Seasonal persistence of the nitrogen oxides production in Mexico City

This study investigates the seasonal influence on the nitrogen oxide NOx pollution records at four monitoring sites in Mexico City from 2010 to 2018. The analysis employs the second-order structure function to examine the trends in NOx concentra-tion fluctuations. The findings reveal that the fluctuations follow a power law pattern characterized by Hurst exponents, predominantly in the statistical persistence regime, with a scaling range spanning three orders of magnitude. Specifically, the autumn period exhibits fluctuations with an exponent of H=0.72 , indicating relatively smaller fluctuations compared to other seasons, but with the potential for NOx concentrations to surpass those in other periods. In contrast, for spring, summer, and winter, the fluctuations are characterized by exponents ofH=0.59,H=0.61 , and H=0.62 , respectively, demonstrating greater fluctuations with lower NOx concentrations compared to autumn. These results are consistent with various studies conducted worldwide. Additionally, a negative correlation between NOx and ozone (O3) has been established during the winter season, as NOx and O3 fluctuations display persistent and anti-persistent behavior, respectively.