Locating and quantifying the impact of local sources of air pollution

A new hybrid receptor model is described, which uses 1-min observations of pollutant concentrations along with back trajectories to estimate the average concentration at the receptor given that air has passed over a nearby area. The points on each back trajectory are associated with the pollutant concentration when the trajectory arrives at the monitor. The average value of the pollutant at the monitor given that air has passed near a geographical point on a grid is calculated by nonparametric regression of the pollutant concentrations over all the back trajectories passing near the point for the period of interest. A method is given of apportioning the average pollutant concentrations to local sources in geographically distinct regions and is illustrated by application to 1-min sulfur dioxide data from Long Beach, CA for May, June, and July 2005. Limitations of the model are discussed.