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

from municipal sewage, storm runoff, and atmospheric deposition. Similar experiments
conducted throughout the United States have also suggested an increase in Pb concentrations in
the upper sediment layer concomitant with increases in anthropogenic inputs (Bloom and
Crecelius, 1987; Case et al., 1989; Ritson et al., 1999; Chillrud et al., 2003).
Sediment Pb concentration profiles and isotope analysis have also been used to identify
specific anthropogenic sources. For example, Flegal et al. (1987) used isotopic ratios to trace
sources of Pb in mussels from Monterey Bay, CA to a specific slag deposit. Several
investigators have examined isotopic tracers to determine potential regional sources of Pb in
eastern North America and the Great Lakes (Flegal et al., 1989b; Graney et al., 1995; Blais,
1996). Water samples from Lake Erie and Lake Ontario were collected and analyzed. Lead
isotope ratios ( 206 Pb: 207 Pb) from the lakes were compared to known ratios for Pb aerosols derived
from industrial sources in Canada and the United States and found to correlate positively. This
indicated that a majority of Pb in the lakes was derived from those industrial sources (Flegal
et al., 1989b). Similarly, Gallon et al. (2006) used 206 Pb: 207 Pb ratios in sediment cores collected
from a 300 km transect in Canadian Shield headwater lakes to differentiate Pb contributions from
smelter emissions relative to Pb contributions from other anthropogenic inputs. The authors
were able to estimate the amounts of smelter-derived Pb in sediment collected along the 300 km
transect. Lead isotopes in sediment cores from Quebec and Ontario, Canada were also used to
distinguish between the amount of Pb deposited from local Canadian sources (28.4 to 61.7%)
and U.S. sources (38.3 to 71.6%) (Blais, 1996). Examination of Pb isotopes in sediment and
suspended sediment in the St. Lawrence River were used to identify potential anthropogenic Pb
sources from Canada (Gobeil et al., 1995, 2005). Graney et al. (1995) used Pb isotope
measurements to describe the differing historic sources of Pb in Lake Erie, Ontario and in
Michigan. Temporal changes in Pb isotopic ratios were found to correspond to sources such as
regional deforestation from 1860 through1890, coal combustion and or smelting through 1930,
and the influence of leaded gasoline consumption from 1930 to 1980.
The historic record of atmospheric Pb pollution has been studied to understand the natural
background Pb concentration and the effects of Pb accumulation on ecosystems (Bindler et al.,
1999; Renberg et al., 2000, 2002; Brännvall et al., 2001a,b). The most extensive work in this
area has been conducted at pristine locations in Sweden (Bindler et al., 1999). In this study, soil,
sediment, and tree rings were sampled for Pb concentrations and isotopic analyses were
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