The rate coefficient of the OH reaction with the perfluoroaldehydes C3F7CHO and C4F9CHO have been determined in the temperature range 252–373 K using the pulsed laser photolysis–laser induced fluorescence (PLP-LIF) method: kC3F7CHO+OH = (2.0 ± 0.6) × 10−12 exp[−(369 ± 90)/T] and kC4F9CHO+OH = (2.0 ± 0.5) × 10−12 exp[−(356 ± 70)/T] cm3 molecule−1 s−1, corresponding to (5.8 ± 0.6) × 10−13 and (6.1 ± 0.5) × 10−13 cm3 molecule−1 s−1, respectively, at 298 K. The UV absorption cross sections of these two aldehydes and CF3(CF2)5CH2CHO have been measured over the range 230–390 nm at 298 K and also at 328 K for CF3(CF2)5CH2CHO. The obtained results for C3F7CHO and C4F9CHO are in good agreement with two recent determinations but the maximum value of the absorption cross section for CF3(CF2)5CH2CHO is over a factor of two lower than the single one recently published. The photolysis rates of C3F7CHO, C4F9CHO and CF3(CF2)5CHO have been measured under sunlight conditions in the EUPHORE simulation chamber in Valencia (Spain) at the beginning of June. The photolysis rates were, respectively, Jobs = (1.3 ± 0.6) × 10−5, (1.9 ± 0.8) × 10−5 and (0.6 ± 0.3) × 10−5 s−1. From the Jobs measurements and calculated photolysis rate Jcalc, assuming a quantum yield of unity across the atmospheric range of absorption of the aldehydes, quantum yields Jobs/Jcalc = (0.023 ± 0.012), (0.029 ± 0.015) and (0.046 ± 0.028) were derived for the photodissociation of C3F7CHO, C4F9CHO and CF3(CF2)5CHO, respectively. The atmospheric implication of the data obtained in this work is discussed. The main conclusion is that the major atmospheric removal pathway for fluoroaldehydes will be photolysis, which under low NOx conditions, may be a source of fluorinated carboxylic acids in the troposphere.
使用脉冲激光光解-激光诱导荧光(PLP-LIF)方法测定了在 252-373 K 温度范围内 OH 与
全氟醛 C3F7CHO 和 C4F9CHO 反应的速率系数:kC3F7CHO+OH = (2.0 ± 0.6) × 10-12 exp[-(369 ± 90)/T] 和 kC4F9CHO+OH = (2.0 ± 0. 5) × 10-12 exp[-(356 ± 70)/T] cm3 molecule-1 s-1,对应于 (5.8 ± 0.6) × 10-13 和 (6.1 ± 0.5) cm3 molecule-1 s-1。这两种
醛类和
CF3(
CF2)5CH2CHO 的紫外吸收截面是在 230-390 纳米范围内于 298 K 测得的, (
CF2)5CH2CHO 的吸收截面也是在 328 K 测得的。C3F7CHO 和 C4F9CHO 的测量结果与最近的两次测定结果十分吻合,但 (
CF2)5CH2CHO 的吸收截面最大值比最近公布的单次测定值低了两倍多。6 月初,在巴伦西亚(西班牙)的 E
UPHORE 模拟室中测量了 C3F7CHO、C4F9CHO 和 (
CF2)5CHO 在日光条件下的光解率。光解率分别为 Jobs = (1.3 ± 0.6) × 10-5、(1.9 ± 0.8) × 10-5 和 (0.6 ± 0.3) × 10-5 s-1。根据乔布斯测量和计算的光解率 Jcalc,假设
醛类在大气吸收范围内的量子产率为统一,则得出 C3F7CHO、C4F9CHO 和 (
CF2)5CHO 的光解量子产率乔布斯/Jcalc = (0.023±0.012)、(0.029±0.015) 和 (0.046±0.028) 。本文讨论了所获数据对大气的影响。主要结论是,
氟醛在大气中的主要清除途径是光解,在低氮氧化物条件下,光解可能是对流层中
氟化
羧酸的一个来源。