Eggs and Air Quality: A Citizen Science Project
The Air Quality Egg Project in Grand Junction, CO
Guest Blogger: Gerald C. (Jerry) Nelson
My wife and I made the decision to retire to the Grand Valley of western Colorado after years of looking for a great place in the west with good weather, beautiful scenery, easy access to mountains, rivers, and desert, plus a reasonable community to live in. We thought we’d found it in Grand Junction, CO at the confluence of the Colorado and Gunnison Rivers, surrounded by mountains and deserts, where we were promised 300 days of sunshine, moderate winters, and low humidity to moderate the effects of the occasional hot days in summer.
Then I returned from a business trip in January to fly into a valley filed with gray layer of smog that rivaled Los Angeles in the 1970s. What the … ?
It turned out I was not the only person in the valley who was concerned about our air quality. I joined a newly formed, informal group called Citizens for Clean Air (Grand Junction) who were also concerned with air quality in the valley. I learned that our air quality problems were complicated, both by geography and business. The geography side of the story is a 10 mile wide valley at 4,500 ft, low range of mountains (the Book Cliffs) to the north that peaked at 7,000 ft, a national monument (the Colorado National Monument) on the south side that topped out at 6,500 ft, a massive flat top mountain (the Grand Mesa) on the east end of the valley that quickly rose a mile above the valley). The west end of the valley leads to the vast deserts of central Utah. So we had the classic conditions for winter inversions that trapped whatever pollution was generated in the valley or arrived there from Utah.
The pollution problems did not stop with smog in the winter. Agricultural burning in the spring and forest fires to our west in the fall contributed to periodic hazy days.
And on top of that we had ozone pollution that was especially bad in the summer. But where did all the pollution come from? Some was obvious (ag burning locally, forest fires to the west), some less obvious but probable (inefficient wood burning stoves used in the winter), and then a range of potential other culprits — leaks of volatile organics from the burgeoning fracking activities in our county and upstream on the Colorado River, vehicle exhaust on I-70 and local roads, and potentially even our native vegetation that produces a volatile organic (isoprene) to ward off the effects of ultraviolet light and ozone.
The local air pollution monitoring stations were limited. One for ozone, one for particulates, none for volatile organics or N2O. To understand where our pollution was coming from, we needed to find a way to increase the number of monitoring stations and scatter them around the valley. But official air monitoring equipment starts at around $2,000 and goes up from there. The question was whether we could use low-cost sensors (in the range of $200 per unit).
Spoiler alert: We don’t know yet.
After some research we identified the air quality eggs, manufactured by Wicked Device, LLC, in Ithaca, NY as a likely candidate.
The eggs claimed to monitor the gasses and particulates we were interested in and the price was right. They came several iterations (all did temperature and relative humidity, and then specialized on pollutants). And original versions we started working with were replaced with version 2 models in 2015. But how to test? We worked with the Mesa County health department, which ran the local monitors, to co-locate our eggs near the air intakes for the official monitors.
That way we could compare our results with official data.
Our initial results were mixed. The temperature and humidity sensors were close to the official readings, but the gas results were less than desirable. After some technical research we discovered that the ozone and NO2 sensors both responded in equal ways to the other gas. So if the official ozone reading were 50 ppb, the NO2 sensor would also read 50 ppb. And vice versa. It turned out that the sensors were designed to operate in a controlled environment.
Temperature and humidity were assumed to be relatively constant and no other polluting gasses. But we had our eggs in the wild, with big swings in temperature and humidity and potentially lots of other pollution types.
So back to the drawing board. The folks at Wicked Device found an NO2 sensor that wasn’t so sensitive to ozone. That potentially allows us to subtract the NO2 true value from the ozone value that was contaminated by NO2. And the egg code was open source so it was possible to modify if needed, and to download raw data that could be used to explore statistically the relationships that we see in the wild that sensor builders never experiment with. But this process is still underway.
For more projects and ways to get involved in monitoring air quality visit http://crowdandcloud.org/airquality