Authors James Dernie, Luke Doman, Ben Fowler, Andrew Kent, Hao Wu and Daniel Wakeling
Compilation date 23 September 2021
Customer Environment Agency, Department for Environment, Food and Rural Affairs, Department of Environment Northern Ireland, Welsh Government and Scottish Government
Approved by Paul Willis
Copyright
EULA http://ee.ricardo.com/cms/eula/

Contract reference 23173 Report reference ED11732 2020 Issue 1

Executive summary

The UK Hydrocarbons Network comprises automatic and non-automatic systems to measure benzene in compliance with the European Directive 2008/50/EC (AQD) (EC, 2008). The UK is required to meet the Directive annual mean limit value of 5 µg m-3 as well as achieving compliance with Objectives in the UK Air Quality Strategy (Defra, 2007). This report details the 2020 data and compares against the UK and EU limit values.

The Directive sets data capture requirements of 90% for benzene. The mean data capture for benzene measured at the non-automatic hydrocarbon monitoring stations in operation from January to December 2020 was 96%. The annual mean concentration across all non-automatic monitoring stations in the UK was 0.53 µg m-3. All 34 monitoring stations used for non-automatic benzene measurements are situated in urban locations.

The Directive also requires the measurement of ozone precursor volatile organic compounds (VOCs). The UK Hydrocarbons Network measures 29 of the 31 listed substances (including 1,3-butadiene) using automatic analysers. There are two urban stations, an urban traffic station on the Marylebone Road, London and a suburban station in Eltham, Greenwich.

Rural automatic stations at Chilbolton Observatory, Hampshire and Auchencorth Moss, Midlothian are used to support The European Monitoring and Evaluation Programme (EMEP) to Level 2. EMEP is a scientifically based and policy driven programme under the Convention on Long-range Transboundary Air Pollution (CLRTAP) for international co-operation to solve transboundary air pollution problems.

The mean data capture for benzene measured by the automatic hydrocarbon network in 2020 was 72%. The annual mean across all automatic monitoring stations in the UK was 0.42 µg m-3.

The results for both automatic and non-automatic monitoring confirm no exceedances of EU or UK limit values and objectives at any of the Rural, Urban Traffic, Centre and Background locations during 2020.

This report also includes some more in-depth analysis of:

  • Long term trends in benzene concentrations;
  • Ozone creation potential for different VOC species.

Key findings for 2020:

  • In 2020, none of the automatic or non-automatic monitoring stations in the UK exceeded the 5 µg m-3 annual mean Limit Value or the Upper Assessment Threshold of 3.5 µg m-3 for benzene set out in the EC Air Quality Directive.
  • The results confirm no exceedances of EU or UK limit values and objectives at any of the Urban, Traffic and Background monitoring stations during 2020.
  • Measurements made at the Chilbolton observatory indicate that, of the 29 species measured, ethene, Meta + Para-Xylene, nbutane, propane and toluene are the largest contributors to regional O3 increment during daylight hours in summer.

1 Introduction

This report provides a summary of the site management activities and data produced in 2020 by the UK Hydrocarbon monitoring network.

The network comprises automatic and non-automatic systems to measure benzene in compliance with the Air Quality Directive 2008/50/EC. The UK’s interpretation of the Directive is that benzene must be measured at a minimum of 34 urban traffic, urban background or urban industrial monitoring stations, and a suggested suite of ozone precursors should be measured at one or more suburban locations in the UK. Up to 29 ozone precursor substances (including 1,3-butadiene) are measured using the automatic system at 4 sites, whereas a more cost effective non-automatic sampling system is used for more widespread benzene measurements.

All hydrocarbon network instruments are co-located at AURN (Automatic Urban and Rural Network) monitoring stations.

The number and location of sites in the network are based upon a preliminary assessment against the sampling requirements in Annex V of the Air Quality Directive, undertaken in 2006 and 2011 (Defra, 2013).

The information and data presented in this report are correct at the time of publication, however, it is possible that data may be rescaled or deleted from the data set if future audits and calibrations identify a need to correct the data. Latest data can always be accessed from UK-AIR.

1.1 Sources of NMVOCs

Figure 1 shows source data from the National Atmospheric Emissions Inventory (NAEI) for Non-Methane Volatile Organic Compounds (NMVOCs) from 1990 to 2019. VOC emissions from road vehicles and fuel use predominated emissions until around 2001. However, the predominant source today is solvent use (Figure 1).