Air Quality at Birmingham International Airport

Annual Report for 2017

Authors	Sion Carpenter
Compilation date	19 July 2018
Customer	Birmingham Airport Ltd
Approved by	Tim Bevington
Copyright	Ricardo Energy & Environment
EULA	http://ee.ricardo.com/cms/eula/

Contract reference

ED62657

Report reference

Issue 1

Executive summary

This report provides details of air quality monitoring conducted at Birmingham Airport during 2017. The work, carried out by Ricardo Energy & Environment on behalf of Birmingham Airport Ltd, is a continuation of monitoring undertaken at Birmingham Airport since 1995. The aims of the programme are to monitor air pollution around the airport, to assess compliance with relevant national air quality objectives, and to investigate changes in air pollutant concentrations over time.

Automatic continuous monitoring was carried out at one location, referred to as Birmingham Airport 2. The site monitored oxides of nitrogen (nitric oxide and nitrogen dioxide), ozone, carbon monoxide, sulphur dioxide and PM₁₀. The PM₁₀ data were measured using a Tapered Element Oscillating Microbalance (TEOM), therefore there was the need to adjust data using the King’s College London Volatile Correction Model (VCM) to correct for potential losses of volatile and semi-volatile components.

The data capture target of 90% (from the European Commission Air Quality Directive) was not achieved for all pollutants in 2017, due to O₃ only achieving a data capture of 86%. The UK AQS hourly mean objective for NO₂ is 200 µg m^-3, with no more than 18 exceedances allowed each year. The monitoring site has registered no exceedances of this value during the year, and therefore met this objective for 2017.

The annual mean AQS objective for NO2 is 40 µg m^-3. This objective was also met in 2017; an annual mean of 21 µg m^-3 was measured. This value is slightly lower than the one measured in 2016 (23 µg m^-3), showing a small decrease in concentration for this pollutant.

PM₁₀ may exceed the 24-hour mean limit of 50 µg m^-3 no more than 35 times per year to meet the AQS objective. During 2017, there were no exceedances of the limit value registered at the site. This AQS objective was therefore met in 2017. The annual mean AQS for PM10 is 40 µg m^-3. This objective was met at Birmingham Airport 2 with an annual mean of 12.9 µg m^-3.

The UK AQS objective for ozone is 100 µg m^-3, as a maximum daily 8-hour mean, not to be exceeded more than 10 days a year. The ozone levels measured at Birmingham Airport monitoring station show that this objective was exceeded on 7 days during 2017. The AQS objective for ozone was therefore met in 2017. Ozone is a transboundary pollutant which is difficult to control by local measures: it is therefore not currently included in the Local Air Quality Management regime.

The AQS objectives for CO and SO₂ were met at Birmingham Airport 2 monitoring station in 2017.

1 Introduction

1.1 Background

Birmingham Airport Ltd (referred to here as “Birmingham Airport”) has undertaken continuous ambient air quality monitoring at a monitoring station on the airport premises since April 1995. This forms part of the Airport’s commitment to monitor air quality through the requirements of the Section 106 Planning Agreement between Solihull Metropolitan Borough Council (SMBC) and Birmingham Airport. The monitoring is intended to provide information on current air quality in the area and the levels of pollution to which the neighbouring community is exposed. The data from the air monitoring station are managed and collated by Ricardo Energy & Environment. This report has been prepared by Ricardo Energy & Environment, on behalf of Birmingham Airport, to provide analysis and commentary on the 2017 dataset.

Data in the annual report have been processed according to the rigorous quality assurance and quality control procedures used by Ricardo Energy & Environment. These ensure the data are reliable, accurate and traceable to UK national measurement standards.

1.2 Aims and objectives

The aim of this monitoring programme is to monitor concentrations of several important air pollutants at the airport. The results of the monitoring are used to assess whether applicable national air quality objectives have been met, and how pollutant concentrations in the area have changed over time. Additionally, meteorological data were used to investigate the importance of various sources of pollution.

It is important to note that the pollutants measured in this study could have been originated from a wide variety of sources, both local and long range. Not all of these sources will be directly connected with the airport.

Monitoring data collected at Birmingham Airport are compared in this report with:

• Relevant UK air quality limit values and objectives.
• Relevant periods of regional/national elevated pollutant concentrations.
• Corresponding results from a selection of national air pollution monitoring sites.

2 Details of the Monitoring Programme

2.1 Pollutants Monitored

The monitoring programme concentrates on the pollutants which may be of concern around airports. These are listed below. The emission statistics presented here all come from the National Atmospheric Emission Inventory (NAEI) ¹.

2.1.1 Nitrogen Oxides (NO_x)

Combustion processes emit a mixture of oxides of nitrogen - NO and NO₂ - collectively termed NO_x.

