Grantee Research Project Results
2010 Progress Report: Improvements in Emissions Inventories using Semi-Continuous Monitoring Data and Concentrations Field Analysis
EPA Grant Number: R834557Title: Improvements in Emissions Inventories using Semi-Continuous Monitoring Data and Concentrations Field Analysis
Investigators: Schauer, James J. , Turner, Jay R. , deFoy, Benjamin
Institution: University of Wisconsin - Madison , Washington University , Saint Louis University - Main Campus
Current Institution: University of Wisconsin - Madison , Saint Louis University - Main Campus , Washington University
EPA Project Officer: Chung, Serena
Project Period: June 1, 2010 through May 30, 2013 (Extended to May 30, 2014)
Project Period Covered by this Report: June 1, 2010 through May 30,2011
Project Amount: $499,777
RFA: Novel Approaches to Improving Air Pollution Emissions Information (2009) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
This project will focus on a three-city study using yearlong datasets from St. Louis, Milwaukee and Los Angeles. Emissions inventory data will be evaluated and improved for fine-particle elemental carbon, ultrafine-particle number concentrations and fine-particle organic carbon (using data from the EPA-funded St. Louis Supersite); speciated mercury compounds (using data from an EPA STAR Project in the Milwaukee region); and fine-particle carbonaceous particulate matter and associated precursor gases (using data from Los Angeles). Concentration Field Analysis (CFA) will be used to map emissions sources and identify unknown or poorly identified source regions during the yearlong study periods using stochastic backward and forward particle trajectories with a temporal resolution finer than 1 hour and spatial resolution finer than 5 km. The integration of high-quality monitoring data with multiple 3-D modeling approaches will assess existing emissions inventories and improve the understanding and representation of the temporal distribution of emissions, spatial distributions of emissions, missing sources, and inaccurate emissions estimates for point, mobile and area sources.
The goal of this project is to couple high-resolution meteorological modeling with existing high time-resolution atmospheric pollutant data sets to assess and improve emissions inventories.
CFA will be used to identify probabilistic source regions from the measurements independent of the emissions inventory data. Forward Lagrangian modeling then will be used to evaluate individual transport events. Cluster analysis will link yearlong trends with the hour-long episodes to assess the statistical relevance of the conclusions. Uncertainties due to the simulation of vertical dispersion will be constrained by comparing measurements and particle transport with forward Eulerian models.
The project will demonstrate the integration of CFA with multiple modeling approaches to develop a new strategy to assess, diagnose and improve emissions inventories. Direct improvements will be obtained for important atmospheric pollutants that historically have had poor emissions data, including fine-particle primary and secondary organic carbon, fine-particle elemental carbon, ultrafine-particle number and speciated atmospheric mercury. The close link between meteorological simulations, particle trajectories, grid modeling and existing data analysis will enable cross-evaluation of the conclusions. Yearlong analyses will improve the statistical relevance of the results. In addition, integration of measurements with meteorological analyses will help improve understanding of complex atmospheric transport such as lake effects, basin flows and urban heat islands.
Progress Summary:
The project consists of analyzing measurement data to evaluate emission inventories for Milwaukee, St. Louis and Los Angeles. We are approaching the research in that order. We have made considerable progress for Milwaukee and started on St. Louis.
For Milwaukee, we are analyzing measurements of mercury from April 2003 to March 2004 at Devil’s Lake State Park and from July 2004 to May 2005 in Milwaukee. We have performed nested, mesoscale meteorological simulations using the Weather Research & Forecast model (WRF) for the entire time period at both locations. We are using the North American Regional Reanalysis (NARR) project to provide meteorological boundary and initial conditions for the simulations. Sensitivity tests were performed on the model parameters for a summer and more recent winter episode. The simulations used three nested domains with grid resolutions of 27, 9 and 3 km. Backward trajectories were calculated for the two measurement sites for every hour of the measurements using WRF-FLEXPART and were converted to gridded fields of “Residence Time Analysis.”
Concentration Field Analysis (CFA) was carried out for the measurements of gaseous elemental mercury, reactive mercury and particulate mercury for both sites, revealing transport patterns and possible source regions. Two weaknesses of the CFA method were encountered: 1) CFA does not account for time-varying emissions, and 2) CFA does not differentiate sources along radial lines when the winds tend to be uniform. Therefore, we have used forward Eulerian modeling to deal with biomass burning and are working on implementing a more sophisticated inversion method to evaluate the emission strengths.
The mercury time series clearly is impacted by episodic biomass-burning events. We have obtained biomass-burning emission inventories based on MODIS fire detection for North America from Christine Wiedinmyer of NCAR. We used these to simulate mercury impacts at the measurement sites using CAMx, a 3-D Eulerian grid model that uses the same meteorological simulations as FLEXPART. This shows that some of the mercury peaks detected clearly are due to biomass-burning episodes.
A new, nested, inverse model is being developed that can handle the backward particle trajectories and the forward biomass-burning time series at the same time. This is based on a least-squares inversion of a matrix that includes the residence-time analysis fields and the CAMx time series. Ideally, the finer the grid used for the residence-time analysis, the higher the resolution of the results. However, the more grid points there are, the greater the degrees of freedom in the inversion method. This is constrained by the number of data points available: if there are too many degrees of freedom, the algorithm will be able to obtain an artificial fit that will not be physically meaningful. Therefore, we are using polar grids with fine resolution close to the site and exponentially increasing grid spacing along the radials. This is providing stable results. We are testing the method with pseudodata obtained from forward model simulations and sulfur dioxide concentrations from the measurement sites.
The purpose of the numerical analysis is to evaluate existing emission inventories. Therefore, we have analyzed the National Emission Inventory (NEI), the Toxics Release Inventory (TRI) and the Wisconsin State Emission Inventory. The TRI is released annually and has significant evolutions in mercury emissions. For the NEI, we analyzed the 2002 inventory and now are looking at changes with the latest inventory (2008). Results of the inverse method are being compared with these. In addition to source strengths, the inverse method provides an estimate of the impacts at the site due to different sources. This provides useful additional information on which sources are the most important when considering Milwaukee air quality.
For St. Louis, we are progressing along similar lines. WRF simulations were carried out for 1 year of measurements, and FLEXPART trajectories are being tested. We are evaluating the meteorological simulations by comparing specific episodes with observations and analyzing the behavior of the trajectories. Currently, we are in the process of analyzing the aerosol measurements in order to begin the CFA.
Journal Articles:
No journal articles submitted with this report: View all 17 publications for this projectSupplemental Keywords:
National Emissions Inventory, Toxics Release Inventory, TRI, mercury, air qualityProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.