Emissions reduction policies and recent trends in Southern California’s ambient air quality

Figures & data

Table 1. PM monitors and samplers used in the CHS

Time period	PM2.5	PM10
1994–1997	CHS 2-week sampler	TEOM
		1-in-6 day HiVol FRM sampler
1998–2004	CHS 2-week sampler	TEOM
	Daily, 1-in-3, and 1-in-6 day FRM sampler	1-in-6 day HiVol FRM sampler
2005–2007	BAM	TEOM
	Daily, 1-in-3, and 1-in-6 day FRM sampler	1-in-6 day HiVol FRM sampler
2008–2011	BAM	BAM
	Daily, 1-in-3, and 1-in-6 day FRM sampler	1-in-6 day HiVol FRM sampler

Figure 1. Map of CHS communities.

Figure 2. Air quality trends (1992–2011) in the CHS communities.

Table 2. Estimated emissions and emission reductions in the SoCAB (1993 to 2012)

Source type	1993 Emissions in tons/day
	NOx	ROG	SOx	PM2.5	PM10
Stationary	151	355	26.8	19.1	24.8
Areawide	38	210	0.6	29.3	92.9
On-road motor vehicles	883	726	21.7	55.4	202.5
Other mobile sources	353	231	17.9	21.2	23.5
Total	1425	1522	67.0	125.0	343.8
	2012 Emissions in tons/day
Stationary	54.5	111.1	18.2	15.7	25.1
Areawide	22.7	146.2	0.9	35.4	99.3
On-road motor vehicles	327.9	144.1	2.1	33.1	152.0
Other mobile sources	245.6	133.3	19.3	14.9	16.9
Total	650.7	534.7	40.4	99.1	293.4
	1993–2012 Emissions change in tons/day
Stationary	–97.0	–244.2	–8.6	–3.4	0.3
Areawide	–15.4	–63.4	0.2	6.0	6.4
On-road motor vehicles	–554.6	–582.2	–19.6	–22.3	–50.5
Other mobile sources	–107.0	–97.9	1.4	–6.4	–6.6
Total	–774.0	–987.7	–26.6	–25.9	–50.4
	1993–2012 Emissions change in percent
Stationary	–64%	–69%	–32%	–18%	1%
Areawide	–40%	–30%	36%	21%	7%
On-road motor vehicles	–63%	–80%	–91%	–40%	–25%
Other mobile sources	–30%	–42%	8%	–30%	–28%
Total	–54%	–65%	–40%	–21%	–15%

Figure 3. Estimated NO_x, ROG, PM_2.5, PM₁₀, and SO_x emissions in the SoCAB from 1992 to 2012.

Table 3. Estimated emissions and emission reductions in Santa Barbara County (1993 to 2012)

Source type	1993 Emissions in tons/day
	NOx	ROG	SOx	PM2.5	PM10
Stationary	9.0	13.8	1.6	0.5	0.9
Areawide	2.2	11.7	0.0	6.5	15.1
On-road motor vehicles	31.2	21.7	0.6	1.3	5.0
Other mobile sources	43.5	8.8	14.8	2.9	3.1
Total	86.0	56.0	17.1	11.3	24.1
	2012 Emissions in tons/day
Stationary	7.3	9.9	4.5	0.5	1.0
Areawide	2.1	10.8	0.0	6.6	16.5
On-road motor vehicles	13.4	5.9	0.1	1.2	5.6
Other mobile sources	73.2	8.5	35.6	5.6	5.8
Total	95.9	35.0	40.2	13.9	28.9
	1993–2012 Emission changes in tons/day
Stationary	–1.8	–3.9	2.9	0.0	0.1
Areawide	–0.1	–1.0	0.0	0.1	1.4
On-road motor vehicles	–17.8	–15.8	–0.5	–0.2	0.6
Other mobile sources	29.7	–0.3	20.8	2.6	2.7
Total	10.0	–21.0	23.2	2.6	4.8
	1993–2012 Emission changes in percent
Stationary	–20%	–28%	177%	–3%	6%
Areawide	–3%	–8%	–1%	2%	10%
On-road motor vehicles	–57%	–73%	–88%	–13%	11%
Other mobile sources	68%	–4%	140%	90%	87%
Total	12%	–37%	136%	23%	20%

Figure 4. Comparison of NO₂ air quality and NO_x emission trends, and PM_2.5 air quality and PM_2.5, PM₁₀, NO_x, and ROG emission trends. The normalized trends (right side) compare air quality and emissions to the baseline values (100%) in 1993 for NO₂ and 1994 for PM_2.5.

Table 4. Major regulatory policies affecting pollution and emission trends in California, 1985–2012

Regulatory policy	Adoption date
On-road emissions:
Low-emission vehicle standards for light-duty and	1990, 1998
medium-duty vehicles (LEV, LEV II)
Reformulated gasoline	1988, 1990, 1991
On-board diagnostics standards for light-duty vehicles	1985, 1989
Medium-duty and heavy-duty truck gasoline emission standards	1995
Heavy-duty diesel truck engine emissions standards	1998, 2001
Clean diesel fuel requirements	2003
Financial incentives for replacement or retrofit high-polluting	1998–2012
vehicles, engines, and equipment (e.g., the Carl Moyer Program)
Cleaner port (drayage) trucks	2007
Off-road emissions:
Cleaner diesel fuel for oceangoing vessels, harbor craft, and trains	2004, 2008
Reduced port auxiliary engines and incinerator use, hoteling	2007
Cleaner locomotive engines in southern California	1997, 2010
Stationary diesel engines standards for in-use agricultural engines	2007
Stationary point sources:
NOx and SOx reductions from Regional Clean Air Incentives Market	1994
(RECLAIM)
New source review (NSR)	1990
Source-specific emissions standards	1988–2002
Area sources:
Low-emission certificate programs for products and equipment	1988–2012
Unpaved and paved road dust control measures	2008
Water heater and small boiler emission standards	1999, 2004

Figure 5. PM_2.5 nitrate air quality trends at CHS and STN monitoring sites.