Authors Louisa Kramer
Compilation date 02 June 2023
Customer Capita Property & Infrastructure Ltd
Approved by James Dernie
Copyright Ricardo Energy & Environment
EULA http://ee.ricardo.com/cms/eula/

Contract reference 4800413464 Report reference May 2023

1 Introduction

This is a monthly summary report for Capita Property & Infrastructure Ltd for the period 2023 May.

This is a dynamic report containing embedded data from which the report tables, plots and graphs are generated. The embedded data allows the reader a level of interaction with some of the report findings, providing additional insight. This approach enables a more easily navigated and streamlined report providing an engaging and intuitive reader experience.

Maps for example can be panned and zoomed with different layers and markers turned on and off and with popup information by clicking on markers or hovering the mouse over them. Tables may contain much more information than initially displayed and can be set to show different numbers of rows, and can be filtered sorted or searched to display only specific information of interest. Some time series plots can be tracked with the mouse cursor to obtain specific time/date stamps and values and the reader can zoom into a specific time window by dragging with the cursor and double left clicking to return to the full plot extent.

The report is easily navigable using the floating table of contents on the left pane which tracks with the reader’s progress through the report and expands and collapses to a level of detail related to the subheadings used. The layout of the report is also dynamic, with some sections split into specific ‘tabs’ (e.g. per pollutant or per site) for ease of access to those sections.

2 Monitoring stations

A summary of site information is presented in the interactive map and table below . Full site information can be obtained using the URL hyperlink in the popup for each monitoring station on the map.


3 Data description

Data contained within this report is managed by Ricardo and stored in a dedicated, secure database. The data within this report is provisional and subject to change, and as such should be treated with caution.

Some of the plots provided in this report use associated meteorological data (typically wind speed and wind direction) in order to show measured pollutant concentrations in a dispersion context. Very few monitoring stations provide quality controlled met data, therefore these reports import data from the Met Office DataPoint 1.

Gaseous pollutant mass units are at 20 °C and 1013mb. NOx mass units are NOx as NO2 μg m-3. Particulate matter concentrations are reported at ambient temperature and pressure.

3.1 Relevant pollution Limit Values

The European Air Quality Directive and Fourth Daughter Directive set out legal limits for different pollutants as Limit Values, Target Values or Long Term Objectives to protect human health. These are summarised in the table below. Local authorities don’t typically measure ozone, benzene, B[a]P or metals that are captured within Defra’s national networks. All pollutants measured have been included in this data summary for completeness, irrespective of their significance for local authority policy interests.


4 Data Analysis

4.1 Summary statistics

The following tables present pollutant statistics for the period from the start of the year to the reported month. The Low, Moderate and High indicates the number of days for a particular pollutant when the concentrations are in the corresponding AQI bands from the beginning of the year until the end of the reported month.

NO2

O3

SO2

Black Carbon

VOCs

4.2 AQ index distribution

The plots below illustrate the distribution of AQ index values for each site by pollutant. It shows the number of days that site concentrations are in each index. More information on the AQ Index is available from UK-Air 2.

NO2

Figure 1: Distribution of AQI for NO2.

O3

Figure 2: Distribution of AQI for O3.

SO2

No AQI index available for SO2.

Black Carbon

No AQI index available for Black Carbon.

4.3 Boxplots

The plots below are box and whisker plots to show the distribution in concentrations for each monitoring station. The boxes demarcate the lower quartile, median and upper quartile. The whiskers extend to the maximum and minimum values within median ± 1.5 times interquartile range (IQR). Values outside the median ± 1.5 times IQR are generally considered as outliers.

NO2

Figure 5: Boxplot for NO2 concentration.

O3

Figure 6: Boxplot for O3 concentration.

SO2

Figure 7: Boxplot for SO2 concentration.

Black Carbon

Figure 8: Boxplot for Black Carbon concentration.

VOCs

Figure 9: Boxplot for VOCs concentration.

4.4 Time series plot

The plots below show the time series of concentrations. Each pollutant is presented on a different tab and all sites are shown on each plot for comparison. A daily average resolution has been chosen as the most appropriate metric over a variety of different time windows. Zooming in on specific periods of the plot can be done by dragging a box over the section of the main plot frame or by using the sliders in the narrow plot frame below. To return to the default (all data) zoom level, double click the plot. Holding the mouse over the lines will highlight specific values and time stamp for that record for each station.

NO2

Figure 10: Time series plot of daily average NO2 concentration.

O3

Figure 11: Time series plot of daily average O3 concentration.

SO2

Figure 12: Time series plot of daily average SO2 concentration.

Black Carbon

Figure 13: Time series plot of daily average Black Carbon concentration.

VOCs

Figure 14: Time series plot of daily average VOCs concentration.

4.5 Time Variation plot

These plots show concentrations over different time intervals such as diurnal, day of week and month of year. The plot showing seasonal variation will show only the three months of the quarter or a dot showing one month depending on the time frame covered in this report. The topmost frame shows the concentrations as they vary by hour of the day and day of the week. The hour of the day variation is summarised on its own in the lower left pane and the variation by day of the week is shown in the lower right pane. These plots often help explain variations in concentration according to the emissions activity associated with them. For example, NOx concentrations at roadside sites tend to exhibit peaks according to morning and evening traffic rush hours and tend to decline over weekends when there is generally lower traffic volumes.

