An evaluation of air pollutant exposures due to the 1991 Kuwait oil fires using a Lagrangian model

Abstract

A Lagrangian model was adapted to simulate the transport, dispersion, and deposition of pollutants from the Kuwait oil fires. Modifications to the model permitted radiative effects of the smoke plume to modify the pollutant's vertical mixing. Calculated SO2 (sulfur dioxide) air concentrations were compared with the observations from several intensive aircraft measurement compaigns as well as longer-term ground-based measurements. Model sensitivity tests and comparison to the aircraft measurements confirmed (1) the magnitude of the tabulated emission rates for SO2 and carbon soot; (2) the most appropriate value for the smoke's specific extinction coefficient was about 4 m2 g−1; (3) that the model was sensitive to the vertical mixing in the first 100 km downwind from the fires; (4) that the SO2 conversion rate was about 6% h−1; and (5) although there were large variations in the height of the initial smoke plume and ground-level concentrations were most sensitive to that height, an average value of 1500 m a.g.l. (above ground level) provided reasonable model predictions. Six ground-level sampling locations, all along the Arabian Gulf Coast, were used for model evaluation. Although the measurements and model calculations were in qualitative agreement, the highest space- and time-paired correlation coefficient was only 0.40. The monitoring stations were located in industrial areas, requiring the subtraction of a background concentration of anywhere from 5 to 34 μg m−3, which at some stations was larger than the contribution from the oil fires smoke. The coastal location and lack of correlation between some of the sites suggested that mesoscale flow features not properly represented in the coarse meteorological data used in the computations may have influenced the smoke transport.