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Foul odor in Southern California appears to be dissipating

September 11, 2012 | 12:17 pm

Salton Sea

Regional air quality managers said on Tuesday they are hoping samples collected in the Coachella Valley near the Salton Sea can put to rest the mystery of the epic stink that descended over much of Southern California. Complaints about the smell, meanwhile, have declined significantly.

And it was an “epic” stink, said Sam Atwood, a spokesman for the South Coast Air Quality Management District.

For context: the smell from huge wildfires burning for days usually doesn’t travel more than tens of miles, he said. The leading theory is that the rotten egg smell, carried aloft on the wings of a powerful storm, traveled from the Salton Sea, about 150 miles away.

Atwood said he doesn’t remember any smell flying that far.

“Lacking any other plausible hypotheses, it’s looking like the most likely candidate is the Salton Sea,” he said. “We sent out a number of inspectors to the Coachella Valley and other places where odors may have originated from landfills and oil refineries. That was all negative.”

The good news is that complaints about the stinky odor have dramatically declined. As of about 5:30 p.m. Monday, there had been 225 complaints, Atwood said. Since then there have been less than 10, though the “sulfur-type” odor still remains in some areas, though greatly diminished in funkiness.

Air quality managers were so astounded that a smell could travel so far that late Monday they called an air quality modeler to use sophisticated computer modeling to see if it was possible on a “theoretical basis,” Atwood said.

“Theoretically, it’s possible,” he said, though he added that the concentration of hydrogen sulfide believed to be causing the smell “would have been so high that it would cause any irreperable harm to human health.” 

Atwood said a meteorologist for the AQMD has looked at the thunderstorm reports, and that along with wind-measuring instruments in the Coachella Valley, they determined that winds of more than 60 mph blowing from the southeast probably blew the rank odor to the Los Angeles Basin.

“That’s unusual because usually the winds are blowing in the opposite direction,” he said.

Experts said the winds from the Sunday night storm likely unsettled the fetid layers of water near the bottom of the Salton Sea, bringing them to the surface. Andrew Schlange, general manager of the Salton Sea Authority, said in the last week a large number of fish died in the 376-square-mile body of water, likely exacerbating the problem.

But for the odor to travel as far as it did, it would need atmospheric help. And Tim Krantz, a professor of environmental studies at the University of Redlands, said he believes the stench got a mighty assist from a southeasterly storm known as a “Chubasco.”

 “The storm originated in the Gulf of California and the Sea of Cortez, and hit the Imperial Valley and Salton Sea,” he said. “We had huge squalls and pretty heavy winds in the Coachella Valley. The winds pull the surface layers of the sea off from the southeast to northwest, and that surface water is replaced from the depth.”

That deeper water is more saline, smelly and less fresh than the water it replaces on the surface, he said. During the hot summers, in particular, there is a buildup at the bottom of sulfur dioxide from decaying algae blooms and other organic material. That explains the rotten egg smell.

It makes the Salton Sea a stinky place on a good day, and the last few days have not been good days.

Krantz said the Salton Sea has lost much of its depth, being only about 50 feet at its deepest point. That means it doesn’t take as potent a weather event as it did in the past to cause an upswell that sends the rank water near the bottom to the top.

Atwood said the AQMD is hoping to have results from the air samples sometime Tuesday afternoon.

“If it’s hydrogen sulfide, we’ve taken samples at the Salton Sea, and took them sort of on an east-west track all the way to Riverside,” he said. “So if you saw a descending concentration with the highest levels at the Salton Sea and diminishing somehow the further you went, that tells you the source of the smell probably is the Salton Sea.”


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Photo: Officials suspect the stench wafting over Southern California is the result of the annual fish die-off at the Salton Sea, shown here in November 2011. Credit: Arkasha Stevenson / Los Angeles Times