Wednesday, September 12, 2012

Southern California Stinks

A strong rotten egg smell had Southern Californians plugging their noses and crying foul Monday as air quality investigators scrambled to determine if the sulfurous scent was coming from the Salton Sea.

Investigators from the South Coast Air Quality Management District spread investigators all over the region in an attempt to track the stench after being flooded with 200 complaints since midnight from across much of the district's 10,000 square miles, said Barry Wallerstein, executive for the agency.

Wallerstein said "several factors" indicate the odor could be coming from the Salton Sea, a 376-square-mile saltwater lake about 150 miles southeast of Los Angeles, but there is no definitive evidence yet of this or any other cause.

"The odor was extremely intense," said Janis Dawson of the Salton Sea Authority. "We actually thought that somebody had an accident, a broken sewage main, that's how strong it was."
Ah, hydrogen sulfide (H2S; with a few other obnoxious sulfur compounds in there for good measure).  Hydrogen sulfide is commonly formed in sediments in salty water by the anaerobic respiration of organic compounds using sulfate as the terminal oxygen acceptor, a process called sulfate reduction.  It is carried out by a large number of bacteria known as sulfate reducing bacteria (SRB for short). SRB are poisoned by oxygen, and can only live in areas where the oxygen has already been used up by other organisms.

Hydrogen sulfide is extremely toxic to us air breathing organisms, more toxic than cyanide (and probably much more common as well).  However, its extremely obnoxious odor makes it difficult to tolerate a lethal dose.  I strongly suspect the hand of evolution in that.  However, the odor fades quickly as you smelling apparatus gets poisoned, and people do succumb to it on a more or less regular basis.

Shallow salty bodies of water, with a high organic carbon production rate are prone to bouts of sulfate reduction in the water column, if for example, a gush of fresh water covers the surface, setting up a salt gradient which allows the bottom water to go anoxic.  It happens here in the Bay most summers, but the deep water is out of the reach of all but the violent mixing.  I've known the Bay to smell of H2S on occaision.

And the problem in Southern California?  It'll blow away, if it hasn't already.

No comments:

Post a Comment