Third Stage Review and Assessment of Air Quality in Hackney

Transcription

1 Third Stage Review and Assessment of Air Quality in Hackney

2 Third Stage Introduction... 4 The National Air Quality Strategy... 4 DETR Guidance... 6 Local Air Quality Management... 7 Central London Cluster Group... 7 Selection of model for the study Sources and Health Effects of Air Pollution Carbon Monoxide (CO) Nitrogen Dioxide (NO 2 ) Sulphur Dioxide (SO 2 ) Fine Particles (PM10) Benzene ,3-butadiene Lead Air Quality Monitoring In Hackney Chemiluminescent Nitrogen Dioxide Analyser Non-dispersive infra-red carbon monoxide analyser Ultra Violet Photometric Ozone Analyser Tapered Element Oscillating Microbalance (TEOM) fine particles PM BS17457 Sulphur Dioxide and Black Smoke Passive Diffusion Tubes (Nitrogen Dioxide) Stage 111 Review and Assessment of Air Quality Introduction and overview London Emissions Inventory Inventory for current emissions NO x, PM 10, VOC Emissions Road traffic sources Major Road Analysis of Major Road Data Replacement of LRC traffic data with DETR Traffic counts Borough Data Minor Roads Cold starts and trip ends Industrial point sources Aggregated grid sources Other Sources SO 2 emissions Point source data Grid source data Predicted 25 Emissions Inventory Current NoX Emissions for London Current PM 10 emissions for London Current NMVOC emissions for London Current SO 2 emissions for London NO X emissions PM 10 emissions NMVOC emissions SO 2 emissions NOx, PM 10 and VOC emissions Major road emissions Adjustment of 24 road traffic emissions

3 Calculation of the adjustment factor Use of dispersion models for air quality predictions] Overview of ADMS urban Methodology Model Input a) Emissions Inventory Model Data and Assumptions Meteorological data Chemistry Scheme Grid Sources vehicle emissions area emissions point emissions Background Concentrations Base year background concentrations NO x, NO 2 and O PM background pollutant concentrations PM NO x, NO 2 and Ozone Possible sources of error Terrain Scenarios modelled using ADMS Urban Validation of model Model Validation for Nitrogen dioxide and PM Model Validation of Sulphur Dioxide Findings of Hackney's Stage 111 Review and Assessment Baseline Runs Meteorological Data (i) Annual Mean NO 2 (Derwent-Middleton Scheme) (Figure 73) (ii) Annual Mean NO 2 (GRS Scheme) (Figure 74) (iii) Maximum NO 2 (Derwent-Middleton Scheme) (Figure 75) (iv) Maximum NO 2 (GRS Scheme) (Figure 76) (v) 99 th percentile of running 24 hour mean PM 10 concentrations (Figure 77). 50 (vi) Annual mean SO 2 (Figure 78) (vii) 99.9 th percentile of 15 minute mean SO 2 concentrations (Figure 79) Meteorological data (i) Annual mean NO 2 (Figure 80) (ii) Maximum NO 2 (Figure 81) (iii) 99 th percentile of running 24 hour mean PM 10 concentration (Figure 82).. 50 (iv) Annual mean SO 2 (Figure 83) (v) 99.9 th percentile of 15 minute mean SO 2 concentrations (Figure 84) Future Scenario Meteorological Data (i) Annual Mean NO 2 (Figure 85) (ii) Maximum NO 2 (Figure 86) (iii) 99 th percentile of running 24 hour mean PM 10 concentrations (Figure 87). 51 (iv) Annual mean SO 2 (Figure 88) (v) 99.9 th percentile of 15 minute mean SO 2 concentrations (Figure 89) Meteorological data (i) Annual mean NO 2 (Figure 90) (ii) Maximum NO 2 (Figure 91) (iii) 99 th percentile of running 24 hour mean PM 10 concentrations (Figure 92). 52 2

4 (iv) Annual mean SO 2 (Figure 93) (v) 99.9 th percentile of 15 minute mean SO 2 concentrations (Figure 94) Public Exposure... Future Developments... Sulphur Dioxide Nitrogen Dioxide Particles (PM 10 ) Designation of proposed Air Quality Management Areas Methodology for selection of Air Quality Management Areas... Areas selected for proposed Air Quality Management Areas... Public Consultation... Public consultation The next steps Appendix XXX Hackney's First Stage Air Quality Review & Assessment Executive Summary Air Pollution Monitoring in Hackney Air Pollution in Hacknev Results of the First Stage Assessment APPENDIX X: CHEMISTRY SCHEMES USED IN ADMS URBAN The Derwent-Middleton Correlation Co-ordinates X Y Co-ordinates Co-ordinates Appendix XXX LAQM. TG1(98) - Monitoring for Air Quality Reviews and Assessments References Additional references Table 1 NAQS Air Quality objectives... Table 2 Base year Greater London Emissions by source type... Table 3 Base year Greater London Emissions by source type %... Table 4 AUN sites and selected roads for which LRC and Borough data were compared... Table 5 Base year SO2 emissions by source type... 3

