Wavelet Based Semblance Analysis of Anthropogenic Aerosol Control on Air Quality During the COVID-19 Pandemic Period

Investigations on air pollutants and air quality were undertaken during the COVID-19 pandemic and pre-pandemic period in Alandur (13.03° N, 80.21° E), Tamil Nadu, India. This comparative study of atmospheric pollutants focuses on the variation between the COVID-19 pandemic period (lockdowns imposed to control the spread of novel coronavirus infection) and the pre-pandemic period with ground-based atmospheric pollution monitoring instruments. The observations were obtained from the Centre for Pollution Control Board (CPCB). The observations from 2018 to 2021 period are used for this investigation. First, the normalizing of the time series revealed the general trends of the atmospheric pollutants present in the specified timeline. Later, spectral estimations were done to unveil the hidden peaks and periodicities during the pre-pandemic period and the COVID-19 period. The power spectral analysis is carried out to comprehend the dispersion and variability of atmospheric pollutants by examining and comparing the power spectrum of a specific station using Blackman–Tukey window analysis, aiming to elucidate the impact of the COVID-19 pandemic on atmospheric pollution dynamics. The results indicate a particular trend at peak business hours (ISTs), with notable periodicities evident throughout each timeline. A significant decrease (~ 42.5%) in the intensities of air pollutants was observed during the COVID-19 period, with no change in O₃ concentrations being observed in the power spectral density windows at either of the two timelines. Thus, the power spectrum analysis provided access to top-to-bottom analysis of anthropogenic pollutants, quantifying the peaks and periodicities present in the pollutants for in-depth analysis and control in the future. Future studies will envisage pollution control technicalities and strategies.