The original National Air Quality Strategy (NAQS) published in 1997 (DOE 1997) set out a framework of standards and objectives for the air pollutants of most concern (SO2, PM10, NOx, CO, lead, benzene, 1,3-butadiene and tropospheric ozone). The aim of the strategy was to reduce the air pollutant impact on human health by reducing airborne concentrations. Different pollutants have differing timescales associated with human health impacts. Therefore concentrations during episodes (both Winter and Summer) are important for some pollutants, but less so for others.
The NAQS identified air quality standards for 8 priority pollutants based on the recommendations of the Expert Panel on Air Quality Standards (EPAQS) or WHO guidance where no EPAQS recommendation existed. EPAQS was set up by the Secretary of State for the Environment in 1991, and is a panel created to “advise, as required, on the establishment and application of air quality standards in the UK… taking account of the best available evidence of the effects of air pollution on human health…”. The NAQS has been subject to periodic review, with consultation documents being published in 1998 and 2000 (DETR 1998a, 2000).
The NAQS then evolved into the Air Quality Strategy for England, Scotland, Wales and Northern Ireland (AQS for ESWNI), with the same goals. A second edition of the strategy was published in 2000 (DETR 2000), identifying further revisions and focused on the incorporation of air quality limit values in European Directives, and the impacts of devolution.
Following a consultation exercise new objectives for:
particles, benzene, carbon monoxide and polycyclic aromatic hydrocarbons were
announced for England in August 2002. More details can be found at the Defra
website (Defra news release 323/02). The situation for Scotland differs
slightly- the Air Quality (Scotland) Amendment Regulations came into force on
12 June 2002. More detailed information can be found on the Scottish Executive
website (Scottish Executive News Release SEen057/2002 on www.scotland.gov.uk). For Wales, the
consultation paper on the same subject is available from the Welsh assembly web
pages (http://www.wales.gov.uk).
In addition to the above, Local Authorities in the UK have a duty, under the 1995 Environment Act: Part IV, to review and assess air quality in their areas. The Air Quality Regulations 2000 define a staged process of review and assessment on the basis of guidance provided by Defra and the Devolved Administrations. The first stage primarily involves the collection of existing data on air quality measurements and emission sources for the 8 pollutants of interest in the AQS for ESWNI. These data are then used to define whether there is likely to be an air quality problem in a specific future year (depending on pollutant). The second and third stages require the use of increasingly sophisticated monitoring and modelling tools to identify hotspots of pollution and to determine whether or not the relevant air quality objectives will be met in each area.
The NAEI is being used as an important source of data for the compilation of appropriate local inventories. Table 4.1 summarises the total 2000 emissions of the 8 priority pollutants covered by the AQS for ESWNI.
Table 4.1 Total UK Emissions of AQS for ESWNI Pollutants
Pollutant |
Total 2000 emission
(kt) |
|
PM10 |
171 |
|
Carbon Monoxide |
4167 |
|
Benzene |
16.4 |
|
1,3 Butadiene |
5.7 |
|
Nitrogen oxides |
1512 |
|
Sulphur dioxide |
1156 |
|
Tropospheric Ozone |
NS1 |
|
Lead |
0.50 |
|
PAH |
2.26 |
|
1 No significant ozone emissions from anthropogenic sources
The following sections provide a discussion of the UK emissions for particulate matter, carbon monoxide, benzene and 1,3-butadiene whilst a full discussion of the other pollutants is included in other chapters of this report as indicated in Table 4.2.
