with singlet oxygen was k(r) = (5.4 +/- 0.1) x 10(7) m(-1) s(-1), which means that the quenching process is mainly reactive.
研究了在过二硫酸根离子（S₂O₈²⁻）或不同来源腐殖质存在下除草剂广灭灵的光降解情况。在闪光光解实验中，测得硫酸根自由基与广灭灵反应的双分子速率常数为(9.4±0.4)×10⁸ m⁻¹ s⁻¹。在广灭灵存在下，过二硫酸盐的稳态光解导致硫酸根自由基的形成，这被证明是该除草剂一种有效的光降解方法。这对于涉及过二硫酸盐作为氧化剂的原位化学氧化过程是一个相关结果。主要反应产物是2 - 氯苄醇和2 - 氯苯甲醛。还研究了在由奥尔德里奇腐殖酸或蚯蚓堆肥提取物（VCE）光解诱导的稳态条件下广灭灵的降解动力学。结果表明单线态氧是导致广灭灵降解的主要物质。通过测量在1270 nm处O₂(a¹Δg)的磷光，测定了VCE在重水（D₂O）中产生O₂(a¹Δg)（λ = 针对除草剂广灭灵在存在过二硫酸根离子（S₂O₈²⁻）或不同来源腐殖质的情况下的光降解进行了研究。在闪光光解实验中，测得硫酸根自由基与广灭灵反应的双分子速率常数为(9.4 ± 0.4)×10⁸ m⁻¹ s⁻¹。在广灭灵存在下，过二硫酸盐的稳态光解导致硫酸根自由基的形成，这被证明是该除草剂一种有效的光降解方法。这对于涉及过二硫酸盐作为氧化剂的原位化学氧化过程是一个相关结果。主要反应产物是2 - 氯苄醇和2 - 氯苯甲醛。还研究了在由奥尔德里奇腐殖酸或蚯蚓堆肥提取物（VCE）光解诱导的稳态条件下广灭灵的降解动力学。结果表明单线态氧是导致广灭灵降解的主要物质。通过测量在1270 nm处O₂(a¹Δg)的磷光，测定了VCE在重水（D₂O）中产生O₂(a¹Δg)（λ = 400 nm）的量子产率，ΦΔ = (1.3 ± 0.1)×10⁻³。发现在重水（D₂O）中广灭灵对O₂(a¹Δg)的总猝灭常数为(5.7 ± 0.3)×10⁷ m⁻¹ s⁻¹。广灭灵与单线态氧反应的双分子速率常数为k(r) = (5.4 ± 0.1)×10⁷ m⁻¹ s⁻¹，这意味着猝灭过程主要是反应性的。 400 nm）的量子产率，ΦΔ = (1.3 ± 0.1)×10⁻³。发现在重水（D₂O）中广灭灵对O₂(a¹Δg)的总猝灭常数为(5.7 ± 0.3)×10⁷ m⁻¹ s⁻¹。广灭灵与单线态氧反应的双分子速率常数为k(r) = (5.4 ± 0.1)×10⁷ m⁻¹ s⁻¹，这意味着猝灭过程主要是反应性的。
