1.1 Background

Jersey is the largest of the Channel Islands at 45 square miles, with a population 107,800 ². Both air and sea transport links to the UK and France make it easy to travel to nearby destinations in less than an hour.

This report describes a programme of air quality monitoring carried out on the island of Jersey in 2022, undertaken by Ricardo Energy & Environment, on behalf of Jersey’s Environment Department. The report presents and summarises the fully validated and quality controlled dataset for the period 1^st January to 31^st December 2022. This is the 26^th consecutive year in which an annual monitoring programme has been carried out; the first was undertaken in 1997. This ongoing monitoring programme has provided a long-term dataset of pollutant concentrations.

The pollutants measured were nitrogen dioxide (NO₂), and a range of hydrocarbon species (benzene, toluene, ethylbenzene and three xylene compounds). NO₂ was measured by an automatic monitor, situated at Beresford Street Market located next to the Central Market in St Helier. This was supplemented by indicative monitoring of NO₂ using low-cost passive samplers (Palmes type diffusion tubes). At the beginning of the year there were 18 locations, however in May 2022 five new sites were installed, meaning there were 23 sites in operation between May to December 2022. The suite of hydrocarbon species were monitored using ‘BTEX’ diffusion tubes at five sites during the year.

This report presents the results obtained in the 2022 survey and compares the data from Jersey with relevant air quality limit values, objectives and guidelines as well as data from selected UK monitoring stations and previous years’ monitoring programmes.

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.

In addition to this report, Jersey has daily access to provisional data from its monitoring sites via their own air quality monitoring page ³ and data from the UK’s national air quality monitoring network, through the Defra UK Air Information Resource (UK-AIR) ⁴. Data is also available via Ricardo’s Jersey Air web page ⁵.

1.2 Aims and Objectives

Monitoring during 2022 is the continuation of a survey that has been carried out since 1997. This report is the latest in a series of annual reports. The objective, as in previous years, was to monitor at sites where pollutant concentrations were expected to be high and compare these with background locations. The monitoring sites consisted of urban and rural background sites, in addition to locations where higher pollutant concentrations might be expected, such as roadside and kerbside sites, as well as locations close to specific emission sources (for example, a petrol station).

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.

1.3 Impact of Covid-19 Restrictions on Monitoring

2020 and 2021 saw severe disruption to daily life for all of the world and Jersey was no different. Previous reports in this series have described the time line of events relating to restrictions as a result of coronavirus and the impacts this had on tourism in Jersey. They also explained the disruption to the monitoring programme, mainly relating to deployment and collection of diffusion tubes.

In 2022 there were 845,000 arrivals by air and sea combined ⁶. This was an increase of roughly 109% on 2021, however still roughly only 72% of the 1.18 million air and sea arrivals in 2019 (pre-coronavrius). Therefore, it can be said that Jersey is continuing to recover from the effects of coronavirus but there is an upward trend in recovery since 2021 which is expected to continue in 2023.

2.1 Pollutants Monitored

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 worldwide, in Europe and the UK.

2.3 Monitoring Sites and Methods

2.3.2 Diffusive Sampling of NO₂ and Hydrocarbons

The automatic monitoring site of Beresford Street was supplemented by indicative monitoring, using diffusion tubes, for NO₂ and BTEX hydrocarbons. Diffusion tubes are ‘passive’ samplers, i.e. they work by absorbing the pollutants direct from the surrounding air and need no power supply. They are located in places and heights of relevant exposure, usually attached to lampposts at approximately 2m-4m above ground.

2.3.2.1 NO₂ Diffusion Tubes

Palmes-type diffusion tubes were used for NO₂. These consist of a small plastic tube, approximately 7 cm long. During sampling, one end is open and the other closed. The closed end contains an absorbent for the gaseous species (in this case NO₂) to be monitored. The tube is mounted vertically with the open end at the bottom. Ambient NO₂ diffuses up the tube during exposure and is absorbed as nitrite. The average ambient pollutant concentration for the exposure period is calculated from the amount of pollutant absorbed.