1. NO is described as a primary pollutant (meaning it is directly emitted from source). NO is not known to have any harmful effects on human health at ambient concentrations. However, it undergoes oxidation in the atmosphere to form the secondary pollutant NO₂.

2. NO₂ has a primary (directly emitted) component and a secondary component, formed by oxidation of NO. NO₂ is a respiratory irritant and is toxic at high concentrations. It is also involved in the formation of photochemical smog and acid rain and may cause damage to crops and vegetation.

Of the NOx emissions (including NO₂) considered to be airport-related, over 50 % arise from aircraft during take-off and landing, with around two-thirds of all emissions occurring at some distance from airport ground-level.

Based on 2016 calendar year emissions data from the 2018 submission of National Atmospheric Emissions Inventory (NAEI) data to the EU, in the UK, civil aircraft taking off and landing (up to a height of 1000m) are estimated to contribute 1.3% to the total reported UK emissions of NO_x.

The Air Quality Expert Group ² (AQEG) has stated that: “Around a third of all NO_x emissions from the aircraft (including ground-level emissions from auxiliary power units, engine testing etc., as well as take-off and landing) occur below 100 m in height. The remaining two-thirds occur between 100 m and 1000 m and contribute little to ground-level concentrations. Receptor modelling studies show the impact of airport activities on ground-level NO₂ concentrations. Studies have shown that although emissions associated with road traffic are smaller than those associated with aircraft, their impact on population exposure at locations around the airport are larger”. Previous rounds of review and assessment within the LAQM process have not highlighted any cases where airports appear to have caused exceedances of air quality objectives for particulate matter measured as PM₁₀. Therefore, in the context of LAQM, the key pollutant of concern from airports is NO₂. Local authorities whose areas contain airports with over 10 million passengers per annum must take these into account in their annual review and assessment of air quality.

2.1.2 PM₁₀ Particulate Matter

Airborne particulate matter varies widely in its physical and chemical composition, source and particle size. The term “PM₁₀” is used to describe particles with an effective size less than 10 µm. These are of greatest concern with regard to human health, as they are small enough to penetrate deep into the lungs. They can cause inflammation and a worsening of the condition of people with heart and lung diseases. In addition, they may carry surface absorbed carcinogenic compounds into the lungs. Larger particles, meanwhile, are not readily inhaled, and are removed relatively efficiently from the air by sedimentation. The main sources of airborne particulate matter in the UK are combustion (industrial, commercial and residential fuel use). The next most significant source is road vehicle emissions. Based on 2013 NAEI data ³, less than 0.1% of UK total PM₁₀ emissions are believed to originate from civil aircraft taking off and landing.

Previous rounds of review and assessment within the LAQM process have not highlighted any cases where airports appear to have caused exceedances of air quality objectives for particulate matter measured as PM₁₀.

2.1.3 Ozone (O₃)

Ozone is not emitted directly into the atmosphere in significant quantities, but is a secondary pollutant produced by reaction between nitrogen dioxide (NO₂) and hydrocarbons, in the presence of sunlight. Whereas nitrogen dioxide (NO₂) contributes to ozone formation, nitrogen oxide (NO) destroys ozone and therefore acts as a local sink. For this reason, ozone levels are not as high in urban areas (where NO is emitted from vehicles) as in rural areas. Ozone levels are usually highest in rural areas, particularly in hot, still, sunny weather conditions giving rise to “summer smog”.

2.1.4 Carbon Monoxide (CO)

Carbon monoxide is a gas that results as a product of the incomplete combustion of fuels. In the presence of an adequate O₂ supply, CO gets oxidized, and turns into CO₂. The highest levels of CO occur generally in areas with intense traffic released by the exhaust pipe of motor engines. Other CO emission sources may include some industrial processes, biomass burning for heating or natural sources like forest fires. CO causes can cause harmful health effects, as it reduces the oxygen delivery to the body’s organs and tissues.

2.1.5 Sulphur Dioxide (SO₂)

Sulphur dioxide is a colourless gas mainly originated by activities related to burning of fossil fuels (diesel burning of heavy vehicles), and burning of coal and oil in power plants. In nature, SO₂ can also be released to the atmosphere from a volcanic eruption. The sulphur reacts with oxygen to form SO₂, which in contact with the moisture in the air can create sulphuric acid, a component of acid rain.

2.2 Air Quality Limit Values and Objectives

This report compares the results of the monitoring survey with air quality limit values and objectives applicable in the UK. These are summarised below.

2.2.1 European Community

Throughout Europe, ambient air quality is regulated by the EC Directive on Ambient Air Quality and Cleaner Air for Europe (2008/50/EC and its update EU/1480) ⁴. This Directive (referred to as the Air Quality Directive) consolidated three previously existing Directives, which set limit values for a range of air pollutants with known health impacts including.

