Identification of Natural Gas Leak Sources Using Ethane/Methane Ratios and Methane Isotopic Signatures

Methane (CH 4 ) is the second largest greenhouse gases in the atmosphere. Its global anthropogenic emissions are equivalent to about 20% of total GHG emissions in CO 2 -equivalent terms. Source identification for atmospheric CH 4 , however, is not straight forward. This study conducted mobile measurements of CH 4 , C 2 H 6 , CO 2 , CO and stable CH 4 carbon isotope composition (δ 13 C-CH 4 ) at three natural gas compressor stations in China to obtain source signatures for ΔC 2 H 6 /ΔCH 4 (C 2 :C 1 ) and δ 13 C-CH 4 . The two northern stations showed consistent ΔC 2 H 6 /ΔCH 4 ratios (0.059 and 0.056) and δ 13 C-CH 4 values (-40.59 ‰ and -40.93 ‰), while the southern station exhibited a lower ratio (0.022) and less 13 C-depleted δ 13 C-CH 4 values (-39.34 ‰), indicating different gas supply sources. Using these signatures, mobile surveys in adjacent urban and suburban areas identified 17 and 9 CH 4 emission sources near the northern and southern stations, respectively, with 58.9% and 66.7% attributed to natural gas leaks. On-road leak magnitudes spanned 0.77-101.69 L/min around Station #1 and 0.38-26.78 L/min around Station #3. In both regions, detections were dominated by small leaks (< 4 L/min), including cases with multiple plume peaks evaluated individually. These findings highlight the effectiveness and practical importance of a dual-tracer approach for mobile platforms to reliably identify and quantify natural-gas-related CH 4 sources along road networks. • Mobile surveys identify natural gas as major CH 4 source using dual tracers. • Distinct CH 4 signatures reveal regional differences in China's gas supply. • Multi-indicator method enhances CH 4 source attribution and inventory accuracy. • Spatial interpolation shows NG source influence ranges from 500 to 1500 meters Synopsis: This study discussed the employment of gaussian models for urban methane emission inversion with implications for greenhouse gas reduction.