Time series analysis of a 22-year record of Be, Pb and gross alpha activities in the Canary Islands (Spain) using Principal Component and Multifractal Detrended Fluctuation Analyses.

The long-term variability of a 22-year dataset of Be, Pb and gross alpha concentrations in surface aerosols collected in the Canary Islands has been analysed in this study. These "time series" were collected on a weekly basis. Various analytical techniques, including Principal Component Analysis (PCA), K-means clustering, correlation analyses, and back-trajectory were used to determine the variability of the data and assess the statistical importance of the source of the air masses reaching the study area. Monthly and annual variations for the time series were also studied. As expected, Be, Pb time series showed common variability, while gross alpha concentrations were strongly correlated with average PM10 concentration in air. The fractal properties of the time series were studied to gain a deeper understanding of the underlying structure and dynamics of the data. Multifractal Detrended Fluctuation Analysis (MF-DFA) and Multifractal Detrended Cross-Correlation Analysis (MF-DCCA) techniques were also used to detect and analyse the multifractal characteristics of the Be, Pb, and gross alpha time series. Multifractality was observed, with values of 0.28, 0.67, and 0.61 for Be, Pb, and gross alpha, respectively. Long-range correlation was found to be the source of the observed multifractality in the three parameters. Multifractal detrended cross-correlation analysis supports the correlation between Be - Alpha, Pb - Alpha, and Be - Pb pairs. The results from this study will help model the transport and destiny of natural radionuclides in the atmosphere at this site. The evolution and interactions between Be, Pb, and gross alpha, reported herein occurred not just locally but also across extensive temporal domains, leading to the emergence of multifractal behaviour in their concentrations. These long-range behaviours/correlations might result from various factors such as atmospheric circulation patterns, global transport mechanisms, or large-scale environmental processes.