The chemical composition of bulk precipitation across the mountains of Snowdonia, U.K.

Abstract

Bulk precipitation chemistry was monitored monthly for 18 months at 10 mountain sites and one coastal site in north Wales, U.K. The sites ranged in altitude from sea level to 891 m above sea level in an area where annual rainfall ranges from 1300 to 4000 mm. The precipitation was acidic (weighted mean H + of 23 μeq l −1, pH 4.64), although ionic composition was dominated by sea-salts. However, ≅70% of the SO 4 was not of sea-salt origin. Concentrations of excess SO 4 and NO 3 were small (42 and 11 μeq l −1, respectively) relative to polluted areas of Europe, although deposition rates were large (1.62 g S m −2 year −1 and 0.54 g N m −2 year −1 as NO 3) due to the high annual rainfall. There was considerable spatial variability in the solute concentration and deposition data which resulted from the effects of the complex topography of the area. Simple linear relationships between solute deposition and rainfall quantity were not generally observed except for sea-salt deposition on seaward north-west facing slopes.