2002a. Characterization of dusts emitted by cotton gins in terms of true PM10

Agricultural operations across the United States are encountering difficulties in complying with the current air pollution regulations for particulate matter (PM). Cotton gins are most frequently regulated based on results obtained from dispersion modeling that utilize emission factors from EPAs 1996 AP-42 or emission factors derived from source sampling. PM10 emission factors are typically determined from source sampling based on EPAs Method 201a sampling protocol. Method 201a utilizes a cyclone in the sampling system to remove the larger particles and allow the smaller particles to penetrate to the filter. EPA has documented the performance characteristics of the cyclones used in Method 201a, which are similar to the performance characteristics of an ambient PM10 sampler. Recent research has shown that ambient PM10 samplers can over-estimate the true PM10 in the ambient air when the sampler is exposed to dust with a mass median diameter larger than 10 µm. The purpose of this manuscript is to explore the potential impacts associated with determining PM10 emission values for cotton gin exhausts using the EPAs Method 201a. Two theoretical methods were introduced to estimate the true PM10 emitted from the 10 process streams associated with a standard cotton gin. Estimates from the first and second methods showed that the true PM10 was about 38 and 63 % lower than that obtain by PM10 source sampling. This corresponds to estimates of the true PM10 percent of 28 and 24 % for methods 1 and 2, respectively. Whereas the current estimate of the true PM10 percent is 39%, as defined in EPAs 1996 AP-42. Therefore, when cotton gins are regulated based on PM10 emissio