UPDATE ON THE DEVELOPMENT OF PARTICULATE MATTER EMISSION FACTORS FOR COTTON HARVESTING

Accurate particulate matter emission factor data from modern cotton harvesting operations is not available for regulatory use. Thus, the objective of this work was to develop accurate dust emission factors for modern cotton harvesting operations in terms of PM10, PM2.5 and TSP. Particulate matter sampling of cotton harvesting operations was conducted on three farms in Texas during 2006 and 2007. Two protocols were used to develop emission factors in terms of TSP, PM10, and PM2.5 from the operations. The first protocol used the regulatory dispersion models ISCST3 and AERMOD to back calculate emission flux values for a two-row John Deere model 9910 cotton picker and six-row John Deere model 9996 cotton picker from measured downwind concentrations and meteorological data collected onsite. The second protocol employed a novel source sampling system onboard the six-row cotton picker to measure emission concentrations emitted from the basket as the machine operated in the field. The results from the first protocol indicated that the two-row harvester emission factors were higher than the six row machine and the mean difference in the PM10 emission factors developed in ISCST3 and AERMOD were 1.08 and 3.61 kg/ha, respectively (0.96 and 3.22 lb/ac, respectively). These differences were found to be insignificant for ISCST3 but significant for AERMOD. The emission factors developed under the source sampling protocol exhibited much higher precision and lower uncertainty than those developed under the first protocol. The TSP, PM10, and PM2.5 emission factors developed using the sourc