Chemical characterization in coastal fog and rain at Mount Monduver fog-collection station, Mediterranean Iberian Peninsula

Abstract

An experimental site was selected for fog- and rain-water quality analyses. The selected location corresponds to Mount Monduver of 843 m elevation, being geographically centered in the Mediterranean Iberian Peninsula. Single fog- and rain-water samples were taken manually with a dedicated fog and rain collectors, to prevent any contamination with dry-deposition. Besides, a permanently exposed fog collector and a rain gauge were also used for the collection of water samples affected by dry deposition. Results indicated that all chemical analyses complied with Spanish drinking water regulations, except for the particular case of the dry-deposition contaminated water samples. A further statistical data analysis, together with five-day air mass backward trajectories, was performed. Two sample clusters could be differentiated which were also discriminated against by the two principal components obtained. Cluster-1 members comprised higher levels of conductivity and ion concentration, while cluster-2 members corresponded to lower levels of solutes. The second principal component related to pH levels showed the majority of samples centered at neutral values. The backward trajectory analysis indicated that the origin and route followed by the air masses leading to sample members in cluster-1 were over the Mediterranean Sea and mainly obtained in summer and autumn; while trajectories associated to sample members in cluster-2 had their origin primarily over the Atlantic Sea occurring only in winter and spring. The larger ion loads presented in fogs developed from Mediterranean air masses may be explained through the role of sea breezes on the confinement of pollutants into the atmosphere.