Apportionment of visibility degradation to sources of PM_2.5 in rural and urban Kansas

Visibility is the most apparent reflection of air pollution caused by fine particles and gaseous pollutants. The EPA has suggested identifying the key pollutants and sources that are degrading visibility. Previous studies have identified PM_2.5 sources in Kansas including agricultural, industrial, soil, traffic, diesel, and burning using Unmix and PMF models. The objectives of this study were to investigate the temporal visibility variation in rural and urban Kansas from 2001 to 2016, to detect the impacts of PM_2.5 sources to visibility under various weather condition, and to quantify impacts from PM_2.5 sources and metrological parameters. The speciated PM_2.5 data from IMPROVE network Flint Hills and CSN network Kansas City sites were representing suburban and urban site in Kansas. Visibility and historical weather data were from the NOAA database. Tobit model analysis was employed in quantifying visibility impact factors. The annual averaged visibility was 8.7 miles in urban site, and 9.03 miles in rural site. Summer afternoon visibility was found higher than winter mornings, due to the favorable weather condition. Precipitation was a significant impact factor in both site, lead to a 0.5-mile and 0.86-mile visibility degradation in rural and urban site, respectively. RH greater than 50% was negatively related with visibility impairment. Based on the Tobit model result, agricultural PM_2.5 source was described the most significant impact factor of visibility degradation in both sites.