The 2023 period mean from the automatic monitor at Beresford Street Market was 16 μg m-3, showing a decrease in annual mean concentration compared to 2022. The annual mean NO2 concentration measured at Beresford Street Market was within the EC Directive limit value and AQS objective of 40 μg m-3 for annual mean NO2 but was higher than the WHO annual guideline of 10 μg m-3. 

Data capture at Central Market Osiris and Howard Davis Park Osiris were both below the recommended 90% data capture required to create an annual average. Therefore, no comparisons to limit values and objectives can be made. 

Annual mean concentrations of NO2 did not exceed the EC Directive limit value of 40 μg m-3 at any of the diffusion tube sites. However most sites recorded annual mean NO2 concentrations greater than the WHO annual guideline of 10 μg m-3. For comparison annual averages had a bias adjustment factor applied which gave lower annual averages for all sites. Diffusion tubes measure over a monthly period therefore, the results are an average and not applicable to measuring peaks or low levels of pollution at any specific time. 

The diurnal variation in NO2 concentrations at Beresford Street Market showed some similarities to an urban site, showing an early and sharp peak at morning rush hour followed by 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 occasionally leave vehicles running. 

The pattern of monthly averaged concentrations throughout the year showed that concentrations of NO2 were typically highest in the winter months. Bivariate plots of NO2 concentration indicated that nearby sources, such as vehicles using Beresford Street, were likely contributing factor of elevated NO2 concentrations. 

Diurnal variations of particulate matter concentrations at Central Market Osiris showed a broad morning peak followed by a smaller peak in the afternoon. Similar to NO2 concentrations at Beresford Street, this is likely attributed to market operations and idling vehicles. Particulate matter concentrations measured at Howard Davis Park showed a similar trend to those measured at Central Market Osiris with a broad morning peak followed by a smaller afternoon peak, although to a lower magnitude due to this site being located in the centre of Howard Davis Park. Concentrations at Central Market Osiris and Howard Davis Park indicate that elevated particulate matter concentrations generally occur in unsettled conditions, particularly at high wind speeds from the southwest, in the direction of the port and marinas. 

Since 2000, there is shown to be an overall decreasing trend in NO2 concentrations at long-running NO2 diffusion tube monitoring locations. This decrease is likely linked to increased vehicle efficiency and cleaner fuels as well as the overall decline in the use of diesel vehicles in Jersey. Few sites have shown small increases in NO2 concentrations in 2023 which is likely due to the continued reuptake in travel following the COVID-19 Pandemic restrictions imposed between 2020 and 2021. 

Each of the hydrocarbon sites provided annual means below that required of the EC Directive limit value for benzene (5 μg m-3 as an annual mean, to be achieved by 2010). Since the introduction of catalytic converters in 1991 and the limiting of benzene concentrations in petrol to 1% in the year 2000, ambient measured concentrations have declined in the UK.

Hydrocarbon concentrations were generally similar when comparing 2023 to 2022, except for toluene concentrations at Faux Bie Terrace and Harrington's Garage where there were shown to be small increases in annual mean concentrations (although still significantly below occupational exposure levels). Over the long term, hydrocarbon concentrations have generally decreased at all sites that have been operational for 5 years or more. Long term trends at Rue de Pres and Beresford Street will be seen after these sites remain in operation for future years.