Controlling Dust to Improve Air Quality
Focus Resource Concern for May 2012
PHOENIX, May 24, 2012 – Dust consists of particles, in the atmosphere, that come from various sources such as soil that is lifted by wind (such as our Haboobs-an unfortunate reality of our arid environment), volcanic eruptions, and pollution. Dust is comprised of various sized particles from sand grains that can pit your car’s windshield to particles that you cannot see. Particles that are not seen include the PM10 and PM2.5 sized particles.
PM10 is particulate matter that is ten micrometers or less in diameter (a human hair is about 70 micrometers). These are very small particles that can invade the natural defense mechanism of the human respiratory tract, penetrating deep into the lungs where it can be lodged. The Federal Clean Air Act requires that emissions from all significant sources in areas not meeting the National Ambient Air Quality Standards be controlled through effective programs. Air quality problems occur when the amount of particles released into the air increase in concentration, exceeding air quality standards. Large concentrations of PM10 could potentially violate one of the federal air quality standards. To reduce dust emissions and meet Arizona Air Quality Standards there are a few things you need to know.
Know the Non-Attainment Areas in Arizona
Currently, Arizona has non-attainment areas for PM10 in Maricopa, Yuma, Pinal, Pima, Santa Cruz, and Cochise Counties. Agricultural activities have been identified as a source, in the above counties, that contribute to producing PM10. And, Agriculture is playing a role in helping to meet the federal clean air standards by implementing an Agricultural Best Management Practices (Ag BMP) Program.
Know the Agricultural Best Management Practices Program
This program is made up of various categories with participants selecting Best Management Practices (BMPs) from a menu of measures from each category. Best Management Practices have been defined as techniques verified by scientific research that is practical, economically feasible and effective in reducing PM10 on a case by case basis. Most methods for controlling PM10 emissions parallel the controls for wind erosion. A wide range of variation in soils and cropping systems exists, thus not all BMPs will work equally well on every farm. Such factors should be considered by individual farmers to ensure they implement effective BMPs. The manipulation or disturbance of soil is inherent to the practice of farming. Best management practices are not designed to eliminate particle emissions 100 percent, but they are designed to reduce the activities that can lead to the increased concentration of PM10.
Know and Implement the Most Appropriate Practices
Disturbed soil that is broken down into smaller particles can also become a soil conservation problem. Conservation Practices recommended by the Natural Resources Conservation Service (NRCS) are used to control wind erosion on croplands. These practices include: crop rotations, reduced tillage (mulch till, strip till, no-till, ridge till, seasonal residue management), cover crops, and irrigation water management. There are other BMP’s , often in association with the above practices, used to address soil erosion and reduction of PM10 from associated farming activities such as adjoining dirt roads or road shoulders on farmland. Examples of effective BMPs farmers might implement to reduce PM10 or dust includes:
Limiting activity during high wind events. This is performing no tillage or soil preparation activity when measured wind speed is more than 25 mph. You can receive a notification from the Arizona Department of Agriculture in advance on these days.
Create wind barriers. This is reducing PM10 emissions and wind erosion by constructing a fence or structure, or providing a woody vegetative barrier by planting a row of trees or shrubs, perpendicular or across the prevailing wind direction to reduce wind speed by changing the pattern of air flow over the land surface.
Applying aggregate cover. This is applying gravel, concrete, recycled road base, caliche, or other similar material to non-cropland to a depth sufficient to reduce dust generated from vehicle movement, wind or other erosive forces.
Install a track-out control system. This is reducing PM10 emissions by using a device or system to remove mud or soil from a vehicle or equipment before the vehicle enters a paved public road. Some examples of track-out control devices are pavement, gravel pads, and grizzlies. The farmer should conduct periodic inspections, maintenance, reapplication of gravel, and cleaning of paved access road surfaces to accomplish track-out control.
Combining tractor operations. This is reducing soil compaction and the number of passes across a commercial farm by using a tractor, implement, harvester, or other farming support vehicle to perform two or more tillage, cultivation, planting, or harvesting operations at the same time. Combining tractor operations reduces the number of passes or trips that a tractor makes across a field, thereby reducing the amount of soil disturbed.
For more information on Ag BMPs consult the Guide to Agricultural PM10 Best Management Practices.