University of California, Riverside

Bourns College of Engineering

David Cocker

Faculty Profile

Faculty Profile

David Cocker

Professor of Chemical & Environmental Engineering
David Cocker

Ph.D. Environmental Engineering Science
Caltech, 2001

Bourns Hall A221
University of California, Riverside
Riverside, CA 92521

Telephone: 951-827-2408
Fax: 951-827-5696
Personal Webpage

Former Institutions: None


  • Ph.D., Environmental Engineering Science (2001), Caltech
  • M.S., Environmental Engineering Science (1998), Caltech
  • B.S., Environmental Engineering (1996), UC Riverside
  • B.S., Chemistry (1996), UC Riverside


  • Bourns College of Engineering Excellence in Teaching Award, 2004 - 2005
  • NSF Career Award, 2005


  • NSF Graduate Fellowship
  • NSF Career Award

Research Areas

My research program focuses on the physical and chemical processes leading to aerosol formation in the atmosphere. Aerosols, defined as fine liquid or solid particles suspended in the atmosphere, cause visibility degradation, property damage, act as cloud condensation nuclei, and are associated with increased morbidity and mortality. Identifying the atmospheric processes, which lead to aerosol formation, is critical in understanding how particles affect, both directly and indirectly, regional and global air quality. Specific areas of interest include: Gas-to-particle conversion processes; physical and chemical characterization of emissions; ambient and indoor air quality; health effects.

Gas-to-Particle Conversion: My experimental work investigates gas-to-particle conversion processes driven by gas-phase oxidation of hydrocarbons. Studies of aerosol formation and growth combine the challenges of both gas-phase chemistry and aerosol dynamics. Because of the difficulty in isolating chemical and microphysical processes in the atmosphere itself, independent of flow and mixing, chamber studies are used to develop mechanistic understanding of such processes. The reaction chamber used is a well-mixed batch reactor, in which the chemical processes of interest can be isolated directly.

Current research is directed at identifying the role of NOx on secondary organic aerosol (SOA) formation, prediction of SOA formation from a hydrocarbon mixture, the effect of relative humidity and temperature on the extent of gas-to-particle conversion processes, and the impact of ammonia and other light gaseous species on SOA formation. Aerosol formation within the chamber is measured using scanning electrical mobility spectrometers. Particle microphysical properties, such as particle hygroscopicity, are tracked using tandem differential mobility analyzers. This research leads to improved predictions of atmospheric SOA formation from hydrocarbon precursors.

Physical and Chemical Characterization of Emissions: Research in this area involves the development of improved chemical source profiles and emission inventories for on and off-road engines. A cornerstone to this research is the development and application of a Mobile Emissions Laboratory (MEL) designed to measure in-use emissions at the QA/QC specifications dictated by the U.S. Congress Code of Federal Regulations. The laboratory is housed in a 53-foot trailer and is equipped with state-of-the-art emission benches and sampling systems for the analyses of regulated emissions (PM, CO, NOx, THC) and toxic emissions. A new secondary dilution system provides the temperature control and sampling flexibility to monitor detailed VOCs, sVOCs, and PM. A fast-scan SEMS has been developed and implemented into the laboratory in collaboration with Dr. Richard Flagan at Caltech.

Within the last two years we have characterized (including detailed chemical profile) using the MEL on-road emissions for class VIII heavy heavy duty diesel vehicles, back-up generators, and several locomotives following a variety of specified driving/operation cycles. Additional field sampling has been conducted on airplanes and large marine engines. Our test matrix includes various PM control devices (oxidation catalysts, fuel-borne catalysts, diesel particle traps) and fuel types.

A current focus of the research is interpreting the role of congestion on vehicle emissions. We have recently published a paper in ES&T demonstrating that the per mile emission rates of these vehicles increase significantly (after normalization for fuel consumed) while the vehicles operate under heavily congested conditions compared to free flow conditions. Furthermore, the basic chemical make-up (EC vs. OC) of the particles are heavily dependent upon the type of traffic conditions encountered.

Ambient and Indoor Air Quality: Recently completed studies on urban aerosol in the Mira Loma region of Western Riverside County, California and New Delhi, India have investigated the role of mobile sources on the particulate matter responsible for degradation of air quality and serious health effects. The study in Western Riverside County has produced a large database of atmospheric pollutants in the indoor (residential, classroom, portable classroom) and outdoor environment. The Mira Loma air quality study has resulted in four publications to date that 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. A recent publication in Atmospheric Environment highlighted a number of sources of PM in the Delhi region.

Health Effects: Current research, in collaboration with Rancho Los Amigos, University of Southern California, and University of California, Los Angeles, is investigating the role of diesel exhaust as a trigger for asthmatic response. My role has been the development and characterization of a suitable chamber for delivery of representative diesel particulate matter.

Selected Publications

  • S.D. Shah, D.R. Cocker, J.W. Miller, J.M. Norbeck, ''Emission Rates of Particulate Matter and Elemental and Organic Carbon from In-Use Diesel Engines,'' Environmental Science and Technology, 38, 9, 2544-2550, 2004.
  • A.A. Sawant, K. Na, X. Zhu, K.M. Cocker, S. Butt, C. Song and D.R. Cocker, ''Characterization of PM2.5 and Selected Gas-phase Compounds at Multiple Indoor and Outdoor Sites in Mira Loma, California,'' Atmospheric Environment, 38, 37, 6269-6278, 2004.
  • C. Song, K. Na, D.R. Cocker, ''Impact of the Hydrocarbon to NOx Ratio (HC:NOx) on Secondary Organic Aerosol Formation,'' Environmental Science and Technology, 39, 3143-3149, 2005.
  • S.D. Shah, T. Ogunyoku, J.W. Miller, D.R. Cocker, ''On-Road Emission Rates of PAH and n-Alkane Compounds From Heavy-Duty Diesel Vehicles,'' Environmental Science and Technology, 39, 5276-5284, 2005.
  • K. Na, D.R. Cocker, ''Organic and Elemental Carbon Concentrations in Fine Particulate Matter in Residences, Schoolrooms, and Outdoor Air in Mira Loma, California,'' Atmospheric Environment, 39, 3325-3333, 2005.

More Information 

General Campus Information

University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

College Information

Bourns College of Engineering
446 Winston Chung Hall

Tel: (951) 827-5190
Fax: (951) 827-3188