All Member States of the European Union are required to transpose the requirements of the Directive into their national law. The original Directives were transposed into UK law via the Environment Act 1995 and subsequent Statutory Instruments.

2.2.2 The UK Air Quality Strategy

The Environment Act also placed a requirement on the Secretary of State for the Environment to produce a national Air Quality Strategy containing standards, objectives and measures for improving ambient air quality. The original Air Quality Strategy was published in 1997, and contained air quality objectives based on the recommendations of the Expert Panel on Air Quality Standards (EPAQS) regarding the levels of air pollutants at which there would be little risk to human health.

The Air Quality Strategy has since undergone a number of revisions. These have reflected improvements in the understanding of air pollutants and their health effects. They have also incorporated new European limit values, both for pollutants already covered by the Strategy and for newly introduced pollutants such as polycyclic aromatic hydrocarbons and PM_2.5 particulate matter. The latest version of the strategy was published by Defra in 2007 ⁵.

All Air Quality Strategy (AQS) objectives must be at least as stringent as the EC limit values. The current UK air quality objectives for the pollutants monitored at Birmingham Airport are presented below.

2.2.3 Monitoring sites and Methods

The monitoring site is located on the airfield near airport buildings to the east of the runway and north-west of the Main Terminal (OS grid ref. 417395, 284240), having previously been located to the west of the apron area, approximately 300 m due west of the Main Terminal. The site relocation occurred in January 2006. The current location of the monitoring site is shown below. A map showing the old and new locations is included in Appendix 1.

2.3 Automatic Monitoring Techniques

The following techniques were used for the automatic monitoring of NO_x (i.e. NO and NO₂), PM₁₀, O₃, CO and SO₂:

• PM₁₀ - Tapered Element Oscillating Microbalance (TEOM);
• NO, NO₂ - Chemiluminescence;
• O₃ - UV absorption analyser;
• CO - Non dispersive infrared absorption (NDIR);
• SO₂ - Ultraviolet Fluorescence (UVF).

Further information on these techniques is provided in Appendix 2 of this report. These analysers provide a continuous output, proportional to the pollutant concentration. This output is recorded and stored every 10 seconds, and averaged to 15-minute mean values by internal data loggers. The analysers are connected to a modem and interrogated through a GPRS internet device to download the data to Ricardo Energy & Environment. Data are downloaded hourly. The data are converted to concentration units at Ricardo Energy & Environment then averaged to hourly mean concentrations.

Fortnightly calibrations are performed by Local Site Operators (LSOs) based at Birmingham Airport, to monitor the performance of the analysers. Data from these fortnightly checks, and from six-monthly independent QA/QC audits carried out by Ricardo Energy & Environment, are used to scale and ratify the data. This data scaling and ratification is carried out by Ricardo Energy & Environment. The analysers are also serviced on a six-monthly basis to ensure their continued operation.

All ambient concentration measurements in the report are quoted in micrograms per cubic metre (µg m^-3) or in the case of carbon monoxide milligrams per cubic metre (mg m^-3) at reference conditions of 20°C, 1013 mbar.

Improvement to our data management systems meant that between 2016 and 2017 there was an increase in the data precision that we are able to report. For pollutants with very low concentrations (such as CO and SO₂) this means a much reduced level of noise on the hourly data which in turn manifests itself in an apparent step change in averages. This step change should therefore simply be considered as improved accuracy, not any significant change in ambient concentrations.

2.4 VCM Correction of PM₁₀ Data

The TEOM particulate monitor uses a 50°C heated sample inlet to prevent condensation on the filter. Although necessary, this elevated temperature can result in the loss of volatile and semi-volatile components of PM₁₀, such as ammonium nitrate.

It is not possible to address this problem by applying a simple correction factor. However, King’s College London (KCL) have developed a Volatile Correction Model ⁶, which allows TEOM PM₁₀ data to be corrected for the volatile components lost as a result of the TEOM’s heated inlet. The model is available at http://www.volatile-correction-model.info/Default.aspx. It uses data from nearby TEOM-FDMS particulate analysers, which measure the volatile and non-volatile components of the PM₁₀. The volatile component (which typically does not vary much over a large region), can be added to the TEOM measurement. KCL state that the resulting corrected measurements have been demonstrated as equivalent to the gravimetric reference equivalent. In this report, the VCM has been used to correct PM₁₀ data where applicable. Where this has been done, it is clearly indicated.

3 Results and discussion

3.1 Units

Measured concentrations are reported in microgrammes per cubic metre (μg m^-3).

