a comparison study of nitrogen dioxide concentrations along two … · 2019. 7. 5. · a comparison...

A comparison study of nitrogen dioxide concentrations along two cycle routes in the city of London Report for the Unblock the Embankment campaign group

ED12627 | Final_Version_2 | Date 05/07/2019

A comparison study of nitrogen dioxide concentrations along two cycle routes in the city of London | i

Ricardo Confidential Ref: Ricardo/ED12627/Final_Version_2

Ricardo Energy & Environment

Customer: Contact:

Unblock the Embankment Paul Willis Ricardo Energy & Environment Gemini Building, Harwell, Didcot, OX11 0QR, United Kingdom

Ricardo is certificated to ISO9001, ISO14001 and OHSAS18001

Customer reference:

ED12627

Confidentiality, copyright & reproduction:

This report is the Copyright of Unblock the Embankment and has been prepared by Ricardo Energy & Environment, a trading name of Ricardo-AEA Ltd under contract NO2 personal exposure monitoring near the Embankment dated 01/03/2019. The contents of this report may not be reproduced, in whole or in part, nor passed to any organisation or person without the specific prior written permission of Unblock the Embankment. Ricardo Energy & Environment accepts no liability whatsoever to any third party for any loss or damage arising from any interpretation or use of the information contained in this report, or reliance on any views expressed therein, other than the liability that is agreed in the said contract.

Author:

James Southgate, Stephen Stratton

Approved By:

Paul Willis

Date:

05 July 2019

Ricardo Energy & Environment reference:

Ref: ED12627- Final_Version_2

A comparison study of nitrogen dioxide concentrations along two cycle routes in the city of London | ii



Executive summary

Ricardo Energy & Environment were contracted by the Unblock the Embankment campaign group to

undertake measurements of nitrogen dioxide (NO2) concentrations along two cycle routes located

within the city of London. The aim of the study is to gain an insight as to which route is likely to

exposure commuter cyclists to higher levels of NO2 pollutants during rush hour traffic.

Route 1 begins opposite Blackfriars station and initially runs in a southwest direction before joining the

embankment stretch of the super-highway cycle lane. The route runs east along the super-highway

until reaching the junction of Dock Street.

Route 2 begins opposite Blackfriars station and runs east through Queen Victoria street before joining

Cornhill street at the Bank junction. The route continues through Leadenhall street and Aldgate high

street before ending outside Aldgate east station.

Mobile monitoring was carried out using Alphasense electronic diffusion tubes (EDT). Quality

assurance and quality control (QA/QC) was applied and took the form of two co-location exercises to

assess the inter-relationship between the two EDT’s and derive a correction factor by comparison to a

reference oxides of nitrogen (NOx) analyser. It is important to emphasise that the EDT’s are an

indicative method and so the results in this report should be treated as such. In addition, the

monitoring carried out only provides a snap-shot of NO2 concentrations that are likely to be

experienced along the monitoring routes.

The monitoring results indicate the following:

Average NO2 concentrations over all the monitoring exercises were 13% higher along Route

1 than that measured along Route 2.

The most notable differences were seen on 07/06/2019 and 11/06/2019 where average NO2

concentrations were 38% and 65% higher along Route 1 compared to Route 2, respectively.

On 07/06/2019 and 11/06/2019, NO2 hotspots were identified on Route 1 along the A3211

between the A10 junction and Blackfriars Underpass.

The maximum 1-minute average concentration of 552 g m-3 was measured on Route 2 at

the Queen Victoria St/Poultry junction on 06/06/2019.

In general, increased NO2 concentrations were measured at junctions where road traffic is

more likely to be slow moving or queuing.

A comparison study of nitrogen dioxide concentrations along two cycle routes in the city of London | iii



Table of contents 1 Introduction ................................................................................................................ 1

1.1 Purpose of the study ......................................................................................................... 1 1.2 General approach taken .................................................................................................... 1

2 Pollutants investigated .............................................................................................. 1

2.1 Nitrogen Dioxide (NO2) ...................................................................................................... 1 2.2 Air Quality Strategy Objectives .......................................................................................... 1

3 Methodology .............................................................................................................. 2 3.1 Monitoring Equipment ....................................................................................................... 2 3.2 Monitoring Exercises ......................................................................................................... 2 3.3 Sensor calibration .............................................................................................................. 3 3.4 Geographical Information System ..................................................................................... 5

