Detecting and sourcing GHGs and atmospheric trace gases in a municipal waste treatment plant using coupled chemistry and isotope compositions

Landfill operations and waste processing facilities are important and highly heterogeneous sources of both greenhouse gases (GHGs) and non-GHG air pollutants in the atmosphere. This arises the need for detailed apportionment of waste sources in order to locate and subsequently reduce emissions from landfills. Here, a time series of in situ measurements of atmospheric trace gases and spatial allocation of specific emission source types under different processing phases and environmental conditions were conducted in and in the surroundings of a Municipal Solid Waste Treatment Plant (MSWTP) in south-western Poland. Results revealed that several individual GHG sources dominated across the waste processing facility and that GHGs concentrations displayed spatial seasonality. An increase in the ground-level CH₄ concentrations, from ∼ 30.3 to 56.3 ppmv, was observed close (∼5 - 10 m) to the major emission sources within the MSWTP. While hotspot areas generally yielded elevated CH₄ concentrations near the soil surface, these were relatively low (2.4 to 8.9 ppmv) along the facility's fence line. The study of the corresponding δ¹³C delineated the extent of dispersion plumes downwind emission hotspots, characterized by a ¹³C depletion (around 4.0 ‰) in the atmospheric CH₄ and CO₂. For CH₄, emissions were isotopically discriminated between the extraction wells at active quarters/cells (δ¹³C = -58.3 ± 1.1 ‰) and biogas produced in the biological waste treatment installation (δ¹³C = -62.7 ± 0.7 ‰). Most of the trace compounds (non-methane hydrocarbons, halocarbons, oxygen-bearing organic gases, ketones, nitrogenous and sulphurous gases, and other admixture compounds) detected at the ground surface were linked to the CH₄- and CO₂-rich spots. Despite the relatively high variability in the concentrations of organic and inorganic compounds observed at the MSWTP active zones, our results suggest that they do not have a meaningful impact on the surrounding air quality.