Vertical distribution of ambient air pollutants (PM, PM, NO, and NO); A systematic review.

Background: Numerous investigations have explored variations in vertical air pollutant concentrations, yielding diverse findings. So, we have conducted this systematic review to gain a more comprehensive understanding of the vertical distribution of air pollutant concentrations (PM, PM, NO, and NO) and the influencing factors.

Methods: Relevant studies were identified by searching the three central electronic databases, PubMed, Web of Science, and Scopus, from the beginning of 2000 to the end of 2023. This study included original articles published in English that examine the pollutant concentration variations below 500 m.

Finding: Of 3614 articles, 57 studies met our criteria. Our findings showed a decline in PM and NO concentrations as altitude increased, while NO concentrations exhibited an increase. Conversely, no statistically significant relationship was identified between altitude and PM concentrations. The regression analysis yielded coefficients for the relationship between concentration and altitude (0-500 m) as follows: PM (-0.11), PM/PM (0.0008), NO (-0.11), and NO (0.13). Conducting additional research on this topic and investigating the impact of meteorological parameters on pollutant concentrations at different altitudes enhances our understanding of the vertical distribution of pollutant concentrations.