NO2

Figure  15: Time variation of hourly NO~2~ concentration.

Figure 15: Time variation of hourly NO2 concentration.

O3

Figure  16: Time variation of hourly O~3~ concentration.

Figure 16: Time variation of hourly O3 concentration.

SO2

Figure  17: Time variation of hourly SO~2~ concentration.

Figure 17: Time variation of hourly SO2 concentration.

Black Carbon

Figure  18: Time variation of hourly Black Carbon concentration.

Figure 18: Time variation of hourly Black Carbon concentration.

VOCs

Figure  19: Time variation of hourly VOCs concentration.

Figure 19: Time variation of hourly VOCs concentration.

4.6 Calendar plot

The plot below shows daily variation in concentrations by pollutant (one on each tab) across the period of the report, as laid out in a calendar style. This allows intuitive viewing of day to day headline trends in the wider context of the period. The background colours shown for each day relate to the concentration. 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.

NO2

Luton Airport FutureLuToN

Figure 20: NO2 calendar plot.

O3

Luton Airport FutureLuToN

Figure 21: O3 calendar plot.

SO2

Luton Airport FutureLuToN

Figure 22: SO2 calendar plot.

Black Carbon

Luton Airport FutureLuToN

Figure 23: Black Carbon calendar plot.

Benzene

Luton Airport FutureLuToN

Figure 24: Benzene calendar plot.

Toluene

Luton Airport FutureLuToN

Figure 25: Toluene calendar plot.

Ethylbenzene

Luton Airport FutureLuToN

Figure 26: Ethylbenzene calendar plot.

mp-Xylene

Luton Airport FutureLuToN

Figure 27: mp-Xylene calendar plot.

o-Xylene

Luton Airport FutureLuToN

Figure 28: o-Xylene calendar plot.

4.7 Back trajectory analysis

The back trajectory plot shows data from the HYSPLIT model (NOAA HYSPLIT 3) run in analysis mode. This shows the air mass back trajectories for the period covered by the report. Two different kinds of plot are shown. One statistically groups the trajectories into similar clusters and shows the proportion of time during the report period that each represents (Figure 29). This is useful to get an overview of air mass origins during the report period. Plots in Trajectories associated with top ten most polluted days provide information on the trajectory direction associated with the top 10 measured concentrations.

4.7.1 Trajectory clusters

4-day air mass back trajectories arriving at the sites for 2023 are grouped into 4 clusters.

Figure  29: Back trajectory clusters for the month reported.

Figure 29: Back trajectory clusters for the month reported.

Air mass back trajectories over these spatial scales do not vary locally so the receptor location used in this report has been selected from a range of national receptor locations maintained by Ricardo Energy & Environment. The receptor point is used here is London Bridge Place which is 46.2km away from the centre of all monitoring stations analysed in this report.

4.7.2 Trajectories associated with top ten most polluted days

The average daily concentration for each pollutant across all the sites is calculated, with the top 10 most polluted days identified and linked to its back trajectory data in the plot below.

NO2

Figure 30: Trajectory plot for top ten highest daily NO2 concentration.

O3

Figure 31: Trajectory plot for top ten highest daily O3 concentration.

SO2

Figure 32: Trajectory plot for top ten highest daily SO2 concentration.

Black Carbon

Figure 33: Trajectory plot for top ten highest daily Black Carbon concentration.

Benzene

Figure 34: Trajectory plot for top ten highest daily Benzene concentration.

Toluene

Figure 35: Trajectory plot for top ten highest daily Toluene concentration.

Ethylbenzene

Figure 36: Trajectory plot for top ten highest daily Ethylbenzene concentration.

mp-Xylene

Figure 37: Trajectory plot for top ten highest daily mp-Xylene concentration.

o-Xylene

Figure 38: Trajectory plot for top ten highest daily o-Xylene concentration.

4.8 Polar plot map

The maps below show polar plots for each pollutant at each monitoring station superimposed on the region to help understand the relative strength and direction of sources. The distance from the plot origin shows the wind speed.

These plots are useful to help identify primary pollutants which are emitted directly into the atmosphere, especially when multiple plots are used in conjunction to ‘triangulate’ a common source. For pollutants with a secondary component (i.e. formed through chemical reactions in the atmosphere, e.g. NO2, PM2.5 and O3) the directional signature seen in the measurements may not be as strong.

NO2

Figure 39: Polar plot for NO2.

O3

Figure 40: Polar plot for O3.

SO2

Figure 41: Polar plot for SO2.

Black Carbon

Figure 42: Polar plot for Black Carbon.

Benzene

Figure 43: Polar plot for Benzene.

Toluene

Figure 44: Polar plot for Toluene.

Ethylbenzene

Figure 45: Polar plot for Ethylbenzene.

mp-Xylene

Figure 46: Polar plot for mp-Xylene.

o-Xylene

Figure 47: Polar plot for o-Xylene.



For further information, please contact:

Name David Madle
Address Ricardo Energy & Environment, Gemini Building, Harwell, Didcot, OX11 0QR, United Kingdom
Telephone +44 1235 753257
Email david.madle@ricardo.com