Evaluation of origin and distribution of wet deposition recorded in the Spanish Basque country

Abstract

Within the framework of the EPOCA programme (Estudios en el Pirineo Occidental de la Contaminación Acida), wet deposition of inorganic pollutants was measured at five rural sites in the Spanish Basque Country between Dec 85 and Apr 91.

Na⁺, Ca²⁺, SO₄ ^2‐ _exc, and NH₄ ⁺ ions were the main species found in the rainwater samples. The average pH value ranged between 4.9 and 5.6 depending on the site.

Relationship between the ionic concentrations and the back‐trajectories showed that trajectories coming from Europe resulted in the highest NO₃ ^‐, SO₄ ^2‐ _exc and H⁺ concentrations. NO₃ ^‐ and H⁺ incursion in the study area by a long‐range‐transport phenomenon was estimated in 20 μeq 1^‐1 for each ion.

By means of both the one‐way analysis of variance and the range tests for the wet deposition, two of the sites resulted to be able to represent both qualitatively and quantitatively the wet deposition collected at all sites.

Key words:

• Acid precipitation
• air mass trajectory
• acid rain
• chemical composition
• ionic concentration