2010 Progress Report: Impact of Global Change on Urban Air Quality via Changes in Mobile Source Emissions, Background Concentrations, and Regional Scale Meteorological FeedbacksEPA Grant Number: R833372
Title: Impact of Global Change on Urban Air Quality via Changes in Mobile Source Emissions, Background Concentrations, and Regional Scale Meteorological Feedbacks
Investigators: Kleeman, Michael J. , Chen, Shuhua , Schauer, James J.
Institution: University of California - Davis , University of Wisconsin Madison
EPA Project Officer: Hunt, Sherri
Project Period: March 1, 2007 through February 28, 2011 (Extended to February 28, 2013)
Project Period Covered by this Report: March 1, 2010 through February 28,2011
Project Amount: $900,000
RFA: Consequences of Global Change For Air Quality (2006) RFA Text | Recipients Lists
Research Category: Climate Change , Air , Global Climate Change
Objective:The current project aims to quantitatively assess the consequences of Global Change on California air quality by (1) measuring emissions from mobile sources powered by alternative fuels as a function of temperature and humidity, (2) creating a source-oriented PM module for the Weather Research & Forecasting (WRF) model to quantify feedback between air quality and regional meteorology, and (3) calculating California air quality in the year 2030 during a range of O3 and PM2.5 pollution events.
The WRF-CHEM framework was enhanced to allow nested domains when using the 6D PM chemistry variable and the 4D gas chemistry variable. This allows simulations with fully source-oriented variables in nested domains to study feedback effects at all spatial scales of interest. All domains are initialized with specified concentrations. Outer domains also have specified boundary conditions while inner domains receive their boundary conditions from the parent domain and pass their concentrations back to the parent domain using 2-way feedback algorithms.
Plume-rise calculations were added into the WRF-CHEM framework with the 6D PM chemistry variables and 4D gas chemistry variables. These calculations are performed during the WRF simulation so that the thermal plume rise can be calculated as a function of atmospheric conditions.
The State Air Pollution Research Center (SAPRC) chemical mechanisms have been added to the source-oriented WRF-CHEM model. These chemical mechanisms have demonstrated their ability to predict nitrate buildup in the San Joaquin Valley during winter stagnation events. The SAPRC gas-phase mechanisms can also be easily used in a source-oriented configuration to support future calculations for nitrate and sulfate source apportionment within WRF-CHEM.
A source-oriented cloud variable has been incorporated into the WRF-CHEM model to follow source-oriented particles as they activate to form cloud droplets. Particle activation is based on the chemical composition of each source-oriented particle combined with Kohler theory. The microphysics calculations are being incorporated into the Lin microphysics scheme. Preliminary testing is being conducted simulating fog events in the San Joaquin Valley, with further extension to full cloud cycles planned in the coming year.
A time-averaged output variable has been created in the source-oriented WRF-CHEM model to save hourly-averaged surface concentrations for 6D PM chemistry variables and 4D gas chemistry variables. This option reduces disk space requirements and speeds up model simulations due to reduced storage requirements.
The capability to restart simulations has now been included to the 6D aerosol and 4D gas-phase concentration arrays by seeking advice from the architects of the WRF and WRF-CHEM model.
Simulations have been carried out over California using spatial resolution ranging from 36 km down to 0.25 km. The domains with the finest resolution below ~1 km employ the Large Eddy Simulation (LES) feature of WRF. These simulations are being used to study a variety of problems, including source contributions to elemental carbon concentrations in Oakland and nitrate production mechanisms with feedback to meteorology in the San Joaquin Valley.
Data analysis has been completed for a study examining emissions from a commercial agricultural tractor operating with a range of biodiesel blends, including B0, B25, B50, B75 and B100. The results show the use of biodiesel fuel for economic or climate change mitigation purposes can lead to reductions in PM emissions and a co-benefit of EC emissions reductions. A manuscript describing results will be submitted during summer 2011.
Data analysis has been completed for a study examining emissions rates and composition of hazardous air pollutants from a commercial agricultural tractor operating with a range of biodiesel blends. Diluted and aged exhaust was analyzed for carbonyls, Volatile Organic Compounds (VOCs) and Polycyclic Aromatic Hydrocarbons (PAHs). The results show that the use of biodiesel fuel for economic or climate change mitigation purposes can lead to reductions in emissions of hazardous air pollutants, and decrease the toxicity risk of overall emissions from diesel engines. A manuscript describing the results will be submitted during summer 2011.
Data analysis has been completed for a study to examine the effect of changes in ambient temperature and fuel type in fine particle emissions from light-duty vehicles including a gasoline-electric hybrid vehicle, a CNG-gasoline dual fuel vehicle, an ethanol-gasoline blends flex fuel vehicle and a CNG powered vehicle. These vehicles were tested in a chassis dynamometer under controlled conditions of ambient temperature following three back-to-back LA92 unified driving cycles under hot start. Although an increase in ambient temperature results in decreases of about 30% in total particle emissions throughout a whole test, particle number concentrations as a function of time, and particle number size distributions showed that for all tested vehicles, there is no clear effect of ambient temperature in fine particle emissions at the selected ambient temperature range.
Data analysis has been completed for a study to examine the implications of changes in black carbon emissions through the strategic use of biodiesel blends. The results indicate that blending biodiesel with traditional diesel produces important reductions in BC emissions from an agricultural tractor. Comparisons to projections of global and North American CO2 and BC emissions leads to the conclusion that the strategic use of biodiesel blends in diesel-powered vehicles could produce an immediate reduction in global warming rates.
Future Activities:Four to five manuscripts are in preparation with submission planned during summer 2011 describing: (1) the role of ambient temperature of diesel engine emissions, (2) the impact of biofuels on current and future on-road diesel engine technologies, and (3) the role of seed aerosol on emissions of particulate matter from gasoline and diesel engines.
During the coming reporting period, we will fully link the source-oriented variables and the cloud chemistry models in the WRF-CHEM calculations. Simulations will be conducted for the State of California during the years 2000 and 2050. Results will be compared to simulations using the WRF model coupled (offline) with the UCD source-oriented air quality model.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other project views:||All 6 publications||6 publications in selected types||All 6 journal articles|
||Okuda T, Schauer JJ, Olson MR, Shafer MM, Rutter AP, Walz KA, Morschauser PA. Effects of a platinum-cerium bimetallic fuel additive on the chemical composition of diesel engine exhaust particles. Energy & Fuels 2009;23(10):4974-4980.||