Salton Sea Dust Study


Last updated 8/8/2017 at 9:03am

Below is an extract from an article in 'Medical Health News' discussing findings relating to the dust problems at the Salton Sea.

Anyone who lives along the shore of the Salton Sea will tell you how the winds can rake across stretches of exposed lakebed and send dust floating through their neighborhoods. But until recently, no one had real estimates of how much dust from the lakebed is in the air around the lake on any given day.

Now scientists from the University of California, Riverside, have looked into that question, and they have an initial answer.

The researchers examined soil from exposed lakebed, or playa, around the shrinking lake and also took samples from the surrounding desert. They measured particles in the air – specifically PM10 – at Bombay Beach and Salton City in August 2015 and February 2016.

And how much of the lung-harming particles in the air came from the dusty lakebed on average?

Approximately 10 percent.

The rest of the PM10 in the air included dust from the surrounding desert (approximately 45 percent of the particles) as well as other manmade air pollution.

Those results come with several caveats. The researchers took air samples during periods totaling 18 days, and not during a dust storm or especially windy weather. Their study also didn’t include air samples from other communities near the lake. But the research did show that a significant amount of dust in the air is coming from the exposed lakebed – and the lake is about to shrink dramatically in the coming years.

“Of course we expect that more playa will be exposed, so we expect the contribution of playa to go up,” said Roya Bahreini, an associate professor of environmental sciences who led the study. “For human health, the first concern is just the increased particulate matter concentration.”

PM10 is airborne particulate matter less than 10 microns in size, or about one-seventh the thickness of a human hair. The particles are small enough to reach the deepest parts of the lungs, and studies have shown links between high levels of particulate matter and higher rates of asthma as well as respiratory and cardiovascular diseases.

Imperial County already has the highest rate of asthma-related emergency room visits for children in California, and the problem is expected to get worse as tens of thousands of acres of lakebed are left high and dry around the lake over the next decade.

In their study, Bahreini and her research team cited concerns that heavy metals and pesticides may be in the dust that’s given off from the dry shorelines. They noted that previous studies have found selenium, cadmium, nickel and other elements at “levels of ecological concern” within the lakebed soil.

The researchers collected 25 soil samples from the playa around the saltwater lake and 88 soil samples from the surrounding desert, and analyzed those samples for 15 elements ranging from aluminum to potassium.

They found that the salty, crusty soil of the dry lakebed, when compared to the soil from other desert sites, has significantly higher levels of calcium, selenium and, not surprisingly, sodium. Establishing the “signatures” of playa dust and desert dust, Bahreini said, enabled the researchers to examine how much of the airborne dust came from the lakebed.

The scientists also analyzed their PM10 samples to see whether trace elements including cadmium, selenium, chromium, arsenic, manganese and nickel were in the air at toxic levels. They found the average concentrations of each of those elements – most of which are heavy metals – were well below the California Environmental Protection Agency’s chronic toxicity levels, which are referred to as “reference exposure levels.”

Nickel was the only one that ever exceeded that threshold during the study, and only during three of the 25 sampling periods. On average, nickel was well below the threshold.

“At these levels, we don’t see toxicity concerns – at least with the elements,” Bahreini said. “So that’s good.”

They didn’t analyze the dust for pesticides, however, and various other questions remain to be studied.

Bahreini stressed that measurements should be taken over longer periods of time and at more sites to fill in more of the unknowns. More monitoring, she said, would show how much dust emissions from the playa change depending on the weather conditions, and to what extent the amounts of dust vary around the lake.

The study was co-authored by researchers Alexander Frie, Justin Dingle and Samantha Ying, and was published last month in the journal Environmental Science and Technology. The findings were announced by UC Riverside this week.

Rich Reynolds, a professor of Earth sciences at the University of Minnesota who researches dust, said he thinks the scientists did good work within the scope of their study, “but we don’t know anything really about the longer term potential for the toxicity of future dust, or lack thereof.”

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