Temporal variations of ambient air pollutants and meteorological influences on their concentrations in Tehran during 2012–2017

Abstract

We investigated temporal variations of ambient air pollutants and the influences of meteorological parameters on their concentrations using a robust method; convergent cross mapping; in Tehran (2012-2017). Tehran citizens were consistently exposed to annual PM 2.5 , PM 10 and no 2 approximately 3.0-4.5, 3.5-4.5 and 1.5-2.5 times higher than the World Health Organization air quality guideline levels during the period. Except for O 3 , all air pollutants demonstrated the lowest and highest concentrations in summertime and wintertime, respectively. The highest O 3 concentrations were found on weekend (weekend effect), whereas other ambient air pollutants had statistically significant (P < 0.05) daily variations in which higher concentrations were observed on weekdays compared to weekend (holiday effect). Hourly O 3 concentration reached its peak at 3.00 p.m., though other air pollutants displayed two peaks; morning and late night. Approximately 45% to 65% of AQI values were in the subcategory of unhealthy for sensitive groups and PM 2.5 was the responsible air pollutant in Tehran. Amongst meteorological factors, temperature was the key influencing factor for PM 2.5 and PM 10 concentrations, while nebulosity and solar radiation exerted major influences on ambient SO 2 and o 3 concentrations. Additionally, there is a moderate coupling between wind speed and NO 2 and CO concentrations.

Changes in air pollution during COVID-19 lockdown in Spain: A multi-city study

“…However, many of the other cities had no significant differences in CO levels, although robust conclusions cannot be extracted. The reduced CO, which is also a precursor of O 3 like NO and NO 2 ( Yousefian et al., 2020 ) in Barcelona and Sevilla are in agreement with the higher O 3 level found there during the lockdown (see Figs. 3 , 4 and 7 ).…”

“…On the one hand, dry and sunny weather leads to thermal inversion, which prevents vertical pollutant dispersion, so that their concentration increases, and they generate significant smog episodes. On the other hand, higher wind speed can reduce air pollution ( Mao et al., 2020 ; Radzka, 2020 ; Yousefian et al., 2020 ). Nevertheless, it is important to highlight that very low wind speed can also be associated with reduced PM in the air due to higher deposition ( Xu et al., 2020 ).…”

A field indoor air measurement of SARS-CoV-2 in the patient rooms of the largest hospital in Iran

“…We conducted the present study on March 17, 2020 in hospital wards with confirmed COVID-19 at Imam Khomeini Hospital Complex in Tehran, Iran. Tehran, with about 9 million residents and the day time population of near 13 million people who commute into the city from other cities, is the capital and most populous city of Iran (Faridi et al, 2018;Yousefian et al, 2020). On March 31, 2020, Tehran province with the highest confirmed COVID-19 cases ranked the first place among all provinces in Iran.…”

A city-level analysis of air pollution, climate and COVID-19 early spread during the Spanish lockdown

“…Indeed, sunny weather also favors photochemical reactions(P. Xu et al, 2020) while dry conditions prolong aerosols and atmospheric loadings (Lemou et al, 2020). The increase of wind speed can also decrease PM2.5 levels (Radzka, 2020;Yousefian et al, 2020), while lower wind speeds can promote a reduction of particulate matter in the air because of a significant increase of deposition (Xu et al, 2020). The rise of atmospheric pressure seems to positively affect PM formation (Hoque et al, 2020).…”