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Soundings: Local air some of nation’s worst

In the early 1970s, the oil-exporting states of the Middle East attempted to use oil as a political tool. They throttled back their exports, leading to long lines (and worse) at gas stations in the United States.

In the American car market, fuel efficiency suddenly became fashionable.

In the mid-1800s, French engineer Sadi Carnot found that the hotter the fire within an engine, the higher its efficiency.



Auto engineers in the 1970s redesigned their engines to run hotter.

When gasoline burns, atoms of carbon and hydrogen collide with, then combine with, atoms of oxygen from the air to create molecules of carbon dioxide and water, releasing energy in the process.




But air is only one-fifth oxygen; the other four-fifths is nitrogen. Nitrogen is almost inert – it hardly reacts. Rather, all those nitrogen molecules come between oxygen and carbon or hydrogen, slowing the reaction. Were it not for the interfering nitrogen molecules, wildfires would burn hotter and faster; they’d be harder to put out. (Cutting torches use pure oxygen).

Nitrogen is not totally inert, however; get it hot enough and it will combine with oxygen.

Nitrogen and oxygen atoms combine in various combinations to form NOx (pronounced “knocks”) – oxides of nitrogen. The oxide of nitrogen composed of a single nitrogen and a single oxygen atom – NO, nitric oxide – quickly latches onto another oxygen atom, to form NO2 – nitrogen dioxide, the reddish-brown gas that often poisons the sky over Sacramento.

But before it becomes NO2, nitric oxide can cause the formation of an odd form of oxygen – a molecule with three atoms of oxygen, instead of the usual two: ozone.

Ozone is hell on organic compounds – chemicals made from carbon (chemists once thought that such molecules could only be made within living organisms). Ozone attacks rubber and flesh: tires and lungs.

With its own exhaust adding to the “ozone precursor” molecules blowing east from the Bay Area, Sacramento has a hellatious ozone problem. The EPA has given the city until 2013 to clean up its air.

Downwind of Sacramento, the Sierra foothills also have an ozone problem, but with a difference.

During the day in the valley, sunlight converts other forms of NOx into NO, magnifying the amount of ozone created.

Once the sun goes down, however, the same nitric oxide that reacts to make ozone, reacts with ozone itself, and destroys it. Sacramento’s ozone readings drop after sunset, and continue dropping ’til dawn.

But because NO also reacts quickly with oxygen to become NO2, it doesn’t make it into the foothills. The air in the foothills remains rich in ozone throughout the night. When the sun comes up the next day, ozone levels climb higher yet.

On a 24/7 basis, foothill communities suffer a higher ozone burden than the upwind cities that create the ozone precursors. According to the American Lung Association, Nevada County residents breathe some of the unhealthiest air in the nation.

But that’s on average. On the eighth day of May, according to Joe Fish and Sam Longmire of the Northern Sierra Air Quality Management District, we had the dirtiest air in the United States. Several other days this month have been almost as bad.

A plan is being written to reduce Sacramento’s pollution loading of the air … and thereby clean the air of Nevada County. Conceding what a tough job this will be – especially given the increased traffic (“induced traffic”) that will come with the new roads Sacramento is planning – the plan would set a new deadline for Sacramento to clean up its air: 2020.

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Alan Stahler trained as a biologist and is an amateur astronomer. He teaches private enrichment classes for students of all ages. His science programs can be heard at noon on alternate Tuesdays on KVMR-FM (89.5).


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