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Research Program


The study of atmospheric fine particulate matter (defined as particles having an aerodynamic diameter of 2.5 mm or less) is of critical importance to both the scientific community as well as society at large, due to several studies indicating its role in increased morbidity and mortality for people living in urban areas. My research group has adopted the following multidimensional approach towards acquiring a greater understanding of atmospheric fine particulate matter.


  1. Measurement of source profiles for a number of important, but undefined, sources.
  2. Estimation and prediction of secondary aerosol formation.
  3. Investigation of the health effects of fine particulate matter.


All of these dimensions include both a laboratory and a field component. The advantage of a combined research program is that it allows us to address these important scientific and societal issues in a holistic manner.


David R. Cocker’s Web Page


My research is in the broad area of air quality systems engineering with emphasis on the investigation of the chemical and physical characteristics of atmospheric aerosols.  I am interested in investigating secondary organic aerosol (SOA) formation, source characterization of combustion derived particulate emissions, and field measurements of particulate in the atmosphere.  Atmospheric aerosols are of significant interest as they negatively impact human health, degrade visibility, and impact the Earth’s global radiation balance.


Current Research Group:


Visiting Scholars: Hiroyuki Hagino (JARI), His-Hsien Yang (Chaoyang University of Technology)


Assistant Research Engineer: Kwangsam Na


Post Doctoral Researcher: None


Ph.D. Students: Bethany Warren, Abhilash Nigam, Quentin Malloy, Ajay Chaudhary, Harshit Agrawal, Qi Li, Kent Johnson, Varalakshmi Jayaram, Shunsuke Nakao


Undergraduate Researchers: Lindsay Yee, Christina Zapata, Dylan Switzer, Clayton Stothers, Rebecca Austin, Karel Jansen, Anthony Turgman, Christina Hall, Mary Sheppe, Ravi Kurani, Tanfang Cao (Sam) 


Recent graduates: Chen Song (now at Pacific Northwest National Laboratory), Aniket Sawant (now at Johnson-Matthey), Sandip Shah, Ph.D. (now at Ford Motor Company), Cameron Switzer, Jean Wang, Karel Jansen, Hanhphuc Nguyen, Marisol Torres, Temitope Ogunyoku, Shimkiri Syiem, Nichlaus Elliott, Sheraz Butt, Gregory Aniol, Sampson Tang, Katrina Hess


Current Projects


Secondary Organic Aerosol Formation


Secondary organic aerosol is an important contributor to the atmospheric aerosol burden in urban areas.  SOA is derived from atmospheric reactions within the atmosphere that leads to oxidation products of low volatility that can partition from the gas-phase into the aerosol-phase.  Such studies are facilitated by the use of an environmental controlled chemical reactor.  We have recently completed the construction of a new state-of-the-art smog chamber to investigate the role of temperature, relative humidity, NOx, and hydrocarbons on the formation of atmospheric SOA.  These studies will increase our fundamental understanding of such processes and lead to the development of valuable models that simulate air quality on the urban, regional, and global scale.  Funding includes U.S. EPA and NSF.


Emissions from non-road engines


Considerable current research is being conducted on a variety of non-road sources.  This research focuses on the efficient transportation of goods and the impact of major ports on air quality.  We have recently conducted measurement campaigns to characterize emissions from marine vessels, locomotives, aircraft, yard-hostlers, and other port related equipment.  This work includes analyses of future control technologies and changes in fuel composition on emissions from these sources as well as comparison of the magnitude of each emission source. 


Emissions from Heavy-Duty Diesel Engines


Another research focus is on the role of diesel emissions from on- and off-road heavy-duty engines.  Diesel fuel powered vehicles are a significant contributor to air pollution in many urban areas and have become a focus of attention due to new EPA mandated emissions standards.  This work uses a mobile emissions laboratory (MEL) that is housed in a 53’ trailer that allows analyses of particulate and gaseous emissions from diesel fuel powered vehicles while transiting on-road at the level of quality specified by the US Code of Federal Regulations.  Current research focuses on the role of vehicle congestion and driving mode on emissions of gaseous, semi-volatile, and particle-phase emissions; the impact of the chemical composition of diesel emissions on the effectiveness of new control technology for particulate matter; the derivation of a chemical profile for in-use diesel emissions for estimating the impact of diesel emissions on local and regional air quality; and improvement of the emission inventories for such engines.  Funding for this research includes US EPA, California Air Resources Board (ARB), California Energy Commission (CEC), South Coast Air Quality Management District (SCAQMD), Cummins Engine Company, Detroit Diesel Corporation, International Truck & Engine, Caterpillar Incorporated, Volvo Truck Corporation, and Mack Trucks Incorporated.


Cocker, D.R., Shah, S.D., Johnson, K.C., Miller, J.W., Norbeck, J.M.  Development and Application of a Mobile Laboratory for Measuring Emissions From Diesel Engines I. Regulated Gaseous Emissions.  Submitted to Environmental Science and Technology, August 2003.  Accepted January 2004.


