Application of stable isotope analysis for improved understanding of the methane budget: comparison of TROICA measurements with TM3 model simulations

Presented is a detailed comparison of CH₄ and δ¹³C–CH₄ measurements with simulations of the global transport model TM3. Experimental data were obtained during campaigns along the Trans-Siberian railroad in the framework of the TROICA project. Two summer (1999 and 2001) and one spring (2003) expeditions are evaluated. Model simulations include sensitivity tests to further investigate the isotopic composition of natural gas and emissions from Siberian wetlands. Comparison of the average mixing ratio of methane and its isotopic composition (δ¹³C) has been performed for different geographic zones, including the European part of Russia, Western Siberia and Central Siberia. Simulations are in reasonable agreement with the measurements for the European part of Russia and confirm a high contribution of natural gas to the observed methane levels. An increase of emission from bogs shifts the simulated methane isotopic composition closer to the observations. The relative importance of the Western Siberia emissions in current inventories is underestimated in comparison with other wetland regions in the former USSR. Simulated average mixing ratios are in a good agreement with the observations in Central Siberia, while ¹³C(CH₄) values tend to be higher than measured in all considered scenarios. These results point to a bias in the modeled source mixture over Russia, which could be repaired by shifting emissions from isotopically heavy methane sources (e.g. coal, oil or biomass burning) to light sources (e.g. wetlands, ruminants, waste treatment). Alternatively, the average isotopic signature of Siberian wetlands may be lighter than expected.     

Observations of the Atmospheric Composition over Russia: TROICA Experiments

Izvestiya, Atmospheric and Oceanic Physics - Results obtained in the course of unique observations (as part of the TROICA project) of the composition and state of the atmosphere over Russia have...     

Trace Gas Measurements Between Moscow and Vladivostok Using the Trans-Siberian Railroad

Using a laboratory wagon traveling along the Trans-Siberian railroad, O₃, NO, NO₂, CO, CH₄, SF₆ and black carbon aerosol have been measured during the summer of 1996. The expedition from Niznij Novgorod (500 km east of Moscow) to Vladivostok (and back to Moscow) has shown the great potential of the train method; here the first results are presented and discussed. A wealth of boundary layer air data was obtained during the over 18000 km travel without serious contamination problems from the electric train itself. The diurnal O₃ cycle peaked generally below 50 nmole/mole, showed the effects of changes in J(NO₂), and often dropped to a few nmole/mole at night time during inversions. Over the vast Siberian lowlands situated between the Ural mountains and the river Yenisey, CH₄ levels were consistently elevated at around 1.95 µmole/mole, which we mainly attribute to wetland emissions. Over eastern Siberia, however, CH₄ levels were generally lower at 1.85 µmole/mole. In contrast, over the west Siberian lowlands, CO levels were relatively low, often reaching values of only 110 nmole/mole, whereas over eastern Siberia CO levels were higher. Very high CO levels were detected over a 2000 km section east of Chita, along the river Amur, which represented an enormous polluted air mass. ¹⁴C analysis performed on several CO samples confirms that the origin was biomass burning. SF₆, which was measured as a general conserved tracer, showed an eastward attenuation from 4.0 to 3.9 pmole/mole, with peaks in a number of places due to local Russian emissions.     

Atmospheric CO along the Trans-Siberian Railroad and River Ob: source identification using isotope analysis

The concentration, radiocarbon (¹⁴C) and stable isotope (¹³C and ¹⁸O) content of CO have been determined in air samples collected across Russia (about 8,500 km) and along the Ob river during the summer of 1999 to study the CO sources and sinks. An instrumented carriage on the Trans-Siberian railway and a boat on the river Ob were used as atmospheric measurement platforms. In general, CO mixing ratios, CO stable isotope ratios, as well as the abundances of ¹⁴CO over West Siberia were similar to those found at remote northern hemispheric baseline monitoring stations. Identified sources of CO along the Ob appear to be connected to methane oxidation based on an inferred δ¹³C_source = −36.8 ± 0.6‰, while the value for δ¹⁸O_source = 9.0 ± 1.6‰ identifies it as burning. Thus flaring in the oil and gas production can be supposed to be a source. The extreme ¹³C depletion and concomitant ¹⁸O enrichment for two of the boat samples unambiguously indicates contamination by CO from combustion of natural gas (inferred values δ¹³C_source = −40.3‰ and δ¹⁸O_source = 17.5‰). For these two samples, that have strongly elevated ¹⁴CO concentrations, the industrial area near Tomsk is identified as a source area using meteorological calculations. Along the Trans-Siberian Railroad background CO was to various degrees contaminated with CO from methane combustion (δ¹³C_source = −35.7 ± 6.2‰ and δ¹⁸O_source = 10.3 ± 1.8‰). The impact of industrial burning was discernable in the vicinity of Perm-Kungur.     

A Double Portrait: The Contributions G.S. Golitsyn and P.J. Crutzen Made to Studying the Physics and Chemistry of the Atmosphere

Izvestiya, Atmospheric and Oceanic Physics - This is the introductory article for the special issue of Izvestia, Atmospheric and Oceanic Physics dedicated to the 2019 Lomonosov Gold Medal of the...     

Methane, carbon monoxide, and carbon dioxide concentrations measured in the atmospheric surface layer over continental Russia in the TROICA experiments

The principal statistical regularities typical of the behaviors of the CH₄, CO, and CO₂ concentrations in the atmospheric surface layer over the continental Russian territory are revealed from the measurements performed in 1997–2004 along the Trans-Siberian Railroad from Moscow to Khabarovsk with a mobile laboratory. The data obtained under the conditions of the atmosphere free of anthropogenic pollutants are analyzed. For near-background conditions, the typical continental methane, carbon monoxide, and carbon dioxide concentrations and characteristic features of their large-scale spatial distributions and daily variations, including those caused by surface inversions, are determined. Variations in the concentrations of these trace gases over industrial regions are analyzed. Our results are compared to the data obtained at background stations of the world network of atmospheric monitoring and to the data of a numerical simulation.     

Photochemical Production of Carbon Monoxide in Snow

Carbon monoxide concentrations were measured over an 8-day period (March 1997) in freshly fallen snow samples collected at Mount Sonnblick (Austria). Diurnal changes were systematically observed in the snow, with higher CO during daytime, indicating that light-dependent CO production processes are active in surface snow layers. Mean daytime CO concentrations in snow varied significantly from one day to another and were found to be well correlated with the daily mean atmospheric CO concentrations. Thus, the more polluted the air mass during the snow fall, the more CO was produced through photolytical processes. Furthermore closed chamber experiments were made, giving similar observations: rapid increases of CO concentration occurred within the chamber when the snow was exposed to sunlight. In the dark, however, CO concentrations decreased. CO fluxes between the surface of the snowpack and the atmosphere were estimated at 0.6 ppb/day which may be significant in the local CO budget but not on a global scale. Laboratory experiments showed that CO was rapidly formed when melted snow samples were exposed to the light from a solar simulator and that the initial CO formation rate was strongly correlated with the concentrations of Total Organic Carbon in the melted snow samples. This correlation indicates that organic compounds present in snow precipitation are the major substrate for the photochemical CO production observed in freshly fallen snow. Recent studies have reported high formaldehyde concentrations in the snowpack and we suggest HCHO photolysis to be partly responsible of CO production in snow.