Seasonal persistence of the nitrogen oxides production in Mexico City

This study investigates the seasonal influence on the nitrogen oxide NO_x 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 NO_x concentration 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 \(\overline{H}=0.72\) $\overline{H}=0.72$ , indicating relatively smaller fluctuations compared to other seasons, but with the potential for NO_x concentrations to surpass those in other periods. In contrast, for spring, summer, and winter, the fluctuations are characterized by exponents of \(\overline{H}=0.59\) $\overline{H}=0.59$ , \(\overline{H}=0.61\) $\overline{H}=0.61$ , and \(\overline{H}=0.62\) $\overline{H}=0.62$ , respectively, demonstrating greater fluctuations with lower NO_x concentrations compared to autumn. These results are consistent with various studies conducted worldwide. Additionally, a negative correlation between NO_x and ozone (O₃) has been established during the winter season, as NO_x and O₃ fluctuations display persistent and anti-persistent behavior, respectively.