Particulate Matter Emission Factors for Almond Harvest as a Function of Harvester Speed

Abstract

Almond harvest accounts for substantial particulate matter less than 10 m in aerodynamic diameter (PM 10 ) emissions in California each harvest season. This paper addresses the reduction of harvester ground speed from a standard 8 km/hr (5 mph) to 4 km/hr (2.5 mph) as a possible mitigation measure for reducing PM 10 emissions. Ambient total suspended particulate (TSP) and PM 10 sampling was conducted during harvest with alternating control (8 km/hr [5 mph]) and experimental (4 km/hr [2.5 mph]) treatments. On-site meteorological data were used in conjunction with both Industrial Source ComplexShort Term version 3 (ISCST3) and the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD) dispersion models to backcalculate emission rates from the measured concentrations. Baseline annual emission factors for nut pickup of 381 Ϯ 122 and 361 Ϯ 123 kg PM 10 /km 2 ⅐yr were determined using ISCST3 and AERMOD, respectively. Both of these values are substantially lower than the current PM 10 emission factor for almond pickup of 4120 kg PM 10 / km 2 ⅐yr. The particulate matter less than 2.5 m in aerodynamic diameter (PM 2.5 ) emission factors for nut pickup developed from this study were 25 Ϯ 8 kg PM 2.5 /km 2 ⅐yr and 24 Ϯ 8 kg PM 10 /km 2 ⅐yr were determined using ISCST3 and AERMOD, respectively. Reducing harvester speed resulted in an emissions reduction of 42% for TSP, but no differences were detected in emissions of PM 10 and PM 2.5 . Differences detected in the emission factors developed using ISCST3 and AERMOD were not statistically significant, indicating that almond harvest emission factors previously developed using ISCST3 may be applied appropriately in AERMOD.

Evaluation of Particulate Matter Abatement Strategies for Almond Harvest

“…They found that reducing harvester ground speed without reducing the power take-off speed of the tractor led to lower opacity measurements in the plume relative to emissions from harvesters operating at typical speeds. In a follow-up study, Faulkner et al 6 again used measured ambient PM concentrations and inverse dispersion modeling from nut pickup operations to test the effect of reduced harvester ground speed on PM emissions. In line with the findings of Downey et al, 4 Faulkner et al 6 reported that TSP emission rates were lower for the slower harvester speed, but no differences were detected in PM 10 or PM 2.5 emission rates as a result of changing harvester ground speed.…”

“…Tests from each plot lasted approximately 1 hr. Data collection and analysis were conducted using the methods described by Faulkner et al 6 In summary, the particle size distribution (PSD) of PM collected on TSP filters having more than 200 g of PM were analyzed using a particle size analyzer (Mastersizer 2000, Malvern Instruments, Inc.). The PSD (described by a log-normal mass distribution) of each sample was determined and characterized by a mass median diameter (MMD) and geometric standard deviation (GSD).…”

“…This shape factor was a departure from earlier work described by Faulkner et al. 6 In the study presented here, a particle shape factor of 1.05 was used given the slightly aspherical shape of soil particles collected from the orchards during sampling as seen using a scanning electron microscope ( Figure 4). where p is in grams per cubic centimeter and is the shape factor.…”

“…Additional meteorological parameters were calculated according to U.S. Environmental Protection Agency guidance. 13 The dimensions of each test plot and corresponding meteorological data were then used with the American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) to determine fluxes (g/m 2 ⅐sec) from each of the downwind samplers for each sampling period according to the protocol described by Faulkner et al 6 Each of the four sampler sets used at each plot provided an independent measurement of concentration, leading to four independent estimates of the emissions flux for each plot. These four fluxes were considered replicated measurements of emissions for a given plot, such that eight average fluxes (4 TSP; 4 FRM PM 10 ) were used to determine the emissions for each sweeping treatment.…”

Fugitive Particulate Matter Emissions to the Atmosphere from Tracked and Wheeled Vehicles in a Desert Region by Hybrid-Optical Remote Sensing

“…These include movement of vehicles on unpaved roads (Gillies et al, 2005;Du et al, 2011b), movement of helicopters over unpaved surface (Du et al, 2011b), movement of agricultural tractors (Holmén et al, 1998) and harvesters (Faulkner et al, 2009), and open burning and detonation (Yuen et al, 2014). Fugitive PM EFs of military and civilian vehicles have been compared using flux tower method, for vehicles traveling from 10 to 80 km/hr, and vehicle masses between 1 and 17 tonnes (Gillies et al, 2005).…”