Wet deposition of 210Pb aerosols over two areas of contrasting topography

Deposition fluxes of Pb-210 on low and moderately high-elevation sites of Edinburgh (Scotland) and mid-Wales, respectively, have been measured. The excess Pb-210 fluxes in moorland Edinburgh soils did not vary significantly and ranged from 71 to 92 Bq m(-2) y(-1) with a mean value of 78 +/- 9 Bq m(-2) y(-1), for all the measured sites where both altitude and the mean annual rainfall are similar. On the other hand, the excess Pb-210 measured in moorland soils of mid-Wales sites increased by a factor of 2.4 at or near the summit (741 m asl) relative to the coast (similar to 15 m asl), whereas rainfall increased by a factor of 1.8 over the same height range. On average, the summit to valley ratio of Pb-210 concentration in rainfall was a factor of 1.3 due to scavenging of the feeder clouds by the seeder rain. These results are consistent with results for both modelled and field studies on the wet deposition of pollutants in complex terrain reported by several researchers. The long-term Pb-210 wet deposition field data will provide an important input parameter for the modelling of wet deposition of aerosols throughout the uplands of the UK and elsewhere where the seeder-feeder process is of common occurrence.