Variation in seasonal precipitation chemistry with altitude in the northern Pennines, UK

Bulk precipitation was collected and analysed for major cations and anions over a 3-year period along an altitudinal gradient between 171 and 845 m in the northern Pennines in the UK. There was a gradient in volume weighted c oncentrations of inorganic N and S in precipitation, confirming the need fo r orographic corrections to deposition estimates. The ratios of the ion con centrations collected at 845 m to those at 171 m for H+, NH4+, NO3- and SO4 2- were 2.3, 1.7, 1.9 and 1.2, respectively, with an increase in mean annua l rainfall of 1.5. Marked seasonal patterns emerged for concentrations of N a+, Mg2+, Cl- and marine SO42- in bulk precipitation, which were largely co nsistent between years, and showed maxima in spring and minima in summer. N o such patterns were observed for inorganic N species, Ca2+, K+ or acidity. Wet deposition of N and S was found to be consistent between years, yet lo wer than previous estimates for the summit of Great Dun Fell. Rainfall comp osition at the lowest elevation site was found to be strongly affected by l ocal sources, equivalent to the changes due to altitudinal enhancement. (C) 1999 Elsevier Science Ltd. All rights reserved.