Spatial and temporal variability of ground-level ozone in Castilla-León (Spain).

Ozone is a secondary air pollutant that has received extensive attention in the literature, mainly because of the adverse effects that exposure to it can cause, particularly in vegetation during the growing season. Because meteorological conditions strongly influence the efficiency of photochemical processes leading to ozone formation and destruction, ground-level ozone air pollution is currently being considered as a regional-scale phenomenon rather than a local one. This role of O3 as a regional-scale pollutant often implies the handling of large data sets in order to obtain information about its spatial and temporal variability patterns over a given broad region. Rotated principal component analysis (RPCA) is known to be one of the most powerful mathematical tools that can be used to achieve this aim. RPCA was applied in this paper to the summer and winter hourly time series of ground-level O3, concentrations recorded during 2 consecutive years (1996-1997) at 26 urban and suburban sites in Castilla-León (Spain). This procedure permitted the identification of different subregions where O3 concentrations show different spatio-temporal variability patterns. These variability patterns are mainly associated with the interaction of regional-level meteorological and anthropogenic factors. Some differences between winter and summer patterns were also found.