日期: January 28, 2022
Jonathan Bent, Ph.D., Senior Application Scientist, Environmental
ORDEQ Near-road Site
Picarro’s G2307 formaldehyde (H2CO) and methane (CH4) instrument ran during summer wildfire season in the town of Tualatin, OR at the near-road site operated by Oregon’s Department of Environmental Quality. The Tualatin site sits immediately adjacent to Interstate 5, south of Portland, serving as an important record of air quality in Northwest Oregon. Picarro loaned the G2307 to ORDEQ for a project to evaluate the instrument’s readings against concurrently-sampled 4,2-DNPH cartridges (EPA Method TO-11A for carbonyls).
By chance, the G2307 instrument recorded a significant wildfire signal in the days between August 11-17, the result of the nearby Bull Complex Fire (OR), and Schneider Springs Fire (WA), among many others. In Tualatin, over fifty miles from the nearest blaze, 5-minute averages of formaldehyde soared as high as 16 ppb, while federal reference method instrumentation at the near-road site displayed carbon monoxide values as high as 630 ppb, and PM2.5 as high as 54 ug/m3. Measurements of nitrogen oxides (NOx) dropped over the same period, suggesting the strong H2CO, CO, and PM signals did not directly stem from higher-than-normal traffic influence. Typical 8-hour average values for formaldehyde during summer months may exceed 5 ppb, but seldom reach much higher in the US without significant influence from fugitive emissions or wildfire smoke.
The remarkable record, a relative rarity due to the complexity of real-time H2CO monitoring, demonstrates the value of the Picarro G2307. Sitting with no adjustments for a month, the instrument was able to accurately and rapidly capture formaldehyde values which would have been completely missed by DNPH, which is typically measured for 8- or 24-hr averaged periods once every six days. Over the loan period, only five DNPH values were captured , with bookending samples recorded on Aug 12th and 20th significantly missing the peak concentrations observed by the Picarro. With the Picarro, not only were measurements reported with ~1 Hz temporal resolution, but in real time, not weeks later after laboratory analysis.
While the formaldehyde data from August of 2021 are remarkable, they represent only a briefly- and distantly-observed record of an air quality phenomenon—persistent widespread wildfire smoke—that has become increasingly common across the American West in recent years, one certain to continue as global temperatures rise due to climate change. The G2307 formaldehyde instrument offers a unparalleled capability to monitor this carcinogen so that officials can better understand the drivers of public health. The instrument also offers a timely opportunity for regulators to adopt new technology that meets the critical need identified by the Biden administration to modernize and simplify pollutant monitoring.
Operation and integration of the Picarro instrument was performed in collaboration with Matthew Shrensel, Air Quality Monitoring Metrologist at Oregon Department of Environmental Quality.