PM₁₀ is conventionally reported in units of μg m^-3, microgrammes per cubic metre. In this report PM₁₀ measured using the TEOM instrument has been converted to gravimetric equivalent using the King’s College London Volatile Correction Model5 where appropriate.

In this report, the mass concentration of NO_x has been calculated as follows:
NO_x μg m^-3 = (NO ppb+NO₂ ppb)*1.91 and is termed “NO_x reported as NO₂”.

This conforms to the requirements of the EC Directive on Ambient Air Quality and Cleaner Air for Europe and is also the convention generally adopted in air quality modelling.

3.2 Summary statistics

Overall data capture statistics for Birmingham International are given in Tables 2-6. These represent the percentage of valid data for the whole reporting period. A data capture target of 90% is recommended in the Defra Technical Guidance LAQM.TG(16) ⁷. This target was achieved for all pollutants except O₃. This data capture target does not include losses due to regular calibration or maintenance of the instrument. Any data capture rate above 75% is deemed representative of the full annual period. We will continue to review, assess and advise MAG if this situation changes.

Also displayed are pie charts showing the percentage and number of readings in each of the Air Quality Index bands for each polutant with the exception of SO₂ and CO, both of which stayed in Band 1 the entire period.

The following significant gaps occurred in the data:

• During November it was found that there was an issue with the manifold and so data for all gasious polutants was nulled between 1/11/17 and 28/11/17.

NO₂

SO₂

CO

O₃

PM₁₀ (VCM Corrected)

3.3 Comparison with Air Quality Objectives

None of the AQS objectives for O₃, CO, SO₂, NO_x or PM₁₀ were exceeded at Birmingham Airport 2 monitoring location in 2017. Details of UK air quality standards and objectives are provided in Table 1.

• The AQS objective for hourly mean NO₂ concentration is 200 µg m^-3 which may be exceeded up to 18 times per calendar year. During 2017 there were no hourly mean NO₂ measurements exceeding 200 µg m^-3. The lower threshold of the Defra “Moderate” air quality band is 201 µg m^-3 as an hourly mean. Therefore NO₂ levels at stayed within the Defra “Low” band for the whole year. The AQS objective was achieved for 2017.
  
• The annual mean AQS objective for NO₂ is 40 µg m^-3. This objective was also met at Birmingham Airport 2, where the calculated annual mean was 21 µg m^-3.
• The AQS objective for PM₁₀ is 50 µg m^-3 for the daily mean, not to be exceeded more than 35 times a year. Results show that no exceedances of this objective were registered, with a maximum daily mean of 45.8 µg m^-3 after VCM correction. The site met the AQS objective for 24 hour mean PM₁₀.
• The annual mean AQS objective for PM₁₀ is 40 µg m^-3. The site measured an annual mean of 12.9 µg m^-3 after VCM correction; this objective was therefore met.
• The AQS objective for maximum daily 8-hour running mean O3 is 100 µg m^-3 (not to be exceeded more than 10 days a year). There were 52 occasions when any 8-hour running mean exceeded 100 µg m^-3, on 7 separate days. Birmingham Airport 2 therefore met the AQS objective for ozone on 7 days during 2017, compared with the permitted maximum of 10 days. The maximum hourly mean concentration of ozone was 177 µg m^-3: this was measured registered on 21^st June 2017.

Ozone is a secondary pollutant; it is formed by chemical reactions in the air, involving precursor pollutants, rather than emitted directly from source. It is therefore trans-boundary in nature. As a result, Local Authorities have little control over ozone concentrations in their areas. The Government has recognised the problems associated with achieving the air quality objective for ozone, and this is not included in the LAQM regime.

CO and SO₂ measured at Birmingham Airport 2 met all the AQS objectives for 2017, both with zero exceedances during the year.

3.4 Time series plot

Daily average and hourly time series plots of all pollutant data for the full year, as measured by the automatic monitoring site, are shown below. Data for the entire historical record is available with only the most recent year appended to the plot. The plots are interactive and can be manipulated to show specific time periods or concentration bands.

It must be noted that an improvement to our data management systems meant that between 2016 and 2017 there was an increase in the data precision that we are able to report. For pollutants with very low concentrations (such as CO and SO₂) this means a much reduced level of noise on the hourly data which in turn manifests itself in an apparent step change in averages. This step change should therefore simply be considered as improved accuracy, not any significant change in ambient concentrations.

NO₂ Daily

NO₂ hourly

SO₂ Daily

SO₂ hourly

CO Daily

CO hourly

O₃ Daily

O₃ hourly

PM₁₀ (VCM Corrected)

3.5 Smooth trend plot

Below are smoothed time series plots of with points representing monthly concentration and bold lines representing trend modelled by Generalised Additive Model (GAM).