5 Third Stage Review and Assessment of Air Quality in Hackney 1.0 Introduction This report provides the final part of the three-stage review and assessment process for the London Borough of Hackney, which forms part of the Local Air Quality Management process, laid down by Part 1V of the Environment Act The purpose of the Review and Assessment of air quality is to enable local authorities to appraise current and future air quality for their geographical area, against the current National Air Quality Strategy (NAQS) objectives, for the year 25. These are set out in the Air Quality Regulations If the results of this assessment are such that the objectives are unlikely to be met by the year 25, the local authority is then required to designate Air Quality Management Area (AQMA) and prepare a written action plan. The council has followed the phased approach required by the Government and has undertaken the first stage of the review and assessment. The stage 1 review and assessment report indicated the possibility of an exceedence of the NAQS objectives for the following pollutants. Nitrogen Dioxide Fine Particulate Matter Sulphur Dioxide It was also concluded from the first stage review and assessment that a second stage review and assessment of air quality in Hackney would not produce any useful additional information. Hackney therefore, decided to proceed to a third stage review and assessment for nitrogen dioxide, sulphur dioxide and particulate matter. In the third stage review and assessment, local authorities are required to undertake an accurate and detailed review and assessment of current and future air quality. Department of the Environment Transport and the Regions (DETR) Statutory Guidance advises that Local authorities will need to predict whether a failure to achieve an air quality objective by the end of 25 is likely. This will be a crucial factor, which will trigger the designation of AQMAs. The guidance further advises that a local authority should investigate the areas within its boundaries where there is the likelihood of a failure to achieve air quality objectives and the potential for exposure of individuals. The authority should also estimate the magnitude and geographical extent of such exceedences. The National Air Quality Strategy In 1997 the Government published a National Air Quality Strategy for the UK with the aim of creating a more strategic and integrated approach to air quality issues. The Strategy attempts to embody the principles of sustainable development in formulating the Government s standards, objectives and targets for the improvement of air quality in the UK. 4

6 The Strategy highlighted eight main air pollutants: benzene, 1,3-butadiene, carbon monoxide, lead, nitrogen dioxide, ozone, sulphur dioxide and fine particulates. Standards are set for each of these pollutants based on health related recommendations made by the Expert Panel on Air Quality Standards (EPAQS). The Air Quality Regulations 20 set Air Quality Objectives for seven of the eight pollutants (summarised in Table 1) which are to be achieved at varying dates up to 31 December 25. The NAQS sets out a range of policy options for achieving the objectives, including a combination of national and international policies as well as a nation-wide system of local air quality management, in which local authorities are required to review and assess the quality of air in their areas and to take action where health-based objectives are unlikely to be met.. Local Authorities are required to carry out a comprehensive three-stage review and assessment of air pollution levels in their borough, and to assess whether the air quality targets set by the government will be met by 25.This review and assessment process involves; Identifying major sources of pollution - either from roads or industry. Collating information on traffic flows and speeds. Monitoring levels of air pollution. Identifying proposed developments, which may have an impact on future air quality. Using computer models to make future predictions about air pollution levels. Identifying where air quality targets will not be met in 25. 5

7 Table 1 NAQS Air Quality objectives Pollutant Air Quality Objective Levels Benzene 5pbb or less, when expressed as a running annual mean by 31 December 23 1,3-Butadiene 1ppb or less, when expressed as a running 8 hour mean by 31 December 23 Lead 0.5 μg.m -3, when expressed as an annual mean by 31 December 24 and 0.25 μg.m -3 or less, when expressed as an annual mean by 31 December 25 Nitrogen 2 μg.m -3 (105 ppb) not to be exceeded more than 18 times a Dioxide year, when expressed as an hourly mean by 31 December 24 and 40 μg.m -3 (21 ppb) or less, when expressed as an annual mean by 31 December 25 PM μg.m -3 or less as a 24 hour mean not to be exceeded more than 35 times a year as expressed by 31 December 24 and 40 μg.m -3 or less, when exceeded as an annual mean Sulphur Dioxide 350 μg.m -3 (132ppb) not to be exceeded more than 24 times a year when expressed as a 1 hour mean by 31 December 24 and 125 μg.m -3 (47ppb) not to be exceeded more than 3 times a year when expressed as a 24 hour mean by 31 December 24 and 266 μg.m -3 (1ppb) not to be exceeded more than 35 times a year when expressed as a 15 minute mean by 31 December 25 Objectives for the protection of human health ozone 1 μg.m -3 (50ppb) not to be exceeded more than 10 times a year when expressed as a daily maximum of running 8 hour mean to be achieved by 31 December 25 Objectives for the protection of vegetation and ecosystems Nitrogen 30 μg.m -3 (16 ppb) when expressed as an annual mean to be oxides achieved by 31 December 20 Sulphur Dioxide 20 μg.m -3 (8 ppb) when expressed as an annual mean to be achieved by 31 December 20 and 20 μg.m -3 3 (8 ppb) when expressed as a winter average (1 October to 31 March) to be achieved by 31 December 20. ppb = parts per billion, ppm = parts per million, μg.m -3 = micrograms per cubic metre DETR Guidance This study has been carried out accordingly, using the most appropriate data and methodology within the time frame allowed. At each stage of the process, the Council has had due regards to technical guidance issued by the Department of the Environment, Transport and the Regions, as well as consulting with academics and other expert groups in order to seek the latest advice. DETR technical guidance notes which have been issued are listed in Appendix XXXX 6

