Heterogeneous Atmospheric
Chemistry of Lead Oxide
Particles with Nitrogen Dioxide Increases Lead Solubility: Environmental
and Health Implications
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Abstract
Heterogeneous chemistry of nitrogen dioxide with lead-containing
particles is investigated to better understand lead metal mobilization
in the environment. In particular, PbO particles, a model lead-containing
compound due to its widespread presence as a component of lead paint
and as naturally occurring minerals, massicot, and litharge, are exposed
to nitrogen dioxide at different relative humidity. X-ray photoelectron
spectroscopy (XPS) shows that upon exposure to nitrogen dioxide the
surface of PbO particles reacts to form adsorbed nitrates and lead
nitrate thin films with the extent of nitrate formation relative humidity
dependent. NO<sub>2</sub>-exposed PbO particles are found to have
an increase in the amount of lead that dissolves in aqueous suspensions
at circumneutral pH compared to particles not exposed. These results
point to the potential importance and impact that heterogeneous chemistry
with trace atmospheric gases can have on increasing solubility and
therefore the mobilization of heavy metals, such as lead, in the environment.
This study also shows that surface intermediates that form, such as
adsorbed lead nitrates, can yield higher concentrations of lead in
water systems. These water systems can include drinking water, groundwater,
estuaries, and lakes