NO₂

SO₂

CO

O₃

PM₁₀ (VCM Corrected)

3.6 Time Variation plot

NO₂

SO₂

CO

O₃

PM₁₀ VCM Correced

3.7 Seasonal Variation

NO_x, CO and PM₁₀ at Birmingham Airport 2 showed typical seasonal patterns for urban areas though 2017, as can be observed in the above ‘month’ plots. The highest concentrations of these pollutants occurred during the winter months. This pattern was also observed in previous years and is typical of urban monitoring sites. The highest levels of primary pollutants tend to occur in the winter months, when emissions may be higher, and periods of cold, still weather reduce pollutant dispersion.

SO₂ seasonal patterns are much less pronounced and are masked by pollution events and the change in data collection system (which changed the accuracy of recorded data) and so does not display typical seasonal variation. SO₂ seasonal variation should follow a typical winter trend, as the major source of this pollutant is the combustion of coal and oil; this increases during winter, mainly because of domestic and industrial heating requirements and reduced pollutant dispersion. The SO₂ measurements are all very low during 2017.

O₃ concentrations registered at Birmingham Airport 2 continue to follow a typical seasonal variation for this pollutant, with higher concentrations being registered in April, May, and June. At low/mid latitudes, high O₃ concentrations are generally observed during late spring and/or summer months, where anti cyclonic conditions (characterized by warm and dry weather systems) help increase photochemical reactions in the atmosphere, responsible for the increasing of ground level ozone production. In addition, the convective fluxes created during hot summer days can also be responsible for an increase of O₃ (stratospheric intrusion). The hot air generated at ground level due to high temperatures is lighter and tends to ascend, being replaced by colder stratospheric air masses coming from above, dragging stratospheric O₃ down into the troposphere (the lowest part of the atmosphere).

3.8 Diurnal Variations

The diurnal variation analyses viewed in the ‘hour’ plots showed typical urban area daily patterns for NO₂, SO₂ and CO. Pronounced peaks can be seen for these pollutants during the mornings, corresponding to rush hour traffic at around 07:00-09:00. Concentrations tend to decrease during the middle of the day, with a much broader evening road traffic rush-hour peak in building up from early afternoon. NO generally show a much smaller peak than NO₂ in the afternoons. This is likely to be because concentrations of oxidising agents in the atmosphere (particularly ozone) tend to increase in the afternoon, leading to enhanced oxidation of NO to NO₂.

The concentration of O₃ at Birmingham Airport 2 follows a typical diurnal pattern. O₃ concentrations always increase during daylight hours due to the photochemical reactions of NO₂ and photo oxidation of VOC’s, CO, hydrocarbons, (O₃ precursors). In the afternoon/ night O₃ gets consumed by a fast reaction with NO (titration of O₃ by NO). The absence of sunlight prevents the photolysis of the O₃ precursors.

The diurnal patterns for PM₁₀ are determined by two main factors. The first is emissions of primary particulate matter, from sources such as vehicles. The second factor is the reaction that occurs between sulphur dioxide, NO_x and other chemical species, forming secondary sulphate and nitrate particles. The PM₁₀ at this site showed an evening rush-hour peak during 2017.

3.9 Weekly Variations

The analyses of each pollutants weekly variation showed that the same type of diurnal patterns occur for all the days of the week. NO, NO₂ and CO early morning and late afternoon rush hour peaks are in general much more pronounced on weekdays as opposed to during the weekends. PM₁₀ concentrations don’t appear to vary much during the week. Saturday registers the lowest concentrations of CO, PM₁₀, SO₂, and NO_x (NO/NO₂). Sunday gave the highest readings of O₃.

The SO₂ weekly pattern appears to show little to no variation through out the week.

3.10 Calendar plot

The below calendar plots show how pollutant levels change on a day by day basis and make it easy to identify both short and long term pollution events, along with periods of low pollution. The date is coloured by the wind speed for that day. The actual value can also be seen by hovering the mouse on the cell.

It can be seen that the highest NO₂ value was recorded on the 5^th January, SO₂ on the 25^th May, CO on the 18^th December, O₃ on the 21^rd June and PM₁₀ on the 13^th February.

NO₂

SO₂

CO

O₃

PM₁₀ VCM Corrected

3.11 Polar plot map

In order to investigate the possible sources of air pollution being monitored around Birmingham Airport, real meteorological data measured at the Airport was used to add a directional component to the air pollutant concentrations.

The above plot shows that the prevailing wind direction was from the South West and the mean wind speed was 3.8 m s^-1. The maximum measured wind speed was 16.5 m s^-1. Some of the highest wind speeds occurred during December.

