The Oceano Dunes have been a magnet for research and off-roading for decades.
“Twenty years of research all points to one thing, which is that a long history of off-roading has exacerbated this issue and made the air quality downwind a lot worse on windy days than it otherwise would’ve been,” explained Karl Tupper, a senior air quality scientist for the San Luis Obispo County Air Pollution Control District (SLO APCD).
A study three years in the making by UC San Diego’s Scripps Institute of Oceanography looked at mineral dust particles in the dunes area.
“The elements that go into that mineral dust and estimated the total mineral dust coming from that using standard calculations. We also looked at sea salt, organic components,” said Dr. Lynn Russell, a distinguished professor of atmospheric chemistry for the Scripps Institution of Oceanography at the University of California in San Diego (UCSD).
According to this research led by Dr. Russell, “The association of high PM10 and PM2.5 with high wind conditions, even when recreational vehicles were limited at Oceano Dunes compared to prior years, indicates that dune-derived mineral dust is more likely to be primarily caused by natural forces (i.E. Wind) rather than human activities.”
This previous statement was published in a letter to Sarah Miggins, the deputy director of the Off-Highway Motor Vehicle Recreation Division within the California Department of Parks and Recreation, on Nov. 8, 2021.
“To really investigate the 2007 assumption of the Air Pollution Control District that all of the coarse aerosol was dust,” added Dr. Russell.
A claim that the SLO APCD denies.
“We have certainly maintained the off-roading on the Dunes is responsible for most of the exceedances of the PM standards recorded on the Mesa, but this is not the same thing as saying we expect that the composition of the PM to be all or nearly all mineral dust,” said Tupper. “In fact, as far back as 2007 we were reporting that other components (sea salt, inorganic aerosols) were present along with mineral dust in the PM on high PM days.”
The latest findings were based on samples collected during 30 days during the windy months of April and May.
The research study found “that on average, 14% of the BAM PM10 measured at the CDF site consists of mineral dust and 4% consists of sea salt.”
A number that the SLO APCD disagrees with.
“We are skeptical about the results," Tupper said. "Previous studies suggest that the mineral dust component on high wind days is much higher than 14%.”
As for the long-standing claim about off-roading...
“If the amount of dust is small then it seems like the contribution of off-road vehicles is going to be small too,” explained Dr. Russell. “Until you can show that that it’s a substantial portion, I think it’s hard to justify reducing vehicle usage.”
On Dec. 9, 2021 at 9 a.m., the California State Parks Departments’ Off-Highway Motor Vehicle Recreation Commission is holding a workshop to discuss this study.
In a statement, the agency said it could not discuss the report prior to the meeting.
“Because the Scripps interim year 3 report presented by Dr. Lynn Russell from UC San Diego is part of the agenda items to be discussed during the Off-Highway Motor Vehicle Recreation (OHMVR) Commission’s public workshop on December 9, OHMVR commissioners cannot discuss the report prior to the meeting pursuant to the Bagley-Keene Open Meeting Act,” said Jorge Moreno, information officer for the California State Parks Department.
“The samples were not collected according to any standard method and some of the assumptions that went into the analysis of the data, we don’t agree with,” concluded Tupper. “In contrast to the methods used by the APCD, the Scripps sampling apparatus is not approved by the EPA or any other agency for collecting regulatory PM samples.”
Dr. Russell said she is looking forward to the meeting with the California State Parks Department and added that she is not planning to request more funding to do research at the Oceano Dunes.
“It’s not surprising to me that they are critical of our work, but all of the issues they’ve raised are not relevant to the results,” said Dr. Russell. “It’s implicitly criticizing the fact that they haven’t made measurements of mineral dust until now, and if they have some, they haven’t released them.”
Dr. Russell said she would like the SLO APCD to do more mineral dust measurements to quantify its annual cycle to better understand the dunes.
For more information on the commission meeting, click here.