Weekly patterns and weekend effects of air pollution in the Moscow megacity

The weekly cycle and weekend effect in the O3, NO, NO2, CO, CH4, SO2, NMHC, and PM10 concentrations were investigated in the Moscow megacity using in-situ measurements from January 1, 2005 to December 31, 2014 at 49 stations of the Moscow Environment Monitoring network. Daily variations in the CO, NOx, NMHC, and PM10 concentrations depend mainly on motor transport emissions and the atmospheric boundary layer vertical stratification. The characteristic feature of Moscow is the time coincidence of rush hours and surface temperature inversion during the cold season, which results in pollutant accumulation in the atmospheric surface layer. It was found that the surface concentrations of the pollutants (except ozone and methane) decrease on weekends. Weekday (Tuesday–Friday)-Sunday differences in the daytime (08:00–22:00 LT) NO, NO2, CO, SO2, NMHC, and PM10 concentrations relative to those of weekday period averaged for all stations over 2005–2014 amounted to 23.9 ± 5.8, 16.7 ± 2.8, 13.6 ± 3.3, 7.6 ± 6.5, 6.3 ± 2.2, and 14.5 ± 5.1%, respectively. The ozone concentration increased on Sunday by 16.5 ± 4.8%. The methane concentration on weekends was the same as on weekdays. The weekend effects in all pollutant concentrations were weakened within the greenbelt around Moscow. In different sectors of Moscow the pollutant weekend effects except that in SO2 were approximately the same. The vertical structure of the NO, NO2, and CO weekend effects was analyzed based on data obtained from measurements at the TV tower 500 m in height. These weekend effects decreased nonlinearly with height. Estimates obtained for basic criteria of activity of photochemical processes determining the formation of the weekly cycle and weekend effect of ozone (NMHC/NOx ratio, fraction of radical loss via NOx chemistry, concentration of Ox) show that the VOC-limited chemistry is characteristic of Moscow. •Daily and weekly cycles in O3, CO, CH4, NO, NO2, SO2, NMHC, and PM10 were analyzed.•Measurements at 49 sites in 2005–2014 were used for species weekend effect studies.•Weekend effect in pollutants depends on PBL stratification, city sectors and height.•The VOC-limited chemistry of O3 formation is characteristic of Moscow atmosphere.