Source partitioning of atmospheric methane using stable carbon isotope measurements in the Reuss Valley, Switzerland

Abstract

Measurements of methane (CH4) mole fractions and δ 13 C-CH4 that resolve the diel cycle in the agriculturally dominated Reuss Valley, Switzerland, were used to quantify the contributions of different CH4 sources to the atmospheric CH4 source mix. Both a nocturnal (NBL) and a diurnal convective boundary layer (CBL) approach were employed. A diel course of CH4 mole fractions was found with a daytime minimum (background around 1900 ppb) and a nocturnal maximum (up to 3500 ppb). The δ 13 C value in CH4 only showed small variations during the day (9-21 hours CET, -45.0 ± 0.2 mean ± SE) when the atmosphere was well mixed, but decreased by -4.8 ± 0.1 during the night. Biogenic emissions dominated in both approaches (ranging from 60 to 94%), but non-biogenic sources were rather important (42.2% and 46.0% with CBL, 5.8% and 40% with NBL approach in 2011 and 2012, respectively, of total emissions). The CH4 sink, dominated by tropospheric OH oxidation and only to a minor extend by soil surface uptake, was quantified at roughly 4% of local emissions.

Global inventory of the stable isotopic composition of methane surface emissions, augmented by new measurements in Europe

“…Measurements of CH 4 isotopologues provide additional constraints on the relative contribution of the various source categories, because CH 4 isotopic composition depends on the formation processes (Schoell, 1980;Whiticar, 1999;Quay et al, 1999). Time series of ambient CH 4 isotopic ratios are already used to derive emission scenarios in global models (Bousquet et al, 2006;Schaefer et al, 2016;Turner et al, 2017;Thompson et al, 2018;Fujita et al, 2020;Lan et al, 2021), and at the regional scale (Röckmann et al, 2016;Stieger et al, 2019;Menoud et al, 2020Menoud et al, , 2021bVarga et al, 2021). In addition, isotope measurements have proven to be very successful for source attribution in cities (Phillips et al, 2013;Zazzeri et al, 2017;Maazallahi et al, 2020;Xueref-Remy et al, 2020;Defratyka et al, 2021;Fernandez et al, in review), and larger regions (Tarasova et al, 2006;Fisher et al, 2011;Beck et al, 2012;Warwick et al, 2016;Lu et al, 2021).…”

Baseline surface- and groundwater monitoring prior to an onshore shale gas operation in the Vale of Pickering, UK

“…Quay et al (1999) cited the global average methane δ 13 C as -47.2 to -47.7‰. Both the atmospheric methane content and its δ 13 C vary depending on time of day and location (Bosquet et al 2006, Stieger et al (2019. An atmospheric content of 2 µmole mole -1 and a methane solubility of 31 mg/L at 10°C would imply that one would expect an aqueous methane concentration of <0.1 µg/L for a water sample in equilibrium with the atmosphere.…”

“…The δ 13 C of methane generated by such processes is typically in the range -40 to -62‰ (Baldassare 2010) or -50 to -65‰ according to Whiticar et al (1986) and Schloemer et al (2016). Landfill and sewage gas methane, for example, has a typical δ 13 C of -53 to -58‰ (Dlugokencky et al 2011, Stieger et al 2019.…”

New contributions of measurements in Europe to the global inventory of the stable isotopic composition of methane

“…Time series of ambient CH 4 isotopic ratios are already used to derive emission scenarios in global models (e.g. Bousquet et al, 2006;Schaefer et al, 2016;Turner et al, 2017;Thompson et al, 2018;Fujita et al, 2020;Lan et al, 2021), and at the regional scale (Röckmann et al, 2016;Stieger et al, 2019;Menoud et al, 2020cVarga et al, 2021). In addition, isotope measurements have proven to be very successful for source attribution in cities (Phillips et al, 2013;Zazzeri et al, 2017;Maazallahi et al, 2020;Xueref-Remy et al, 2020;Defratyka et al, 2021;Fernandez et al, 2022), and larger regions (Tarasova et al, 2006;Fisher et al, 2011;Beck et al, 2012;Warwick et al, 2016;Fisher et al, 2017;Lu et al, 2021).…”