Figure 1: NO₂ diffusion tube

2.3.2.2 BTEX Diffusion Tubes

BTEX diffusion tubes are different in appearance from NO₂ tubes. They are longer, thinner, and made of metal rather than plastic. These tubes are fitted at both ends with brass Swagelok fittings. A separate ‘diffusion cap’ is supplied. Immediately before exposure, the Swagelok end fitting is replaced with the diffusion cap. The cap is removed after exposure and is replaced with the Swagelok fitting. BTEX diffusion tubes are very sensitive to interference by solvents.

Figure 2: BTEX diffusion tube

2.3.2.3 Preparation and Analysis

Diffusion tubes were prepared and analysed by Gradko International Ltd. They were supplied to the Water and Air Technical Officers of Jersey’s Government, who carried out the tube changing. The tubes were supplied in a sealed condition prior to exposure. After exposure, the tubes were again sealed and returned to Gradko for analysis. The UK Local Air Quality Management Technical Guidance LAQM.TG(22) ²⁴ states that when using diffusion tubes for indicative NO₂ monitoring, correction should be made where applicable for any systematic bias (i.e. over-read or under-read compared to the automatic chemiluminescent technique; the reference method for NO₂). By co-locating diffusion tubes with the automatic monitoring site at Beresford Street Market, it is possible to calculate a bias adjustment factor, which could be applied to the annual mean diffusion tube measurements in this survey. The NO₂ diffusion tube results in this report are uncorrected except where clearly specified. BTEX diffusion tubes are not affected by the same sources of bias as NO₂ diffusion tubes, therefore the BTEX results have not been bias adjusted.

Each monthly batch of diffusion tubes was accompanied by a ‘travel blank’ NO₂ and BTEX tube. These tubes were taken with the exposure tubes to the site but were not exposed. They were returned to the site operator’s premises and were kept in a sealed bag in a cupboard. When the exposed tubes were collected, the ‘travel blank’ tubes were taken by the operator to the site. The travel blanks were sent with the exposed tubes for analysis. The purpose of these tubes was to indicate if any contamination of the tubes had occurred. This was particularly relevant in the case of the BTEX tubes because they can easily be contaminated by exposure to solvents.

Gradko also retained one tube from each batch, in a sealed bag in their premises, as a ‘laboratory blank’. The travel blank results for NO₂ were not used to apply any correction to the results from the exposed tubes – only to highlight possible contamination issues. BTEX results were blank corrected using the travel blank, or the laboratory blank where the analyst judged this to be appropriate.

2.3.2.4 Calendar of Diffusion Tube Exposure Periods

The calendar of exposure periods used for the NO₂ and BTEX diffusion tubes is shown in Table 1. They were intended to be an approximation to calendar months, while allowing for the tubes to be changed on a consistent day of the week. It was not always possible to stick to the intended dates, actual change over dates are also shown in the below Table 1.

2.4 Monitoring Sites

Automatic monitoring of oxides of nitrogen was carried out at the Central Market, Beresford Street, in St Helier shown in Figure 3 between 1^st January and 31^st December. The site represent a roadside location where levels of NO₂ are expected to be high and where members of the public are regularly exposed for periods of one hour or more. The inlet funnel (circled), is located on a column at a hight of approximately four meters. The chemiluminescent NO_x analyser itself shown in Figure 4 is located within the building. The analyser is calibrated by the Government of Jersey’s Water and Air’s Technical officers. Details of the calibration procedure is provided in Appendix 2.

Figure 3: Beresford Street Market air quality monitoring site

Figure 4: Automatic NO_x analyser at Beresford Street, St Helier

As explained above, diffusion tubes were used to monitor NO₂ at sites in a range of different environments around Jersey. Diffusion tubes were also co-located with the automatic monitoring site at Beresford Street Market, and the results of this co-located monitoring have been used to assess the precision and accuracy of the diffusion tubes, relative to the automatic chemiluminescent analyser, which is defined within Europe as the reference method for NO₂. The tubes at this site were exposed in triplicate, to allow assessment of precision. All other diffusion tube sites use single tubes.

