Phenomenology and geographical gradients of atmospheric deposition in southwestern Europe: Results from a multi-site monitoring network

Abstract

This article presents the results of atmospheric deposition from a 15-sites network which cover remote, agricultural, urban and industrial areas in the Iberian Peninsula and the Balearic Islands, with the aim of exploring geographical, climatic and natural vs anthropogenic gradients. Annual average fluxes of global deposition, discriminating insoluble (3,5–20,7 g m year) and soluble-inorganic (7,1–45,5 g m year) aerosols are discussed, seasonal patterns are regarded, and an attempt to estimate the impact of the main sources is presented. The wide range of atmospheric deposition fluxes (DF) regarding soluble (DF) and insoluble (DF) has been investigated taking into consideration the contribution from nearby to long-distance sources, such as African dust, or regional-to-nearby ones, which include agricultural dust in the Ebro Valley, industrial emissions at different parts, urban dust at all cities, or saline dust resuspension from a dissicated lake bed. DF is made up of marine aerosols, prevailing in coastal areas, with few exceptions in the Ebro Valley; nitrogen-species, homogeneously distributed across the network, with few exceptions due to agricultural sources; mineral dust, enhanced in the Ebro Valley owing to regional and agricultural emissions; and phospathe, displaying comparable values to other studies in general, but three hotspots at regional background environments have been identified. DF particles followed the aridity pattern, especially where anthropogenic emissions take place. Our estimates indicate that the regional dust to DF in the Ebro Valley represented 23–30%, overpassing 50% at intensive agricultural areas. Similarly, urban-metropolitan contributions accounted for 37–45% at the four cities, and 55% at the industrial one. African dust deposition was enhanced in the Central Pyrenees (75–80%) as a result of the magnification of atmospheric washout processes, and in south-eastern Iberia (69%) owing to the higher frequency of dust outbreaks.