Abstract
The Environmental Simulation Chamber made of Quartz from the University “Alexandru Ioan Cuza” from Iasi (ESC-Q-UAIC), Romania, was used to investigate for the first time the gas-phase reaction rate coefficients for four nitrocatechols towards OH radicals under simulated atmospheric conditions. Employing relative rate technique at a temperature of 298 ± 2 K and total air pressure of 1 atm, the obtained rate coefficients (in 10−12 cm3×s−1) were as followed: k3NCAT = (3.41 ± 0.37) for 3-nitrocatechol, k4NCAT = (1.27 ± 0.19) for 4-nitrocatechol, k5M3NCAT = (5.55 ± 0.45) for 5-methyl-3-nitrocatechol and k4M5NCAT = (0.92 ± 0.14) for 4-methyl-5-nitrocatechol. For the investigated compounds the photolysis rates in the actinic region, scaled to atmospheric relevant conditions, were evaluated as well. In this case the photolysis rate coefficient values were obtained only for 3-nitrocatechol and 5-methyl-3-nitrocatechol: J3NCAT = (3.06 ± 0.16) × 10−4 s−1 and J5M3NCAT = (2.14 ± 0.18) × 10−4 s−1, respectively. Considering the obtained results our study suggests that photolysis may be the main degradation process for 3-nitrocatechol and 5-methyl-3-nitrocatechol in the atmosphere. Results are discussed in terms of the reactivity of the investigated four nitrocatechols towards OH-radical initiated oxidation and their structural features. The rate coefficient values are also compared with those estimated from the structure-activity relationship for monocyclic aromatic hydrocarbons. Additional comparison with similar compounds is also presented underlining the implications towards possible degradation pathways and atmospheric behavior.
Highlights
Aromatic hydrocarbons (AHs) are a class of volatile organic compounds (VOCs) present as primary pollutants in the 25 atmosphere mainly because of the anthropogenic activities
The Environmental Simulation Chamber made of Quartz from the University “Alexandru Ioan Cuza” from Iasi 10 (ESC-Q-UAIC), Romania, was used to investigate for the first time the gas-phase reaction rate coefficients for four nitrocatechols towards OH radicals under simulated atmospheric conditions
The present study aims to determine and discuss, for the first time upon our knowledge, the OH kinetic rate coefficients for 75 four nitrocatechols: 3-nitrocatechol (3NCAT), 4-nitrocatechol (4-NCAT), 5-methyl-3-nitrocatechol (5M3NCAT) and 4methyl-5-nitrocatechol (4M5NCAT) by using the Environmental Simulation Chamber made by Quartz from University “Alexandru Ioan Cuza” from Iasi, Romania (ESC-Q-UAIC)
Summary
Aromatic hydrocarbons (AHs) are a class of volatile organic compounds (VOCs) present as primary pollutants in the 25 atmosphere mainly because of the anthropogenic activities. AHs are present due to the use of solvents, incomplete combustion of fossil fuels, car engines emissions and industrial processes (Piccot et al, 1992). Various monocyclic aromatics occur from biomass burning in rural and remote areas (Schauer et al, 2001). Atmospheric removal of these compounds occurs via reactions with different oxidants (Finlayson-Pitts and Pitts, 2000) and by wet and dry deposition (Calvert et al, 2002). Discussion started: 8 July 2021 c Author(s) 2021.
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