Table 4.2 Location of Emissions and Discussion of AQS for ESWNI Pollutants
Pollutant |
Location |
PM10 |
Chapter 4: AQS Pollutants |
Carbon Monoxide |
Chapter 4: AQS Pollutants |
Benzene |
Chapter 4: AQS Pollutants |
1,3 Butadiene |
Chapter 4: AQS Pollutants |
Nitrogen oxides |
Chapter 5: Acidifying Gases & Ozone Precursors |
Sulphur dioxide |
Chapter 5: Acidifying Gases & Ozone Precursors |
Tropospheric Ozone |
Chapter 5: Acidifying Gases & Ozone Precursors |
Lead |
Section 6.3: Heavy Metals |
PAH |
Section 6.2: Persistent Organic Pollutants |
Historically, interest in particulate matter focused mainly on smoke which can cause health problems especially in combination with other pollutants. The classic example was emissions of smoke and sulphur dioxide leading to the London smogs in the 1950s and early 1960s when several thousand excess deaths were recorded. Smoke emissions have fallen significantly as a result of the Clean Air Acts eliminating domestic coal combustion in many urban areas. However, there is increasing interest in the measurement of fine particles, such as those arising from the combustion of diesel fuel in the transport sector, and aerosol concentrations in the atmosphere from other sources which may have harmful effects. Recent epidemiological evidence is also linking concentrations of particles in the atmosphere with human health effects. Indeed, current ambient mass concentrations are thought to be sufficient to lead to increased mortality and morbidity (EPAQS, 1995).
Particles can vary widely in size and composition. Particles larger than about 30 mm (a mm is a "micrometre", or one thousandth of a millimetre) fall rapidly under gravity and those larger than about 100 mm fall out of the atmosphere so rapidly they are not usually considered. At the other end of the size scale are particles less than a tenth of a mm which are so small they do not fall under gravity appreciably, but coagulate to form larger particles that are then removed from the atmosphere.
The US PM10 standard was a monitoring standard designed to measure the mass of particles less than 10 mm in size (more strictly, particles that pass through a size selective inlet with a 50% efficiency cut-off at 10 mm aerodynamic diameter). This corresponds to the International Standards Organisation thoracic convention for classifying those particles likely to be inhaled into the thoracic region of the respiratory tract. The epidemiological evidence of the effects of particulates shows good correlation in the UK between PM10 concentrations and mortality or morbidity (EPAQS 1995, 2001). Therefore PM10 has become the generally accepted measure of particulate material in the atmosphere in the UK and in Europe. There is also an increasing interest in the correlation between PM2.5 and health indicators. PM10 measurements are being made in the UK (Bower et al, 1994, 1995 a & b, 1996, 1997) and their emissions have been included in the NAEI since 1995.
For many years the monitoring of particulate levels was based on the measurement of “Black Smoke”. Levels were estimated using a simple non-gravimetric reflectance method in which air is sampled through a filter and the resulting blackening measured. The method was calibrated for domestic coal smoke. When most of the emissions come from coal combustion the blackening should be approximately proportional to the mass concentrations. In the 50s and 60s, domestic coal combustion was the dominant source of black smoke and hence this method gave an indication of the concentration. The NAEI estimates of black smoke emissions were extended in 1988 to include emissions from all fuel combustion. Prior to 1988 only emissions from coal combustion had been estimated and published in the DOE Digest of Environmental Statistics. However, there have been no recent emission measurements to confirm these factors are still accurate.
Smoke from different sources has a different blackening effect and so there is no simple relationship between black smoke and the mass of particulate emissions. For example, typically diesel emissions have a blackening effect three times greater, mass for mass, than coal emissions, while petrol emissions are effectively an order of magnitude less. Black smoke is a poor indicator of the concentrations of particulates in the atmosphere current interest and the NAQS is focused on PM10 (particulate matter less than 10mm i.e. 10 millionths of a metre) and smaller size fractions (EPAQS, 1995). However, black smoke has been shown to have relationships with health effects and is still used as an indicator.
For completeness the following sections present emission estimates and discussion for PM10 , PM2.5 , PM1.0 , PM0.1 and Black Smoke.
PM10 in the atmosphere arises from two sources. The first is the direct emission of particulate matter into the atmosphere from a wide range of sources such as fuel combustion, surface erosion and wind blown dusts and mechanical break-up in, for example, quarrying and construction sites. These are called ‘primary’ particulates. The second source is the formation of particulate matter in the atmosphere through the reactions of other pollutants such as sulphur dioxide, nitrogen oxides and ammonia to form solid sulphates and nitrates, as well as organic aerosols formed from the oxidation of VOCs. These are called ‘secondary’ particulates. This inventory only considers primary sources. For further information on secondary particulate see the third Quality of Urban Air Review Group report (QUARG, 1996) and the report from the Airborne Particles Expert Group (APEG, 1999)- see http://www.aeat.co.uk/netcen/airqual/reports/quarg/q3intro.html and http://www.defra.gov.uk/environment/airquality/airbornepm/index.htm respectively.
