Sources of nickel, vanadium and black carbon in aerosols in Milwaukee

Detailed analysis of the health effects of particulate matter shows that metals and black carbon have significant impacts of their own. A summer intensive study was performed in Milwaukee, Wisconsin in July and August 2010 to identify potential sources of nickel, vanadium and black carbon in the atmosphere. An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to collect single-particle mass spectra and an Aethalometer was used to measure black carbon. Comparison with the National Emissions Inventory was performed using mesoscale meteorological simulations based on the Weather Research and Forecasting model (WRF) and the Comprehensive Air-quality Model with eXtensions (CAMx). The analysis suggests that nickel and vanadium are primarily emitted by industrial point sources in the Menomonee valley and that black carbon is primarily associated with mobile sources and emissions of nitrogen oxides. Evaluation of ship emissions from the port of Milwaukee suggest that they are responsible for approximately 5% of nickel and vanadium and approximately 10% of black carbon in Milwaukee. Elevated concentrations of air pollutants were found to occur mainly during wind stagnation events suggesting that local sources dominate over regional transport.