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Algae overtaking the Salton Sea due to high nutrient load(eutrophic conditions). Source: https://desertsearat.wordpress.com/2011/12/07/algal-blooms-fish-die-offs-oh-my/

In the past few months the Salton Sea has been putting off a worrisome odor with increasing frequency. The smell has been strong enough that the South Coast Air Quality Management District (SCAQMD)[1] has issued odor warnings to people living in the immediate area. For residents of the Coachella Valley, the key questions here are, “What makes the Salton Sea stink?” and “Is that smell dangerous?”

So what does make the Salton Sea stink? In short, hydrogen sulfide, H2S, is bubbling up from the Sea itself, the same chemical that gives rotten eggs their odor.[2] Every lake emits some hydrogen sulfide but the Salton Sea is in a particularly extreme situation for two reasons. First, the Sea has high levels of fertilizer from agricultural runoff which supports dense algal blooms. Second, it has chronically low oxygen levels (anoxic conditions) due to these thriving algae populations.[3] These two factors together make the Salton Sea a perfect breeding ground for bacteria which consume algae and nutrients and release enough H2S gas to stink up the whole Coachella Valley.

How dangerous is hydrogen sulfide? It all depends on the dose. According to the Occupational Safety Hazard Administration (OSHA), if H2S in the air reaches a concentration of 2 to 5 parts per million (ppm) it will make you nauseous, cause your eyes to tear up, cause headaches, and aggravate asthma. At above 50 ppm, one is likely to have a very upset stomach and loss of appetite. Above 100 ppm there is coughing, eye irritation, and loss of the sense of smell in a matter of minutes. Above 1000 ppm hydrogen sulfide exposure will kill you in an instant. All that aside, there is no known long term health effects from low concentrations of hydrogen sulfide exposure.[4]

Now that we’ve established a scale of effects, consider that South Coast Air Quality Management District (SCAQMD) issued their advisory about the Salton Sea when the hydrogen sulfide levels reached 0.03 ppm. That’s more than 50 times lower than the lowest level OSHA recognizes as causing headaches. However, 0.03 ppm (30 parts per billion) is well beyond the smell threshold for hydrogen sulfide—in fact, it just down right stinks.

What can be done about the smell? There are a few options. As mentioned earlier, the fertilizers that enter the Salton Sea are the cause of algal blooms that lead to the production of hydrogen sulfide. Phosphorus, one of the nutrients involved, could be removed by adding aluminum sulfate to the Sea, which would make aluminum phosphate a compound that could settle out of the sea, limiting nutrients and preventing algae from growing. However, that would be somewhat expensive and involve $13 million dollars of alum a year (priced in 2008 dollars) just to treat the New River, before considering other costs such as construction and personnel.[3] A long-term solution is for farms to stop dumping un-treated agricultural runoff into the Sea. However, this would then contribute to the eventual drying of the Sea, and all the problems that entails. An alternative option could be harvesting the algae from the sea to produce biofuels as an economically minded approach.[6]

Written by: Samuel Patton

[1] South Coast Air Quality Management District. “SCAQMD Issues Odor Advisory due to Elevated Hydrogen Sulfide Levels Near Salton Sea,” October 12, 2015. http://www.aqmd.gov/home/library/public-information/2015-news-archives/h2sadvisory101215.

[2] Reese, Brandi Kiel, Michael A. Anderson, and Christopher Amrhein. “Hydrogen Sulfide Production and Volatilization in a Polymictic Eutrophic Saline Lake, Salton Sea, California.” Science of the Total Environment 406, no. 1–2 (November 2008): 205–18. doi:10.1016/j.scitotenv.2008.07.021.

[3] Rodriguez, I., C. Amrhein, and M. Anderson. “Reducing Dissolved Phosphorus Loading to the Salton Sea with Aluminum Sulfate.” In Developments in Hydrobiology, 201:37–44, 2008.

[4] Occupational Safety and Health Administration. “Safety and Health Topics – Hydrogen Sulfide,” n.d. https://www.osha.gov/SLTC/hydrogensulfide/hazards.html.

[6] Shelef, G, A Sukenik, and M Green. “Microalgae Harvesting and Processing: A Literature Review.” Solar Energy Research Institute, August 1984.