There is currently a programme sponsored by Defra and the Society of Motor Manufacturers and Traders (SMMT) to measure PM10 emissions from road transport. This programme has developed measurement techniques and aims to produce improved PM10 emission factors, particulate characterisation and particle size distribution.
The main sources of primary PM10 are briefly described below:
· Road Transport. All road transport emits PM10. However diesel vehicles emit a greater mass of particulate per vehicle kilometre than petrol-engined vehicles. Emissions also arise from brake and tyre wear and from the re-entrainment of dust on the road surface. Emission estimates for the re-entrainment of dust have been made. However this does not fall within the UN/ECE reporting format and consequently has been reported separately.
· Stationary Combustion. Domestic coal combustion has traditionally been the major source of particulate emissions in the UK. However, the use of coal for domestic combustion has been restricted in the UK by the Clean Air Acts, and as a result other sources are more important nationally. Domestic coal can still be a significant source in some smaller towns and villages, in Northern Ireland and in areas associated with the coal industry. Other fossil fuels emit PM10, but emissions from gas use are small. In general, particles emitted from combustion are of a smaller size than from other sources.
· Industrial Processes. These include the production of metals, cement, lime, coke, and chemicals, bulk handling of dusty materials, construction, mining and quarrying. Emissions from these sources are difficult to quantify due to the contribution of fugitive emissions (i.e. those diffuse emissions which are released directly into the atmosphere from a process rather than being collected in a controlled manner and then vented to atmosphere). Few UK measurements are available for these fugitive releases. Nonetheless, there have been substantial improvements in the estimation of PM10 emissions from industrial processes in recent years. Usually a substantial fraction of the particles from these sources is larger than 10 mm but the large quantities emitted ensure that the fraction less than 10 mm is still substantial.
Emissions of PM10 are shown in Table 4.3 and Figure 4.1. Emissions of PM10 from the UK have declined since 1970. This is due mainly to the reduction in coal use. Domestic emissions have fallen from 222 tonnes (41% of the total emission) in 1970 to 28 tonnes (16%) in 2000.
Emission estimates for the resuspension of dust from roads is not included in the standard UN/ECE reporting format (and hence not included in Table 4.3). However for completeness it is given in Table 4.4 below. Estimates for resuspension are based on the deposition of primary particles form all UK sources (including vehicle tailpipes and from brake and tyre wear) that are returned to the air from the turbulence of passing vehicles. As such, resuspension to some extent double counts the emissions, but is important in reconciling road side concentration measurements.
Table 4.3 UK Emissions of PM10 by UN/ECE Source Category and Fuel (kt)
|
1970 |
1980 |
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
BY UN/ECE CATEGORY1 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy
Prod. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Public Power |
67 |
76 |
70 |
70 |
66 |
55 |
49 |
38 |
35 |
24 |
25 |
20 |
22 |
13% |
Petroleum Refining Plants |
5 |
5 |
3 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
3 |
3 |
1% |
Other Comb. & Trans. |
16 |
2 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
Comb. in
Comm/Inst/Res |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Residential Plant |
222 |
102 |
52 |
55 |
51 |
53 |
43 |
33 |
35 |
33 |
33 |
34 |
28 |
41% |
Comm/Pub/Agri Comb. |
22 |
11 |
8 |
8 |
8 |
7 |
7 |
6 |
6 |
7 |
6 |
5 |
5 |
3% |
Combustion in
Industry |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel Comb. |
8 |
