Fate and speciation of NOx in an arid climatic region: factors assessment

NO and NO₂ continuously recycle in the lower atmosphere through a complex series of reactions involving NO, VOCs, NO₂, and O₃. Therefore, the NO₂/NO_x ratio can be utilized in dispersion models as an important substitute to understand the fate of NO and NO₂ in the atmosphere. In this work, random forest regression was used to analyze the significance of meteorological parameters that affect the prediction of the NO₂/NO_x in Kuwait’s three distinct regions—rural, urban, and industrial for the years 2004 to 2014, where different sources of pollution are present in each of these areas. The NO₂/NO_x ratio did not change much over time for all the studied locations. The measured mean NO₂ concentration in the urban regions is two times higher than that in the industrial area, implicating vehicular sources as the major contributor to air pollution compared to stationary sources. The coefficient of determination for NO₂/NO_x for the four monitoring stations ranged between 0.62 and 0.81. Results indicate that although extreme temperature and intense solar radiation conditions are prominent in each of these areas, wind speed is the relatively important feature that significantly affects the NO₂/NO_x ratio in urban areas.