Research Program Area: Emissions Monitoring & Control
The objectives of this project were (1) to investigate both primary and secondary sources of chloroform (CHCl3) in the South Coast Air Basin (SCAB) and (2) to identify and quantify the emission sources responsible for observed atmospheric concentrations. Of particular interest was the identification of possible chloroform precursors and atmospheric reactions which result in chloroform formation. The major elements of Phase I of the project were construction of a chloroform emission inventory for the SCAB, a literature review of atmospheric concentrations and reactions, a modeling exercise to compare measured ambient concentrations with those based upon emission estimates, and a review of chloroform sampling and analytical techniques. Phase II included ambient sampling, source testing at two wastewater treatment plants and a swimming pool, and laboratory studies of atmospheric chemistry.
Total emissions of chloroform in the SCAB are estimated to be 370 tons per year. The largest source appears to be drinking water chlorination, which accounts for about 51% of the annual total. Swimming pool chlorination accounts for another 39.5%. Pulp and paper manufacturing plants have a significant potential for chloroform generation, although their emissions occur at wastewater treatment plants. CHCl3 produced by chlorination of final treated wastewater effluent is not likely to be significant unless ammonia has been removed during tertiary treatment; most of the chloroform emissions from wastewater treatment plants occur through release of influent chloroform during primary treatment. Emissions from domestic bleach use, industrial and utility cooling towers, laboratories, and pharmaceutical manufacturing total about 14.6 tons per year. Chloroform emissions from chlorinated rubber manufacturing, combustion of leaded gasoline, chlorodifluoromethane production, grain fumigation, contamination of chlorinated products, and marine organisms are negligible.
SAIC collected wastewater samples from the influent and effluent of the Hyperion Treatment Plant and the Riverside Water Quality Control Plant. Emissions from the two plants are estimated to be 15 lb and 0.5 lb/day, respectively; production of chloroform by postchlorination of tertiary-treated effluent at Riverside was taken into account. Ambient air sampling with a portable gas chromatograph found CHCl3 concentrations above treatment processes to be one to three orders of magnitude higher than in the rest of the basin. Concentrations increased through primary treatment.
Chloroform emissions from a residential swimming pool were measured with an emission isolation flux chamber. Significant emissions were found under all tested chlorine doses and water surface conditions; fluxes increased greatly when the water surface was agitated. Chloroform levels in the pool were 5 to 9 times those in the municipal water, but flux rates did not appear to be related to chloroform concentration.
Our analysis of ARB data found that 24-hour average chloroform concentrations at four sites in the Basin were distributed log normally for each receptor. Mean 24-hour concentrations between January 1983 and July 1984 (December 1984 for El Monte) were 45.1 ppt at Dominguez Hills, 47.8 ppt at El Monte, 60.5 ppt at Los Angeles and 46.6 ppt at Riverside. The mean concentration at the Los Angeles site is significantly greater (p < 0.05) than those for the remaining sites. F-Tests on the variances for all paired sites were not significant (p > 0.05), indicating that variation in the four samples is similar.
In the present study, SAIC collected air samples on carbon molecular sieve (CMS) traps at a 24-hour sampling site in Fullerton, a six-hour sampling site in Hermosa Beach, and one-hour samples at 12 sites off the coast of the SCAB and at 41 sites throughout the basin. Samples were analyzed by cryogenic preconcentration and gas chromatography with electron capture detection for chloroform, 1,1,1-trichloroethane (methyl chloroform), carbon tetrachloride, trichloroethylene (TCE), tetrachloroethylene (perchloroethylene), and ethylene dibromide (EDB). Since this was, to the best of our knowledge, the first large-scale use of CMS for ambient halocarbon sampling, considerable trial and error was necessary for developing suitable sampling and analytical methods.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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