Estimation of biogenic CH4 and CO2 emissions and dry deposition of O3 using 222Rn measurements in TROICA expeditions

Abstract

On the basis of simultaneous measurements of surface concentrations of CH4, CO2, O3, and 222Rn during 6 TROICA (TRanscontinental Observations Into the Chemistry of the Atmosphere) expeditions along the Trans-Siberian Railway from Moscow to Vladivostok in 1999–2008, we have estimated the biogenic emissions of CH4 and CO2 from terrestrial ecosystems and the nighttime sink of O3 on the underlying surface from data on the accumulation rate of 222Rn under conditions of near-surface temperature inversion. The regional emissions of CH4 were the highest in summer in the Far East (0.87 ± 0.52 μg m−2 s−1) and in West Siberia (0.77 ± 0.41 μg m−2 s−1), which is associated with significant methane flows from wetlands and moist soils that are typical for these regions. The biogenic emissions of CO2 vary on average from 0.18 ± 0.04 μg m−2 s−1 in West Siberia to 0.89 ± 0.07 μg m−2 s−1 in East Siberia. The nighttime sink of O3 has a seasonal maximum in summer and varies from 0.05 ± 0.01 μg m−2 s−1 in West Siberia to 0.07 ± 0.01 μg m−2 s−1 in Central Siberia; the dry deposition rate of O3 varies from 0.10 ± 0.08 cm s−1 in West Siberia to 0.33 ± 0.21 cm s−1 in East Siberia and the Far East.