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.
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