The urban atmosphere: An important source of trace metals to nearby waters?

Atmospheric deposition of trace metals from urban environments on the perimeter of large water bodies is a potential source to these systems. There is little data, however to support or refute this notion. Here we discuss a study of Baltimore's urban air and its potential impact on the northern Chesapeake Bay and compare our results to those of other studies. Elevated concentrations of metals, especially lead, zinc and mercury were measured at an urban sampling site compared to a rural location. The difference was most marked for lead with the annual depositional flux almost three times higher in the city. Normalized fluxes at a rural site were mostly similar to those measured previously around the Chesapeake Bay and were also similar to those measured recently at other rural sites in Maryland and around the Great Lakes. The results of our study suggest that local atmospheric inputs from urban sources should be included in any evaluation of atmospheric deposition to lacrustrine, coastal or estuarine systems.