Effects of sweeping depth on particulate matter emissions from almond harvest operations

Abstract

Almond harvest accounts for substantial PM10 emissions in California each harvest season. This paper addresses the effects of sweeper depth on particulate matter (PM) emissions from sweeping and pickup operations. Ambient PM sampling was conducted during harvest with alternating control (conventional sweeper setting) and experimental [sweeper depth 1.27cm (0.5 in.) lower than recommended] treatments. On–site meteorological data were used in conjunction with dispersion modeling using the American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) to back–calculate emission rates from the measured concentrations. PM10 emissions from pickup of windrows formed using lower sweeper settings were approximately 2.5 times those from pickup of windrows formed using conventional sweeper settings. Emissions from nut pickup were higher than those reported in previous studies but over 70% lower than the emission factor of 4 120kg PM10 km−2 yr−1 currently in use by the California Air Resources Board. The results of this research indicate the importance of proper equipment setup for reducing PM emissions and that the total PM10 emissions from modern almond harvest operations are substantially lower than current emission factors.