From the May 2022 exposure five new diffusion tube NO₂ sites were installed at Lewis Street, Aquila Road, Brighton Road, Janvrin Road and Roseville Street (South). These tubes were installed at the request of the Parish of St Helier as there are plans to improve these areas and limit traffic. This should provide baseline data to determine if there is an improvement in air quality following the road improvements in the next few years. Following the November 2022 collection multiple site changes were made by the Government of Jersey including lowering of tubes and relocating some tubes to nearby lamp posts, all due to safety concerns. As these site changes were all less than 10m from the previous location the site names have remained the same. Details of site specific changes in November are listed in Table 2.

BTEX hydrocarbons were monitored at five sites during 2022 shown on Figure 5. The aim was to investigate sites likely to be affected by different emission sources and compare these with background sites. Following the November 2022 collection two sites were moved close to the previous sites, as these site changes were all less than 10m from the previous location the site names have remained the same. Details of site specific changes in November are listed in Table 2.

Le Bas Centre is intended to monitor hydrocarbon concentrations at an urban background location. Rue de Pres Trading Estate, in an industrial estate near to a paint spraying business. The Faux Bie site is located near a fuel filling station, a potential source of hydrocarbon emissions including benzene. The monitoring site is between a fuel filling station and a nearby block of flats and is intended to represent public exposure to emissions from the filling station. The fuel supplier uses a vapour recovery system to reduce emissions when filling the storage tanks and has done so since December 2003. A Stage 2 Vapour Recovery System was later installed at the fuel filling station in 2016, and the replacement of the fuel storage tanks during August 2017. The Harrington’s Garage site was introduced as a replacement to the Airport Fence location and has been in operation since January 2019. The site is located on the A13 Rue de Genets, aiming to assess levels of BTEX from a typical garage with petrol and diesel storage and dispensing facilities where there is no Vapour Recovery system currently in place.

Figure 5 shows a map of the locations of all monitoring sites used in this study. The map can be zoomed in and out and more information on the monitoring sites can be obtained from clicking on the marker. Note the following regarding site classifications:

• Kerbside: less than 1m from kerb of a busy road.
• Roadside: 1 - 5m from kerb of a busy road.
• Background: > 50m from the kerb of any major road.

3.1 Quality Assurance and Quality Control

A full intercalibration audit of the Jersey Beresford Street Market air quality monitoring site takes place annually, summarised in Table 3 and Table 4. In addition to instrument and calibration standard checking, the air intake sampling system is cleaned, and all other aspects of site infrastructure are checked. An additional audit, which counted as a commissioning audit for Beresford Street took place in January 2022, this also brought audits back in line following delayed audits from 2021 due to coronavirus restrictions.

Following the instrument and calibration gas checking, and the subsequent scaling and ratification of the data, the overall accuracy and precision figures for the pollutants monitored at Jersey can be summarised as shown in Table 5. These are given in ppb, the “native” unit of the automatic data.

4.2 Diffusion Tube Uncertainty and Detection Limits

Diffusion tubes are an indicative technique, with greater uncertainty than more sophisticated automatic methods. The reported margins of uncertainty on the analysis are shown in Table 8. However, uncertainties arising from the exposure phase also contribute to the overall uncertainty; it is usually estimated that the overall uncertainty on diffusion tube measurements are approximately ± 25% for NO₂ and BTEX hydrocarbons.

The limits of detection in ambient air depend partly on the exposure time, and therefore vary to some extent from month to month. The analytical limit of detection was in the range 0.028 μg NO₂ to 0.031 μg NO₂. The ambient concentration that this equates to depends on the exposure period, but for the 4-week and 5-week periods used in this study, the limit of detection ranged from 0.491 μg m^-3 to 0.636 μg m^-3. For benzene, the limit of detection equated to an ambient concentration between 0.21 μg m^-3 and 0.27 μg m^-3. The laboratory advises that results lower than 10 times the limit of detection, LOD, will have a higher level of uncertainty. In the case of the NO₂ sites, ambient concentrations are well above this threshold, apart from at Les Quennevais and Rue des Raisies. Therefore, the NO₂ measurements at these two sites are likely to have overall uncertainty greater than ± 25% and should be treated as indicative only. However, for BTEX hydrocarbons in Jersey, this was not the case for most measurements except for benzene, toluene and m+p xylenes at some sites and other isolated measurements. The BTEX hydrocarbon measurements are therefore likely to have overall uncertainty greater that ± 25% and should be treated as indicative only.

