Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

(1981) noted that Pb losses from a spruce forest A-horizon soil in Sweden were influenced by
season; with highest Pb fluxes being observed during warm, wet months. He suggested that
DOC production and Pb movement were tightly linked.
Surface soils across the United States are enriched in Pb relative to levels expected from
solely natural geogenic inputs (Friedland et al., 1984; Herrick and Friedland, 1990; Francek,
1992; Erel and Patterson, 1994; Marsh and Siccama, 1997; Yanai et al., 2004; Murray et al.,
2004). While some of this contaminant Pb is attributed to paint, salvage yards, shooting ranges,
and the use of Pb arsenate as a pesticide in localized areas (Francek, 1997), Pb contamination of
surface soils is essentially ubiquitous because of atmospheric pollution associated with metal
smelting and production, the combustion of fossil fuels, and waste incineration (Newhook et al.,
2003; Polissar et al., 2001). Surface soils in Michigan, for example, typically range from 8 to
several hundred ppm Pb (Francek, 1992; Murray et al., 2004). Soils collected and analyzed
beneath 50 cm in Michigan, however, range only from 4 to 60 ppm Pb (Murray et al., 2004).
In remote surface soils from the Sierra Nevada Mountains, litter and upper soil horizons are 20 to
40 ppm Pb, and approximately 75% of this Pb has been attributed to atmospheric deposition
during the 20th century (Erel and Patterson, 1994). Repeated sampling of the forest floor
(O horizon) in the northeastern United States demonstrates that the organic layer has retained
much of the Pb load deposited on ecosytems during the 20th century. Total Pb deposition during
the 20th century has been estimated at 1 to 3 g Pb m Γ2 , depending on elevation and proximity to
urban areas (Miller and Friedland, 1994; Johnson et al., 1995a). Forest floors sampled during the
1980s and 1990s, and in early 2000 had between 0.7 and 2 g Pb m Γ2 (Friedland et al., 1992;
Miller and Friedland, 1994; Johnson et al., 1995a; Kaste et al., 2003; Yanai et al., 2004; Evans
et al., 2005). The pool of Pb in above- and below-ground biomass at the HBEF is on the order of
0.13 g Pb m Γ2 (Johnson et al., 1995a).
The amount of Pb that has leached into mineral soil appears to be on the order of 20 to
50% of the total anthropogenic Pb deposition. Kaste et al. (2003) and Miller and Friedland
(1994) demonstrated that Pb loss from the forest floor at Camel’s Hump Mountain in Vermont
depended on elevation. While the mineral soil in the deciduous forest had between 0.4 and 0.5 g
Pb m Γ2 (out of 1 to 2 g Pb m Γ2 in the total soil profile), at higher elevations the thicker coniferous
forest floor retained more than 90% of the total Pb deposition (Kaste et al., 2003). Johnson et al.
(1995a) determined that the forest floor at HBEF in the mid-1980s had about 0.75 g Pb m Γ2 .
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