Cocker, D.R., Shah, S.D., Johnson, K.C., Miller, J.W., Norbeck, J.M.  Development and Application of a Mobile Laboratory for Measuring Emissions From Diesel Engines II. Sampling for Toxics and Particulate Matter.  Submitted to Environmental Science and Technology, August 2003.


Shah, S.D., Cocker D.R., Miller, J.W., Norbeck, J.M.  Elemental and Organic Carbon Emissions from Heavy-Duty Diesel Trucks.  Submitted to Environmental Science and Technology, September 2003.  Accepted January 2004.


Mira Loma Air Quality Study-Indoor and Outdoor Air Quality


We collected air quality samples in Mira Loma, California from September to January attempting to analyze the impact of mobile sources, particularly heavy-duty diesel vehicles, on indoor and outdoor air quality in the region.  Air samples were collected at ten different outdoor locations, inside twenty residences, and inside six rooms within the local high school.  24 hour integrated samples include chemical speciated PM2.5 samples (elemental analysis, ions (NH4+,NO3-,SO42-,Cl-), organic and elemental carbon), gas-phase ammonia, nitric acid, and carbonyls were collected for all locations.  The study in Western Riverside County has produced a large database of atmospheric pollutants in the indoor and outdoor environment.  Current research focuses on the relative exposure of a population to air pollutants outside of and within the homes and schools in the area.  We are currently mining this data set to provide valuable insight on the relative importance of indoor air quality, the transport of outdoor pollutants into the home, and the relative impact of indoor versus outdoor sources on air quality.  Funded by Riverside County and South Coast Air Quality Management District.


Publications related to this work include:


Na, K, Song, C., Sawant, A.A., Cocker, D.R. Primary and secondary carbonaceous species in the atmosphere of Western Riverside County, California.  Submitted to Atmospheric Environment, May 2003.


Na, K., Cocker D.R.  Trace Elements in Fine Particulate Matter within a Community in Western Riverside County, CA: Focus on Residential Sites and the Local High School.  Submitted to Atmospheric Environment, September 2003


Na, K., Cocker D.R.  Characterization and Source Identification of Trace Elements in PM2.5 in Western Riverside County, CA, Atmosphere.  Submitted to Atmospheric Environment, September 2003.


Sawant, A.A., Na, K., Zhu, X., Cocker, K., Song, C., Butt, S, Cocker, D.R.  Characterization of PM2.5 and selected gas-phase compounds at multiple indoor and outdoor sites in Mira Loma, California.  Submitted to Atmospheric Environment, January 2004.


Sawant, A.A., Na, K., Zhu, X., Cocker, D.R.  Chemical characterization of outdoor PM2.5 and gas-phase compounds in Mira Loma, California.  Submitted to Atmospheric Environment, January 2004.


India Air Quality Study


The study of ambient air quality is in its growth stage in India. Until approximately three years ago, New Delhi was widely regarded as the most polluted city in India. Its very large registered vehicle population was widely blamed for the high pollutant levels, especially two-stroke two-wheeled and three-wheeled vehicles. The focus of local agencies until recently has been largely on measurement of levels of U.S. EPA criteria pollutants such as oxides of carbon, sulfur and nitrogen, and particulate matter (total suspended particulate, or TSP, and particulate matter <10 µm aerodynamic diameter, or PM10) (Aneja et al., 2001). There have been no significant attempts at chemical characterization of urban particulate matter in India to date. Chemical characterization of particulate matter from emissions sources and ambient air facilitates the use of chemical mass balance-based source apportionment for estimation of the source contribution to ambient air quality in a particular area.


Last year, CE-CERT was able to obtain ambient samples of respirable suspended particulate matter (RSPM) through collaboration with local agencies, and to characterize emissions from two-stroke and four-stroke two and three-wheeled vehicles running on gasoline and compressed natural gas. A student from the prestigious Indian Institute of Technology Delhi (IIT-Delhi) was trained in chemical analysis and characterization of collected samples using GC-MS. A paper detailing the findings of our work has been published in Atmospheric Environment.  Funded by Ford Motor Company.


Sharma, D.N., Sawant, A.A., Uma, R., Cocker, D.R. 2003.  Preliminary chemical characterization of particle-phase organic compounds in New Delhi, India.  Atmospheric Environment.  37: 4317-4323.


Exacerbation of Allergenic Inflammation in the Lower Respiratory Tract by diesel exhaust particles


This study focuses on the relationship between allergenic inflammation in the lower respiratory tract and diesel exhaust particulate.  Our role has been the design and characterization of a small chamber designed for human exposure to diesel exhaust.  This project is in collaboration with UCLA, USC, and Rancho Los Amigos Medical Center. HEI funded.