Problem statement: Mining operations are important sources of airborne metal and metalloid contaminants: smelting may lead to emissions of metals and metalloids, while wind erosion of mine tailings mobilizes dust particles containing trace metals. Contaminant transport by atmospheric aerosols in arid and semiarid climates, such as the Southwestern US, may become increasingly important with predicted regional climate change, with potential deleterious effects on human health and ecology. Fine particulates (size <1 μm) resulting from smelting operations may penetrate deep into the lungs and disperse more readily into the environment than coarser soil dusts. Approach: In this work, results are presented on the size-resolved chemical characterization of atmospheric aerosols at a mining site in Arizona. Aerosols were collected with a 10-stage (between 0.054 and 18 μm aerodynamic diameter) multiple orifice uniform deposit impactor (MOUDI) and a total suspended particulate (TSP) collector located at a sampling site in the vicinity of mine operations. Results: Metal concentrations from the MOUDI were compared with TSP and PM 10 results and show good agreement. The MOUDI results show that arsenic and lead concentrations in the aerosols follow a bimodal distribution with particle size, with means around 0.3 and 7 μm. Conclusion: We hypothesize that the arsenic and lead in the fine size range (<1 μm) are the product of condensation and coagulation of smelting vapors. In the coarse size range (3-18 μm), contaminant presence is thought to be part of aeolian dust generated from mine tailings.