Focusing on the tropospheric chemistry of volatile organic compounds
Volatile organic compounds are emitted in substantial quantities from both biogenic and anthropogenic sources and are centrally important on the chemistry of the lower atmosphere. It is well established that the gas phase degradation of oxygenated VOCs plays an important role in the generation of ozone and a variety of secondary pollutants. Unfortunately, these coproducts may have a harmful impact on human and ecosystem health. In order to assess the environmental impact of large-scale emissions of these chemicals, a thorough understanding of the timescale and mechanism of their degradation is a prerequisite. Work performed within the MOST project has yielded a significant body of mechanistic and kinetic information to help define the degradation rates and major pathways of a series of vinyl ethers. Important atmospheric oxidation pathways for these unsaturated ethers are reactions with OH and NO3 radicals, as well as with ozone (O3), and consequently these loss processes were addressed within the project. The results showed that these unsaturated organic compounds will be oxidised very rapidly near their source. Although, atmospheric lifetimes derived from the kinetic data were limited to only a few hours, the impact of vinyl ethers is further defined by the persistence of their oxidation products. The formation of coproducts such as alkyl formates was found to reduce significantly the local impact of unsaturated ethers. The substantial progress made in the detection and quantification of products from the degradation of volatile organic compounds (VOCs) will contribute to the elucidation of details in the oxidation mechanism. These are important information regarding the photochemical history of air masses present over a given region; in particular, because of the attention paid to the local impact of sources of air pollution as a share in the full impact.
