Quantifying fine-scale variability in pollutant deposition in complex terrain using 210Pb inventories in soil

The accumulation of Pb-210 in organic material within the surface (0 to 20 cm depth) horizons of soil is used to quantify local variability in the atmospheric inputs through wet deposition, cloud droplet deposition and dry deposition of aerosols. The method has been applied to quantify the long-term (similar to 50 yr) average enhancement in deposition as a consequence of orographic effects on a 800 m mountain in southwest Scotland. The Pb-210 inventory increases by a factor of 2.5 up the hillslope and is comparable to the modeled increase in wet deposition of major ions, and larger than the increase in rainfall with altitude by a factor of two. A second study sire examined the increase in deposition beneath a Norway spruce canopy relative to open grassland at an elevation of 450 m in the Scottish Borders. The inventory of Pb-210 under the forest canopy exceeded that in the grassland by approximately 35 %, in good agreement with deposition estimates obtained from a continuous record of cloud frequency and meteorological variables.