A large-scale, order-of-magnitude mass balance for lead in the near field of Chicago (the source) is presented. Both experimental data and simple physical modeling are used to estimate the transport of lead from the major sources to the near-field sinks of Southern Lake Michigan, its watershed soil, and the surroundings (losses from the system under question). The results show that atmospheric transport of lead aerosols to a sink like Lake Michigan is about two orders of magnitude greater than other transport mechanism. To perform a detailed (small-scale) mass balance for lead,, in support of the large-scale results, a complete model of atmospheric, aerosol transport and deposition is necessary and dominant.