Seasonal and Spatial Variation of Volatile Organic Compounds in Ambient Air of Almaty City, Kazakhstan  
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chronic exposure [6]. It was observed that outdoor workers in Almaty are at high risk of respiratory diseases in the cold season [7].  
The number of studies based on the assessment of air quality in Almaty is very limited. The majority of existing studies use data of inorganic air pollutants from information bulletin published by the National Hydrometeorological Service of Kazakhstan \"Kazakhstan \"Kazhydrot\", which is the only legally responsible organization in Kazakhstan continuously monitoring the air pollution. Currently, the monitoring program of \"Kazhydrot\" determines only two volatile organic compounds (VOCs), formaldehyde and phenol.  
VOCs, a diverse group with a biogenic (BVOCs) and anthropogenic origin, include hazardous to health air pollutants [8] and contribute to the formation of ozone [9; 10], the main component of photochemical smog [11]. Ozone air pollution negatively affects agriculture [12] and causes respiratory and cardiovascular mortality [13]. Although most BVOCs are not hazardous, they should be controlled with anthropogenic VOCs and NOx [14]. Exposure to individual VOCs can lead to the possible development of respiratory diseases such as asthma [15], chronic obstructive pulmonary disease [16], etc. A group of VOCs known as BTEX (benzene, toluene, ethylbenzene, and xylenes) deserves special emphasis [17] due to high toxicity and well-known carcinogenicity (benzene--Group 1 by IARC) [18].  
Previous studies were aimed at the effect of inorganic air pollutants on human health [2; 6; 7], evaluation of air pollution data and environmental situation [19], spatiotemporal variations and contributing factors of inorganic air pollutants [20], characteristics [21], and traffic component of air pollution in Almaty [22], quantification of VOCs, including BTEX in Almaty under the application of developed simple and cost-effective methods [23; 24], and accessing of air quality during COVID-19 lockdown [25].  
Data on the VOCs concentrations are not available for all cities in Kazakhstan, except Almaty, where only several short-term studies were carried out [22; 23; 24; 25; 26]. Based on partial order methodology [26], environmental pollution studies ranked Almaty the 8 th most polluted city by BTEX in 20 major cities worldwide. According to the previous study [23], average concentrations of BTEX in ambient air of Almaty on 31 March-4 April 2015 were 53, 57, 11, and 14 \(\mu\)g m\({}^{-3}\), respectively. The maximum benzene concentration was 237 \(\mu\)g m\({}^{-3}\), comparable with highly polluted cities, such as New Delhi, Cairo, and Rome [23]. On 30 March-4 April 2019, the mean concentrations of benzene homologues, alkanes, polycyclic aromatic compounds, and chlorinated VOCs were in the range of 0.1-81, 5-123, 1.3-2.6, and 0.1-53 \(\mu\)g m\({}^{-3}\), respectively [24].  
Air pollution in Almaty has a complex nature [25]. It may be caused by various factors, including the geographical location of the city, meteorological conditions, several manufacturing enterprises, a vast number of vehicles, and coal combustion at power plants. The appropriate identification of the sources of emissions in Almaty remains a challenge due to the lack of capacity, outdated methodologies, scarcity of data, and nontransparent energy statistics. In addition, previous short-term studies are insufficient for a detailed description of VOCs concentrations and their sources in the air of Almaty. The assessment of spatial and seasonal variations of VOCs and their possible sources are needed for developing effective measures for air quality improvement by reducing harmful emissions.  
Therefore, the goals of this study were to evaluate (1) seasonal variation of VOCs in the air in 2020, (2) spatial distribution of total VOCs (TVOCs) by season, and (3) to identify the emission sources of BTEX.