Evaluation of Conservation Management Practices for Reducing PM Emissions from Almond Harvesting Operations

Almond harvest accounts for a significant amount of PM10 emissions in California each harvest season. This paper addresses the adjustment of sweeper depth and its effect on PM10 emissions from sweeping and pickup operations. Ambient total suspended particulate (TSP) and PM10 sampling was conducted during harvest with alternating control (proper sweeper setting) and experimental treatment (sweeper depth 1.27cm [0.5 in.] that is lower than recommended treatments). On-site meteorological data was used in conjunction with inverse dispersion modeling using the American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) to develop emission rates from the measured concentrations. The emission factors developed from this study using proper sweeper settings are 1,725 +1,345 kg PM10/km/yr for sweeping and 2, 232 + 1,929 kgPM10/km/yr for pickup operations. The emission factor for sweeping is significantly higher than those reported in previous studies and is higher than the emission factor currently in use by the California Air Resources Board. The emission factor for nut pickup is similar to those reported in previous studies but lower than the emission factor of 4,120 kg PM10/km currently in use by the California Air Resources Board. The results of this research showed no differences in emissions of regulated pollutants during the sweeping process as a function of sweeper depth, but emissions during pickup were significantly lower (by about half) for windrows formed using proper sweeper settings versus those formed using improper sweeper settings (i.e. 2,232 versus 4,858 kg PM10/km/yr).