Aerosol Emissions from Cotton Field Operations David R. Miller ， Junming Wang, Ted Sammis, April Hiscox

Research Personnel David R. Miller, Professor of Micrometeorology, University of Connecticut Britt A. Holmén, Associate Professor of Environmental Engineering, University of Connecticut Theodore Sammis, Professor of Agronomy, New Mexico State University Junming Wang, Research Associate, New Mexico State University April Hiscox, PhD Candidate, University of Connecticut Wenli Yang, PhD Candidate, University of Connecticut

Research Project Objectives: Measure and account for atmospheric particulate emissions from field operations Characterize chemistry and size distribution of particulate emissions Quantify the particulate emissions Relate the wind and turbulence flow field to the amounts, movements and dispositions of particle emissions.

General Methods Measure particle size distributions and chemical makeup of the emissions collected with low pressure cascade impactors Measure the amount, movement and disposition of the particles emitted with elastic-backscatter LIDAR Measure and characterize the wind and turbulence fields with fast response sonic anemometers and thermal sensors

Cotton Field Operations in the 2005 growing season Plowing: soil H20 = ? %, # passes =11 Crushing: soil H20 = 72%, # passes = 22 Disking: soil H20 = 62%, # passes = 26 Leveling: soil H20 = 52%, # passes = 12 Listing : soil H20 = 50%, # passes = 31 Planting : soil H20 = 55%, # passes = 16 Harvesting: soil H20 = 94%, # passes = 16

Dust from Leveling Operation Lofting into Atmospheric Boundary Layer, Rio Grande Valley NM, April 2005

Co-located samplers, generator and exhaust pipe on sampler tractor

PM 2.5, PM 10, TSP samplers

GT-640A particulate monitors (Met One Instruments, Inc., Grants Pass, OR) Real-Time Mass Monitors Used to characterize the real-time mass concentrations of total suspended particles (TSP) and PM10.

ELPI, MOUDI and PQ200 Samplers

ELPI- Electrical low pressure impactor (ELPI, Dekati LTD., Finland) The ELPI is capable of measuring the particle number concentration over a wide size range (7 nm – 8 μm) in real time with 1-2 second resolution.

MOUDI. A micro-orifice uniform deposit impactor (MOUDI; Model 110, MSP Corporation) Used to collect particle size distribution for mass and chemical analysis. Particles from 56 nm to 18 μm in 10 rotating stages

PQ200. A PQ200 sampler (BGI Inc. Waltham, MA) used to collect PM2.5 generated during the field crop operations. EPA required sampler for enforcement

UCONN Elastic Backscatter Aerosol Lidar

UCONN Elastic Backscatter Scanning Aerosol Lidar

Lidar Hardware Wavelength1064nm Energy per Pulse125mJ Repetition Rate50Hz Pulse Width<15ns Pulse to pulse stability±3% Detector TypeAvalanche photodiode High Quantum Efficiency40% Useful Area7mm 2 Sampling Resolution17ns (2.55 m)

3-D Sonic Anemometer

NMSU Leyendecker Experimental Farm Layout

Disk Operation

Particle mass distribution measured by MOUDI for individual field operations

Mean size distribution measured by ELPI for individual field operations

Figure 5. ELPI total particle number concentration (TPN) and Met One particle monitor mass concentration of TSP and PM10 for cotton field disking

mass concentration of TSP and PM10 for cotton field harvest operations.

Average Weather Conditions – Disking Operations U (m/s) 5.4 Udir (degrees) 257 Stddev Udir 90 ζ -1.2 T (C) 14.7 RH (%) 12.5

Atmospheric Stability Parameter  = (z)/L L is the Obukov length L= mechanical turbulence/heat flux turbulence L= -(  cp T u*^3)/(k g H) u* = ^0.5 H=  cp

Lidar Real Time Scan Display: Elevation 0.5 degrees ~ 3 m

Dust Cloud on Real Time Display

Post Process Scans Example series of horizontal slices through a single dust cloud from disking operation 3/31/05 First (lowest) slice is 3 m above ground (z). Highest slice is 30 m above ground

Slice through Dust Cloud at z=3m

Slice through Dust Cloud at z=6 m. Note Dust Devil appearing at Upper Right Hand Edge of Scan

Slice at z=9m

Slice at z=12 m

Slice at z = 14 m

Slice at z = 18 m

Slice at z = 24m

Slice at z = 27 m

Slice at z = 30 m

Tractor Dust (left) and Dust Devil (right)

Dust Devil Slice

Unknown source plume– located at the lower right in slice – Tractor dust plume at left.

Tractor Dust and pesticide spray (from nearby field) volumes.

NMSU Leyendecker Experimental Farm Layout

Dust Plumes over experimental field from nearby orchard harvest operation.

Finding σ s Δz Location of maximum backscatter (B m )

The “Mobile Office-Lab-Lidar- aerosol-micrometeorology Research Complex” ready for another experiment