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 concentrations of inorganic N and S in precipitation, confirming the need for orographic corrections to deposition estimates. The ratios of the ion concentrations collected at 845 m to those at 171 m for H+, NH4+, NO3− and SO42− were 2.3, 1.7, 1.9 and 1.2, respectively, with an increase in mean annual rainfall of 1.5. Marked seasonal patterns emerged for concentrations of Na+, Mg2+, Cl− and marine SO42− in bulk precipitation, which were largely consistent between years, and showed maxima in spring and minima in summer. No 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 lower than previous estimates for the summit of Great Dun Fell. Rainfall composition at the lowest elevation site was found to be strongly affected by local sources, equivalent to the changes due to altitudinal enhancement.