The Los Angeles Aerosol Characterization and Source Apportionment Study: A Meteorological—Air Quality Analysis

Abstract

During 1983, and 1987–88 as part of LA-ACSAS, fine particulate (d _p 3.5 μm) sampling was carried out on 127 days at Duarte, a residential community about 20 miles east-northeast of downtown Los Angeles, and downwind of major emission sources in the South Coast Air Basin. Average fine particle concentrations were measured over the period noon to 8:00 PM, local time. Measurements included those for total mass, sulfates, nitrates, and particulate carbon (through thermogram analyses). These data were analyzed in conjunction with routinely available aerometric data to achieve two objectives: to characterize the meteorology of the 127 sampling days by season and year; and to develop statistical models for estimating fine particle air quality at Duarte through the use of routinely available data. Findings were as follows: (1) The winter sampling period of 1987–88 had a far greater meteorological potential for fine particle air pollution than did the winter sampling period of 1983, but despite this, winter sulfate concentrations decreased by 46 percent from 1983 to 1987–88. (2) The summer sampling period of 1987–88 had a moderately greater meteorological potential for fine particle air pollution than did the summer sampling period of 1983, yet summer sulfate concentrations decreased by 31% from 1983 to 1987–88. (3) Equations were developed to estimate total fine particulate, and fine carbonaceous aerosol at Duarte from routine measurements of associated gaseous air quality and meteorology. The equations were developed for each of four categories formed from the initial data set of 127 LA-ACSAS sampling days. In all of the equations, the most important variable relating to total fine particulate, and fine carbonaceous aerosol was either the average carbon monoxide or nitrogen dioxide concentration during the noon to 8:00 PM sampling period, linking total fine particulate, and fine carbonaceous aerosol strongly to mobile source emissions.