Sources of metals and NMHCs from motor vehicle roadways

A systematic approach was employed to quantify the emissions of metals present in the particulate matter emissions from on-road motor vehicles. A consistent set of sampling and chemical analysis techniques were used to measure the chemical composition of PM10 and PM2.5 emissions, including trace metals by inductively coupled plasma mass spectrometry (ICPMS) from motor vehicle roadway tunnels, motor vehicle brake wear, motor vehicle tire wear, resuspended road dust, and tailpipe emissions from gasoline and diesel powered vehicles. Profiles for these sources are presented and discussed. The profiles are used in a chemical mass balance (CMB) model that quantifies the relative contribution of brake wear, tire wear, resuspended road dust, gasoline vehicle tailpipe emission, and diesel vehicle tailpipe emissions to the measured emissions of metals from motor vehicle roadway tunnels. Additionally, roadway emissions of volatile non-methane hydrocarbons (NMHC) in the tunnel tests and in vehicle cold-start emissions were used to evaluate impacts of cold-start emissions and seasonal fuel formulation changes on the composition of roadway emissions and ambient concentrations of NMHCs.; These measurements were supplemented by the parallel measurements of atmospheric particulate matter and associated metals at three urban locations: Milwaukee, WI, Waukesha, WI, and Denver, CO. Samples were collected every 6th day for one year and were analyzed by the same chemical analysis techniques that were used for the source samples. The two Wisconsin sites were used to assess the spatial differences of trace metals in an urban airshed in the context of mass and individual constituents of atmospheric particulate matter. The ambient measurements were evaluated to help understand source and seasonal trends in atmospheric concentrations of trace metals.; The ICPMS methods that were used for metals analysis have not been widely used for the analysis of ambient aerosols in the past, but have a wide range of advantages over traditional techniques for atmospheric particulate matter analysis. An example is presented applying ICPMS techniques in a preliminary study to assess the leachability of trace metals present in atmospheric particulate matter samples and motor vehicle source samples in a synthetic lung fluid.