Poor regional air quality in some states across the US cotton belt has resulted inincreased pressure on agricultural sources of particulate matter (PM) from air pollutionregulators. Moreover, inaccurate emission factors used in the calculation of annualemissions inventories led to the identification of cotton harvesting as a significant sourceof PM10 in California and Arizona. As a result, cotton growers in these states are nowrequired to obtain air quality permits and submit management practice plans detailingthe actions taken by the producer to reduce fugitive PM emissions from field operations.The objective of this work was to develop accurate PM emission factors for cottonharvesting in terms of total suspended particulate (TSP), PM10, and PM2.5.Two protocols were developed and used to develop PM emission factors fromcotton harvesting operations on three farms in Texas during 2006 and 2007. Protocolone utilized TSP concentrations measured downwind of harvesting operations withmeteorological data measured onsite in a dispersion model to back-calculate TSPemission flux values. Flux values, determined with the regulatory dispersion modelsISCST3 and AERMOD, were converted to emission factors and corrected with resultsfrom particle size distribution (PSD) analyses to report emission factors in terms of PM10and PM2.5. Emission factors were developed for two-row (John Deere 9910) and sixrow(John Deere 9996) cotton pickers with protocol one. The uncertainty associatedwith the emission factors developed through protocol one resulted in no significantdifference between the emission factors for the two machines. Under the second protocol, emission concentrations were measured onboard thesix-row cotton picker as the machine harvested cotton. PM10 and PM2.5 emission factorswere developed from TSP emission concentration measurements converted to emissionrates using the results of PSD analysis. The total TSP, PM10, and PM2.5 emission factorsresulting from the source measurement protocol are 1.64 ? 0.37, 0.55 ? 0.12, and 1.58E-03 ? 4.5E-04 kg/ha, respectively. These emission factors contain the lowest uncertaintyand highest level of precision of any cotton harvesting PM emission factors everdeveloped. Thus, the emission factors developed through the source sampling protocolare recommended for regulatory use.
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