5.2 NO₂ Diffusion Tube Results

NO₂ diffusion tube results are presented in Table 9. Although reported by the analyser to two decimal places, the monthly mean results reported here have been rounded to one decimal place, in view of the estimated uncertainty of ± 25% on diffusion tube measurements. Details of site closures and openings during 2022 are given in section 2.4.

Diffusion tubes are affected by several artefacts, which can cause them to under-read or over-read with respect to the reference technique. It has therefore become common practice to calculate and apply a “bias adjustment factor” to annual mean NO₂ concentrations measured by diffusion tubes, using co-located diffusion tube and automatic analyser measurements. This bias adjustment factor is calculated as the ratio of the automatic analyser result to the diffusion tube result. This factor can then be used to correct the annual means measured at the other monitoring locations. The bias adjustment factor was calculated using unrounded values from all months. On this basis, the bias adjustment factor was calculated to be 0.78.

Please note:

• Only the annual mean concentration (not individual monthly values) should be adjusted in this way. This is because diffusion tube bias can vary considerably from month to month due to meteorological and other factors.
• Even after application of a bias adjustment factor, diffusion tube measurements remain indicative only.

Table 9 includes monthly values from each site and Table 10 shows the raw 2022 annual mean and the Bias adjusted 2022 annual mean. Sites that recorded a data capture less than 75% have been annualised as per guidance in LAQM.TG(22) ²⁷ using data from Bournemouth, Southampton, Charlton Mackrell and Yarner Wood as the nearest sites in the UK national network to Jersey. The annual mean for 2021 is included for comparative purposes. Raw (not bias adjusted) monthly values are reported to allow for comparison against past data recorded before bias adjustment was introduced. Individual monthly mean NO₂ results ranged from 3.6 μg m^-3 (in November at the Rue des Raises site) to 47.4 μg m^-3 (in March at the St Saviours Hill site). The annual mean for the majority of sites remained relatively consistent between 2021 and 2022 with most sites being within +/- 3 μg m^-3. For this report the annual mean will be used unless otherwise stated.

Table 11 lists the missing diffusion tube results throughout 2022, including outliers and missing tube results.

The typical pattern in UK urban areas is for NO₂ concentrations to be generally higher in the winter and lower in the summer. The highest concentrations were generally recorded in the winter months of January, March and December. The spring and summer months between May and September had consistently average concentrations with very little variation. Sites with some of the highest concentrations include St Saviours Hill, Beaumont and Gloucester Street (Hospital), whilst Rue des Raises consistently sits below all other sites.

5.3 Comparison with NO₂ Guidelines, Limit Values and Objectives

Limit values, AQS objectives and WHO guidelines for NO₂ are described in earlier sections of this report. These are based on the hourly and annual means. The Air Quality Directive ²⁸ contains limit values for NO₂ as follows:

• 200 μg m^-3 as an hourly mean, not to be exceeded more than 18 times per calendar year. To have been achieved by 1^st January 2010.
• 40 μg m^-3 as an annual mean, for protection of human health. To have been achieved by 1^st January 2010.
• There is also a limit for annual mean total oxides of nitrogen (NO_x), of 30 μg m^-3, for protection of vegetation (relevant in rural areas).

The UK Air Quality Strategy ²⁹ contains objectives for NO₂, which are very similar to the Directive limits above, the only difference being they had to be achieved by 31^st December 2005.

The 1-hour mean at the Beresford Street automatic monitoring sites did not exceed 200 μg m^-3 in 2022. Therefore, this site met the EC Directive limit value and AQS objective for this parameter.

The period mean concentration of 17 μg m^-3 as measured by the automatic analyser at Beresford Street was well within the EC limit value of 40 μg m^-3.

The updated WHO guidelines introduced in 2021 advise an annual mean limit for NO₂ of 10 μg m^-3. Jersey Beresford Street did not meet this guideline during 2022.

Due to the long sampling period of diffusion tubes, it is only possible to compare the results from the diffusion tube sites in this study against limit values relating to the annual mean. Neither the raw nor bias adjusted annual average calculated in this report showed a site exceeding the annual mean limit value of 40 μg m^-3.

