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

Figure AX7-1.2.1. Long-term (1982-1989) annual trends in lead concentrations (µg/L) in
Lewes, Delaware precipitation.
Source: Scudlark et al. (1994)
The role of dry deposition in the total deposition of Pb to terrestrial ecosystems is not
constrained well. Researchers have estimated that dry deposition accounts for anywhere
between 10 to >90% of total Pb deposition (Galloway et al., 1982; Wu et al., 1994; Sabin et al.,
2005). Migon et al. (1997) found total, wet, and dry Pb deposition to be 8.6, 1.6 and
7.0 µg/m2/d, respectively, over the Ligurian Sea, France. Dry deposition velocities were
estimated at approximately 0.2 cm/sec, similar to anthropogenic element deposition velocities
measured at remote lakes around Lake Michigan (Yi et al., 2001). Yi et al. (2001) found that dry
deposition velocities for elements were correlated with particle concentrations in the following
order: coarse > total particle > fine particle. Refer to Table 2-21 for additional information on
dry, wet, and total Pb deposition velocities and fluxes.
Arid environments appear to have a much higher fraction of dry deposition: total
deposition (Sabin et al., 2005). Furthermore, it is possible that Clean Air Act Legislation enacted
in the late 1970s preferentially reduced Pb associated with fine particles, so the relative
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