8 Local Air Quality Management Local authorities are required by the Environment Act 1995 to carry out periodic reviews of air quality in their area, and to review and assess present and likely future quality against the health based standards/objectives set out in the NAQS and prescribed by the Air Quality Regulations 20. The NAQS and associated guidance sets out the manner in which the review and assessment process should be carried out. It recommends a phased approach undertaken in three stages. Pollutants where an initial review indicates there to be no local problem will be excluded from the later stages. Pollutants where air quality problems are anticipated in 25 are likely to progress to the third and final stage of the assessment which will detail both the level and the spatial distribution of noncompliance with the National Objectives. Following the completion of the third stage review and assessment, the local authority must declare Air Quality Management Areas in those locations where the 25 objectives are unlikely to be met. Action Plans detailing the measures to be taken by the local authority to reduce pollutant concentrations and achieve compliance with the objectives must be drawn up within 12 months of declaration of AQMA Central London Cluster Group The central London Cluster group is one of five cluster groups operating within the London Air Quality Network. Each cluster group consists of adjacent London Local Authorities with one of the boroughs being the lead borough. These groups regularly meet to discuss matters concerning air quality initially set up to ensure consistency in air quality monitoring. The Central London Group consist of the following eight boroughs: London Borough of Hackney London Borough of Camden City of Westminster Corporation of London London Borough of Islington Royal Borough of Kensington & Chelsea London Borough of Lambeth London Borough of Southwark 7

9 The Cluster Group have been working together on their Stage III modelling assessment since May 1998, when a joint supplementary credit bid was made to the Department of the Environment, Transport and the Regions to fund the development of a complex computer model which would allow the local authorities to make predictions about current and future air quality. This bid was successful, and consultants were contracted to develop a pollution model specifically for the central London boroughs. 8

10 The local authorities are keen to continue to collaborate as much as possible on future air quality management issues, since air pollution does not respect borough boundaries. This is particularly important in the development of Action Plans, and the local authorities are already beginning to discuss ideas for future joint initiatives. Selection of model for the study The central London cluster group used the ADMS-urban dispersion model provided by Cambridge Environmental Research Consultants (CERC) for the third stage review and assessment of air pollution. Five dispersion models initially appeared to comply with the DETR guidance on choosing a dispersion model. After presentations from the companies providing the models, it was clear that only two models; ADMS and Indic Airviro fulfilled the essential criteria required by the cluster group. This was as follows: An individual licence for each cluster group member to run the software in their own offices Suitability for carrying out a third stage review and assessment Ability to predict oxides of Nitrogen, PM10 particles and Sulphur Dioxide to the limits given in the National Air Quality Strategy and the required percentiles. Ability to produce a course receptor grid output (in other words to plot all eight boroughs on an overview map). Ability to produce a fine receptor grid output (a fine scale map of each borough or part of a borough). Ability to interface with Geographical Information System (a computer map package) Ability to meet the specified timetable and budget. Provision of suitable training and technical support in use of the model. Further more detailed criteria were looked at to separate ADMS-urban and Indic Airviro, after adding up the scores, ADMS scored more highly on technical support and training as CERC s offices are based in Cambridge while Indic Airviro is run by the Swedish Met Office. ADMS also gained a little over Indic on the user-friendliness of the system, as it as based on a PC, while Indic runs from a more specialist Unix Workstation. It was also felt that CERC had more experience of modelling UK cities. 9

11 2.0 Sources and Health Effects of Air Pollution Emissions from road traffic is the main source of air pollution in central London, and accounts for around 80-90% of most of the key urban pollutants such as nitrogen dioxide, carbon monoxide, benzene and particulates (PM 10 ). Other less important sources include industry, power stations, and domestic and commercial heating. The sources and health effects of the main urban pollutants are summarised below: Carbon Monoxide (CO) Carbon monoxide gas is produced in the process of incomplete combustion, be it in a motor car engine, domestic heating, a cigarette or a forest fire. In the indoor environment individuals are exposed to carbon monoxide from sources such as domestic fuel burning heaters and gas cooking appliances. Outdoors, the main source of carbon monoxide in London is road transport, which accounts for 75% of all emissions predominantly from petrol vehicles, diesel vehicles contributing less than 5%. Improvements to vehicle performance and the introduction of catalytic converters has resulted in reduced concentration of carbon monoxide in inner cities. But there may be a slight and steady increase in carbon monoxide concentration if traffic numbers increase as predicted. Unlike many toxic gases, carbon monoxide is both colourless and odourless and lifethreatening concentrations can be breathed without giving any warning to the victim. The first sign of severe poisoning is loss of consciousness and further inhalation of high concentrations readily leads to death. These effects are due to the interference of carbon monoxide with the processes whereby oxygen is taken up by the blood and utilised in the cells in the body. It does this both by interfering with transport of oxygen by red cells in the blood (by the formation of carboxyhaemoglobin, which substantially reduces the ability of the red cell to carry oxygen) and also by blocking essential biochemical reactions in cells. In those people who recover from accidental or deliberate poisoning by carbon monoxide, brain damage of a greater or lesser degree due to lack of oxygen. The formation of carboxyhaemoglobin in the blood of people exposed to carbon monoxide and the amount present depends on both the concentrations in the air and duration of exposure, as well as on the rate and depth of breathing. Thus someone exercising and breathing more rapidly and deeply, will have higher blood concentration than someone resting but exposed to the same concentration. Smokers may have levels of 4% to as high as 15% depending on the number of cigarettes smoked. Uptake of carbon monoxide from multiple sources, such as smoking and traffic, is not additive. It is likely that people who already have a disease affecting delivery of oxygen to the heart or brain are likely to be at particular risk if these delivery systems are further impaired by carbon monoxide. These will include angina sufferers, others with severe heart and lung disease, or anaemia, as well as young infants and the elderly. Nitrogen Dioxide (NO 2 ) Nitrogen dioxide is a gas produced by reaction of nitrogen and oxygen in combustion processes. The main source of nitrogen dioxide in urban areas is from motor 10

