Measurements of Aerosols Emitted From Hog Confinements

Lidar Applications: Hog Confinement Pollution 

Investigators

William Eichinger¹, Daniel Cooper², John Prueger³ , Tim Hart², Forest Goodman²,

Dick Pfeiffer³ , JenniferNichols¹, Robert Knight¹, Gregory Weber¹

Sponsor

National Soil Tilth Laboratory 

of the USDA

Purpose

        To accurately show aerosol movement coming from three hog confinement barns using the miniature elastic lidar, the Raman lidar, 3D sonic anemometers, and chemical detectors. 

Instrumentation

        The Raman lidar is an active, ground-based laser remote sensing instrument that measures vertical profiles of water-vapor mixing ratio and several cloud and aerosol related quantities.  It is also used to help map evapotranspiration (discharge of water to the atmosphere by plants) as well as evaporation from bare surfaces.  The Raman system is fully computer automated, and can run unattended for many days following a brief startup period.  The system is housed in a climate-controlled 8'x8'x20' standard shipping container.  

        The IIHR scanning miniature lidar (SMILI) is a small, scanning lidar which uses elastic backscattering to determine the distribution and properties of atmospheric particulates.  The lidar operates by emitting a pulse of infrared laser light into the atmosphere.  Particulates and molecules interact with the pulse and scatter light back to the lidar.  The amount of returning light collected by the telescope is proportional to the particulate content of the air and the amount of atmospheric attenuation.  The system is capable of both day and night operation.  For further information about the miniature elastic lidar refer to the following web site, http://www.iihr.uiowa.edu/facilities/elastic/ .

        The Sonic Anemometer/Thermometer is a microcomputer based wind sensor capable of measuring wind velocity in one, two, or three axes with reliable accuracy. The instrument is designed to measure wind velocity components by transmitting and receiving sonic signals along fixed orthogonal directions.  The microcomputer electronics then processes this information and calculates the wind speed in three axis. Since there are no moving parts to come into dynamic equilibrium with the air flow, the Sonic Anemometer/Thermometer responds rapidly to wind velocity fluctuations. It responds linearly to wind velocity and is free from contamination from other velocity components as well as pressure, temperature, and relative humidity.

        The mass spectrometer is an instrument which can measure the masses and relative concentrations of atoms and molecules. It makes use of the basic magnetic force on a moving charged particles.

        The tunable diode laser is a laser device with an adjustable wavelength.  The device contains a detector which measures the intensity of reflection off of molecules in the air.  Different wavelengths will reflect off of different molecules.

Location and Experimental Methods

        To take advantage of the southerly wind during the summer months, the equipment was setup to the north of the hog confinements.  The Raman lidar was set up approximately 400 meters north north-east of the complex while the miniature elastic lidar was set up approximately 542m north north-east of the complex.  Along with the Raman and miniature elastic lidar, five equipment towers with chemical detectors were stationed north of the complex.  The complex was bordered by a soybean field to the east and west, a corn field to the north, and a county road to the north.  The complex was surrounded by a barbed wire fence.  Refer to the diagrams below for further information on the layout of the experiment site.  

Experiment Layout  (Not drawn to scale)	Hog confinement complex located in Boone County north-west of Ames, Iowa.  To the far left is the Raman lidar, and to the right are two of five 3D sonic towers.

       Using the Raman and miniature elastic lidar, vertical and horizontal scans were taken of the complex to visually depict aerosol movement.  Data was collected on June 3, 9, and 11 of 2003 using the two lidar systems.   Below in the results section are a vertical (left) and horizontal (right) scan taken during the experiment.  The 3D sonic anemometers and chemical detectors were mounted on five towers.  The 3D sonic anemometers measured turbulent wind conditions and dispersion of the experiment site.  This data is used to calculate wind direction, wind speed, and temperature.  The mass spectrometer on the 3D sonic tower was used to measure the concentration of ammonia.  The tunable diode laser measured ammonia and nitrogen dioxide levels.  Using the values of concentration of the plume and dispersion, emission rate can then be calculated.

Results

Fan blowers on the hog confinements

        Previous experiments dealing with emission rates coming from hog confinements measured the concentration using a chemical detector placed outside the fan blowers shown in the picture to the right.  However, our research indicates that the plume is contributed to not only the fan blowers but also in large part by the openings on the side of the hog confinements.  Emission rates calculated using detectors in front of fan blowers underestimates the total emission rate of the hog confinement. 

        Below are two scans taken with the miniature elastic lidar.  The image to the bottom-left is a vertical scan, and the image to the bottom-right is a horizontal scan. The vertical scan shows the plume coming off from the hog confinement reached an approximate height of 30 m.  Previous attempts at measuring plume behavior coming from hog confinements suggest the plume travels horizontally from the barns and can be modeled as a line source.  The data from the Raman and miniature elastic lidar shows that the plume rises vertically before it travels horizontally in the direction of the wind.  The vertical rise can be attributed to turbulence in the atmosphere due to the pressure change around the barns themselves and the buoyancy of hotter air within the pig barns.  Further research is needed to accurately determine the causes of such a dramatic vertical rise of the plume.

        Our data demonstrates that the plume coming from the hog confinements rises vertically before it begins to travel horizontally in the direction of the wind- disproving the idea of line source travel and also renders the use of shelterbelts (such as trees and shrubs that are planted close to the confinement barns to induce mixing and dispersion) of little practical value.

Vertical scan - View movie	Horizontal scan - View movie

View Field Pictures