Middle East oil and gas methane emissions signature captured at a remote site using light hydrocarbon tracers

Abstract

The observational characterization of anthropogenic methane (CH₄) emissions in the Eastern Mediterranean and Middle East (EMME) region, known for its significant oil and gas (OG) production, remains limited. Light alkanes, such as ethane (C₂H₆), are co-emitted with CH₄ by OG activities and are promising tracers for identifying the CH₄ emissions from this sector at the wider regional scale. In this study, in-situ measurements of CH₄ and alkanes (C2–C8 were collected during a field campaign at a regional background site (Cape Greco, Cyprus). A mobile laboratory housed the instrumentation at the south-eastern edge of the island between December 2021 and February 2022. This specific location and time of year were selected to capture air masses originating from distant southern and eastern regions, primarily impacted by sources from the Middle East. Based on these observations we 1) evaluate the significance of long-range transported versus local sources in Cyprus, 2) identify and document regional anthropogenic CH₄ sources with the help of the concomitant alkane measurements, and 3) assess the accuracy of the EDGAR sectoral emission inventory over the EMME region. The highest alkane mixing ratios observed were associated with the Middle Eastern OG CH₄ signal. Surprisingly, the Middle Eastern emissions of CH₄ were found to be heavily influenced by the breeding and waste management sectors. By investigating the measured CH₄ mixing ratios together with an atmospheric dispersion model (FLEXPART), we derive a comprehensive characterization of the pollution sources at a regional scale over the Eastern Mediterranean region. Our results indicate that CH₄ emissions from the Middle Eastern OG sector are likely underestimated by ca. 69 %. These findings underscore the efficacy of using experimental observations of alkanes for CH₄ source identification at receptor sites. This tracer approach would also benefit from a substantial revision of light hydrocarbon emission inventories.