A METHOD OF PREDICTING POINT AND PATH-AVERAGED AMBIENT AIR VOC CONCENTRATIONS, USING METEOROLOGICAL DATA

A method of predicting point and path-averaged ambient air VOC concent rations is described. This method was developed for the case of a plum e generated from a single point source, and is based on the relationsh ip between wind directional frequency and concentration. One-minute me ans of wind direction and wind speed were used as inputs to a Gaussian dispersion model to develop this relationship. Both FTIR spectrometry and a whole-air sampling method were used to monitor VOC plumes durin g simulated field tests. One test set was also conducted using only wh ole-air samplers deployed in a closely-spaced network, thus providing an evaluation of the prediction technique free of any bias that might exist between the two analytical methods. Correlations between observe d point concentrations and wind directional frequencies were significa nt at the 0.05 level in most cases. Predicted path-integrated concentr ations, based on observed point concentrations and meteorological data , were strongly correlated with observed values. Predicted point conce ntrations, based on observed path-integrated concentrations and meteor ological data, accurately reflected the location and magnitude of the highest concentrations from each test, as well as the shape of the con centration-versus-crosswind distance curve.