The 30 μg m^-3 limit for protection of vegetation is only applicable at rural sites and is therefore only relevant to Rue des Raisies. The annual mean NO₂ concentration of 4.9 μg m^-3 at this rural site was well within the limit value.

5.6 Calendar Plot

Figure 13 shows interactive versions of calendar plots. The date is coloured by the NO₂ concentration (μg m^-3) for that day. The actual value can also be seen by hovering the mouse on the cell, along with the wind speed.

5.7 Back Trajectory Analysis

The back trajectory plot shows data from the HYSPLIT model ³⁰ run in analysis mode. This shows the air mass back trajectories for the period covered by the report. Three 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. This is useful to get an overview of air mass origins during the report period. On additional tabs, the trajectories associated with exceedances of the LV (1-hr for NO₂) are shown. A plot of the trajectories associated with the top 10 measured concentrations is also presented.

Trajectory Clusters

72-hour air mass back trajectories arriving at Jersey for the reporting period are grouped into 4 clusters, shown in Figure 14. This shows the approximate proportion of time air masses were arriving from each compass point during 2022.

Figure 14: 72-hour air mass back trajectories arriving at Jersey during 2022

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 used here is Jersey.

5.8 Comparison with UK NO₂ Data

Table 12 compares the annual NO₂ concentration measured at Beresford Street Market with those measured at a selection of UK air quality monitoring stations in the national Automatic Urban and Rural Network and in Guernsey, both using automatic (chemiluminescent) NO₂ analysers. The sites used for comparison are listed below.

• Brighton Preston Park – an urban background site in Brighton, Sussex.
• Exeter Roadside – a roadside site in the centre of Exeter, Devon.
• Plymouth Centre – an urban centre site in the coastal city of Plymouth, Devon.
• Yarner Wood – a rural moorland site in Devon.
• Guernsey Bulwer Avenue - a roadside site in the north east of Guernsey.

The annual mean NO₂ concentrations, from diffusion tubes with exposure periods between 4 and 5 weeks, measured at the kerbside and roadside sites in Jersey (rounded to the nearest integer) ranged from 12 to 37 μg m^-3. However, bias adjusted annual averages ranged from 10 to 29 μg m^-3.
The mean concentrations measured at Exeter Roadside, 18 μg m^-3, and Plymouth Tavistock Road, 16 μg m^-3, are similar to the 17 μg m^-3 as measured by the automatic analyser at Beresford Street Market. The Jersey urban background site at Le Bas Centre had an annual mean NO₂ concentration of 19 μg m^-3, higher than that of the automatic analyser at Beresford Street. The residential background/school site at Les Quennevais (new site) measured an annual mean NO₂ concentration of 9 μg m^-3, higher than the rural Yarner Wood site in Devon. The annual mean of 4.9 μg m^-3 (3.8 μg m^-3 when bias adjusted) at the Jersey rural background site, Rue des Raisies, was similar to that measured at the Yarner Wood site. A comparison between 2022 averages for Jersey Beresford Street Market and Guernsey Bulwer Avenue show that whilst the Jersey site is slighly higher than the Guernsey site, both are well within the 40 μg m^-3 annual limit set by the European Union. All of the UK mainland sites with the exception of Plymouth Centre showed a decrease in levels compared to 2021. A comparison cannot be made for Beresford Street in 2022 as this was the first full calendar year of operation.

5.9 Trends in NO₂ at Long-running Sites

The annual mean NO₂ concentrations for diffusion tube sites which had over 75% data capture are illustrated in Figure 16, the five new sites are not included in as they did not run the entire year. The data is not adjusted for diffusion tube bias as there was no reliable information on which to carry out bias adjustment prior to 2002. Therefore, for consistency, unadjusted data is used in this section.

Broad Street became pedestrianised on the 23^rd of May 2020 in order to allow greater social distancing for pedestrians, this is reflected in a 27% reduction in the annual mean concentrations in 2020. This has been followed by further reductions in 2021 and 2022 to 17 and 16 μg m^-3 respectively.

