Weekend/Weekday Ozone Observations in the South Coast Air Basin

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20.0 1981-84 16.0 12.0 8.0 4.0 0.0 20.0 Sun Mon Tue Wed Thu Fri Sat 1985-89 16.0 12.0 8.0 4.0 0.0 20.0 Sun Mon Tue Wed Thu Fri Sat 1990-94 16.0 12.0 8.0 4.0 0.0 Sun Mon Tue Wed Thu Fri Sat 20.0 1995-98 16.0 12.0 8.0 4.0 0.0 Sun Mon Tue Wed Thu Fri Sat N. Long Beach Anaheim Lynwood LA-N.Main Reseda Burbank Pico Rivera La Habra Azusa Pomona Upland Rubidoux Figure 2.6-2. Average daily NMHC/NOx at maximum ozone in the SoCAB by day of the week. 2-36
3. CHARACTERIZATION OF THE CURRENT WEEKEND OZONE EFFECT IN THE SOUTH COAST AIR BASIN This section summarizes current observations of the weekend effect for the summers of 1999 and 2000 based upon ambient data from the South Coast Air Quality Management District (SCAQMD) Photochemical Assessment Monitoring Stations (PAMS) in Azusa, Pico Rivera, and Upland and the California Air Resources Board ozone precursor trends monitoring at the SCAQMD monitoring station in downtown Los Angeles – North Main. The analyses focused on relating weekday differences in the diurnal variations of CO, NMHC, NO, and NO2, and NOx with variations in ozone, VOC/NOx ratios, and the ratios of O3 to potential ozone (i.e., O3 plus NOx). Weekday variations of ozone are also related to VOC reactivity, photochemical aging, and estimated photolysis rate parameter for NO2. Current weekdays and weekends observations of the VOC and NOx mixing ratios are superimposed on an ozone isopleth plot along with similar observations from 1987 PAMS ozone precursor monitoring is conducted annually in California during the peak ozone season (July 1 to September 30). The enhanced ambient air monitoring at PAMS was established under Title I, Section 182, of the 1990 CAAA. There are five PAMS sites in operation in the SoCAB. The PAMS network includes sites to characterize precursor emission sources within the area (Type 2), and transport of ozone and its precursors into (Type 1) and out of the area (Type 3 and 4). Each station measures speciated hydrocarbons, ozone, oxides of nitrogen, and surface meteorological data. Sampling for carbonyl compounds is required at Type 2 sites only. PAMS network operations in the South Coast Air Basin (SoCAB) began in 1994 at the Pico Rivera (Type 2) and Upland (Type 4) monitoring stations. The network was completed with the addition of PAMS operations at Azusa (Type 3) in 1995, and at Hawthorne (Type 1) and Burbank (Type 2) in 1997. In addition, the ARB continues to measure speciated nonmethane organic compounds (NMOC) at Los Angeles – North Main as part of the long-term trends network that was originally established by the NMOC program. PAMS use EPA methods TO-14 and TO-11 for sampling and analysis of speciated hydrocarbons (EPA, 1991) and carbonyl compounds, respectively. The database consists of 55 individual hydrocarbons, total NMOC, and three carbonyl compounds (formaldehyde, acetaldehyde, and acetone). ARB collects one 3-hour sample every third day at Los Angeles – North Main beginning at 0600, PDT. Eight 3-hour hydrocarbon samples (0000-0300, 0300-0600, 0600-0900, 0900-1200, 1200-1500, 1500-1800, 1800-2100, and 2100-2400, PDT) are collected every day at Type 2 PAMS sites and every third day at all other PAMS sites. In addition, one 24-hour sample is required every sixth day yearround at Type 2 sites and during the summer monitoring period at all other sites. Several terms are used in this section that represent subsets of VOC. These terms are operational definitions and reflect the sensitivity and selectivity of the analytical methods. Nonmethane hydrocarbons (NMHC) are defined as C 2 through C 11 hydrocarbons collected in stainless steel canisters and measured by gas chromatography with flame ionization detection (GC-FID) by EPA method TO-14A (U.S. EPA, 1997). Known halocarbons and oxygenated compounds (e.g., aldehydes, ketones, ethers and alcohols) are excluded from NMHC. Carbonyl compounds are aldehydes and ketones, the most common being formaldehyde, acetaldehyde, and acetone. Carbonyl compounds are operationally defined as C 1 to C 7 oxygenated compounds measured by collection on acidified 2,4-dinitrophenylhydrazine (DNPH)-impregnated C 18 or silica gel cartridges and analyzed by high performance liquid chromatography with UV detection 3-1
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WEEKEND/WEEKDAY OZONE OBSERVATIONS
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obtained by DRI from the Phase II f
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TABLE OF CONTENTS Preface..........
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Table No. Table 1.4-1 Table 1.4-2 T
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periods by day-of-week at Los Angel
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Figure 1.4-13. Hourly average nitro
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Figure 3.1-2 Mean day-of-the-week v
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Figure 4.4-1b. Mean estimated sourc
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1. STUDY PERSPECTIVE AND SUMMARY Th
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40 percent. Consequently, the contr
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dioxide (NO 2 ) 4 , and carbon mono
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and upwind samples before and after
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where J 1 is the photolysis frequen
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transported from an urban center to
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of the week on Friday and Saturday.
