MTBE concentration profiles near MTBE manufacturing plant: modeling approach and modeling uncertainty

The methyl tert-butyl ether (MTBE) concentration profiles near a MTBE manufacturing plant were monitored on two occasions. The US EPA's atmospheric dispersion model (industrial source complex short-term) was used to model the ambient MTBE levels with the input of local meteorological data as well as MTBE emissions from the plant. The measured ambient MTBE concentrations range from 6 to 76 microgm(-3) with the average value about 33 microgm(-3). These values are similar to those values reported in ambient air in the vicinity of service stations of 4-12 microgm(-3) and tollbooths at a highway of 10-22 microgm(-3), but lower than those values reported in ambient air near gas stations of 50-690 microgm(-3), and higher than those values reported in atmospheric of 0.9-3.0 microgm(-3). Since the model has not been validated for the simulated MTBE profiles, there exist differences between the observed and mode-predicted data. The sensitivity and uncertainty of model parameters were then analyzed. The effects of wind direction, wind velocity and atmospheric stability are discussed in terms of their impact on model sensitivity/uncertainty.