Monitoring of Multiple Air Pollutants in a Rural Northwest Valley: NASA AERONET, EPA Fine Particulate Matter and Local Sulfur Species

The Lewis Clark Valley (LCV) resides on the border of Washington and Northern Idaho and is home to nearly 50,000 residents along with a paper mill and other industries. With over 4.5 million deaths each year attributed to outdoor air pollution, air monitoring is important in both urban and rural areas. This study focuses on aerosol optical depth (AOD) at 440 nm to 500 nm, fine particulate matter (PM2.5), and sulfur species including sulfur dioxide (SO2) and total reduced sulfur (TRS) in the LCV. A NASA AERONET CIMEL Electronique CE-318 Sun-sky radiometer, an Idaho Department of Environmental Quality beta attenuation monitoring (BAM) PM2.5, and a Teledyne T102 ultraviolet-fluorescence sulfur analyzer were used to obtain ground-based data. Between July 2021 and June 2022, a correlation between aerosols and PM2.5 was present. High daily averages of AOD (3) and PM2.5 (128 μg/m3) occurred during the summer months when wildfire smoke was present. SO2 and TRS concentrations were not correlated with aerosols, but daily averages were as high as 2 ppbv and 8 ppbv, respectively. Continuous monitoring of these air pollutants through 2022 will discern long term trends in the area.