The below plots show hourly mean concentrations of NO₂, SO₂, CO, O₃ and PM₁₀ at Birmingham Airport 2 against wind speed and wind direction. These plots should be interpreted as follows:

• The wind speed is indicated by the distance from the centre of the plot; the grey circles indicate wind speeds in 2 m s^-1 intervals.
• The pollutant concentration is indicated by the colour (as indicated by the scale).

These plots therefore show how pollutant concentrations varied with wind direction and wind speed.

The plots do not show distance of pollutant emission sources from the monitoring site. However, in the case of primary pollutants such as NO, the concentrations at very low wind speeds are dominated by emission sources close by, while at higher wind speeds, effects are seen from sources further away.

NO₂, which has both a primary and secondary component, shows significant sources to the north the direction of the Birmingham residential areas, as well as the highest wind speeds, and a smaller source to the south east where the terminal and drop off area is situated. High concentrations were also registered at low wind speeds, which indicates that a proportion of the NO₂ measured has its origin from local emission sources, and mainly by the fast reaction of NO with O₃ in the presence of UV light.

The pollution rose for VCM-corrected PM₁₀ shows a major contribution from the south west of the site, which is the direction of thew runway and the cargo area. Two other sources can be identified from an easterly direction where the drop off, car park and external commercial areas are.

As with previous years the plot of CO shows that the highest concentrations are in the centre of the plot (i.e. when wind speeds are low) with lower concentrations as wind speeds increase to the north west and south east. This is in line with what is observed for NO suggesting that the pollutants come from the same emission source.

The bivariate plot for O₃ shows a contrasting pattern to that of the other pollutants in that the lowest ozone concentrations are associated with calm conditions. Being a secondary pollutant ozone is formed from chemical reactions in the ambient air. The plot demonstrates that higher concentrations of ozone are measured at the site when wind speeds are sufficient to bring in ozone-rich air from other areas of the region. At very low wind speeds, when NO concentrations are highest, any ozone present reacts with the NO emitted by the sources in the immediate vicinity. This illustrates that the exceedances of the AQS objectives for ozone are not a direct result of Birmingham Airport’s activities but reflect regional ozone concentrations.

The pollution rose for SO₂ show only one source, to the north in the residential area but concentrations overall remain low.

NO₂

SO₂

CO

O₃

PM₁₀

4 Comparison with Other Local Monitoring Sites

The below table compares the annual mean concentrations at Birmingham Airport with other air quality monitoring sites in Birmingham. The sites selected are all part of the UK’s national Automatic Urban and Rural Network (AURN) and are as follows:

• Birmingham A4540 Roadside: An urban traffic site located on the south side of the A38 in Tyburn outside council owned offices, and approximately 700 metres to the north of the M6 motorway. The site was relocated part way through the year to a location on the east side of the A4540 in Bordesley.

• Birmingham Acocks Green: Another urban background site, located within the grounds of an annex to a large school near Shirley Road.

Annual means for Birmingham Airport 2 and three local AURN monitoring sites, 2017. Units µg m^-3 for all pollutants except CO which is in mg m^-3.

The annual mean concentration of PM₁₀ measured at the Birmingham Airport site in 2017 was comparable with those measured at the other Birmingham site. As in previous years, the annual mean concentration of SO₂ at Birmingham Airport was low. The annual mean concentrations of NO₂ and O₃ measured at Birmingham Airport 2 were comparable with those measured in Acocks Green, an urban background site located away from busy roads.

Concentrations of O₃ are typically higher in rural areas, far away from sources of other pollutants such as NO (which removes O₃ from the air by chemical reaction). The annual mean ozone concentration at Birmingham Airport is comparable to those measured at Birmingham Acocks Green, ozone concentrations at roadside sites are lower.

These statistics together indicate that the pollution levels registered at Birmingham Airport 2 were consistent with those measured elsewhere in the city in 2017.

5 Conclusions

The following conclusions have been drawn from the results of air quality monitoring at Birmingham Airport during 2017. Oxides of nitrogen, particulate matter (as PM₁₀), carbon monoxide (CO), sulphur dioxide (SO₂) and ozone (O₃) were monitored throughout 2017 at one monitoring site in Birmingham Airport (Birmingham Airport 2). The conclusions of the 2017 monitoring programme are summarised below.

1. Data capture of greater than 85% was achieved for all pollutants.

2. The maximum hourly mean NO₂ concentration measured at the site was 102 µg m^-3. This is less than the hourly mean AQS objective of 200 µg m^-3 (which may be exceeded up to 18 times per year). The site therefore met the AQS objective for hourly mean NO₂ in 2017.

3. The annual mean NO₂ concentration measured at the site was 21 µg m^-3. The site therefore met the AQS objective of 40 µg m^-3 for annual mean NO₂ in 2017.