2 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
0% |
Other Ind. Comb. |
89 |
44 |
39 |
39 |
41 |
39 |
38 |
35 |
32 |
30 |
27 |
24 |
20 |
11% |
Production
Processes |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Processes in Industry |
14 |
12 |
14 |
14 |
14 |
14 |
14 |
13 |
14 |
13 |
13 |
12 |
11 |
7% |
Construction |
8 |
3 |
4 |
4 |
3 |
3 |
3 |
4 |
4 |
4 |
4 |
4 |
4 |
2% |
Quarrying |
22 |
21 |
29 |
26 |
25 |
25 |
27 |
26 |
23 |
24 |
23 |
21 |
21 |
12% |
Road Transport |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Combustion |
44 |
53 |
59 |
58 |
56 |
54 |
52 |
48 |
45 |
39 |
35 |
32 |
26 |
15% |
Brake & Tyre Wear |
2 |
3 |
4 |
4 |
4 |
4 |
4 |
4 |
5 |
5 |
5 |
5 |
5 |
3% |
Other Trans/Mach |
15 |
13 |
13 |
13 |
12 |
12 |
12 |
11 |
12 |
12 |
11 |
11 |
10 |
6% |
Waste |
1 |
4 |
3 |
3 |
2 |
2 |
3 |
2 |
2 |
1 |
1 |
1 |
1 |
1% |
Agri. & Land
Use Change |
11 |
12 |
12 |
13 |
12 |
12 |
12 |
12 |
13 |
13 |
14 |
14 |
14 |
8% |
By FUEL TYPE |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Solid |
359 |
199 |
138 |
142 |
135 |
124 |
107 |
84 |
80 |
68 |
65 |
60 |
53 |
31% |
Petroleum |
96 |
87 |
83 |
83 |
80 |
78 |
75 |
69 |
66 |
59 |
53 |
49 |
41 |
24% |
Gas |
5 |
6 |
7 |
7 |
7 |
8 |
8 |
8 |
9 |
9 |
10 |
10 |
10 |
6% |
Non-Fuel |
87 |
73 |
86 |
79 |
77 |
77 |
80 |
77 |
74 |
74 |
74 |
69 |
67 |
39% |
TOTAL |
546 |
365 |
313 |
311 |
299 |
285 |
270 |
238 |
230 |
209 |
201 |
188 |
172 |
100% |
1 See Annex 1 for definition
of UN/ECE Categories
Table 4.4 PM10 Emission Estimates from Resuspension
|
1970 |
1980 |
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
Resuspension from Road Trans |
8.2 |
11.2 |
16.9 |
17.0 |
17.0 |
17.0 |
17.4 |
17.8 |
18.3 |
18.7 |
19.0 |
19.3 |
19.4 |
The geographical disaggregation of emissions is shown in Figure 4.2. There is a clear distinction between the important sources in rural and urban areas. Indeed, many of the sources do not occur inside towns and cities. While road transport accounts for only 20% of national emissions, it can account for up to 80% of primary emissions in urban areas such as London (Buckingham et. al., 1997).
Emissions from electricity generation have also recently been declining (since 1991) despite a significant growth in the electricity generated between 1970 and 2000. This is due to the move away from coal to natural gas and nuclear power for electricity generation and to improvements in the performance of electrostatic precipitators at coal-fired power stations. Also the installation of flue gas desulphurisation at two power stations have reduced particulate emissions further.
Figure 4.1 UK Emissions of PM10
The one sector which has shown significant relative growth in emissions since 1970 is road transport, with a contribution to the total UK emission rising from 13% in 1970 to 20% in 2000. In urban areas with little industrial activity, where public power and industrial processes do not make a significant contribution, the contribution of road transport to emissions will be even higher; for example as much as 80% of primary emissions in London. The main source of road transport emissions is exhaust from diesel engined vehicles. Emissions from diesel vehicles have been growing due to the growth in heavy duty vehicle traffic and the move towards more diesel cars, (diesel cars have increased from 3% to 12% of the UK vehicle fleet between 1990 and 2000). Since around 1992, however, emissions from diesel vehicles have been decreasing due to the penetration of new vehicles meeting tighter PM10 emission regulations.
Among the non-combustion and non-transport sources, the major emissions are from industrial processes, the most important of which is quarrying whose emission rates have remained fairly constant. Other industrial processes, including the manufacture of steel, cement, lime, coke, and primary and secondary non-ferrous metals, are collectively important sources of particulate matter although emissions from individual sectors are relatively insignificant.