12 transport and fossil fuel combustion. Of the transport sources, petrol combustion in cars is currently responsible for a greater proportion than diesel, though this relationship is changing with the progressive introduction of the catalytic converters on petrol vehicles. It has been suggested that the gas may have both acute (short-term) and chronic (longer-term) effects on health, particularly in people with asthma. Its properties as an oxidising agent can damage cell membranes and proteins The results showed that people with healthy lungs, whether at rest or exercising, show little response to experimental inhalation of nitrogen dioxide at concentrations well above those occurring in the ambient air, even during pollution episodes. However, in people with asthma, some studies have shown changes in these tests of lung function to have occurred at exposures of around 3ppb (parts per billion) when subject have been exercising. Sulphur Dioxide (SO 2 ) Sulphur dioxide is a gas at normal temperature and pressure. It dissolves in water to produce an acidic solution which readily oxidises to sulphuric acid. The predominant source of sulphur dioxide is from the combustion of sulphur containing fossil fuels, principally coal and heavy oils. Road transport also accounts for a small percentage with the combustion of diesel fuel contributing to background levels. Sulphur dioxide is an irritant when it is inhaled because of its acidic nature. It causes its irritant effects by stimulating nerves in the lining of the nose, throat and the lung's airways. This causes a reflex cough, irritation, and a feeling of chest tightness, and may lead to narrowing of the airways. This is often the case in asthmatics and people suffering from chronic lung disease whose airways are often inflamed and easily irritated. There is clear evidence that some asthmatics show reductions in breathing capacity after short-term exposure to concentrations of about 4ppb. Healthy individuals have exhibited measurable narrowing of the airways after exposure to sulphur dioxide at concentrations above 1,0ppb. Fine Particles (PM10) Particles in the air may arise from a wide variety of sources, either natural or manmade. Man-made air borne particles result mostly from combustion processes, from the working of soil and rock, from many other industrial processes and from the attrition of road surfaces by motor vehicles The largest single source of fine particles in urban areas is road traffic. Unlike other gaseous pollutants, with which it has often been possible to carry out controlled exposure of volunteers and of animals and thus reach reasonable conclusions about concentrations at which harm is likely to occur, no similar studies with mixtures of particulate pollutants characteristic of ambient PM 10 (fine particles less than 10 microns (μm) in diameter) have to date been technically possible. There is evidence that long-term exposure to particulate pollution may increase the risk of developing lung cancer as well as having an effect on mortality from heart and lung diseases. 11

13 Benzene Motor vehicles are the most important single source of benzene accounting for over 70% of emissions, which is emitted in exhaust gases in both unburned form and also that formed by combustion with other aromatic components of petrol. The effect of long term exposure to benzene of most concern is leukaemia and in particular several types of this disease known collectively as the non-lymphocytic leukaemia. It acts on the genetic material of cells causing malignant effects. At concentrations occurring in the ambient atmosphere, benzene does not have short term or acute effects. The risks of leukaemia in individual workers, exposed to much higher concentrations of benzene, has been related to their calculated lifetime exposure- the more benzene they have been exposed to, the greater the risk. 1,3-butadiene The motor vehicle is by far the largest source of 1,3 butadiene in urban areas. 1,3 butadiene is not present in diesel or petrol, either leaded or unleaded; the emissions in the exhaust gases being produced by the combustion process itself. The chemicals in petrol from which the 1,3-butadiene is derived, higher olefins, have been present in increasing proportion in petrol over the last decade, and it is likely that the amounts of 1,3-butadiene released into the atmosphere have therefore been rising. However, 1,3-butadiene is removed efficiently by catalytic converters on motor cars and levels of 1,3-butadiene are expected to fall. There is evidence that workers exposed to 1,3 butadiene have a slightly higher than expected risk of cancers to the bone marrow, lymphomas and leukaemia. Laboratory studies have shown that 1,3 butadiene causes a variety of cancers in rodents and damages the genetic structures of the cell. It is thus genotoxic carcinogen and, in theory, it is not possible to determine an absolutely safe level for human exposure. Lead The single largest use globally is in the manufacture of batteries. As the compound tetraethyl lead, it has been used as a petrol additive to enhance the octane rating. With the recognition of the adverse effects of lead on human health and the increasing use of catalytic converters, which are poisoned by lead, this use is declining rapidly. At the end of 1985 the maximum permitted lead content of petrol was reduced significantly from 0.40g/l to 0.15g/l. This almost halved levels of lead in urban air in the space of a few months. This improvement in urban lead levels continued with the introduction of unleaded petrol in Since 1993 all new petrol engined cars have been catalyst equipped and must run on unleaded petrol Since 20 no added lead in petrol. Direct human exposure to lead occurs through food, water, dust, soil and air. Most people receive the largest portion of their daily intake via food, although other sources may be important in specific members of the population (e.g. water in areas with lead pipes and a plumposolvent water supply, air in populations living near point 12