4. Ozone exceeded the AQS objective of 100 ug m^-3 as a maximum daily 8 hour mean, on 7 days in 2017. This is less than the permitted 10 days per calendar year. The AQS objective for O₃ was therefore met in 2017.

5. The site met the AQS objective for 24-hour mean of 50 µg m^-3 (not to be exceeded more than 35 times a year) and annual mean of 40 µgm^-3 for PM₁₀. The particulate matter was measured using a TEOM instrument and VCM correction applied.

6. Seasonal variations in pollutant concentrations at Birmingham Airport 2 show that NO, NO₂ , PM₁₀ and CO exhibited higher concentrations during the winter months. Ozone levels were highest during the spring and summer, as is typical. SO₂ showed no overal seasonal pattern and the concentrations are still low.

7. The diurnal patterns of concentrations of all pollutants were similar to those observed at other urban monitoring sites. Peak concentrations of NO, NO₂, particulate matter, SO₂ and CO coincided with the morning and evening rush hour periods, and levels of ozone peaked in the afternoons.

8. Meteorological data was used at Birmingham Airport 2, allowing the effect of wind direction and speed to be investigated. Bivariate plots of NO₂ concentrations and wind data showed that concentrations of these pollutants at the monitoring site were typically high in calm conditions, indicating that the main sources of these pollutants were nearby, with a further large source being the residential area to the north. The pattern was slightly different for PM₁₀, with a strong signal from the south west at higher wind speeds and two appearing from the east. CO concentrations appear to follow a similar profile to NO₂, showing that its origin is both local and long range. SO₂ emissions seem to originate from a single source to the north.

9. Mean concentrations of pollutants at the two Birmingham AURN sites in 2017 were comparable with those measured at Birmingham Airport 2, especially the urban background monitoring station at Acocks Green.

Appendix I

Map of BIA air monitoring sites.

Appendix II

The following continuous monitoring methods were used at the Birmingham Airport 2 air quality monitoring station:

• NO, NO₂: chemiluminescence with ozone.
• PM₁₀: Tapered Element Oscillating Microbalance (TEOM).
  
• O3~~: UV absorption analyser.
• CO: Non dispersive infrared absorption (NDIR)
• SO₂: Ultraviolet Fluorescence (UVF)

These methods were selected in order to provide real-time data. The chemiluminescence and the UV absorption analysers are the European reference method for ambient NO₂ and O₃ monitoring.

The chemiluminescence with ozone analyser is based on the principle that nitric oxide (NO) and ozone react to produce excited NO₂ molecules, which emit infrared photons (represented in the equation below by the photon’s energy, h??,) when going back to lower energy states:

NO + O₃ ??? NO₂* + O₂ -??? NO₂ + O₂ + h??

A stream of purified air (dried with a NafionTM Dryer) passing through a silent discharge ozonator generates the ozone concentration needed for the chemiluminescent reaction. The specific luminescence signal intensity is therefore proportional to the NO concentration. A photomultiplier tube amplifies this signal. NO₂ is detected as NO after reduction in a molybdenum (Mo) converter heated at about 325 °C. The ambient air sample is drawn into the analyser, flows through a capillary, and then to a valve, which routes the sample either straight to the reaction chamber (NO detection), or through the converter and then to the reaction chamber (NO_X detection). The calculated NO and NO_X concentrations are stored and used to calculate NO₂ concentrations (NO₂ = NO_x - NO), assuming that only NO₂ is reduced in the Mo converter.

The UV absorption analyser determines ozone concentrations by measuring the absorption of O₃ molecules at a wavelength of 254 nm (UV light) in the absorption cell, followed by the use of the Beer-Lambert law. The concentration of ozone is related to the magnitude of the absorption. The reference gas, generated by scrubbing ambient air, passes into one of the two absorption cells to establish a zero light intensity reading, I0. Then the sample passes through the other absorption cell to establish a sample light intensity reading, I. This cycle is reproduced with inverted cells. The average ratio R=I/I0 between 4 consecutive readings is directly related to the ozone concentration in the air sample through the Beer-Lambert law.

The Non-Dispersive Infra-Red (NDIR) detectors are the industry standard method of measuring the concentration of carbon monoxide (CO). Each constituent gas in a sample will absorb some infra-red at a particular frequency. By shining an infra-red beam through a sample cell (containing CO), and measuring the amount of infra-red absorbed by the sample at the necessary wavelength, a NDIR detector is able to measure the volumetric concentration of CO in the sample.

The Ultraviolet Fluorescence analyser determines SO₂ by, at first, scrubbing the air flow to eliminate aromatic hydrocarbons. The air sample is then directed to a chamber where it is irradiated at 214 nm (UV), a wavelength where SO₂ molecules absorb. The fluorescence signal emitted by the excited SO₂ molecules going back to the ground state is filtered between 300 and 400 nm (specific of SO₂) and amplified by a photomultiplier tube. A microprocessor receives the electrical zero and fluorescence reaction intensity signals and calculates SO₂ based on a linear calibration curve.

