Terpenes from biogenic sources in the atmosphere are emitted in amounts comparable to those of non-methane organic compounds from antropogenic sources. The aim of this work is to study the reactivity of the terpenesα-pinene, β-pinene, andcamphene toward the NO{sub}3 radical in order to evaluate the importance of these reactions in the atmosphere and their atmospheric impact. The experiments have been carried out under second-order kinetic conditions over the temperature range 298-433 Kusing a discharge flow system and monitoring the NO{sub}3 radical by Laser Induced Fluorescence (LIF). The measured roomtemperature rate constants for reaction of NO{sub}3 withα-pinene, β-pinene, and camphene are (cm{sup}3 molecule{sup}-1 s{sup}-1)(5.9± 0.8) × 10{sup}-12, (2.1± 0.4) × 10{sup}-12, and (0.62± 0.21)× 10{sup}-12, respectively. The proposed Arrhenius expressions, for the three studied reactions, are k{sub}1= (3.5± 1.4) × 10{sub}-13exp(841± 144/T) (cm{sup}3 molecule{sup}-1s{sup}-1), k{sub}2= (1.6± 1.5) × 10{sup}-10exp(-1248±36/T) (cm{sup}3 molecule{sup}-1 s{sup}-1), and k{sub}3 (3.1±10.5) × 10{sup}-12exp(-481± 55/T) (cm{sup}3 molecule{sup}-1 s{sup}-1) A negative activation energy of 7.0± 1.0 kJ mol{sup}-1 hasbeen found from the temperature dependence of the rate constant for the reaction ofα-pinene with NO{sub}3, and positive values of 10.4 ± 0.3 and 4.0 ± 0.5 kJ mol{sup}-1 have been determined forβ-pinene and camphene, respectively. Tropospherichalf-lives for these terpenes have been calculated at night and during the day for typical NO{sub}3 and OH concentrations and show that both radicals provide an effective tropospheric sink for these compounds, and the nighttime reaction with NO{sub}3radical can be an important, if not dominant, loss process for these organics.
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