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VOC reactivity, photochemical aging
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corresponding source attributions a
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multiplicative constant. This const
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Table 1.4-1 Trends in Duration and
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Table 1.4-3 Regression Statistics f
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O 3 Ozone Formation Chemistry NO 2
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200 1981-84 200 1995-98 160 160 120
Page 45 and 46: 100 NO 1000 NMHC (estimated from CO
Page 47 and 48: 5 Sunday - Wednesday (1981-84) 10 T
Page 49 and 50: 10.0 8.0 NMHC/NOx 6.0 4.0 2.0 0.0 S
Page 51 and 52: Ratio of Peak Ozone to Potential Oz
Page 53 and 54: Nitrogen Oxides at Azusa, 9/30/00 t
Page 55 and 56: Ambient NOx Associated with CO and
Page 57 and 58: Source Contribution Estimate (ug/m3
Page 59 and 60: 2.8 2.6 Ozone (ppb) 2.4 log NOx (pp
Page 61 and 62: 2. EVOLUTION OF THE OZONE EFFECT IN
Page 63 and 64: the SoCAB has dropped sharply as sh
Page 65 and 66: the duration of ozone accumulation,
Page 67 and 68: • NO 2 concentrations and NO 2 /N
Page 69 and 70: Table 2-1 Air Quality Parameters fo
Page 71 and 72: 0.18 Azusa, Summer 1995 12.0 0.15 1
Page 73 and 74: 250 200 150 100 50 0 1976 1977 1978
Page 75 and 76: 80 1981-84 60 40 20 0 80 Sun Mon Tu
Page 77 and 78: 1.00 1981-84 0.80 0.60 0.40 0.20 0.
Page 79 and 80: 160 1981-84 120 80 40 0 160 Sun Mon
Page 81 and 82: 5.0 1981-84 4.0 3.0 2.0 1.0 0.0 5.0
Page 83 and 84: 12.00 1981-84 11.00 10.00 9.00 8.00
Page 85 and 86: NMHC (ppbC) 1000 800 600 400 200 4-
Page 87 and 88: 10.00 1981-84 8.00 6.00 4.00 2.00 0
Page 89 and 90: Sunday 1981-84 Time (PDT) 16 15 14
Page 91 and 92: 16 Sunday 1990-94 35 Time (PDT) 15
Page 93 and 94: 40 Sunday O3 Accumulation Rate (ppb
Page 95: 15.0 1981-84 12.0 9.0 6.0 3.0 0.0 1
Page 99 and 100: 3.2 Weekday Differences in Diurnal
Page 101 and 102: timing hypothesis, which requires a
Page 103 and 104: through the conversion of NO to NO
Page 105 and 106: Weekday Differences in Diurnal Vari
Page 107 and 108: activity including [HNO 3 ]/[H 2 O
Page 109 and 110: Table 3.2-1 Day-of-the-Week Variati
Page 115 and 116: Table 3.3-1b Day-of-the-Week Differ
Page 117 and 118: 120 Los Angeles - N. Main - Saturda
Page 119 and 120: 160 140 Upland - Saturdays mean Ozo
Page 121 and 122: maximum 1hour ozone (ppb) 100 90 80
Page 123 and 124: NMHC/NOx ratio 14 12 10 8 6 4 2 0 S
Page 125 and 126: Los Angeles - N. Main Azusa 140 140
Page 127 and 128: Los Angeles - N. Main Azusa 140 140
Page 129 and 130: 2.8 2.6 PAN (ppb) 2.8 2.6 HCHO (ppb
Page 131 and 132: NO2 Photolysis Rate Parameter 0.35
Page 133 and 134: 4. WEEKDAY VARIATIONS IN THE SOURCE
Page 135 and 136: 9 a.m. andnoon. Sampling was conduc
Page 137 and 138: interfaced to an Entech model 7100
Page 139 and 140: values measured at the regional sit
Page 141 and 142: into a category named "UNID." The s
Page 143 and 144: more than a few percent of the tota
Page 145 and 146: period, the amount of NOx associate
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weekend/weekday differences during
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• Day-of-the-week changes in the
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Table 4.4-1 Default Source Composit
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Table 4.4-1a Number of observations
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Table 4.4-1c Number of observations
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Table 4.4-2a Number of observations
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Table 4.4-2c Number of observations
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Table 4.4-3a CMB Performance Parame
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Table 4.4-3c Source Contribution Es
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Table 4.5-2 Weekend/Weekday Differe
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800 700 600 Wednesday NO and NOy (p
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Estimated NOx Estimated NOx (ppb) 5
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VOC/NOx Ratios 6.0 5.0 4.0 Mon, 10/
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Nitrogen Oxides at Azusa 80 60 02-0
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Nitrogen Oxides at Pico Rivera 180
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Nonmethane Organic Gas at Azusa 500
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Nonmethane Organic Gas at Pico Rive
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NMOG/NOx Ratios at Azusa 20 15 02-0
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estimated contribution by source (u
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500 Nonmethane Hydrocarbons 400 NMH
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5 Azusa, Weekdays 6-9 a.m (10/2/00-
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2.0 Azusa, Weekdays 6-9 a.m (10/2/0
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Ambient NOx Associated with CO and
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Pico Rivera 150 120 BC-Associated C
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Nitrogen Oxides 800.00 700.00 600.0
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5. REFERENCES Altshuler, S.L., T.D.
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Fujita, E.M., J.G. Watson, J.C. Cho
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Roberts, J.M. (1983) Measurements o
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Weekend/Weekday Ozone Observations in the South Coast Air Basin

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