Annual mean NO₂ concentrations at historic kerbside, roadside and urban background sites (Weighbridge, Georgetown, Beaumont, The Parade, Broad Street, and Le Bas) from 2004 onwards show a decreasing trend. In 2022 all sites remained below 40 μg m^-3. Many sites saw concentrations increase compared to 2021, likely down to the relaxation of restrictions imposed due to coronavirus over the previous two years.

Figure 16 illustrates how since 2012 annual mean NO₂ concentrations at several of the sites have remained stable with typical fluctuations from year to year due to meteorological conditions and other factors. As traffic volumes have increased since monitoring began, fluctuations in concentrations are likely linked to increased vehicle efficiency and cleaner fuels. A recent study into vehicle emissions in Jersey ³¹ found that newer petrol vehicles produce fewer NO_x emissions. It also found that there is an increase in newer petrol cars compared to a decline in diesel on the island, with plans to introduce MOT style testing in the future. This will further increase visibility of emissions and potentially reduce the number of heavily polluting vehicles on the roads, in turn contributing to a continued reduction in ambient concentrations.

As a more focused example of the differences between site locations; it is interesting to note the lower trend of readings from the now discontinued New Street site compared to Union Street. The two locations were very close with the Union Street tube located on the corner of Union Street and New Street which run perpendicular to each other. New Street is access only and therefore, carries much lower traffic volumes. As the prevailing wind is from the West with the least wind coming from the North, very little of the pollution from Union Street is carried to the more southerly New Street location. This indicates how localised NO₂ distribution can be with certain mitigating factors.

5.10 Hydrocarbons

Full monthly results of the hydrocarbon survey for the five BTEX sites and a summary of the annual average hydrocarbon concentrations are shown below in Table 14 and Table 15 respectively. Travel blank values are included and gave consistently lower results than the exposed tubes which the exception of most pollutants in January 2022 which had elevated levels in the Travel Blank. The following exposures were noted to have loose end caps and it is therefore possible that the elevated concentrations reported were influenced by this:

• January 2022 - Rue de Pres Trading Estate
• May 2022 - All BTEX sites
• September 2022 - Harrington’s Garage & Faux Bie Terrace
• December 2022 - Le Bas Centre, Harrington’s Garage & Faux Bie Terrace.

For most of the deployments listed above these corresponded with elevated concentrations by the BTEX tubes, therefore these measurements should be treated with caution.

For BTEX tubes monthly data by pollutant is displayed in Figure 17 to Figure 19.

6.1 NO₂ Results

1. The period mean NO₂ concentration measured by the automatic analyser at Beresford Street Market was 17 μg m^-3 (rounded to the nearest integer). This site recorded 98% data capture for the 2022 calendar year, above the limit required to report an annual mean. This is therefore within the EC Directive limit value and AQS objective of 40 μg m^-3 for annual mean NO₂. Having achieved compliance by 2010 as required by all European Union member states the Government of Jersey are advised to continue to demonstrate ongoing compliance as has been done since 2010.
2. 2022 was the first full calendar year of monitoring at Beresford Street Market, therefore it is difficult to make direct comparisons between this site and others. Jersey is also continuing it’s recovery from coronavirus, therefore making comparisons between previous years difficult. It is recommended that monitoring is continued at Beresford Street Market for further years to enable these comparisons.
   
