US Particulate Matter Air Quality Improves except in Wildfire-Prone Areas. McClure, C. D. & Jaffe, D. A. 115(31):7901–7906.
US Particulate Matter Air Quality Improves except in Wildfire-Prone Areas [link]Paper  doi  abstract   bibtex   
[Significance] Wildfires are a major source of fine particulate matter (diameter $<$2.5 µm; PM2.5), which is a health hazard. Since the mid-1980s, the total US area burned by wildfires has been increasing, with fires in the Northwest United States accounting for ∼50-60\,% of that increase. In the Northwest United States, we find a positive trend in the 98th quantile of PM2.5 in contrast to other areas of the country where PM2.5 is decreasing. This positive trend in PM2.5 is closely associated with total carbon (a marker of wildfire emissions). These results support model predictions of increasing wildfire occurrence and PM2.5 in a warming world. [Abstract] Using data from rural monitoring sites across the contiguous United States, we evaluated fine particulate matter (PM2.5) trends for 1988-2016. We calculate trends in the policy-relevant 98th quantile of PM2.5 using Quantile Regression. We use Kriging and Gaussian Geostatistical Simulations to interpolate trends between observed data points. Overall, we found positive trends in 98th quantile PM2.5 at sites within the Northwest United States (average 0.21 ± 0.12 µg·m-3·y-1; ±95\,% confidence interval). This was in contrast with sites throughout the rest of country, which showed a negative trend in 98th quantile PM2.5, likely due to reductions in anthropogenic emissions (average -0.66 ± 0.10 µg·m-3·y-1). The positive trend in 98th quantile PM2.5 is due to wildfire activity and was supported by positive trends in total carbon and no trend in sulfate across the Northwest. We also evaluated daily moderate resolution imaging spectroradiometer (MODIS) aerosol optical depth (AOD) for 2002-2017 throughout the United States to compare with ground-based trends. For both Interagency Monitoring of Protected Visual Environments (IMPROVE) PM2.5 and MODIS AOD datasets, we found positive 98th quantile trends in the Northwest (1.77 ± 0.68\,% and 2.12 ± 0.81\,% per year, respectively) through 2016. The trend in Northwest AOD is even greater if data for the high-fire year of 2017 are included. These results indicate a decrease in PM2.5 over most of the country but a positive trend in the 98th quantile PM2.5 across the Northwest due to wildfires.
@article{mcclureUSParticulateMatter2018,
  title = {{{US}} Particulate Matter Air Quality Improves except in Wildfire-Prone Areas},
  author = {McClure, Crystal D. and Jaffe, Daniel A.},
  date = {2018-07},
  journaltitle = {Proceedings of the National Academy of Sciences},
  volume = {115},
  pages = {7901--7906},
  issn = {0027-8424},
  doi = {10.1073/pnas.1804353115},
  url = {https://doi.org/10.1073/pnas.1804353115},
  abstract = {[Significance] Wildfires are a major source of fine particulate matter (diameter {$<$}2.5 µm; PM2.5), which is a health hazard. Since the mid-1980s, the total US area burned by wildfires has been increasing, with fires in the Northwest United States accounting for ∼50-60\,\% of that increase. In the Northwest United States, we find a positive trend in the 98th quantile of PM2.5 in contrast to other areas of the country where PM2.5 is decreasing. This positive trend in PM2.5 is closely associated with total carbon (a marker of wildfire emissions). These results support model predictions of increasing wildfire occurrence and PM2.5 in a warming world.

[Abstract] Using data from rural monitoring sites across the contiguous United States, we evaluated fine particulate matter (PM2.5) trends for 1988-2016. We calculate trends in the policy-relevant 98th quantile of PM2.5 using Quantile Regression. We use Kriging and Gaussian Geostatistical Simulations to interpolate trends between observed data points. Overall, we found positive trends in 98th quantile PM2.5 at sites within the Northwest United States (average 0.21 ± 0.12 µg·m-3·y-1; ±95\,\% confidence interval). This was in contrast with sites throughout the rest of country, which showed a negative trend in 98th quantile PM2.5, likely due to reductions in anthropogenic emissions (average -0.66 ± 0.10 µg·m-3·y-1). The positive trend in 98th quantile PM2.5 is due to wildfire activity and was supported by positive trends in total carbon and no trend in sulfate across the Northwest. We also evaluated daily moderate resolution imaging spectroradiometer (MODIS) aerosol optical depth (AOD) for 2002-2017 throughout the United States to compare with ground-based trends. For both Interagency Monitoring of Protected Visual Environments (IMPROVE) PM2.5 and MODIS AOD datasets, we found positive 98th quantile trends in the Northwest (1.77 ± 0.68\,\% and 2.12 ± 0.81\,\% per year, respectively) through 2016. The trend in Northwest AOD is even greater if data for the high-fire year of 2017 are included. These results indicate a decrease in PM2.5 over most of the country but a positive trend in the 98th quantile PM2.5 across the Northwest due to wildfires.},
  keywords = {*imported-from-citeulike-INRMM,~INRMM-MiD:c-14620779,~to-add-doi-URL,air-pollution,fire-emissions,human-health,particulate-matter,united-states,wildfires},
  number = {31}
}

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