1Al Farabi Kazakh National University, Faculty of Chemistry and Chemical Technology, Center 5 of Physical-Chemical Methods of Research and Analysis, Almaty, Kazakhstan 6 2Nazarbayev University, School of Engineering and Digital Sciences, Department of Mechanical 7 and Aerospace Engineering, Nur-Sultan, Kazakhstan 8 3Airkaz.org, Almaty, Kazakhstan 9 4National Hydrometeorological Service of Kazakhstan, Nur-Sultan, Kazakhstan 10 5Department of Civil and Environmental Engineering, Nazarbayev University, Nur-Sultan, 11 Kazakhstan 12 6The Environment & Resource Efficiency Cluster, Nazarbayev University, Nur-Sultan, 13 Kazakhstan 14 Abstract 15

Number of cities worlwide experienced air quality improvements during COVID-19 lockdowns; however, such changes may have been different in places with major contributions from nontraffic related sources. In Almaty, a city-scale quarantine came into force on March 19, 2020, which was a week after the first COVID-19 case was registered in Kazakhstan. This study aims to analyze the effect of the lockdown from March 19 to April 14, 2020 (27 days), on the concentrations of air pollutants in Almaty. Daily concentrations of PM2.5, NO2, SO2, CO, O-3, and BTEX were compared between the periods before and during the lockdown. During the lockdown, the PM2.5 concentration was reduced by 21% with spatial variations of 6-34% compared to the average on the same days in 2018-2019, and still, it exceeded WHO daily limit values for 18 days. There were also substantial reductions in CO and NO2 concentrations by 49% and 35%, respectively, but an increase in O-3 levels by 15% compared to the prior 17 days before the lockdown. The concentrations of benzene and toluene were 2-3 times higher than those during in the same seasons of 2015-2019. The temporal reductions may not be directly attributed to the lockdown due to favorable meteorological variations during the period, but the spatial effects of the quarantine on the pollution levels are evidenced. The results demonstrate the impact of traffic on the complex nature of air pollution in Almaty, which is substantially contributed by various nontraffic related sources, mainly coal-fired combined heat and power plants and household heating systems, as well as possible small irregular sources such as garbage burning and bathhouses. (C) 2020 Elsevier B.V. All rights reserved.

In this study, spatial and temporal patterns of PM10, PM2.5, NO2, SO2, and CO in Almaty, the largest city of Kazakhstan, in the period between 2013 and 2018 are explored. Severe degradation of air quality was observed from the data that were used in this study. Annual averages of PM2.5, PM10, and NO2 concentrations exceeded the WHO annual limits by 5.3, 3.9, and 3.2 times, respectively. The maximum levels were observed in the winter, while the minimum levels in the summer. Winter-to-summer difference was more noticeable for PM2.5 than for other pollutants. The winter pollution peaks demonstrate the high contribution of large- and small-scale coal combustion for heating, which could be exacerbated with lower winds and possible more frequent thermal inversions. There was a negative correlation between elevation and levels of SO2, PM2.5, and PM10, while no correlation was observed for NO2 and CO, indicating that the former group could be mainly contributed by point sources located predominantly at lower elevations (e.g., power plants) and the latter group mainly originated from nonpoint sources distributed evenly across the city (e.g., transport). Urgent measures are needed to reduce emissions from the coal-fired power plant and from the domestic heating stoves.