Self-Organized Critical Behavior of Acid Deposition

By employing empirical probability distribution function and power spectrum analysis together with detrended fluctuation analysis (DFA), we show that acid deposition events are analogous to avalanches of granular piles displaying self-organized criticality (SOC). Under a wide variety of circumstances, frequency distributions of hydrogen ion concentration (HIC) and weekly hydrogen deposition (WHD) of precipitation are consistent with double power-law in two different regimes separated by a crossover HIC or a crossover WHD. WHD series can be depicted as 1/fβ noise (β = 0.3–1.3) with long-range correlations (LRC). And we argue that the critical state of atmospheric acid deposition refers to the normal acidity of water in atmosphere, or the environmental capacity. Therefore, acid deposition evolution is consistent with the three criteria of complex SOC systems. We thus suggest that SOC may be a possible mechanism underlying acid deposition evolution.