Analysis of local and regional contributions of oxidant (OX = O3 + NO2) levels based on monitoring data, a review

Air pollution is one of the most critical environmental challenges and threats to humans. Ozone and nitrogen dioxide (their sum is defined as oxidant, OX) are among the criteria air pollutants and have serious health effects. Oxidant is affected by emission sources in local and regional domains. In this work, a systematic and critical review is conducted on the existing studies of the local and regional oxidant contributions. The systematic review focuses on the publication year, journal rank, study location, and keyphrase analysis. The critical review examines the analyzed parameters, and temporal variations and the data analysis of local and regional contributions of oxidant. The systematic review showed that the studies were conducted in 13 different countries and were published in 19 scientific journals. The critical review indicated that O₃, NO, NO₂, NO_x, and OX were used in all the studies. Furthermore, meteorological parameters of temperature and wind speed were mostly employed in the literature. Due to the substantial effects of emission and meteorological parameters on OX, different time scales were defined so that these effects could be evaluated separately. Our findings revealed that the highest OX’s local and regional contributions belong to daily (24-h average) and daylight time scales, respectively. The statistical analysis of the present study shows that the regional contribution values have less variations than the local contribution ones. This is due to the fact that the regional contribution values are influenced by a larger spatial domain and are less dependent on emission sources of each location.