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Deposition fluxes of 210 Pb on low and moderately high-elevation sites of Edinburgh (Scotland) and mid-Wales, respectively, have been measured. The excess 210 Pb 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 210 Pb 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 (∼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 210 Pb 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 210 Pb 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.

Activities of 210 Pb carrier aerosols in an age-graded Sitka spruce conifer, three deciduous (oak, lime and sycamore) foliage and in rain and throughfall samples have been measured during the period of 2001-2002. The 210 Pb concentrations in the agegraded Sitka leaf needles have shown to accumulate until a steady state between accretion and loss of particulate matter is maintained with time. Similarly, the concentrations of 210 Pb on deciduous tree leaves increased with time until the leaves began to senesce. The 210 Pb inventory in bulk precipitation was significantly (r 2 =0.99; P<0.001) large compared with that in throughfall samples, as indicated by a ratio of 1 to 0.1 of 210 Pb deposition in bulk precipitation to throughfall. This suggests that 210 Pb is retained in the Sitka spruce foliage during deposition until transfer to the ground mainly through litterfall. These findings suggest that the presence of woodland is responsible for enhanced 210 Pb deposition fluxes beneath wooded areas relative to open grassland soils.

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