Nevada Count is often subject to summer ozone alerts. These alerts often scare local citizens, perhaps needlessly. Forest Mims III writes at Watts Up With That: Newly discovered EPA report says ozone measurements may be way off – cities may be in compliance
While the EPA has long known that ozone measurements are significantly biased upward by mercury vapor, the agency has required States to use ultraviolet ozone monitors subject to mercury interference. These ozone monitors blow air between an ultraviolet (UV) lamp and a UV detector. Ozone strongly absorbs UV, so reductions in UV arriving at the detector are proportional to the ozone in the air. But mercury vapor and other contaminants in air also absorb UV, thus, artificially inflating the amount of “ozone” that is measured. The bias can range from a few parts per billion to many more.
While writing a book on environmental science last spring, I came across a 1999 EPA report that described the mercury interference problem in detail: “Laboratory Study to Explore Potential Interferences to Air Quality Monitors.”
In the conclusion:
Low levels of mercury vapor show a marked impact on all three UV photometers at both low and high humidity. The two UV photometers with the heated scrubbers were affected the most. While heated metal scrubbers helped to reduce instrument bias for some VOCs, they seemed to increase bias due to mercury vapors.
This is another case where the EPA has caused billions of dollars of economic damage by promoting bad science. Let County leaders know about the WUWT report and demand local agencies to use chemiluminescent ozone monitors that are unaffected by mercury and other interferences.
In September of 2007, Dr. George Rebane wrote a detailed report on the problems of measuring ozone in Nevada County. A copy of that report is HERE. The study identifies flaws in the measuring process and now we find the that the measuring tools are flawed as well. Alert your political leaders to this government malfeasance.