A research program originally established to monitor ammonia from fertilizer applications and other gases from dairy operations has grown to focus on particles of “much greater” size – up to 10 microns or more.
The new study, featuring a team of California State University, Fresno specialists in air emissions monitoring, has expanded to involve not only dairies, but agricultural field operations that can emit particulate matter (PM) into the air.
Particulate matter is much greater in size than a molecule of ammonia, for example, but still smaller than dust and not visible to the human eye without magnification. A particle the size of 10 microns measures 10 micrometers or less in diameter. That’s 0.0004 inches, or one-seventh the diameter of an average human hair.
Increased levels of 10-sized particles in the air have been linked to health hazards such as heart disease, altered lung function and lung cancer.
One objective of the Fresno State study is to assess the PM-reducing potential of a new misting apparatus that can be attached to a common agricultural disk. The research is being led by associate professor Alex Alexandrou along with co-investigator and professor Charles Krauter and research associates Shawn Ashkan and Diganta Adhikari.
“A significant improvement in air quality for the San Joaquin Valley has been ‘attainment’ with regard to PM-10 regulations in the past year,” Alexandrou said.
However, additional regulations – set by the San Joaquin Valley Air Pollution Control District – will require implementation of management practices that reduce the PM generated by practices such as land preparation, cultivation and crop harvesting, the researchers noted.
Emissions research led by Krauter over the past 10 years has improved monitoring accuracy for a variety of emissions such as ammonia and volatile organic compounds (VOCs). That also needs to happen for PM-10 measuring systems in California agriculture, Alexandrou said.
“Commercially available PM-10 samplers are both expensive and cumbersome for use in agricultural environments,” Alexandrou said. “They also may present some serious errors when used for sampling in these environments.”
In 2006 the U.S. Department of Agriculture and Texas A&M University researchers developed and validated a method for measuring agricultural PM. As part of the current project, Texas A&M is providing some monitoring equipment and constructing additional sampling systems for Fresno State. Grant funding also has enabled the purchase of new air sampling equipment that will be tested against the existing equipment.
Monitoring devices include filter units that can be placed around a field to record the amount and size of particles raised by certain types of field work. During PM monitoring, a state-of-the-art mobile weather station is used to record wind velocity, direction and other weather related variables to ensure data is collected under equivalent conditions.
“A weather station is very important for modeling purposes. It ensures that the data which feed the model are accurate,” Adhikari said.
New technologies are being developed to reduce dust plumes generated by vineyard and orchard disking, the researchers noted. One involves spraying a mist of water behind a disk to reduce the plume of heated air that launches PM. Thus the research will actually involve multiple studies, Alexandrou said – of both plume reduction techniques and protocols used to measure the dust levels.
Accurate monitoring of emissions is critical to any regulatory system that is applied to the industry, the researchers said.
“Inappropriate regulation of crop production and dairies due to inaccurate emission factors could drastically affect the agricultural industry in the San Joaquin Valley,” Alexandrou said. “Improved emissions information would allow for the application of appropriate control measures, resulting in both improved air quality and more productive farming.”
Initial funding for this project is for three years. Financial support comes from the California State University Agricultural Research Initiative (ARI) and the California Association of Resource Conservation Districts.