The impact of primary fine particulate matter (PM2.5) from ship emissions within the Southern California Air Basin is quantified by comparing in-stack vanadium (V) and nickel (Ni) measurements from in-use ocean-going vessels (OGVs) with ambient measurements made at 10 monitoring stations throughout Southern California. V and Ni are demonstrated as robust markers for the combustion of heavy fuel oil in OGVs, and ambient measurements of fine particulate V and Ni within Southern California are shown to decrease inversely with increased distance from the ports of Los Angeles and Long Beach (ports). High levels of V and Ni were observed from in-stack emission measurements conducted on the propulsion engines of two different in-use OGVs. The in-stack V and Ni emission rates (g/h) normalized by the V and Ni contents in the fuel tested correlates with the stack total PM emission rates (g/h). The normalized emission rates are used to estimate the primary PM2.5 contributions from OGVs at 10 monitoring locations within Southern California. Primary PM2.5 contributions from OGVs were found to range from 8.8% of the total PM2.5 at the monitoring location closest to the port (West Long Beach) to 1.4% of the total PM2.5 at the monitoring location 80 km inland (Rubidoux). The calculated OGV contributions to ambient PM2.5 measurements at the 10 monitoring sites agree well with estimates developed using an emission inventory based regional model. Results of this analysis will be useful in determining the impacts of primary particulate emissions from OGVs upon worldwide communities downwind of port operations.

The installation of roofing materials with increased solar reflectance (i.e., "cool roofs") can mitigate the urban heat island effect and reduce energy use. In addition, meteorological changes, along with the possibility of enhanced UV reflection from these surfaces, can have complex impacts on ozone and PM 2.5 concentrations. We aim to evaluate the air-quality impacts of widespread cool-roof installations prescribed by California's Title 24 building energy efficiency standards within the heavily populated and polluted South Coast Air Basin (SoCAB). Development of a comprehensive rooftop area database and evaluation of spectral reflectance measurements of roofing materials allows us to project potential future changes in solar and UV reflectance for simulations using the Weather Research Forecast and Community Multiscale Air Quality (CMAQ) models. 2012 meteorological simulations indicate a decrease in daily maximum temperatures, daily maximum boundary layer heights, and ventilation coefficients throughout the SoCAB upon widespread installation of cool roofs. CMAQ simulations show significant increases in PM 2.5 concentrations and policyrelevant design values. Changes in 8-h ozone concentrations depend on the potential change in UV reflectance, ranging from a decrease in population-weighted concentrations when UV reflectance remains unchanged to an increase when changes in UV reflectance are at an upper bound. However, 8-h policy-relevant ozone design values increase in all cases. Although the other benefits of cool roofs could outweigh small air-quality penalties, UV reflectance standards for cool roofing materials could mitigate these negative consequences. Results of this study motivate the careful consideration of future rooftop and pavement solar reflectance modification policies. With 16.8 million people, the SoCAB is the second most populous urban area in the United States. A fossil-fuel-dependent transit and goods movement infrastructure along with a welldeveloped industrial presence within the 27,824-km 2 SoCAB generates significant emissions of oxides of nitrogen (NOx), volatile organic compounds (VOCs), directly emitted primary particulate matter (PM), and secondary PM precursors. Persistent highpressure systems, ample photochemistry, infrequent rainfall, and ventilation-inhibiting topography also contribute to severe airquality problems. The SoCAB currently does not attain federal air-quality standards for 8-h O 3 , 1-h O 3 , annual-averaged PM 2.5 , and 24-h PM 2.5 . Ozone levels within the SoCAB are often the highest in the nation (1).The hot and sunny conditions typically experienced within the SoCAB make urban surface modification a useful strategy to reduce urban temperatures. Meteorological impacts of roofing materials with enhanced solar reflectance (SR, synonymous with "albedo"), colloquially referred to as "cool roofs," are wellstudied and indicate several benefits in urban areas. The replacement of darker materials with high-reflectance surfaces within cities can help mitigate the urban heat...