The origins of PM2.5 in Beijing China during the period of its worst conditions
Philip K. Hopke
Department of Public Health Sciences
University of Rochester School of Medicine and Dentistry
and
Center for Air Resources Engineering and Science
Clarkson University
In the period of 2012 to 2014, Beijing experienced some of its highest PM2.5 concentrations with resulting worldwide publicity. There have been many source apportionment studies reported for Beijing ranging from a 2012 report that traffic only contributed to 4% of the PM2.5 to a 2014 paper claiming that the January 2014 “airpocolypse” was due to secondary organic aerosol and secondary sulfate. In both of these cases, the results made no physical or chemical sense. Several additional studies have been published recently based on PM2.5 particle composition data measured in samples collected at Beihang University in Beijing. The most recent study used an enhanced data set in which water-soluble organic carbon and HULIS were measured and combined with OC/EC thermal fractions and gaseous pollutant data. These results were compared to CMAQ modeling done for the same time. In addition, direct emission measurements were made of the organic carbonaceous material being emitted from typical residential coal burning stoves that burn lump coal or briquettes. Parallel studies on other similar stoves found the emission of primary sulfate given the low temperature combustion of the sulfur during the startup and burnout phases of the fire. Ultimately, these results indicated a major role for residential coal/wood combustion contributions to the Beijing aerosol along with traffic and secondary nitrate as major contributors. The recent lower concentrations being observed may be the result of the effort by China to convert residential coal/wood combustion in the northern provinces to natural gas and electricity for space heating and cooking.
Biosketch: Dr. Philip K. Hopke is the Bayard D. Clarkson Distinguished Professor Emeritus at Clarkson University and Adjunct Professor in the Department of Public Health Sciences of the University of Rochester School of Medicine and Dentistry. Dr. Hopke was the Chair of EPA’s Clean Air Scientific Advisory Committee (CASAC), President of the American Association for Aerosol Research, and was a member of the more than a dozen National Research Council committees and a recent member of the NRC’s Board of Environmental Studies and Toxicology.