A study of the kinetics and products obtained from the reactions of 3-methylfuran with the main atmospheric oxidants has been performed. The rate coefficients for the gas-phase reaction of 3-methylfuran with OH and NO₃ radicals have been determined at room temperature and atmospheric pressure (air and N₂ as bath gases), using a relative method with different experimental techniques. The rate coefficients obtained for these reactions were (in units cm³ molecule⁻¹ s⁻¹) <i>k</i>_OH = (1.13 &plusmn; 0.22) &times; 10⁻¹⁰ and <i>k</i>_NO₃ = (1.26 &plusmn; 0.18) &times; 10⁻¹¹. Products from the reaction of 3-methylfuran with OH, NO₃ and Cl atoms in the absence and in the presence of NO have also been determined. The main reaction products obtained were chlorinated methylfuranones and hydroxy-methylfuranones in the reaction of 3-methylfuran with Cl atoms, 2-methylbutenedial, 3-methyl-2,5-furanodione and hydroxy-methylfuranones in the reaction of 3-methylfuran with OH and NO₃ radicals and also nitrated compounds in the reaction with NO₃ radicals. The results indicate that, in all cases, the main reaction path is the addition to the double bond of the aromatic ring followed by ring opening in the case of OH and NO₃ radicals. The formation of 3-furaldehyde and hydroxy-methylfuranones (in the reactions of 3-methylfuran with Cl atoms and NO₃ radicals) confirmed the H-atom abstraction from the methyl group and from the aromatic ring, respectively. This study represents the first product determination for Cl atoms and NO₃ radicals in reactions with 3-methylfuran. The reaction mechanisms and atmospheric implications of the reactions under consideration are also discussed

The rate constants for the gas-phase reactions of the NO3 radical with a series of unsaturated aldehydes (acrolein, crotonaldehyde, trans-2-pentenal, trans-2-hexenal, trans-2-heptenal, and cis-4-heptenal) have been measured directly using a flow tube system coupled to a laser-induced fluorescence (LIF) detection system where the NO3 radical was monitored. The kinetic study was conducted in the temperature range from 298 to 433 K to investigate the temperature dependence of these reactions. This work is the first temperature-dependence study for the reactions of the nitrate radical with the above-mentioned aldehydes. The measured room-temperature rate constants for the reaction of NO3 with such unsaturated compounds (in units of 10-14 cm3 molecule-1 s-1) are as follows:  acrolein, 0.25 ± 0.04; crotonaldehyde, 1.61 ± 0.19; trans-2-pentenal, 2.88 ± 0.29; trans-2-hexenal, 5.49 ± 0.95; trans-2-heptenal, 9.59 ± 0.19; cis-4-heptenal, 26.40 ± 0.40. The proposed Arrhenius expressions for such reactions of NO3 are, respectively, k 1 = (1.7 ± 3.2) × 10-11 exp[−(3232 ± 355)/T] (cm3 molecule-1 s-1), k 2 = (5.52 ± 0.82) × 10-11 exp[−(2418 ± 57)/T] (cm3 molecule-1 s-1), k 3 = (5.4 ± 0.3) × 10-12 exp[−(1540 ± 200)/T] (cm3 molecule-1 s-1), k 4 = (1.20 ± 0.3) × 10-11 exp[−(926 ± 85)/T] (cm3 molecule-1 s-1), k 5 = (0.8 ± 0.2) × 10-12 exp[−(632 ± 47)/T] (cm3 molecule-1 s-1), and k 6 = (0.2 ± 0.1) × 10-11 exp[−(657± 6.0)/T] (cm3 molecule-1 s-1). Tropospheric lifetimes for these aldehydes have been calculated at night and during the daytime for typical NO3 and OH concentrations showing that both radicals provide an effective tropospheric sink for these compounds and that the night-time reaction with NO3 radical can be an important loss process for these emitted organics and for the NO3 radicals. The present work aims to evaluate the importance of these reactions in the atmosphere and to contribute new data to the study of NO3 reactivity.

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Public health authorities have been paramount in guaranteeing that adequate fresh air ventilation is promoted in classrooms to avoid SARS-CoV-2 transmission in educational environments. In this work it was aimed to assess ventilation conditions (carbon dioxide, CO 2 ) and suspended particulate matter (PM 2.5 , PM 10 and UFP) levels in 19 classrooms – including preschool, primary and secondary education – located in the metropolitan area of Ciudad Real, Central-Southern Spain, during the school’ reopening (from September 30th until October 27th, 2020) after about 7 months of lockdown due to COVID-19 pandemic. The classrooms that presented the worst indoor environmental conditions, according to the highest peak of concentration obtained, were particularly explored to identify the possible influencing factors and respective opportunities for improvement. Briefly, findings suggested that although ventilation promoted through opening windows and doors according to official recommendations is guaranteeing adequate ventilation conditions in most of the studied classrooms, thus minimizing the risk of SARS-CoV-2 airborne transmission, a total of 5 (26%) surveyed classrooms were found to exceed the recommended CO 2 concentration limit value (700 ppm). In general, preschool rooms were the educational environments that registered better ventilation conditions, while secondary classrooms exhibited the highest peak and average CO 2 concentrations. In turn, for PM 2.5 , PM 10 and UFP, the concentrations assessed in preschools were, on average about 2-fold greater than the levels obtained in both primary and secondary classrooms. In fact, the indoor PM 2.5 and PM 10 concentrations substantially exceeded the recommended limits of 8hr-exposure, established by WHO, in 63% and 32% of the surveyed classrooms, respectively. Overall, it is expected that the findings presented in this study will assist the establishment of evidence-based measures (mainly based on ensuring proper ventilation rates and air filtration) to mitigate preventable environmental harm in public school buildings, mainly at local and national levels.