14 sources of lead, soil, dust and paint flakes in young children living in houses with leaded paint or contaminated soil). 13

15 3.0 Air Quality Monitoring In Hackney Hackney has given a high priority to air pollution in the borough since the introduction of the clean air acts 1956 and 1968.In 1992, Hackney became part of the National Diffussion tube survey monitoring nitrogen dioxide concentrations at various throughout the borough. The techniques used to monitor the air quality in Hackney are given in the following sections. Chemiluminescent Nitrogen Dioxide Analyser The determination of oxides of nitrogen is based on the chemiluminescent energy emitted when nitric oxide is reacted with ozone to form chemiluminescent nitrogen dioxide. The analysers are compliant with the international standard for this type of equipment. The quality control procedures as detailed in the National Technology Centre (NETCEN) site operators manual are followed for the equipment. The analysers are calibrated once every two weeks using gases traceable to national standards. All data is scaled in line with fortnightly calibration checks. The analysers also perform overnight span checks and are serviced every 6 months. Non-dispersive infra-red carbon monoxide analyser Carbon monoxide analyser works by transmitting an infra red beam of light through a cell through which ambient air is pumped. The absorbency is related to the carbon monoxide concentration. The analyser is calibrated once every two weeks using gases traceable to national standards. All data is scaled in line with fortnightly calibration checks. The analysers also perform an internal overnight span check and are serviced every 6 months. Ultra Violet Photometric Ozone Analyser Ozone is measured using an ultra violet photometric ozone analyser. Ozone concentration is calculated from the absorption of ultra violet light. The equipment has its own internal analyser for routine zero/span checks. The analyser is serviced every 6 months. Tapered Element Oscillating Microbalance (TEOM) fine particles PM2.5 The PM2.5 fraction is obtained through a separator and this air is passed through an oscillating balance head, which traps the particulate matter. The weight of dust landing on the balance slows down the speed of the oscillation. The energy needed to regain the original frequency is equivalent to the weight of particulate matter; giving an instantaneous concentration. Fifteen-minute average concentrations are collected from the analyser. The inlet is heated to 50 degree Celsius to prevent condensation problems. BS17457 Sulphur Dioxide and Black Smoke 14

16 Hackney Council operates two sites; one at 205 Morning lane and one at Shoreditch Town Hall (both are classified as background sites). They are used to assess the European Union guidelines and limit values, which take account of both sulphur dioxide and black smoke. During the smog of the 1950 s these two pollutants were shown to act synergistically on the lungs; their combined effects on human health are greater than the effects seen individually. The BS17457 monitors were used to monitor the effects of the Clean Air Acts 1956 and AEA Technology operate a quality control procedure for the sites used for the European Union Directive Network. The Shoreditch Town Hall site is part of this Network, the other site is operated to the same standard. This ensures that all pumps and gas meters are operating satisfactorily and all chemicals used are made up to acceptable concentrations. The pumps and gas meters have their flow rates checked weekly and all pumps are serviced annually. The monitors themselves work by Sampling ambient air so that smoke particles are trapped onto a Whatman no. 1 filter and sulphur dioxide is removed from the air by bubbling air through a 1% hydrogen peroxide solution. The concentrations are determined by laboratory analysis. This equipment measures daily average concentrations. The blackness of smoke is assumed to be correlated to concentration and is measured with a reflectometer; these also have to be calibrated annually. Passive Diffusion Tubes (Nitrogen Dioxide) Hackney Council has 12 sites within the borough and they were set up to estimate whether any part of the borough exceeded the European Union Limit and guidelines. Four of the sites were set in schools in the Hackney Wick area to monitor the impact of the M11 link Road project. This is one of the cheapest methods available, but can only give average concentrations over a relatively long time period. The tubes absorb the gas onto an inert medium allowing the concentrations to be determined later in a laboratory. 15