4 Results ........................................................................................................................ 6

5 Conclusions ............................................................................................................. 10

A comparison study of nitrogen dioxide concentrations along two cycle routes in the city of London | 1



1 Introduction

1.1 Purpose of the study





1.2 General approach taken

The approach undertaken in this study was to record NO2 concentrations using two mobile electronic

diffusion tube (EDT) sensors. Each sensor was fixed to a bike which travelled the length of the

predefined routes during rush hour traffic. The sensors recorded NO2 concentrations at one-minute

intervals on a daily basis over a period of five-week days. Each cyclist recorded their GPS position

and time during their trip using a reliable phone app. The GPS position and time was matched to the

data obtained from the mobile NO2 sensors and is shown in the results section of this study.

It is important to emphasise that the EDT’s are an indicative method and so the results in this report

should be treated as such. In addition, the monitoring only provides a snap-shot of NO2

concentrations that are likely to be experienced along the monitoring routes.

2 Pollutants investigated

2.1 Nitrogen Dioxide (NO2)

Nitrogen dioxide (NO2) is formed through the combustion of fuel, such as happens in vehicle engines.

This gas can irritate the lungs and lower resistance to respiratory infections such as influenza.

Nitrogen dioxide is a key air pollutant of concern within the UK Local Air Quality Management regime.

It can irritate the lungs and lower resistance to respiratory infections such as influenza (Barnett et al.,

2005, Bernstein et al., 2004)1, with increased asthma and respiratory admissions typical with higher

NO2 concentrations.

2.2 Air Quality Strategy Objectives

Table 2.1 details the air quality objectives applicable to Local Air Quality Management (LAQM) in

England. Note that no direct comparison can be made between the measurements made for this

study and these objectives and that this table has been provided for information only. This is due to,

firstly, the difference in measurement methodology e.g. the objectives are based around static

measurements whereas mobile measurements were carried out for this study. Secondly, the

timeframe defined for the long-term NO2 objective (40 g m-3 as an annual mean) is greater than the

timeframe the mobile monitoring was carried out in; and the timeframe for hourly objective of

200 g m-3 is greater than the time it takes a cyclist to travel along either route.

1Barnett, A. G., Williams, G. M., Schwartz, J., Neller, A. H., Best, T. L., Petroeschevsky, A. L. & Simpson, R. W. 2005. Air pollution and child

respiratory health: a case-crossover study in Australia and New Zealand. American Journal of Respiratory and Critical Care Medicine, 171, 1272-

1278.




Table 2.1 Air Quality Objectives included in Regulations for the purpose of LAQM

Pollutant Air Quality Objective

Concentration Measured as

Nitrogen Dioxide 200 µg m-3, not to be exceeded more than 18 times a year 1-hour mean

40 µg m-3 Annual mean

3 Methodology

3.1 Monitoring Equipment

Table 3.1 below details the monitoring equipment used for the study.

Table 3.1 Mobile monitoring equipment used

Parameter Instrument type Description

NO2 Alphasense EDT These samplers use an electrochemical sensor to measure 1-

minute average NO2 concentrations.

The Alphasense EDT was chosen as the preferred monitoring device used in this study due to its

portable design, price and reliability in measurement. This study aims to gain an understanding of the

indicative NO2 concentrations cyclists are exposed whilst travelling two routes of interest.

3.2 Monitoring Exercises

The mobile monitoring exercise was carried out during the month of June along two predefined routes

within the city of London. Figure 1 displays an image of the routes undertaken during this study.

Figure 3.1 Map of the two routes used in this study




Description of the routes used in this study:





Cornhill street at the Bank junction. The route continues through Leadenhall street and Aldgate high-


Monitoring method:

This study captured NO2 concentrations along the two routes defined in figure by attaching mobile

NO2 sensors to standard road bikes. The two bikes and sensors were ridden simultaneously along

each route to capture daily NO2 concentrations during rush hour traffic between the following times:

08:00 – 09:30 (am)

16:00 – 17:30 (pm)

Each cyclist also recorded his or her GPS position using a reliable mobile phone app whilst cycling

each route. The cyclist position and time was matched to each measurement recorded by the NO2

sensor. The results are provided in the results section below.

Due to meteorological conditions, it was not possible to collect measures over the period of one

working week. Instead, the measurements were collected over a three-week period during June 2019.

Table 3.2 summarises the measurement exercises carried out.