Figure 4.2, Spatially Disaggregated UK Emissions of PM10
Inventories for PM2.5, PM1 and PM0.1 have been estimated from the PM10 inventory and the mass fractions in these size ranges available for different emission sources and fuel types. A total of 33 different size distributions covering PM2.5 and PM1 emissions from different source sectors were taken from the USEPA (1995) as being applicable to sources in the UK; a fewer number of sectors with size fractions in the PM0.1 range were available from the study by the TNO Institute of Environmental Sciences, Energy Research and Process Innovation in the Netherlands for the Dutch National Institute of Public Health and Environment (RIVM) (TNO, 1997) who produced a particulates emissions inventory for Europe. In general, combustion processes emit a higher proportion of fine particles (<2.5 µm) than mechanical sources such as quarrying and construction. Gaseous fuels also tend to emit finer particles than petroleum and solid fuels.
Each of the detailed source sectors for which a PM10 emission is estimated (a total of 236 individual sectors and sub-sectors) were allocated an appropriate size distribution and used to calculate emission inventories for PM2.5, PM1 and PM0.1. The results are shown in Tables 4.5-4.7 in the same format as for the PM10 inventory.
Figures 4.3-4.5 show trends in emissions of each particle size by source sector. The results show a comparable decline in emissions of each particle size since 1990, although the PM0.1 size fractions indicate a larger decrease. Between 1990 and 2000, UK emissions of PM10 fell by 40%, whereas emissions of PM2.5 fell by 28%, PM1 by 28% and PM0.1 by 40%. There is a gradual change in the relative source contribution with particle size. This is illustrated in Figures 4.2 to 4.5 which show the contribution of each sector to PM10, PM2.5, PM1 and PM0.1 emissions from 1990 to 2000. Road transport becomes an increasingly important sector as the particle size decreases. In 2000, it accounted for 18% of PM10 emissions, but 43% of PM0.1 emissions.
Table 4.5 UK emissions of PM2.5 by sector (ktonnes) estimated for the mass fraction of particles below 2.5 µm in each sector in the PM10 inventory
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
Comb. in Energy
Prod/Trans |
41 |
37 |
34 |
37 |
33 |
34 |
35 |
35 |
36 |
39 |
38 |
19% |
Comb. in
Comm/Inst/Resid |
94 |
83 |
71 |
70 |
67 |
57 |
55 |
56 |
52 |
53 |
46 |
23% |
Combustion in
Industry |
70 |
61 |
53 |
55 |
50 |
44 |
44 |
43 |
41 |
43 |
33 |
17% |
Production
Processes |
16 |
16 |
17 |
18 |
17 |
16 |
16 |
15 |
16 |
16 |
14 |
7% |
Road Transport |
40 |
41 |
43 |
44 |
43 |
43 |
45 |
45 |
46 |
47 |
48 |
24% |
Other Transport |
12 |
13 |
13 |
14 |
12 |
12 |
12 |
12 |
12 |
12 |
11 |
5% |
Waste Treatment
& Disposal |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
3 |
4 |
5 |
4 |
2% |
Agriculture/Forestry |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
5 |
2% |
TOTAL |
277 |
255 |
236 |
244 |
227 |
212 |
212 |
213 |
211 |
218 |
198 |
100% |
Table 4.6 UK Emissions of PM1 by Sector (ktonnes) Estimated for the Mass Fraction of Particles below 1 µm in each Sector in the PM10 Inventory
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
Comb. in Energy
Prod/Trans |
21 |
19 |
17 |
18 |
16 |
17 |
16 |
17 |
17 |
18 |
17 |
12% |
Comb. in
Comm/Inst/Resid |
73 |
64 |
54 |
53 |
51 |
43 |
41 |
42 |
39 |
40 |
34 |
24% |
Combustion in
Industry |
41 |
37 |
34 |
36 |
32 |
29 |
29 |
28 |
27 |
28 |
21 |
15% |
Production
Processes |
8 |
7 |
8 |
8 |
8 |
7 |
8 |
7 |
7 |
8 |
7 |
5% |
Road Transport |
36 |