17 4.0 Stage 111 Review and Assessment of Air Quality 4.1 Introduction and overview This section outlines the methodology used to undertake the stage III review and assessment for nitrogen dioxide, sulphur dioxide and PM 10, in order to assess whether air quality objectives for these pollutants will be met by the 25 deadline. It describes the information and data that was collected for the review and assessment process, and explains how the computer model was used to give predictions of air quality in 25. For Stage III, the government expects local authorities to undertake an accurate and detailed review and assessment of current and future air quality for particular pollutants in question. An air quality management area can not be declared unless a third stage review and assessment has indicated that air quality objectives are not likely to be met by the end of 25. Local authorities are required to investigate locations within its boundaries, where both pollution levels may exceed the objective, and where there is a potential for exposure to people. The authority must then estimate the magnitude and geographical extent of such potential pollution problem areas. The government has indicated in their technical guidance that the level of detail required for a third stage review and assessment will entail local authorities constructing a detailed inventory of all possible sources of pollution. For example, in the action of operating a factory, driving a car, or heating a house, a variety of pollutants are released into the atmosphere and the amount of pollutant which is released will need to be quantified. The authority will also need to use an appropriate validated dispersion model in order to predict current and future air quality. The dispersion model the local authorities decide to use should be from an approved list as recommended by the Department of the Environment, Transport and the Regions. The estimates of current air quality produced from the dispersion model will be required to be validated against continuous automatic air quality monitoring. Where such monitoring is undertaken, local authorities are required to demonstrate that the monitoring data has been quality assured and controlled to an appropriate level and that measurements are traceable to national reference standards. 4.2 London Emissions Inventory The strategic approach in dealing with air pollution requires such details as the sources of the emission, its concentration, rate of emission and a means of determining or estimating future emission. It is also important to determine how the emission will react with other pollutants, how their levels change with time and the resultant effect on air quality An emission inventory is the resultant database that collates all the information about an emission that can be used to determine the above information. The construction of an inventory is dependent on its intended use. The emission inventory used for this stage 111 process was compiled by the London Research Centre (LRC). The LRC was commissioned by DETR to produce an emission 16

18 London road networ Kilometers N 17

19 inventory for London, which was released in It contains information for eight key pollutants that are contained in the NAQS and three additional pollutants. The key pollutants are oxides of Nitrogen, Sulphur dioxide, Carbon monoxide, Non- Methane volatile organic compounds, carbon dioxide, benzene, 1,3 butadiene and particulate matter. The remaining pollutants are black smoke, methane, and total suspended particulate. The inventory was complied for and includes data obtained for all London Boroughs and the City of London. The data was collected and analsyed using 1x1 kilometre Ordnance Surveys s national grid. The sources were divided into three broad groups: area emissions The area emissions are mainly concerned with the emissions from residential areas and large industrial estates, derived from the fuel consumption provided by the fuel supply companies. Line sources including roads and railways point emissions These are the industrial processes that are regulated under the Environmental Protection Act 1990 and are referred to as Part A and Part B processes Inventory for current emissions Atmospheric emissions inventories have been prepared for each of the pollutants of interest and for each of the scenarios modelled which are as follows: a current or base year scenario has been modelled using a base year inventory, representative of recent emissions, and 1996/1997 meteorological data. A summary of emissions rates broken down by source type is shown in Table 2. The total estimated emissions of NO x and PM 10 from Greater London are dominated by the contribution from road traffic in the base year, with SO 2 and VOC emissions arising primarily from non-road sources. Emissions of VOC s have been included for modelling of NO 2 concentrations using the Generic Reaction Set (GRS), (Appendix B). Table 2 Base year Greater London Emissions by source type Source Emission rate (T/Yr) NO x PM 10 VOC SO 2 Major road Minor road Non-road Total

20 Table 3 Base year Greater London Emissions by source type % Source Percentage contribution NO x PM 10 VOC SO 2 Major road Minor road Non-road NO x, PM 10, VOC Emissions The following sources have been considered in the modelling of NO 2 and PM 10 concentrations: Road traffic sources Emissions arising from road traffic have been considered in three categories: Emissions from major roads for which link-based traffic flow data are available, Emissions from minor roads for which link-based traffic flow data are unavailable, Emissions associated with cold starts and trip ends. Major Road The major roads emissions inventory is based primarily on that supplied by LRC. The network (Figure 2) consists of a total of 9020 major road links derived from the LTS transport-planning model. From this network approximately 1650 Central London road links have been explicitly modelled, with the remainder considered as a component of the aggregated grid source emissions (Section ). The selection, in accordance with the DETR s Pollutant Specific Guidance (August 1998) for NO x, represents all roads with an annual average daily traffic flow (AADT) of greater than 2. Also included, are roads with an average speed of less than 10km/h, additional roads specified by the London Cluster Group, and roads which when included reconnect isolated network segments. A plot of these roads for Hackney is shown in Figure XXX. Analysis of Major Road Data In order to validate and improve the inventory, the LRC traffic data have been compared to more recent traffic flow information supplied by the Central London boroughs. The additional data supplied include 1997 DETR annual average daily traffic flow counts for all A roads within the eight Central London boroughs, and 1997/1998 hourly traffic flow counts for a number of roads within the London boroughs of Camden, Southwark and the Corporation of London. The DETR traffic counts formed the basis of a limited evaluation of the LRC traffic data. In order to assess the consistency of the traffic flows between the DETR and LRC data, common roads were compared using ArcView GIS. The comparison focused on a selection of heavily trafficked roads within close proximity of the AUN sites, with the additional aim of ensuring that the traffic data in the vicinity of those AUN sites used for model validation were in good agreement with the DETR counts. The results of the evaluation (Table 2) show some significant differences between the two data sets, with a number of the DETR traffic counts being higher than the LRC flows, there is however no consistent trend within the data considered. 19

