Atmospheric Transfer and Deposition Mechanisms of 210Pb Aerosols onto Forest Soils

Abstract

Activities of 210Pb 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 210Pb concentrations in the age-graded 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 210Pb on deciduous tree leaves increased with time until the leaves began to senesce. The 210Pb 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 210Pb deposition in bulk precipitation to throughfall. This suggests that 210Pb 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 210Pb deposition fluxes beneath wooded areas relative to open grassland soils.