37 |
38 |
40 |
39 |
39 |
40 |
40 |
41 |
42 |
42 |
30% |
Other Transport |
11 |
11 |
12 |
13 |
11 |
11 |
11 |
11 |
11 |
11 |
10 |
7% |
Waste Treatment
& Disposal |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
3 |
3 |
5 |
3 |
2% |
Agriculture/Forestry |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
5 |
3% |
TOTAL |
194 |
180 |
168 |
173 |
161 |
150 |
150 |
152 |
150 |
155 |
140 |
100% |
Table 4.7 UK Emissions of PM0.1 by Sector (ktonnes) Estimated for the Mass Fraction of Particles below 0.1 µm in each Sector in the PM10 Inventory
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
Comb. in Energy
Prod/Trans |
6 |
6 |
6 |
5 |
5 |
4 |
4 |
3 |
3 |
3 |
3 |
10% |
Comb. in
Comm/Inst/Resid |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
3 |
8% |
Combustion in
Industry |
8 |
8 |
8 |
8 |
8 |
7 |
7 |
6 |
6 |
5 |
5 |
15% |
Production
Processes |
2 |
2 |
2 |
2 |
2 |
1 |
2 |
1 |
1 |
1 |
1 |
4% |
Road Transport |
25 |
25 |
24 |
24 |
23 |
22 |
20 |
18 |
16 |
15 |
13 |
43% |
Other Transport |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
2 |
5% |
Waste Treatment
& Disposal |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1% |
Agriculture/Forestry |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
5 |
5 |
15% |
TOTAL |
51 |
51 |
50 |
48 |
47 |
43 |
42 |
38 |
36 |
34 |
31 |
100% |
Figure 4.3 UK emissions of PM2.5
Figure 4.4 UK emissions of PM1
Figure 4.5 UK emissions of PM0.1
There has been less interest in the emissions of black smoke across recent years. This is because PM10 has superceded black smoke as an indicator of particulate material in the air. As a result, black smoke emission estimates are presented here in less detail than previous years. The total emissions are included below in Table 4.8
Table 4.8 UN/ECE1 Total Emission of Black Smoke (kt)
|
1970 |
1980 |
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
TOTAL |
1087 |
605 |
484 |
490 |
478 |
454 |
414 |
375 |
364 |
329 |
289 |
273 |
246 |
1 See Annex 1 for definition of UN/ECE Categories
Carbon monoxide arises from incomplete fuel-combustion and is of concern mainly because of its effect on human health and its role in tropospheric ozone formation. It leads to a decreased uptake of oxygen by the lungs and can lead to a range of symptoms as the concentration increases.
The UK emissions of carbon monoxide are shown in Figure 4.6 and Table 4.9 disaggregated by source and fuel. Over the period 1970-2000 emissions decreased by 53% reflecting significant reduction in emissions from road transport, domestic and agricultural sectors.
Figure 4.6 Time Series CO Emissions
The spatial disaggregation of CO emissions is shown in Figure 4.7. The observed pattern of emissions is clearly dominated by road transport emissions. A large proportion of road transport emissions are from vehicles travelling at slow speeds on urban or minor roads, hence the map shows high emissions in urban conurbations.
Figure 4.7 Spatially Disaggregated UK Emissions of CO
The most important source of CO is road transport and in particular petrol driven vehicles. Emissions from road transport fell only slightly between 1970 and 1990 but in recent years have declined more significantly. This is due primarily to the increased use of catalytic converters and to a lesser extent to fuel switching from petrol cars to diesel cars. The emissions from off-road sources includes portable generators, fork lift trucks, lawnmowers and cement mixers. The estimation of emissions from such machinery is very uncertain since it is based on estimates of equipment population and annual usage time.