Table 3.2 Summary of monitoring exercises carried out

Date Day Routes am/pm

04/06/2019 Tuesday 1 and 2 am

06/06/2019 Thursday 1 and 2 pm

07/06/2019 Friday 1 and 2 pm

11/06/2019 Monday 1 and 2 pm

12/06/2019 Tuesday 1 and 2 am

17/06/2019 Monday 1 and 2 am

17/06/2019 Monday 1 and 2 pm

20/06/2019 Thursday Valid data for Route 1 only am

26/06/2019 Wednesday 1 and 2 pm

3.3 Sensor calibration

In order to compare the measurements collected by the two NO2 monitors, a calibration study was

undertaken between the 20th – 23rd May and 24th – 26th June 2019. The co-location exercises

consisting of placing both monitors alongside each other at a location where NO2 concentrations are

expected to be substantial. For the first co-location, the sensors were also located at the Earls Court

Road automatic monitoring site (https://www.airqualityengland.co.uk/site/latest?site_id=KC5) to

https://www.airqualityengland.co.uk/site/latest?site_id=KC5




enable direct comparison to the reference oxides of nitrogen (NOx) analyser at the site. The results

were then analysed to determine correction factors to scale the NO2 data and to assess the inter-

relationship between the two sensors. Note that at the time of writing this report the NO2 data from

Earls Court Road were provisional, however, they were scaled and processed using the latest

calibration data.

Figure 3.2 provides a visual representation of the results from the co-location study at the Earls Court

Road automatic monitoring site. This co-location enabled correction factors of 1.134 and 1.195, and

estimated measurement uncertainties of ±27% and ±36% (at 200 g m-3) to be derived for EDT-60

and EDT-62, respectively.

Figure 3.2 Orthogonal regression of EDT-60 and EDT-62 compared to the Earls Court Road reference NOx

analyser in May-19 using 15-minute average NO2 concentrations (ppb)

Figure 3.3 shows the inter-comparison between the two EDT sensors. The relationship between the

two sensors was found to be excellent at close to 1:1 and with r2 of 0.93 and 0.81 in May and Jun-19,

respectively.

Figure 3.3 Orthogonal regression of inter-relationship between EDT-60 and EDT-62 in May and Jun-19

using 1-minute average NO2 concentrations (ppb)




3.4 Geographical Information System

ArcGIS was used to create the mapped NO2 concentration plots. 1-minute average concentrations

were combined with recorded GPS coordinates and inverse distance weighted (IDW) interpolation

was used to interpolate between points. The average of the interpolated NO2 concentrations within

25 m2 blocks were then calculated to produce a plot of average concentrations throughout the study

area. This provides a visualisation of the spatial variation of pollutant concentrations along the two

routes.

Please note that the concentrations shown in the plots are indicative as they are the result of a geo-

processing routine in ArcGIS. Also, the pollution gradients can be seen to be wider than the roads,

which are an artefact of the GPS accuracy and the GIS processing. When interpreting the plots all

concentrations shown indicate potential exposure a pedestrian/cyclist might experience when

travelling along the route.

Figure 3.4 shows the GPS points recorded during all mobile sampling exercises. A number of GPS

measurements were recorded every minute with a total of 22,848 points recorded for this study. Each

point was then assigned an NO2 concentration e.g. three GPS points within the same minute would be

assigned the same associated 1-minute average NO2 concentration.

Figure 3.4 GPS points recorded during the mobile monitoring exercises

All map data within this report Contains Ordnance Survey data © Crown copyright and database right 2019.




4 Results

Table 4.1 provides summary statistics for each mobile monitoring exercise. The ‘% Difference’ is

calculated using the Route 2 concentration as the reference. Figure 4.1 charts the average NO2

concentrations measured on each day. Average NO2 concentrations were greater along Route 1

during four of the monitoring exercises and greater along Route 2 for four of the exercises. The most

notable differences were seen on 07/06/2019 (pm) and 11/06/2019 (pm) where average NO2

concentrations were 38% and 65% higher along Route 1 compared to Route 2, respectively. It was

noted on both days that there was medium traffic build up at traffic light junctions along Route 1 and

that the traffic was light along Route 2. The maximum 1-minute average concentration of 552 g m-3

was measured on Route 2 at the Queen Victoria St/Poultry junction on 06/06/2019. Average NO2

concentrations over all the monitoring exercises were 13% higher along Route 1 than that measured

along Route 2.