The analysers for NO_x, O₃, CO and SO₂ are equipped with an automatic calibration system, which is triggered daily under the control of the data logger. Fully certificated calibration gas cylinders are also used at each site for manual calibration.

Each analyser provides a continuous output, proportional to the pollutant concentration. This output is recorded and stored every 10 seconds, and averaged to 15 minute average values by the on-site data logger. This logger is connected to a modem and interrogated twice daily, by telephone, to download the data to Ricardo Energy & Environment. The data are then converted to concentration units and averaged to hourly mean concentrations. The TEOM measures the mass collected on an exchangeable filter cartridge by monitoring the frequency changes of a tapered element. The sample flow passes through the filter, where particulate matter is collected, and then continues through the hollow tapered element on its way to an electronic flow control system and vacuum pump. As more mass collects on the exchangeable filter, the tube’s natural frequency of oscillation decreases. A direct relationship exists between the tube’s change in frequency and mass on the filter. The TEOM mass transducer does not require recalibration because it is designed and constructed from non-fatiguing materials. However, calibration is yearly verified using a filter of known mass. The PM₁₀ TEOM analyser cannot be calibrated in the same way as the gas analysers and these data are scaled using the results of 6-monthly checks. In these checks, the flow rate through the analyser is measured and the mass determination checked with pre-weighed filters.

The PM₁₀ monitoring data recorded by TEOM monitors were corrected with the King’s College Volatile Correction Model (VCM) ⁸. This online tool allows TEOM measurements to be corrected for the loss of volatile components of particulate matter that occur due to the high sampling temperatures employed by this instrument. The resulting corrected measurements have been demonstrated as equivalent to the gravimetric reference equivalent. The VCM works by using the volatile particulate matter measurements provided by nearby FDMS (Filter Dynamic Measurement System) instruments (within 130 km) to assess the loss of PM₁₀ from the TEOM; this value is then added back onto the TEOM measurements.

References

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1. National Atmospheric Emissions Inventory (2017) (online). Available at (http://www.naei.org.uk) (accessed 23 April 2018).↩

2. Air Quality Expert Group (2004) Nitrogen dioxide in the United Kingdom [online]. London, UK: Department for Environment, Food and Rural Affairs. Available at: http://uk-air.defra.gov.uk/library/aqeg/publications [Accessed 22 May 2018].↩

3. National Atmospheric Emissions Inventory (2017) (online). Available at (http://www.naei.org.uk) (accessed 23 April 2018).↩

4. EC (2008) Council Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe [online]. Available from: http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32008L0050:EN:NOT (accessed 23 April 2018). And Commission Directive (EU) 2015/1480 of 28 August 2015 amending several annexes to Directives 2004/107/EC and 2008/50/EC of the European Parliament and of the Council laying down the rules concerning reference methods, data validation and location of sampling points for the assessment of ambient air quality (Text with EEA relevance). Available from http://data.europa.eu/eli/dir/2015/1480/oj (Accessed 23 April 2018).↩

5. Defra (2007). The Air Quality Strategy for England, Scotland, Wales and Northern Ireland (Volume 1). Department for Environment, Food and Rural Affairs in partnership with the Scottish Executive, Welsh Assembly Government and Department of the Environment Northern Ireland. July 2007. https://www.gov.uk/government/publications/the-air-quality-strategy-for-england-scotland-wales-and-northern-ireland-volume-1 (accessed 23 April 2018).↩

6. King’s College London Volatile Correction Model (online). Available at http://www.volatile-correction-model.info/Default.aspx . July 2008. (Accessed 23 April 2018).↩

7. Department for Environment, Food and Rural Affairs (2018). Part IV of the Environment Act 1995. Local air quality management - Technical Guidance LAQM.TG (16) [online]. London, UK: Department for Environment, Food and Rural Affairs in partnership with the Scottish Executive, Welsh Assembly Government and Department of the Environment Northern Ireland. Available from: https://laqm.defra.gov.uk/documents/LAQM-TG16-April-16-v1.pdf [Accessed 23 April 2018].↩

8. King’s College London Volatile Correction Model (online). Available at http://www.volatile-correction-model.info/Default.aspx . July 2008. (Accessed 23 April 2018).↩

For further information, please contact:

Name	Tim Bevington
Address	Ricardo Energy & Environment, Gemini Building, Harwell, Didcot, OX11 0QR, United Kingdom
Telephone	01235 753484
Email	Tim.Bevington@ricardo.com