Table 4.9 UK Emissions of Carbon Monoxide by UN/ECE1 Source Category and Fuel (kt)
|
1970 |
1980 |
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
BY UN/ECE CATEGORY2 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy
Prod. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Public Power |
117 |
121 |
114 |
113 |
110 |
99 |
106 |
104 |
102 |
71 |
73 |
61 |
60 |
1% |
Petroleum Refining Plants |
8 |
8 |
7 |
7 |
7 |
8 |
7 |
8 |
8 |
8 |
8 |
7 |
6 |
0% |
Other Comb. & Trans. |
45 |
24 |
22 |
22 |
20 |
20 |
20 |
22 |
23 |
23 |
26 |
27 |
28 |
1% |
Comb. in
Comm/Inst/Res |
|
|
|
|
|
|
|
|
|
|
|
|
|
0% |
Residential Plant |
1237 |
608 |
345 |
369 |
347 |
369 |
324 |
260 |
268 |
246 |
239 |
244 |
215 |
5% |
Comm/Pub/Agri Comb. |
46 |
26 |
23 |
23 |
21 |
21 |
20 |
19 |
19 |
19 |
18 |
18 |
18 |
0% |
Combustion in
Industry |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel Comb. |
776 |
221 |
390 |
369 |
382 |
382 |
346 |
352 |
350 |
357 |
343 |
347 |
245 |
6% |
Other Ind. Comb. |
217 |
130 |
125 |
120 |
121 |
121 |
123 |
122 |
113 |
115 |
101 |
137 |
136 |
3% |
Production
Processes |
173 |
135 |
178 |
171 |
163 |
163 |
168 |
172 |
177 |
178 |
163 |
142 |
135 |
3% |
Extr./Distrib. of
Fossil Fuels |
2 |
2 |
7 |
3 |
3 |
2 |
3 |
3 |
3 |
3 |
3 |
1 |
1 |
0% |
Road Transport |
5409 |
5367 |
5240 |
5076 |
4858 |
4528 |
4271 |
4003 |
3966 |
3728 |
3508 |
3290 |
2881 |
69% |
Other Trans/Mach |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Off-Road Sources |
584 |
512 |
428 |
445 |
453 |
439 |
428 |
407 |
408 |
407 |
407 |
406 |
405 |
10% |
Other3 |
30 |
28 |
32 |
30 |
29 |
28 |
26 |
26 |
26 |
25 |
23 |
22 |
21 |
1% |
Waste |
3 |
45 |
31 |
28 |
27 |
27 |
35 |
24 |
25 |
20 |
21 |
17 |
16 |
0% |
Land Use Change |
288 |
449 |
266 |
228 |
165 |
4 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0% |
By FUEL TYPE |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Solid |
2237 |
989 |
877 |
879 |
867 |
870 |
792 |
730 |
727 |
686 |
663 |
651 |
521 |
12% |
Petroleum |
6061 |
5930 |
5718 |
5569 |
5356 |
5012 |
4740 |
4450 |
4414 |
4172 |
3949 |
3727 |
3316 |
80% |
Gas |
43 |
35 |
40 |
40 |
43 |
49 |
54 |
57 |
61 |
58 |
60 |
66 |
60 |
1% |
Non-Fuel |
593 |
723 |
573 |
514 |
440 |
279 |
292 |
285 |
285 |
285 |
262 |
273 |
270 |
6% |
TOTAL |
8934 |
7677 |
7208 |
7002 |
6707 |
6210 |
5877 |
5522 |
5487 |
5201 |
4934 |
4718 |
4167 |
100% |
1 UK emissions reported in IPCC format (Salway, 2001) differ slightly
due to the different source categories
used.
2 See Annex 1 for definition of UN/ECE Categories
3 Including railways,
shipping, naval vessels, military aircraft
Other emission sources of CO are small compared with transport and off-road sources. Combustion-related emissions from the domestic and industrial sectors have decreased by 83% and 51% respectively since 1970 due to the decline in the use of solid fuels in favour of gas and electricity. The sudden decline in emissions from the agricultural sector reflects the banning of stubble burning in 1993 in England and Wales. Currently energy production accounts for only 1% of UK emissions.
Studies have shown that exposure to benzene gives rise to an increase in the risk of developing leukaemia, and that benzene exerts its effect by damaging the genetic make-up of cells i.e. it is a genotoxic carcinogen. Consequently it is important to understand sources of benzene and their relative strengths, and ensure that emissions do not give rise to unacceptably high concentrations of benzene.
Benzene emissions arise predominately from the evaporation and combustion of petroleum products. Emissions of benzene are dominated by the road transport sector, accounting for 47% of the 2000 emission estimate total. As benzene is a constituent of petrol, emissions arise from both evaporative and combustion of petrol. Benzene emissions for 1990 to 2000 are given in Table 4.10 and Figure 4.8 below.
