Dust Control Study

Las Cruces has a dust problem. Since we are in the desert, this is not a new topic of discussion. There are days where you cannot see the Organ Mountains or even two feet in front of you; though those large events are not commonplace, we see smaller events more periodically. These smaller events include construction sites or dirt roads that can cause a disturbance of dust containing particulate matter in sizes from 10 micrograms (µg) to 2.5 micrograms (µg). Though these sizes may seem arbitrary, the 10ug particulate matter can be deposited in the nose and high throat area, and the 2.5µg particulate matter can be deposited deep within lung tissue. These particles could trigger asthma attacks, or they could contain bacteria or viruses that could be devastating to the immune system. They could also cause cardiovascular issues and even death.

The video below shows what a dust storm looks like in Las Cruces. It was taken on December 19, 2012 at the Fabian Garcia Horticulture Farm.

The Environmental Protection Agency (EPA) regulates a national dust ordinance, which Las Cruces fails every year due to our periodic massive dust storms. This term is called "nonattainment" or failure to meet federal regulation. This non-attainment status results from one or two large dust storms. We cannot fix the large dust storms, but we can help with the smaller, localized, and preventable dust storms.

Since work on the study began, The City of Las Cruces worked out a new, stricter dust control ordinance than that was in place. This new ordinance targets new and old construction sites. Since the recession began, many housing developments have been abandoned or ignored; therefore, the dust coming from those scoured plots has had an impact on those properties surrounding them, including property damage and increased negative health effects.

Study

A study is currently underway by New Mexico State University's College of Agriculture, Consumer, and Environmental Science department to determine the best and most cost effective dust control treatment to help those who would be affected by the strict regulations, i.e. construction companies.

Three plot sites were selected in the Las Cruces area: Colinas, Sonoma Ranch, and Diamond Springs. Each plot was a total of 600 foot in length and 100 foot in width and was broken into twelve (12) 100ft x 50ft sections. Six treatments were selected with a buffer zone between each treatment.

The treatments being tested are a wind barrier fence, pecan mulch, two different chemical suppressants (Earth Bound and Dirt Glue), and natural glycerin.

Illustration of Study Plot Sites

Wind Fence

A wind barrier fence is designed to slow the flow of air across the top few inches of ground. If a solid wall is in the path of wind an interesting phenomenon occurs. As the wind is forced over the fence, the wind speed is increased and a slight vacuum is created on the other side of the fence. On this side the wind loses its energy, the speed is reduced and any particles in the wind (such as sand) are dropped. There are two areas where sand will pile around a fence: (1) on the ‘upwind’ side, or in front of the fence, where it will pile at a 45 degree angle up to the fence height; and (2) the ‘downwind’ side, where it will be dropped between 5 and 15 times distance to the fence height. To prevent this phenomenon, a commercially available orange safety fence is being used at 4ft in height with 1x1 inch openings. On May 9, 2012 a wind storm tore the initial fence down. This was replaced and a double layer was used. If the fencing is damaged again, chicken wire fencing will be used to stabilize and strengthen the fencing.

Wind Fence

Mulch

Pecan mulch was acquired from Stahmann Farms, a local producer of pecans that are shipped around the globe. Debris during harvest (leaves and twigs) are collected and placed into a holding area until spring. They are then integrated into the soil to help the nutrient balance for the coming growing season. When plant material is broken down, nitrogen and other essential nutrients are integrated into the soil structure and increase the vitality of the plant growth in that area.

Mulch and BSNE

Chemical Suppressants

The chemical suppressants being used are polymer binders that are biodegradable through UV exposure. These will be broken down within a couple of months and will give a good idea of effectiveness versus longevity.

Top Seal and Dirt Glue are commercially available chemicals that provide temporary dust suppression through polymer binding and curing within and on top of the top soil profile. According to material provided, each compound has a life expectancy of 6 months to one year. During the breakdown process the layers are scoured off by the wind and sand creeping and saltation.

Chemical Binder Diagram

The Glycerin compound that is being used has been supplied by Rio Grande Biofuels. The compound is recycled cooking oil, or mono-alkyl ester of fatty acids derived from vegetable oils and animal fats. According to the National Biodiesel Board, crude glycerol/glycerin is biodegradable, nontoxic, and free of sulfur and aromatics.

Spraying Top Seal

Sampling, Data Collection and Analysis

The primary dust collection method will be using a Big Spring Number Eight (BNSE) sampler. The BSNE sampler is wedge-shaped instrument that creates a partial vacuum system, using a screen top to form a low pressure system inside to prevent wind turbulence during a wind storm. The manufacturer states that efficiency tests using fine sand less than 0.84mm diameter has a 90% collection efficiency which is not dependent on wind velocity. Once particles are settled within the sampler, the dust can be collected and weighed using the dry weight method at the Jornada Research Facility on NMSU campus. Collection of samples will be performed after a high wind event where wind exceeded 25 miles per hour in the plot area.

Image of a BSNE

This video features two of our graduate students showing how to empty the BSNE sampler.

Statistical Analysis Software (SAS) will be used to perform the statistical analysis of effective dust suppression between each treatment method. I will use inferential and descriptive statistics.

Treatment Sites

The set-up for the Colinas site is pictured below

Colinas Site Setup

Media

Below is a short video from KRWG News 22. It includes a short description of the dust control study and the poor air quality of the city.

Elizabeth Smith
Email: kitkatz@nmsu.edu