Benzene and toluene in the surface air of northern Eurasia from TROICA-12 campaign along the Trans-Siberian Railway

Abstract

Abstract. Volatile organic compounds (VOCs) were measured by proton transfer reaction mass spectrometry (PTR-MS) on a mobile laboratory in a transcontinental TROICA-12 (21 July-4 August 2008) campaign along the TransSiberian Railway from Moscow to Vladivostok. Surface concentrations of benzene (C 6 H 6 ) and toluene (C 7 H 8 ) along with non-methane hydrocarbons (NMHCs), CO, O 3 , SO 2 , NO, NO 2 and meteorology are analyzed in this study to identify the main sources of benzene and toluene along the TransSiberian Railway. The most measurements in the TROICA-12 campaign were conducted under low-wind/stagnant conditions in moderately (∼ 78 % of measurements) to weakly polluted (∼ 20 % of measurements) air directly affected by regional anthropogenic sources adjacent to the railway. Only 2 % of measurements were identified as characteristic of highly polluted urban atmosphere. Maximum values of benzene and toluene during the campaign reached 36.5 and 45.6 ppb, respectively, which is significantly less than their short-term exposure limits (94 and 159 ppb for benzene and toluene, respectively). About 90 % of benzene and 65 % of toluene content is attributed to motor vehicle transport and 10 and 20 %, respectively, provided by the other local-and regional-scale sources. The highest average concentrations of benzene and toluene are measured in the industrial regions of the European Russia (up to 0.3 and 0.4 ppb for benzene and toluene, respectively) and south Siberia (up to 0.2 and 0.4 ppb for benzene and toluene, respectively). Total contribution of benzene and toluene to photochemical ozone production along the Trans-Siberian Railway is about 16 % compared to the most abundant organic VOC -isoprene. This contribution, however, is found to be substantially higher (up to 60-70 %) in urbanized areas along the railway, suggesting an important role of anthropogenic pollutant sources in regional ozone photochemistry and air quality.

Isoprene and monoterpenes over Russia and their impacts in tropospheric ozone formation

“…VOC concentrations have been measured routinely since 2008. The TROICA carriage-laboratory is equipped in accordance with the measurement requirements of the Global Atmospheric Watch (WMO), and is located just after the electric locomotive to minimize various effects of near-surface air perturbations due to moving train (Skorokhod et al 2017). The possible impact of oncoming trains as well as human activities in the train (all conveniences were placed at the end part of the train) on the measurements is expected to be generally non-significant as demonstrated previously in Crutzen et al (1996), Elansky et al (2000) and Panin et al (2001).…”

“…The possible impact of oncoming trains as well as human activities in the train (all conveniences were placed at the end part of the train) on the measurements is expected to be generally non-significant as demonstrated previously in Crutzen et al (1996), Elansky et al (2000) and Panin et al (2001). This paper is a continuation one from Skorokhod et al (2017), where benzene and toluene were investigated. Thus, it describes the data from the same experimental period and setup.…”

“…Generally, straightforward quantification of the effects of atmospheric dilution and absolute strength of the associated nearby emission sources is inhibited in data analyses. Yet, the passage of each location twice (in the forward and return paths of the TROICA campaign) allows for some qualitative assessment of the impact of weather conditions, since the time between the two subsequent measurements is of the order of one week, which is comparable to the characteristic time of the boundary layer ventilation in mid-latitudes (Skorokhod et al 2017).…”

“…The minimum NO and NO 2 concentrations detectable with these instruments are equal to 0.05 ppb, which makes it possible to measure the so-called background con- hours along the each trajectory centrations not influenced by the pollution sources. NO x concentration is the sum of NO and NO 2 concentrations (Skorokhod et al 2017).…”

“…Ozone concentration was measured with Dasibi 1008RS and 1008AH gas analyzers. These instruments are based on the photometric method (Skorokhod et al 2017). They allow measuring the ozone concentration in the range from 1 to 1000 ppb with a total error of ±1 ppbv.…”