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United States Department of Agriculture

Agricultural Research Service

Research Project: AIR QUALITY ISSUES RELATED TO AGRICULTURAL OPERATIONS AND PROCESSES Title: Update on the development of particulate matter emission factors for cotton harvesting

Authors
item Wanjura, John
item Faulkner, W - TEXAS A&M UNIV
item Parnell, JR., C - TEXAS A&M UNIV
item Shaw, B - TEXAS A&M UNIV
item Capareda, S - TEXAS A&M UNIV

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: February 29, 2008
Publication Date: June 1, 2008
Citation: Wanjura, J.D., Faulkner, W.B., Parnell Jr, C.B., Shaw, B.W., Capareda, S.C. 2008. Update on the development of particulate matter emission factors for cotton harvesting. In: Proceedings of the Beltwide Cotton Conferences, January 8-11, 2008, Nashville, Tennessee. 2008 CDROM. p. 533-545.

Interpretive Summary: Poor air quality in some states across the US cotton belt has led to increased air pollution regulation for agricultural producers. The increased regulation comes in the form of air quality permit requirements and mandated management practice plans to help reduce fugitive dust emissions from field operations. Little to no data is available on the level of dust emissions from modern cotton harvesting operations. Further, no objective data is available to regulators or producers quantifying differences in dust emissions from cotton harvesting operations utilizing machinery with different per-pass harvesting capacities. The perception exists that larger per-pass harvesting capacity machines (e.g., six-row vs. two-row machines) emit less dust when harvesting a given area since they require less time in the field. Thus, producers can receive a management practice credit for using larger harvesting machinery. 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. Two measurement protocols were used to develop the emission factors from the harvesting operations. The first protocol used mathematical dispersion models to back-calculate emission factors for a two-row and six-row cotton picker from concentrations and meteorological data measured onsite. 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). The difference in the two-row and six-row harvester emission factors was not significant in ISCST3 but was significant in AERMOD. The second measurement protocol utilized a system designed to measure emission concentrations onboard the six-row cotton picker as it operated in the field. The emission factors developed under the second 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 source measurement protocol are 1.64 ± 0.37, 0.55 ± 0.12, and 1.58E-03 ± 4.5E-04 kg/ha, respectively (1.46 ± 0.33, 0.49 ± 0.11, and 1.41E-03 ± 4.01E-04 lb/ac, respectively). The emission factors developed under the second protocol are considered appropriate for regulatory use in permitting modern day cotton harvesting operations.

Technical Abstract: 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 source measurement protocol are 1.64 ± 0.37, 0.55 ± 0.12, and 1.58E-03 ± 4.5E-04 kg/ha, respectively (1.46 ± 0.33, 0.49 ± 0.11, and 1.41E-03 ± 4.01E-04 lb/ac, respectively). Further analysis of the emission factors developed with the source sampling protocol indicate that it is appropriate to report cotton harvesting particulate matter emission factors in terms of mass per bale harvested. In terms of kg/bale, the TSP, PM10, and PM2.5 emission factors from the source measurements of PM emissions from the six row machine were 0.22 ± 0.019, 0.07 ± 0.007, and 2.15E-4 ± 1.49E-5 kg/bale, respectively (0.48 ± 0.04, 0.15 ± 0.015, and 4.74E-4 ± 3.3E-5 lb/bale, respectively). Particle size distribution (PSD) analyses on the PM collected by the downwind TSP samplers and by the source sampling system indicates that the PSD of the dust emitted from cotton harvesting operations is closely approximated by a lognormal density function characterized by MMD and GSD values of 14 um and 2.2 respectively.

Last Modified: 10/30/2014
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