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Study Overview


Updated April 19, 2006




California Regional Particulate Air Quality Study (CRPAQS)


The California Regional PM10/PM2.5 Air Quality Study is a comprehensive public/private sector collaborative program with two main goals:

  1. to provide an improved understanding of particulate matter and visibility in central California, and
  2. to provide decision-makers with the tools needed to identify equitable and efficient control methods.


The study is intended to evaluate both the national and State air quality standards for particulate matter smaller than 10 micrometers in diameter (PM10) and for particulate matter smaller than 2.5 micrometers (PM2.5). Both these standards are consistently exceeded in central California, compromising the health of more than 10 million people. Excess particulate matter reduces visibility, affects crop yields, causes materials damage, and adversely impacts the overall quality of life.

The study has involved extensive planning and preparatory research, including:
  • literature review of previous studies,
  • development of conceptual models for episode behavior,
  • a multi-year assessment of agricultural practice contributions to particulate emissions,
  • a preliminary field monitoring program, the 1995 Integrated Monitoring Study (IMS95), to understand high particulate episodes and evaluate monitoring equipment and data collection needs,
  • analysis and modeling of historic and IMS95 data, and
  • development and improvements to the emissions inventory.

Field Study

A field study was designed to address annual particulate levels as well as fall and winter episodic conditions. Data was collected for 14 months (December 1999 through February 2001) throughout the San Joaquin Valley (SJV) and surrounding regions. Enhancements included short-term, intensive monitoring during the fall and winter, when PM concentrations are highest, and during the summer, complemented by data obtained from the Central California Ozone Study (CCOS). Key components included:

  • Sampling Locations - the backbone of the annual monitoring used the existing PM10 network, as well as new PM2.5 networks established by the ARB and local air pollution control districts. Over 70 PM10 sites and 50 PM2.5 sites comprised this backbone network. Enhancements for the study included full scale “anchor” monitoring sites which measured gaseous and aerosol species, through both filter-based and continuous species specific methods. In addition, “satellite” monitoring sites measured aerosol species using portable PM monitors and nephelometers. Surface and aloft meteorological measurements were collected utilizing a network of surface meteorological sites, radar profilers, and sodars. A special 100-meter tower collected additional meteorological and air quality data at several elevations.
  • Fall Program - took place in the central portion of the San Joaquin Valley in October and November of 2000, corresponding to periods of historically high PM10 concentrations dominated by geological material. Specific issues addressed included identification of the sources of geological material, determination of their zone of influence, and development of improved data on dust suspension and deposition. The fall program included neighborhood-scale saturation monitoring as well as measurement of organic species and particle morphology.
  • Winter Program - took place December 2000 through February 2001. PM2.5 concentrations are historically highest during the winter months, dominated by secondary ammonium nitrate and carbonaceous material. Specific issues addressed included identification of the sources of carbonaceous material, determination of the limiting precursors for secondary PM species, surface and aloft transport and mixing mechanisms under low wind speed conditions, and the zone of influence of both primary and secondary sources of PM. The winter program also included an expanded set of anchor sites, and an enhanced upper-air monitoring network. On days forecast to have the highest PM concentrations, additional measurements were taken, including organic species tracers, fog chemistry, time-of-flight mass spectrometry, and wet deposition. Special emphasis was placed on collection of continuous and species-specific particulate measurements to support both receptor and grid-based modeling. Methods for collecting information aloft included use of the 100-meter tower, an elevated site in the Sierra Nevada mountains, and a remotely piloted blimp, which has been specially designed to fly under low visibility, stagnant conditions.
  • Source/Emissions Inventory Data - Episode specific and enhanced emission inventory estimation data were also collected. Several projects were targeted at collecting improved information for transportation sources, including development of updated chemical speciation profiles, and vehicle traffic counts. Other emissions projects include development of a GIS-based ammonia inventory, and collection of day-specific emissions. A comprehensive emissions inventory for the region is being developed to complement the field measurements.


The Study is directed by the same Policy Committee that managed the highly successful 1990 San Joaquin Valley Ozone Study (SARMAP Ozone Study).  The San Joaquin Valley Ozone Study was a landmark example of collaborative environmental management.  The proven methods and teamwork established in the Ozone Study will provide a solid foundation for the PM10/PM2.5 program.

The budget for the CRPAQS is $27.5 million.  Funding is provided through a cooperative partnership between the public and private sectors (See Study Sponsors).


The Concept for the Study was initiated in 1991 by the agricultural community when they approached the United States Environmental Protection Agency (EPA) for funding.  Government entities and industries endorsed the Study, and full-scale planning began in 1992.  Large-scale field monitoring programs are conducted in from 1999 through 2001, with completion of the project anticipated in 2005.

Study Output

The Study is intended to provide products to support the development of effective PM10 and PM2.5 attainment plans for Central California.  It is uniquely positioned to produce needed data within the implementation schedule specified for the new PM standards.

The information developed will allow apportionment of high PM10 and PM2.5 concentrations to contributing sources, thereby avoiding burdens on the regulated community from unnecessary or ineffective control requirements.  Implementation of the control plans that are derived from CRPAQS information, will result in significant improvements in visibility, and the health and well-being of the citizens of Central California.

The methods and tools for monitoring, emission estimation, control methods evaluation, and atmospheric modeling that are developed by the Study can be used outside of California.  The San Joaquin Valley Ozone Study produced numerous products that advanced the state-of-the-science throughout the United States.  For example, the modeling system developed under the Ozone study has been distributed to 20 organizations nationwide.  In a similar manner, it is anticipated that greater than 50 percent of the CRPAQS funding will result in products with national significance and transferability.

Take a look at our CRPAQS presentation in Microsoft PowerPoint (awma317.ppt - March 17, 1999).

Central California Ozone Study (CCOS)


The Central California Ozone Study (CCOS) consists of a field program, data analysis, emission inventory development, and modeling. The field program of the CCOS was conducted during the summer of 2000. Emission inventory development, data analysis and modeling are on-going projects. The entire effort is expected to be completed by 2011. The California Air Resources Board (CARB) and local air pollution control districts plan to use the results of the CCOS to prepare the demonstration of attainment for the ozone standard for non-attainment areas in central California.





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