Weekend/Weekday Ozone Observations in the South Coast Air Basin

VOC mix. Sonoma Technology, Inc. conducted concurrent traffic and emission source surveys
during the field study
Supplemental measurements by DRI at the monitoring stations included hourly C 2 to C 11
VOC by automated gas chromatography with ion-trap mass spectrometry at Azusa, continuous
black carbon by light absorption with an aethalometer at Azusa and Pico Rivera, and 3-hour
composite Tenax samples for C8 to C18 hydrocarbons. The California Air Resources Board
collected canister samples at Los Angeles – N. Main for speciated hydrocarbons on the same
schedule, and SCAQMD measured 3-hour average speciated VOC with an automated gas
chromatograph at Pico Rivera.
4.1 Field Measurement Program
Desert Research Institute (DRI) conducted a 9-day field study in the Los Angeles area
from September 30, 2000 to October 8, 2000 as part of Phase II of this Weekend Ozone Study.
The study was conducted in accordance with the study plan in Chapter 4 of the August 23, 2000
draft report for Phase I (Fujita et al., 2000a). The plan presented in the draft report was modified
in response to comments from the National Renewable Energy Laboratory (NREL),
Coordinating Research Council (CRC), and the California Air Resources Board (ARB). This
section describes the experimental approach and methods used in field study.
The field study focused on detailed time-resolved measurements to test the hypothesized
relationship between emissions sources and the diurnal and day-of-the-week variations in VOC
and NOx, and VOC/NOx ratios. The field measurements involved two approaches: supplemental
measurements at existing SCAQMD monitoring sites and mobile sampling during periods that
coincide with overnight carryover, ozone inhibition, and ozone accumulation. Supplemental
measurements made by DRI at the monitoring stations included hourly C 2 to C 11 volatile organic
compounds by automated gas chromatography with ion-trap mass spectrometry at Azusa,
continuous black carbon by light absorption with an aethalometer (approximately 5-minute
averages) at Azusa and Pico Rivera, and 3-hour composite Tenax samples for C 8 to
C 18 hydrocarbons beginning at 2, 6, and 9 a.m. PDT on September 30, October 1,2,4,6,7, and 8.
ARB also collected canister samples at Los Angeles – N. Main for speciated hydrocarbons on the
same schedule, and SCAQMD measured 3-hour average speciated VOC with an automated gas
chromatograph at Pico Rivera. Figure 4.1-1 shows the locations of District monitoring stations
along with the locations of freeway loops and regional/background sites used during the mobile
sampling.
Primary pollutants (CO, NO, black carbon [BC] and speciated hydrocarbons) were
measured simultaneously in a mobile van along several freeway loops in different areas of the
Basin. Carbon monoxide, NO/NOy and black carbon estimated from light absorption were
measured continuously with averaging times of 1, 1, and 5 minutes, respectively. Canister and
Tenax cartridge samples were integrated over a period of approximately 50 minutes for each
freeway loop and fixed locations. Sonoma Technology, Inc. conducted concurrent traffic and
emission source surveys during the field study.
Mobile sampling was conducted during the carryover period between 2-5 a.m. (PDT), the
ozone inhibition period between 6 to 9 a.m., and during the ozone accumulation period between
4-2