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Dunes dust 

Are offroad vehicles creating air pollution on the Nipomo Mesa?

Whirling dust clouds rise in the air over the Nipomo Mesa in the springtime winds, kicking up concerns over the health impacts on people who breathe in the airborne particles.

Local air quality officials are taking a closer look at the blowing dust to see just where it’s coming from and what can be done about it. The nearby sand dunes are thought to be a major source—and the question is whether offroad vehicles at Oceano Dunes State Vehicular Recreation Area are contributing to the dust.

A year-long $200,000 scientific study of the dust is now underway, using a network of sophisticated sandcatchers to analyze the particles in the air.

Charged with finding a solution to the pollution problem, the San Luis Obispo County Air Pollution Control District has contracted with scientists from the Delta Group at the University of California at Davis to do the complicated analysis.

“We’re violating every state and federal standard for particulate matter in the air on the Nipomo Mesa. It’s a significant health concern, especially for the elderly, the very young, and people with respiratory problems,” explained Air Pollution Control Officer Larry Allen.

The tiny particles can lodge deep in the lungs once they’re breathed in, causing such health issues as asthma.

The air-district study is designed to show whether the windblown dust is coming from the natural sand dunes, the offroad vehicle riding area, farmland where crops are grown, the Conoco Phillips refinery coke pile, or the area’s dirt roads.

Samples of the airborne particles will be compared with the “fingerprint” of the soil from these sources, according to Dr. David Barnes, a research scientist with the Delta Group at UC Davis.

An earlier study showed that the tiny particles are “earth crustal matter—essentially sand,” Allen said. “The sand dunes are a major source, directly upwind of our monitoring sites. But we haven’t been able to determine if offroad vehicle use is contributing to the problem, or if it’s a natural phenomenon.”

The latest study uses sophisticated sandcatchers to trap dust blowing off the dunes at several locations: the offroad riding area of the Oceano Dunes State Vehicular Recreation Area; the Rancho Guadalupe Dunes Preserve, just across the county line south of the offroad riding area, where offroad vehicles aren’t allowed; and another non-riding area north of the State Vehicular Recreation Area. The goal is to determine whether offroad vehicle activity destabilizes the sand dunes and creates more windblown dust than the non-riding dune areas.

The possibility that the SVRA could be the major source of the windblown pollutant “seems to have some folks worried,” Allen said. But if the study points to the offroad riding area as the culprit, reducing the windblown sand could be as simple as planting a row of trees as a wind screen, he added.

“The high winds occur only over about six weeks in spring. Perhaps a few areas could be off-limits to riding during the windy period. But we would really have to sit down with State Parks and study what to do,” Allen said.

If unpaved roads in the area are shown to be the main contributor to the pollution problem, techniques are available to reduce road dust such as wetting the soil or lowering speed limits.

Research scientist Barnes of the Delta Group explained that the sandcatchers will operate continuously over six weeks, collecting and separating the windblown particles into eight different sizes for analysis.

“We get a signature of 24 elements from each sample, from sodium to lead, potassium to magnesium. We use an advanced light source—I like to call it the world’s biggest flashlight. We can discriminate between road dust and dust from China, for example,” Barnes said in a phone interview from his UC Davis office.

“Our data is statistically really good, with really good accuracy. It really takes a lot of time to see what is going on there. It’s not our intent to do any harm to the SVRA, it’s our intent to understand what’s going on,” Barnes said.

He praised the local Air Pollution Control District Board of Directors—made up of county supervisors, mayors, and city councilmembers from around SLO County—for “doing a really good job of trying to get the bottom of what’s going on,” adding, “They’re mandated to take care of the problem.”

Sampling of the airborne dust will continue until next February, with a draft report of the analysis expected by fall 2009.

Contributor Kathy Johnston may be reached at

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