21 Replacement of LRC traffic data with DETR Traffic counts Given the inconsistencies between the two data sets, DETR traffic data were used to perform a limited adjustment to emissions from road sources. This adjustment was performed during the validation study in order to assess the effect of incorporating the measured traffic counts on the resultant concentrations. This is discussed further in In order to maintain consistency with the majority of the LRC major roads inventory, the emission rates of the selected roads shown in Figure 4 and listed in Table 2 were scaled according to the relative difference in the AADT, as follows: E new AADTboro = E LRC (1) AADT LRC where Enew is the new emission rate, E LRC is the LRC emission rate, AADTboro is the DETR traffic data supplied by the Boroughs and AADT LRC is the traffic data supplied by LRC. Table 4 AUN sites and selected roads for which LRC and Borough data were compared Monitoring site Comments Road LRC Borough name AADT(7) AADT(7) 1997 Bloomsbury Nearest to site A Bridge Place Sections equivalent to A A Cromwell Road A road N of site A * Earls Court A AUN on road A Hackney A road N of site A A road S of site A Marylebone A road on which site A lies North Kensington B road 50m E of site 7837 No road to compare Old Kent Road Sections equivalent to A Swiss Cottage Sections equivalent to A A road on which site No road to lies compare B road to E of site No road to compare B road to E of site A B road to SE of site A Walworth A road on which site A lies Islington A road to E of site A Senator House A road on which site A lies *revised traffic flow for Cromwell Road as given by the NETCEN National Air Quality website (DETR traffic count is 60865) 20

22 Calculation and comparison of diurnal profiles LRC data In order to use the traffic data from the Emissions Inventory supplied by the LRC, segmented roads had to be joined together, and two-way flow along roads added. The following steps were then performed on the data, in order to calculate single diurnal profiles from the LRC road traffic data. 1. From the data provided by the LRC the annual average hourly traffic counts (AAHT) were calculated from the daily traffic flows, and then the total average AAHT was calculated. 2. A diurnal profile was extracted from the data, using the variation in number of cars through 24 hours. 3. From the above the diurnal variation in traffic, diurnal profiles for weekday, Saturday and Sunday traffic were determined from data given in the LRC inventory as: Weekday counts=(variation in car numbers for a 24 hour)x1.04 Saturday counts=(variation in car numbers for a 24 hour)x0.94 Sunday counts=(variation in car numbers for a 24 hour)x0.85 Borough Data The hourly traffic count data supplied by the London Boroughs of Camden, Southwark and the Corporation of London, have been utilised in the derivation of a diurnal emissions profile representative of the hourly patterns of traffic flow on Weekdays, Saturdays and Sundays on roads across Central London. Each of the three boroughs provided information on weekday flows, and in addition Southwark and the Corporation of London provided weekend traffic flow data. These data were analysed and then combined proportionally to create a single set of diurnal profiles for Weekday, Saturday and Sunday traffic. Plots of the LRC and adjusted diurnal profiles for weekdays, Saturdays and Sundays are shown in Figure 5. Comparison of the profiles supplied by LRC and the borough 21

23 0 4 8 Kilometers N Adjusted for DETR traffic data LRC road network 22

24 profiles show that the weekday values are in reasonable agreement, but that the Saturday and Sunday profiles are significantly different. Because the profiles derived from the hourly traffic counts are based on actual traffic counts specific to Central London, as opposed to modelled data generated for the whole of Greater London, the borough diurnal profiles have been adopted in the model. Minor Roads Traffic emissions from the minor road network, have been considered as a component of the total grid source emissions. The LRC minor road network accounts for all roads for which link-based traffic flow data are unavailable, and is based upon the difference between the DETR s Rotating Traffic Census estimate of total vehicle kilometres travelled in London in 1995 and the kilometrage accounted for by the major road network. Cold starts and trip ends Cold start emissions (additional emissions associated with inefficient engine performance at low operating temperatures) and trip end emissions (associated with evaporative emissions of hydrocarbons from the hot engine and fuel system when the engine is switched off) have been considered as a component of the total grid source emissions. Industrial point sources For the purpose of modelling NO x and PM 10 concentrations all industrial point sources emissions with the exception of two sites (the South East London Combined Heat and Power Plant, Lewisham and London Underground Power Station, Chelsea) have been considered as a component of the aggregated grid source emissions. The Lewisham and Kensington sources emit 960 T/a and 469 T/a of NO x respectively, accounting for almost 1% of the total Greater London NO x emissions and equivalent to over 3% of the total non-road source emissions. The majority of industrial sources have not been modelled explicitly as it has been ascertained that their individual contributions are unlikely to have a significant impact on exceedences of the PM 10 or NO 2 objectives. Aggregated grid sources NO x and PM 10 emissions from all other identifiable sources have been considered within the km total aggregated grid sources covering the whole of Greater London. Figures 6,7 and 8 show the total grid source emissions of NO x, PM 10 and VOC for Greater London. Other Sources The inventory and hence the calculated pollutant concentrations do not allow for intermittent sources such as those occurring during bonfire night or construction activities. SO 2 emissions The SO 2 emissions data have been split into two types: point source data and grid sources. The point source data includes any significant emissions of SO 2 mainly from industrial sources, such as power stations and boilers. The grid source data 23

