ИСТИНА

Cities are prone to air pollution caused by emissions associated with population activities such as road transport, industry, heating, and residential sector. The concentration and chemical composition of particulate matter (PM) is of particular importance as the parameter of air quality measurements. Concerning impact on urban air quality and hazardous health effects accompanied by the capacity for long-range atmospheric transport, polyromantic hydrocarbons (PAHs) are numbered among priority pollutants in the national and international regulatory activities. PM10-bound PAHs characterization were carried out in urban background of Moscow megacity, the largest as well as the northernmost megacity in Europe. Sampling was performed at the newly developed Aerosol complex MSU (PEEX Arctic-Boreal Newsletter). Composition of 16 PAHs which are numbered in the EPA list of ‘Priority Pollutants’, are considered for three periods: spring (from mid-April to the end of May2018, when a positive average daily temperature is set in Moscow), autumn (from the end of September to the end of November, 2019), and winter (from early December to mid-January 2019, when the average daily temperature reliably drops below zero). The sum of 16 PAHs was ranged over the observation period from 0.4 to 10 ng/m3, with increase of the median concentration from spring and autumn to winter due to emissions from thermal power plants in autumn-winter as well as the transition of PAH from PM to the gas phase with an increase of the temperature in spring. Variation of sum of low molecular weight (LMW) Σ 3PAH and Σ 4 PAH with 3 and 4 rings, respectively) and high molecular weight (HMW) PAHs (Σ 5-6 PAH with 5-6 rings) during autumn 2019 shows the higher impact of HMW except in the end of November (Fig.1). Strong pollution episode at that time is identified by increase of diagnostic relationships such as pyrene to benzo[ghi]perylene (PYR/BghiP), benz[a]anthracene to benzo[ghi]perylen (BaA/ BghiP), pyrene to benz[a]anthracene (PYR/ BaA) (Fig.1), in comparison with non-event period (background). Additional increasing of phenanthrene indicate the industrial origin of emissions with prominent petrogenic one of oil refinery impact. Diurnal (day-to-night) sampling was carried out in spring 2021. The sum of 16 PAHs was ranged over the observation period from 0.8 to 10.5 ng/m3, with prominent difference between median nocturnal of 3,3 ng/m3 and daily 1,5 ng/m3. Average PAH toxic equivalent (TEQs) were higher in winter and autumn than those in summer and spring. Increased concentrations for BaA, BaP, BgP, Cry, and BbF due to high wind speeds indicate a distant source and a long-range transfer of pollutants. While the presence of maxima of concentrations at medium or low wind speeds can serve as an indication of the proximity of sources, as well as the weakening of atmospheric circulation, which leads to accumulation of pollutants (ANT, PYR, BbF, DiBaA, BLU, PHE, BkF) in the measurement area. Based on the statistical processing, high (> 0.75) positive correlations for all individual PAHs were obtained in autumn and winter. This indicates the high stability and the absence of significant transformation of PAH due to physical and photochemical reactions. At higher temperature in spring compared to autumn-winter, low correlations for phenanthrene was observed due to evaporation of the lowest molecular weight PAHs could proceed more intensively on the aerosol surface.