Air pollution levels and PM2.5 concentrations in Khovd and Ulaanbaatar cities of Mongolia

Ulaanbaatar, the capital of Mongolia, is one of the world's leading cities in terms of air pollution. However, due to a lack of detailed research on air pollution in other urban settlements of Mongolia, they might be more polluted than Ulaanbaatar city. Thus, Khovd city, known as an urbanized center in the Western region of Mongolia, has been chosen as one of our study sites besides Ulaanbaatar. The purpose of the study was to compare the PM2.5 concentrations of these two cities. We focused on the PM2.5 concentration levels of Ulaanbaatar city from 2017 to 2020 and the PM2.5 of Khovd city in 2020. The study results show that the PM2.5 concentrations of Ulaanbaatar have been declining since 2018. However, the PM2.5 of Ulaanbaatar from January through March 2020 was 129 +/- 57, 71.1 +/- 32.9 and 33.1 +/- 12.4 mu g/m(3), respectively. Meanwhile, the PM (2.5) concentrations of Khovd from January to March 2020 were 175.6 +/- 59 mu g/m(3), 101.2 +/- 47.3 mu g/m(3) and 20.8 +/- 18.9 mu g/m(3) respectively. PM2.5 of Khovd city has a lower concentration than Ulaanbaatar in the semi-heating and non-heating periods while Khovd has a higher concentration and longer duration of pollution than Ulaanbaatar in the heating season. The firing hours of ger areas coincide with the increase of PM2.5 concentrations in Khovd and further research is necessary to identify other contributing factors. Our study results also suggest that there is an urgent need to implement a national program to reduce air pollution in Khovd city.