Benzene emissions also arise as stack emissions and, more importantly, fugitive emissions from its manufacture and use in the chemical industry. Benzene is a major chemical intermediate, being used in the manufacture of many important chemicals including those used for the production of foams, fibres, coatings, detergents, solvents and pesticides.
Benzene emissions have been steadily decreasing since 1990. These decreases are primarily due to the introduction of cars equipped with catalytic converters since 1991, although emissions from the domestic and industrial sectors are also falling. However, it is the increasing number of cars in the national vehicle fleet that are equipped with catalytic converters which maintains the decreasing total of benzene emissions as the reductions from other source sectors are small by comparison.
The most noticeable decrease between 1999 and 2000 arises from the road transport sector. This is because the benzene content of petrol was substantially decreasesd between 1999 and 2000- resulting in a corresponding decrease in emissions.
Table 4.10 UK emissions of Benzene by UN/ECE1 Source Category (ktonnes)
|
1990 |
1991 |
1992 |
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000 |
2000% |
BY UN/ECE CATEGORY1 |
|
|
|
|
|
|
|
|
|
|
|
|
Comb. in Energy Prod. |
|
|
|
|
|
|
|
|
|
|
|
|
Petroleum Refining Plants |
0.00 |
0.00 |
0.01 |
0.01 |
0.00 |
0.01 |
0.01 |
0.01 |
0.01 |
0.01 |
0.01 |
0% |
Other Comb. & Trans. |
0.29 |
0.29 |
0.29 |
0.29 |
0.32 |
0.13 |
0.15 |
0.18 |
0.18 |
0.20 |
0.18 |
1% |
Comb. in Comm./Inst/Res |
|
|
|
|
|
|
|
|
|
|
|
|
Residential Plant |
4.04 |
4.20 |
4.17 |
4.16 |
3.62 |
3.14 |
3.32 |
3.16 |
3.23 |
3.34 |
3.00 |
18% |
Comm/Pub/Agri Comb. |
0.11 |
0.13 |
0.13 |
0.12 |
0.13 |
0.14 |
0.15 |
0.14 |
0.14 |
0.15 |
0.16 |
1% |
Combustion in Industry |
|
|
|
|
|
|
|
|
|
|
|
|
Iron & Steel Comb. |
0.31 |
0.32 |
0.30 |
0.30 |
0.23 |
0.24 |
0.24 |
0.26 |
0.24 |
0.23 |
0.22 |
1% |
Other Ind. Comb. |
0.41 |
0.39 |
0.37 |
0.37 |
0.53 |
0.56 |
0.59 |
0.60 |
0.57 |
0.54 |
0.60 |
4% |
Production Processes |
4.37 |
4.46 |
4.67 |
4.55 |
4.66 |
4.59 |
4.05 |
3.43 |
2.26 |
2.04 |
1.65 |
10% |
Extr./Distrib. of Fossil Fuels |
1.02 |
1.07 |
1.12 |
1.15 |
1.13 |
1.08 |
0.95 |
0.99 |
0.96 |
0.72 |
0.67 |
4% |
Road Transport |
|
|
|
|
|
|
|
|
|
|
|
|
Combustion |
40.07 |
39.16 |
37.54 |
34.64 |
32.14 |
29.50 |
27.30 |
24.55 |
22.01 |
19.69 |
7.42 |
45% |
Evaporation |
2.41 |
2.38 |
2.33 |
2.17 |
2.01 |
1.84 |
1.72 |
1.58 |
1.34 |
1.22 |
0.29 |
2% |
Other Trans/Mach |
2.44 |
2.52 |
2.52 |
2.44 |
2.36 |
2.27 |
2.31 |
2.30 |
2.22 |
2.19 |
2.17 |
13% |
Waste |
0.10 |
0.10 |
0.10 |
0.09 |
0.09 |
0.08 |
0.08 |
0.08 |
0.07 |
0.07 |
0.06 |
0% |
Land Use Change |
0 |
0 |
0 |
0 |
0 |
0 |
0 |