25 includes the emissions from all the sources, including residential, roads and also all the point source emissions previously mentioned. Point source data The LRC London atmospheric emissions inventory contains details of all Part A and Part B processes within London. The data were used in conjunction with information provided by the Environment Agency (Part A sources) and the individual London borough councils (Part B sources) to form the inventory of point sources. A complete listing of all Part A sources considered is given in Appendix C. Sources which lie outside London and which emit significant amounts of SO 2, were also included in the modelling. Table 3 shows the distribution of emissions between source types, while a map showing the location of all point sources considered is shown in Figure 9. Grid source data The modelled grid source emissions data covers an area of approximately 60 by 50km, bounded by the M25. Each emission on the grid covers an area of 1km 2. The data used was supplied by LRC, and it is assumed that Part A and B point sources have been aggregated onto the grid. Figure 10 shows the SO 2 grid source emissions throughout London. Table 5 Base year SO2 emissions by source type SO 2 emissions (T/Yr) Central Whole of London Study Area* Greater London Base year emissions Outside Greater London Total All sources Explicitly modelled Part A processes * The Central London Study Area emission rates shown are approximations, based on the assumption that emissions from grid squares dissecting borough boundaries are allocated in terms of the area in each borough. Predicted 25 Emissions Inventory This section outlines the procedures undertaken in the preparation of the emissions inventory for 25. A summary of 25 emissions rates by source type is given in Tables 8a-d, and Figures show the gridded emissions of NOx, PM 10 and VOCs for

26 N NMVOC (T/a) > Kilometers 25

27 Location of SO2 point sources # Kodak Ltd # Didcot Power station Guinness # Nestle (UK) Ltd # # Johnson Matthey plc # Londonwaste Ltd # # # # ## Mobil # # # # # Shell K ingsnorth Power station ## # # # Grain Power station # Rugby Group Plc # Shell UK Ltd UCL Union Min-oxyde SOAS # # # # Citigen Ltd # Ford Birkbeck College Seabright Industries British Museum # Cohen & Co Lots Road Power station Cargill # # # Britannia ref-metals # Clinical waste (PTY) Littlebrook Power station # # # NP Tilbury Blue Circle 26

28 N NOx (T/a) > Kilomete Current No Emissions for London X 27

29 N PM10 (T/a) > Kilometers Current PM emissions for London 10 28

30 Current NMVOC emissions for London. 29

31 N SO2 (T/a > Kilometers Current SO emissions for London 2 30

32 N NOx (T/a) > Kilometers 25 NO emissions X 31

33 N NOx (T/a) > Kilometer 25 PM emissions 10 32

34 N NMVOC (T/a) > Kilometer 25 NMVOC emissions 33

35 N SO2 (T/a) > Kilometers 25 SO emissions 2 34

36 25 NOx, PM 10 and VOC emissions With the exception of the London Underground industrial point source in Kensington and Chelsea which will no longer be in operation in 25, only emissions from road transport have been calculated for 25. Emissions from all other sources have been assumed to remain constant. The calculated road emissions take into account projected traffic growth, future UK fleet composition, new European vehicle emission factors, and changes in fuel composition and vehicle speed. 24 Major road emissions Emissions rates for NOx, PM 10 and VOC have been calculated on a link-by-link basis using 24 traffic data for Greater London supplied by LRC. The 24 network has been derived from the LTS traffic model output (courtesy of MVA and Government Office for London (GOL)). Adjustment of 24 road traffic emissions A comparison of the base year and 24 traffic data identified an incompatibility between the road networks used for the base year and for 24. Initial processing revealed a negative rate of growth in terms of annual vehicle kilometres travelled between the base year and 24 scenarios; although the 24 scenario was expected to exhibit some growth over the 1996 base case. The discrepancy arises from the fact that the two road networks originate from different versions of the LTS traffic model, with the 25 road traffic forecast carried out using a later and substantially updated version of the LTS model (version B1.10). The updated LTS model has been found to predict significantly lower total vehicle kilometrage than those predicted for the same year using the earlier model version, version F3.3 (LTS technical note 25 B1.10 Base Forecast Validation ). This is illustrated in Table 4, which gives a comparison for the two versions of LTS of the total vehicle kilometrage forecast for the 1991 morning peak traffic. As can be seen, the total vehicle kilometrage forecast by the updated version of LTS was found to be 27% lower than that forecast by the earlier version in Central London, 22% lower in Inner London and 13% lower in Outer London. LRC regard this as a confirmation of a suspected tendency in the base year major road network to overpredict traffic flows, compared to independent traffic counts (Charles Buckingham, LRC private communication). The extent of this problem is not readily quantifiable, although Technical Note 25 contains evidence to suggest that any overprediction is within 5 percent on a London-wide basis. LRC still consider the existing inventory to be a satisfactory representation of the situation in Table 6 Comparison of the two versions of LTS 1991 total annual vehicle kilometres-morning peak period. F3.3 B1.10 Percentage lower Central London Inner London Outer London