Non-Methane Volatile Organic Compound Sources and Sinks in England and Scotland, UK

Abstract

Non-methane volatile organic compounds (NMVOCs) in the atmosphere have garnered considerable attention worldwide because of their significance in atmospheric chemistry and their usefulness in identifying emission sources and chemical sinks. Despite the importance of VOCs, their routine measurement in the UK and across Europe is somewhat limited, and as such, there is limited information available regarding their sources, particularly in sensitive locations such as densely populated urban areas. In this study, hourly NMVOC concentration data measured between January 2015 and December 2023 were analyzed across four monitoring sites spanning an urban-to-rural gradient in England. The Marylebone and Eltham sites showed significantly higher concentrations of alkanes, alkenes, and aromatic hydrocarbons compared to the rural sites of Chilbolton and Auchencorth, with highest recorded VOC values of 29.9 ± 9.1 and 15.3 ± 4.3 µg m−3, respectively. Ethane (C2H6) and propane (C3H8) showed their highest ozone formation potential (OFP) levels at Marylebone Road, with the contribution of ethane to ozone formation ranging from 4% in Eltham to 8% in Chilbolton. This indicates that the emissions from vehicles and industries have a greater impact on the reactivity of these compounds. The potential source contribution function (PSCF) showed that the Marylebone and Eltham sites are mainly impacted by local traffic sources, while Chilbolton and Auchencorth receive VOC emissions from wider geographical areas. The COVID-19 lockdowns caused significant reductions in VOC concentrations at urban sites, which resulted in total VOCs declining by 26% at Marylebone Road and 11% in Eltham, while rural sites remained unaffected. The study results demonstrate new insights into NMVOC long-term temporal patterns and source identification across different UK environments, with important implications for air quality management and emission control policies.