Description of the seasonal pattern in ozone concentration time series by using the strange attractor multifractal formalism.

Ozone is a secondary pollutant that, at high concentrations in urban environment, affects human health. Thus, suitable knowledge of ozone dynamics is essential for avoiding undesirable effects on the population. Ten-minute ozone concentration time series recorded at Córdoba (southern Spain) in 2007, for January, April, July and October, have been analysed by using the strange attractor multifractal formalism with the aim of describing the seasonal pattern of this pollutant. The multifractal nature of ozone concentration was detected in a study of the mass exponent functions for autumn-winter and spring-summer seasons. Multifractal spectra showed a greater heterogeneity in the low values of the time series. The presence of rare values in ozone data sets was also investigated, showing that the multifractal approach provided considerable detailed information on the time series structure that completes the statistical descriptive analysis.

The impact of agricultural soil erosion on the global carbon cycle.

Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 petagram per year(-1) to a sink of the same magnitude. By using caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, we estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year(-1) resulting from erosion in the world's agricultural landscapes. Our analysis directly challenges the view that agricultural erosion represents an important source or sink for atmospheric CO2.