Date/Time
Date(s) - 28/11/2024
1:30 pm - 2:20 pm

Title: Advances in Source Apportionment for PM and VOCs

Date: Thursday November 28, 2024

Time: 1:30-2:20pm

Room: ABB 165

Host: Dr. Joseph Okeme & Dr. Greg Slater

Abstract: 

As part of the characterization of air pollutants to provide input into health assessments or development of mitigation strategies, it is necessary to identify the pollutant sources such that the most important ones can be targeted for control to provide effective and efficient air quality improvements. The most commonly used tool for deconvoluting the composition patterns in particulate matter (PM) or volatile organic compounds (VOCs) into source contributions is positive matrix factorization (PMF). With the advent of the U.S. Environmental Protection Agency’s version in 2014, it quickly became widely applied.  Although it works well, further improvements are possible.  Factor analysis methods like PMF depend on having samples with zero or very low contributions from each source type. However, the meteorology also plays a role in the ambient concentrations since pollutants are emitted into the air with different volumes of air depending on time of day, solar radiant energy, and wind speed. Thus, an approach has been developed to normalize the data to reduce the influence of differences in the dispersion conditions.  Multiple applications have now demonstrated its value for both hourly and 24-hour integrated sample analyses. VOCs represent a greater analytical challenge because of the differences in their chemical reactivity depending on just which compounds are being included. Some highly reactive compounds like isoprene are critical since it is the most abundant biogenic VOC, but it is also highly reactive. Thus, the analysis would like underestimate the biogenic VOC contributions. Using a photochemical age-based parameterization method, it is possible to estimate the “initial” concentration of the VOCs. The “initial” concentration is that which would have been present if there had been no reactive losses. The analysis of the actual dispersion normalized concentrations provides the “original” concentrations.  The source specific VOC concentrations at the measurement site represent the values to which the population is exposed.  The difference between the “initial” and “original” source specific concentrations represents the “consumed” VOCs.  Those consumed VOCs are important for policy development since it is the compounds that were reacted away that went to form secondary ozone and secondary organic aerosol.  These advances provide more reliable estimates of the source-specific impacts of PM and/or VOCs and thus, more robust health effects estimates and more reliable mitigation strategies.

Biography: 

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. He was the founding Director of the Center for Air Resources Engineering and Science (CARES), and the Founding Director of the Institute for a Sustainable Environment (ISE). Dr. Hopke was the Chair of EPA’s Clean Air Scientific Advisory Committee (CASAC), President of the American Association for Aerosol Research (AAAR) and was a member of the more than a dozen National Research Council committees and a member of the NRC’s Board of Environmental Studies and Toxicology. He is a fellow of the International Aerosol Research Assembly, the American Association for the Advancement of Science, the Air and Waste Management Association, and the AAAR. His research interests include: Chemical characterization of ambient aerosol samples; Multivariate statistical methods for data analysis; Emissions and properties of solid biomass combustion systems; Characterization of source/receptor relationships for ambient air pollutants; Experimental studies of homogeneous, heterogeneous, and ion-induced nucleation;  Indoor air quality; Exposure and risk assessment.  He is currently a Co-Editor-in-Chief of Science of the Total Environment. He currently has 941 peer reviewed journal publications. Professor Hopke received his B.S. in Chemistry from Trinity College (Hartford) and his M.A. and Ph.D. degrees in chemistry from Princeton University.