Measurement of Real-world Herbicides in Vapor and Particle Phases on a Cotton Field in Las Cruces, NM

JOHN KASUMBA (1), Britt Holmén (1), April Hiscox (2), Junming Wang (3), David Miller (4)

(1) University of Vermont, Burlington, VT 05401 (2) University of South Carolina, Columbia, SC 29208 (3) Tennessee State University, Nashville, TN 37209 (4) University of Connecticut, Storrs, CT 06269

     Abstract Number: 597
     Last modified: May 14, 2010

Abstract
Recently, research has shown a relationship between elevated levels of inhalable particulate matter (PM), herbicide concentrations and agricultural practices, especially in the vicinity of agricultural fields. Airborne particle concentrations, herbicide concentrations and meteorological variables were measured during nine agricultural field events on a cotton field in Las Cruces, NM in March 2008. A variety of real-time and integrated PM10 and total suspended particles (TSP) samplers were used during sampling. The field events were designed to measure PM and herbicide concentrations at different heights, - and two distances downwind of the disking tractor:near-source (4 meters) and far-source (20 – 100 meters). Particle concentrations decreased with increasing distance from the ground for near-source disking events, whereas particle concentrations were almost independent of height for background events. Near-source disking event particle concentrations were 4 to 7 times higher than those for far-source disking and background events. Near-source disking PM10 emission factors ranged from 71 – 237 mg m^-2, while those for far-source disking ranged from 10 – 162 mg m^-2. PM10 plume heights for near-source disking events were between 3 – 5 m, whereas those for far-source disking events were between 6 and 8 m. Meteorological variables such as wind speed showed a strong nonlinear relationship with PM emission factors. No clear relationship was found between soil moisture content and emission factors probably because the measured range of soil moisture was small. Atmospheric stability estimated for each event based on sonic anemometer data collected at two heights will be compared to PM and herbicide vertical concentration profiles to provide insight for field-scale emissions modeling. Laboratory analysis of herbicides in the field gas and particle samples will quantify the relationships between herbicide gas/particle partitioning and PM10 fluxes.