Project at a Glance

Title: Impact of industrialization of the California delta area

Principal Investigator / Author(s): Smith, T. B.

Contractor: Meteorology Research, Inc.

Contract Number: A5-064-87

Research Program Area: Ecosystem & Multimedia Effects

Topic Areas: Ecosystem Impacts, Field Studies, Impacts


A field study was conducted in August-September 1976 to investigate the potential effects of industrialization of the Montezuma Hills on downwind air quality. The study consisted of meteorological and air quality observations as well as the release and downwind sampling of tracer material. A total of eight tracer tests were carried out with sampling as far downwind as 50-70 km. The program was a cooperative study conducted by Meteorology Research, Inc. (MRI), California Institute of Technology (Caltech) and the Air Monitoring Center of Rockwell International (AMC).

The principal area of impact interest dealt with the potential formation and transport of oxidants into the Central Valley as a result of emissions at Montezuma Hills. The study was therefore conducted during the summer period when photochemical reactions might be expected. Tracer releases were made at different periods during the day to obtain a sample of the effects of diurnal variations on downwind concentrations.

It was found that the predominant wind pattern at Montezuma Hills (day and night) during the summer is from the west with moderate wind velocities. This pattern carries potential emissions from the site toward and beyond the Lodi-Stockton-Tracy area. Tracer releases from the site showed a consistent pattern within the first 10-km but considerable variation in trajectory occurred thereafter. During the tests conducted, material was observed as far north as Lodi and as far south as Tracy often with considerable variation within a given test. Tracer releases from Pinole and Martinez showed that material from these areas followed two paths, eastward through the Montezuma Hills and southeastward through Concord and into the Livermore Valley.

Substantial hydrocarbon (NMHC) concentrations were found during morning sampling at Carquinez Strait as the result of flow from the San Pablo Bay area. Later in the day it appeared that these concentrations were replaced with cleaner air of a more marine nature. Evidence was obtained of ozone production in this morning air as it passed through and downwind of the Montezuma Hills. At the same time, NOx concentrations appeared to decrease as a result of dilution.

Significant impact of potential emissions from the Dow site would largely be confined to the immediate downwind areas where NOx (NO ~) concentrations might be relatively high, assuming rapid conversion from NO to NO2. In addition, the consistency of the tracer trajectories suggest that these concentrations would be realized in nearly the same location each day. Estimates were made of possible ozone generation resulting from potential emissions of NMHC at the Montezuma Hills site. These estimates were based on initial NMHC concentration values and results of chamber tests as well as stoichimetric arguments. Two scenarios were considered for the potential ozone formation. One of these was the introduction of emissions from the site during the afternoon when irradiation could occur between the site and the vicinity of Stockton. The second
scenario involved the transport of NMHC in fairly large concentrations to the vicinity of Stockton in the early morning hours when stable dispersion conditions existed. Thereafter, the NMHC and NOx concentrations could be irradiated during the day as the air parcels moved past Stockton and into the Central Valley, diluting with time. In both cases, it appeared that upper bound arguments led to a release rate estimate of 10 tons per day of NMHC at the Montezuma Hills site before a significant impact on ozone (e.g., an increase of 0.01 PPM) in the vicinity of Stockton might occur.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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