Table 4.1 Summary statistics of NO2 concentrations measured during each monitoring exercise (g m-3)

Date Average

% Difference Maximum Minimum

Route 1 Route 2 Route 1 Route 2 Route 1 Route 2

04/06/2019 (am) 110 118 -7% 197 169 14 41

06/06/2019 (pm) 68 72 -6% 399 552 8 8

07/06/2019 (pm) 102 74 38% 202 176 14 20

11/06/2019 (pm) 122 74 65% 197 151 14 26

12/06/2019 (am) 84 91 -8% 399 163 10 16

17/06/2019 (am) 91 81 12% 133 141 30 26

17/06/2019 (pm) 76 71 7% 193 176 14 10

20/06/2019 (am) - 89* - - 231 - 26

26/06/2019 (pm) 70 70 0% 399 88 10 24

Average: 90 81 13% - - - - *Note that the average is calculated using only paired data – this measurement has not been included.

Figure 4.1 Average NO2 concentrations measured during each mobile monitoring exercise




Figures 4.2 to 4.4 show mapped 1-minute average NO2 concentrations as measured over all mobile

monitoring exercises, as measured on 07/06/2019, and as measured on 11/06/2019, respectively. In

order to reduce possible bias in the plots, the top 1% of measurements were removed from the

mapped data. This helps with identifying hotspots that would otherwise be masked if these high data

remained.

In general, increased NO2 concentrations were measured at junctions where road traffic is more likely

to be slow moving or queuing. More specifically, NO2 hotspots were seen on Route 1 along the

A3211 at the junctions with the A10, the A300 and at the Blackfriars Underpass. Hotspots were also

seen on Route 2 at the junctions of Queen Victoria St and the A3211, Queen Victoria St and Cornhill,

Leadenhall St and the A10, and Leadenhall St and Aldgate. The most apparent hotspots were seen

along the A3211 (Route 1).

Figure 4.2 Mapped 1-minute average NO2 concentrations over all mobile monitoring exercises (g m-3)





In order to investigate the marked differences in NO2 concentrations between Route 1 and Route 2

measured on 07/06/2019 and 11/06/2019, mapped concentration plots have been provided for these

two days in Figures 4.3 and 4.4, respectively. As can be seen in Figure 4.3, maximum NO2

concentrations are highlighted on Route 1 along the A3211 between the A10 junction and Blackfriars

Underpass on 07/06/2019. Similarly, in Figure 4.4 on 11/06/2019, NO2 hotspots are highlighted on

Route 1 along the A3211 between the A330 and A10 junctions.

Figure 4.3 Mapped 1-minute average NO2 concentrations on 07/06/2019 (g m-3)





Figure 4.4 Mapped 1-minute average NO2 concentrations on 11/06/2019 (g m-3)





5 Conclusions









Cornhill street at the Bank junction. The route continues through Leadenhall street and Aldgate high


Mobile monitoring was carried out using Alphasense electronic diffusion tubes (EDT). Quality

assurance and quality control (QA/QC) was applied and took the form of two co-location exercises to

assess the inter-relationship between the two EDT’s and derive a correction factor by comparison to a

reference oxides of nitrogen (NOx) analyser. It is important to emphasise that the EDT’s are an

indicative method and so the results in this report should be treated as such. In addition, the

monitoring carried out only provides a snap-shot of NO2 concentrations that are likely to be

experienced along the monitoring routes.

The monitoring results indicate the following:

Average NO2 concentrations over all the monitoring exercises were 13% higher along Route

1 than that measured along Route 2.

The most notable differences were seen on 07/06/2019 and 11/06/2019 where average NO2

concentrations were 38% and 65% higher along Route 1 compared to Route 2, respectively.

On 07/06/2019 and 11/06/2019, NO2 hotspots were identified on Route 1 along the A3211

between the A10 junction and Blackfriars Underpass.

The maximum 1-minute average concentration of 552 g m-3 was measured on Route 2 at

the Queen Victoria St/Poultry junction on 06/06/2019.

In general, increased NO2 concentrations were measured at junctions where road traffic is

more likely to be slow moving or queuing.

The Gemini Building

Fermi Avenue

Harwell

Didcot

Oxfordshire

OX11 0QR

United Kingdom

t: +44 (0)1235 753000

e: [email protected]

ee.ricardo.com

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