Contributions to CO concentrations from biomass burning and traffic duringhaze episodes in Singapore

Prediction of ambient carbon monoxide (CO) due to haze in the presence of t ransportation sources at a busy expressway site in Singapore was made using street Canyon and Gaussian line source modules of a reeional-scale Indic A irviro dispersion model for the haze episodes that occurred in the years 19 94 and 1997. The fleet average emission factors for each vehicle category w ere estimated from US EPA MOBILE 5 A guidelines as a function of speed, veh icle deterioration rates and model pears. One hour CO concentrations during the non-haze period for the year 1995 were first simulated and compared wi th measured readings to test the accuracy of the proposed approach. The cal ibrated model was then used to compute hourly CO values for the 1994 and 19 97 haze episodes. The difference between the modeled CO values with and wit hout haze provided CO contribution due to haze. An analysis of CO values es timated through modeling with experimental measurements made during haze pe riods confirmed this unique approach to establish concentration of CO due t o haze in the presence of transportation sources. (C) 2001 Elsevier Science Ltd. All rights reserved.