Spectroscopic signatures of ozone at the air–water interface and photochemistry implications

Abstract

First-principles simulations suggest that additional OH formation in the troposphere can result from ozone interactions with the surface of cloud droplets. Ozone exhibits an affinity for the airwater interface, which modifies its UV and visible light spectroscopic signatures and photolytic rate constant in the troposphere. Ozone cross sections on the red side of the Hartley band (290-to 350-nm region) and in the Chappuis band (450-700 nm) are increased due to electronic ozone-water interactions. This effect, combined with the potential contribution of the O 3 + hν → O() photolytic channel at the interface, leads to an enhancement of the OH radical formation rate by four orders of magnitude. This finding suggests that clouds can influence the overall oxidizing capacity of the troposphere on a global scale by stimulating the production of OH radicals through ozone photolysis by UV and visible light at the air-water interface.atmospheric chemistry | heterogeneous processes | reactive oxidant species | computer simulations O zone, which is generated in the stratosphere, is well known to strongly absorb solar radiation in the UV region and contribute to the radiative forcing of the atmosphere, thereby influencing climate (1, 2). Changes in ozone abundances can perturb UV radiation levels in the atmosphere and at Earth's surface, and thus the extensive quantification of ozone distributions is critical to understanding its impact on the global environment. Stratospheric ozone distribution changes can affect the temperature in the stratosphere as well as impact photochemical processes in the troposphere. Tropospheric ozone can be produced photochemically in situ or transported down from the stratosphere. Tropospheric ozone exhibits significant radiative forcing, because O 3 is a greenhouse gas, but it also acts as a pollutant; its concentration is one of the measures to indicate the air quality worldwide.The photochemistry of ozone in the troposphere is, on the other hand, an important source of hydroxyl radicals, which are key to the chemistry of the atmosphere and determine the fate of anthropogenically emitted organic compounds (3). Hydroxyl radicals are mainly produced through the reactions Field measurements over the equatorial Pacific found significant variability of tropospheric ozone and hydroxyl radical concentrations, which has been suggested to affect the oxidizing efficiency of the troposphere (4). On the other hand, different experiments have suggested that current atmospheric models are missing a source of OH radicals. Discrepancies between models and observations in forested and polluted environments, for instance, indicated that OH chemistry is not fully understood (5-8). Frost and Vaida (9) were the first to propose that ozone in the low atmosphere could form a weakly bound complex with water, whose photodissociation could account for up to 15% of the available OH in the troposphere. The implicit assumption is that the long-wavelength absorption of ozone may be enhanced as a result of complexation with...

Mixing state of oxalic acid containing particles in the rural area of Pearl River Delta, China: implications for the formation mechanism of oxalic acid

“…The modeling studies from Ervens et al (2014) suggest that oxalic acid production from glyoxal and glyoxylic acid in the aqueous phase significantly depends on q OH availability (Ervens et al, 2014). The main sources of aqueous-phase q OH in cloud droplets include direct uptake from the gas phase (Jacob, 1986), ozone photolysis by UV and visible light at the air-water interface (Anglada et al, 2014) and also aqueous-phase chemical reactions (Gligorovski et al, 2015). For the last kind of source, q OH radicals could be generated through Fenton or Fenton-like reactions and photolysis of H 2 O 2 , NO − 3 , NO − 2 and chromophoric dissolved organic matter (CDOM) (Badali et al, 2015;Ervens, 2015;Herrmann et al, 2015;Tong et al, 2016).…”

Reaching multi‐nanosecond timescales in combined QM/MM molecular dynamics simulations through parallel horsetail sampling

“…In the present study, we focus on the electronic properties and geometric structure of H 2 O 2 at the water liquid–vapor interface. As shown in previous works for other ROS and several organic compounds, interface solvation effects can be significantly different from solvation effects in bulk, even qualitatively. Study of such effects is therefore compulsory to assess the potential contribution of cloud water droplets to the overall oxidizing capacity of the troposphere .…”

“…Study of such effects is therefore compulsory to assess the potential contribution of cloud water droplets to the overall oxidizing capacity of the troposphere . For instance, the OH formation rate from ozone photolysis is accelerated by 3–4 orders of magnitude at the air–water interface compared to gas phase …”

“…A cutoff radius of 12.331 Å was used. Although the Lennard‐Jones parameters for the QM system may be optimized for a particular application, in this work we have used the parameters from the water TIP3P potential, which have been successfully used to study other reactive oxygen species (ROS) at the water liquid–vapor interface …”

Computational Insights into the CH3Cl+OH Chemical Reaction Dynamics at the Air–Water Interface

“…[11] The heterogeneousc hemistryo ccurring at the airwater interface of water droplets in the tropospherei st herefore ah ighly relevant research topic that deserves furthere xploration.…”