Overall elemental dry deposition velocities measured around Lake Michigan

Overall dry deposition velocities of several elements were determined by di viding measured fluxes by measured airborne concentrations in different par ticle size ranges, The dry deposition measurements were made with a smooth surrogate surface on an automated dry deposition sampler (Eagle II) and the ambient particle concentrations were measured with a dichotomous sampler. These long-term measurements were made in Chicago, IL, South Haven, MI, and Sleeping Bear Dunes, MI, from December 1993 through October 1995 as part o f the Lake Michigan Mass Balance Study. In general, the dry deposition flux es of elements were highly correlated with coarse particle concentrations, slightly less well correlated with total particle concentrations, and least well correlated with tine particle concentrations. The calculated overall dry deposition Velocities obtained using coarse particle concentrations var ied from approximately 12 cms(-1) for Mg in Chicago to 0.2 cms(-1) for some primarily anthropogenic metals at the more remote sites. The velocities ca lculated using total particle concentrations were slightly lower. The crust al elements (Mg, Al, and Mn) had higher deposition velocities than anthropo genic elements (V, Cr, Cu, Zn, Mo, Ba and Pb). For crustal elements, overal l dry deposition velocities were higher in Chicago than at the other sites. (C) 2001 Elsevier Science Ltd. All rights reserved.