In the following soundscapes you can listen to the air quality at study sites established across California by air pollution scientists at the University of California-Berkley's Department of Environmental Science, Policy, and Management, where new efforts are underway to better understand the air we breathe and to devise new efforts to improve our polluted areas.
Take a listen.
The Caldecott Tunnel, Oakland, CA
The Caldecott Tunnel cuts east from Oakland through the Berkley Hills, linking greater Contra Costa County with the Bay area. To capture the direct emissions of cars and trucks (which often vary greatly from projected emissions) we dangled an air sampler from a ventilation passageway above the busy road. What you hear in the soundscape is an eerie mixture of highly unsaturated compounds called "polycyclic aromatic hydrocarbons" (those distinct chirps at the beginning) and complex, saturated heavy hydrocarbons (the long, low droning chords at the end). Both of these result from burning fossil fuels. And many are dangerous carcinogens, mutagens, and teratogens -- linked to cancers, gene mutations, and birth and developmental defects.
The town of Bakersfield sits in the middle of California's Central Valley on swampland reclaimed from the nearby Kern River. It hosts, supposedly, the world's largest ice cream plant (Dreyer's Grand!) and sits in one of our country's most productive oil counties (Kern County). It is also, according to the American Lung Association, America's most air-polluted city. You'll notice it sounds a lot like a contained highway tunnel -- the result of fresh hydrocarbons from a main trucking highway and oil and gas fields surrounding the sampling site.
Several years ago almost 100 air and climate scientists joined forces to resolve a lingering question in atmospheric science: Why do existing air quality models under-predict urban particulate (unhealthy airborne particle) concentrations by a factor of between two and 10? Their efforts met on the campus of Caltech in Pasadena, which sits just downwind of greater Los Angeles.
Because it is so close to LA and major shipping ports, you would expect Pasadena to sound the same as Bakersfield, or perhaps the Oakland tunnels. But in Southern California winds blow in from the ocean and trap the smog of LA at the foot of the surrounding San Gabriel Mountains before carrying it down to Pasadena. The usual hydrocarbon slurry then has a chance to "cook" in the oxidizing atmosphere of the hot mountain foothills. The resulting soundscape is more bubbly than the pure hydrocarbon samples above, as you can hear the new presence of complex oxygenated compounds.
The High Sierras
In a remote pine forest deep in the Sierra Mountains we gathered particulate data from the top of a swaying tower, which was installed to take measurements from above and inside the tree canopy. This soundscape starts with bubbly, diverse tones -- the result of small compounds (smaller compounds show up earlier in the data and hence earlier in the soundscape) that plants release to attract or repel insects. When you smell the sharp tang of pine pitch or fragrance of mountain laurel, you are smelling the volatile chemicals produced by the plant, which have evaporated and taken to the air, where hungry herbivores and pollinators can detect them.