3. The EC Directive limit value (and AQS objective) for 1-hour mean NO₂ concentration is 200 μg m^-3, with 18 exceedances permitted per calendar year. There were no hourly means greater than this value measured at the Beresford Street Market automatic site, the highest hourly value measured was 99.2 μg m^-3. Therefore, this site met the limit value objective.
4. NO₂ diffusion tubes exposed in triplicate alongside the automatic analyser at Beresford Street Market (Central Market 2) measured a 22 μg m^-3 annual mean.
5. Annual mean NO₂ concentrations at all diffusion tube monitoring sites were within the EC limit value of 40 μg m^-3.
6. The updated WHO guidelines introduced in 2021 advise an annual mean limit for NO₂ of 10 μg m^-3. Jersey Beresford Street did not meet this guideline during 2022.
7. The diurnal variation in NO₂ concentrations at Beresford Street Market showed some similarities to an urban site but had a particularly early (and sharp) morning rush hour peak, with a gentle but broad evening peak afternoon rush hour peak. This is thought to be due to traffic patterns around the site; this being early morning traffic associated with the market and use of the short term parking next to the site where drivers regularly leave vehicles running.
8. Seasonal variations in monthly mean NO₂ concentrations at the diffusion tube sites have historically been hard to see, however in 2022 seasonal variations can be seen with the highest concentrations in generally measured in January and March whilst lower concentrations were seen between May and September.
9. Annual mean NO₂ concentrations at Jersey’s urban sites appear to have generally decreased between 2003 and 2012. Since then concentrations have remained largely stable at most sites.
10. Annual mean NO₂ concentrations at all of Jersey’s diffusion tube monitoring sites were similar in 2022 compared with 2021. Pollutant concentrations are expected to fluctuate from year to year, due to meteorological and other factors, the COVID-19 pandemic being the obvious major one for 2020 and beyond.

6.2 Hydrocarbon Diffusion Tube Results

1. Annual mean benzene concentrations at all five sites were within the EC Directive limit value of 5 μg m^-3. Having achieved compliance by 2010 as required, the Government of Jersey must continue to demonstrate ongoing compliance.
2. All sites measured relatively low, however Harrington’s Garage and Faux Bie Terrace do show slightly higher average measurements than the other three sites for most pollutants, possibly as a result of their proximity to fuel filling stations.
3. Annual mean concentrations of benzene and toluene at all sites were similar to those in 2021, except for Harrington’s Garage where an increase of roughly 70% was seen.
   
4. Annual mean concentrations of ethylbenzene, m+p-xylene and o-xylene at Harrington’s Garage and Faux Bie Terrace showed a considerable increase on 2021 concentrations. Rue de Pres Trading Estate and Le Bas Centre were similar to those measured in recent years.

6.3 Recommendations

It is recommended that the monitoring programme be continued as part of Jersey’s Air Quality Strategy. Measured concentrations of BTEX hydrocarbons at most of the sites were very low. The results should therefore only be taken as indicative measurements, for the purpose of confirming that benzene concentrations at the sites are within relevant limit values. However, if accurate measurement of hydrocarbons are required, it may be appropriate to consider installation of pumped-tube sampling at key sites, as used at UK mainland Non-Automatic Hydrocarbon Network sites. To further reduce VOC emissions from petrol stations and Jersey’s fuel farm it is recommended that the States of Jersey consider developing vapour recovery legislation.

Continual review of the diffusion tube network is recommended to assess any sites that no longer represent relevant exposure and can be removed or relocated. The diffusion tube results indicate no sites breaching or close to the annual average NO₂ limit values. As such, an expansion of the automatic NO_x monitoring network is not required, it is recommended that monitoring continues at the Beresford Street Market urban roadside location. This helps for better comparison between the other roadside and kerbside diffusion tube sites and enables an appropriate co-location for diffusion tubes used for annual BIAS adjustment. It also ensures that Jersey’s monitoring network aligns with the strategy stated in LAQM.TG(22) whereby monitoring sites are “sufficiently close to the dominant pollution source (i.e. in the vast majority of cases, at roadside sites)”³⁴. If the Government of Jersey would like to expand the network, monitoring at a background site would be beneficial to “determine long-term trends, as such sites are less likely to be affected by variations in local sources, for example, changes in traffic on a particular road” ³⁵.

Based on the 2019 UK Clean Air Strategy ³⁶ and its emphasis on PM_2.5 reduction the Government of Jersey may wish to install reference equivalent analysers in an aim to expanding their particulate monitoring network and demonstrating compliance with the annual WHO PM_2.5 guideline of 5 μg m^-3.

With ongoing reductions in concentrations and improvements in technology since the Jersey Air Quality Strategy was last published in 2013, now would be a good opportunity to review and potentially update the document. Ricardo understands that with a recent restructure during 2021, with Air Quality monitoring moving to a dedicated scientific team, and Government Plan funding allocation, the Government of Jersey have moved to prioritise the development of the existing Air Quality monitoring programme to meet new and existing environmental challenges.