Characterization of chaos in air pollutants: A Volterra–Wiener–Korenberg series and numerical titration approach

The present study attempts to provide an insight into the chaotic nature of air pollutants by applying the recent developments in the field of nonlinear dynamics. The Volterra–Wiener–Korenberg (VWK) series approach by Barahona and Poon [1996. Detection of nonlinear dynamics in short, noisy time series. Nature 381, 215–217] has been used to investigate the nonlinearity of O3, NO, NO2 and CO time series at two urban stations, namely—Hohenpeissenberg and Jungfraujoch. Nonlinearity has been detected in NO2 and CO time series at both the stations. The numerical titration technique [Poon, C., Barahona, M., 2001. Titration of chaos with added noise. Proceedings of the National Academy of Sciences 98, 7107–7112] reveals that the dynamics of NO2 and CO are indeed governed by deterministic chaos. Cao's method [Cao, L., 1997. Practical method for determining the minimum embedding dimension of a scalar time series. Physica D 110, 43–50] to determine the minimum embedding dimension further reveals that probably the dynamics of both NO2 and CO time series are manifestations of high-dimensional chaos. It is interesting to note that similar chaotic characteristic of NO2 and CO time series have been observed at both the sites indicating a possible universality in their chaotic nature in the ambient urban environment.