Scientific challenge

Air pollution can have wide-ranging effects on the environment, with impacts on biodiversity, water quality and people's health and wellbeing. Long-term, integrated monitoring is important for measuring and understanding atmospheric change. One such monitoring network, the UK Eutrophying and Acidifying Atmospheric Pollutants (UKEAP) network, measures air pollutants at rural sites across the UK to make information on the composition of the background and rural UK atmosphere available for science and policy use. An over-arching objective of the work is on-going high- and low-frequency chemical monitoring and campaign mode measurements of the rural and semi-rural background atmosphere to inform the scientific understanding of the non-urban contributions to particulate matter levels, at urban, UK and international scales.

Project overview

The Defra UKEAP project consists of four monitoring networks measuring atmospheric acidifying and eutrophying species in the rural environment and the operation of the two UK EMEP supersites:

National Ammonia Monitoring Network (NAMN): Monthly ammonia concentrations in air at 85 sites, operational since 1996 (CEH lead)
Acid Gas and Aerosol Network (AGA-Net): Monthly gas phase SO2, HNO3, HCl; major particulate phase inorganic anions and cations at 30 sites, operational since 1999 (CEH lead)
Precipitation Network (Precip-Net): Fortnightly inorganic anion and cation concentrations in precipitation at 39 sites, operational since 1985 (AEA lead)
NO2Net: Four-weekly triplicate NO2 concentrations at 24 sites, operational since 1994 (AEA lead)

Auchencorth Moss supersite, Scotland: upland moorland site, operational since 2006 (CEH)

***From January 2016 Chilbolton is the new UK southern supersite***

This replaces Harwell , Oxfordshire, England: rural, mixed land use site, operational since 2009 by Ricardo Energy and Environment


Measurements from the UKEAP project underpin the capability to understand changes in rural air quality in the UK over time and contribute to validation of atmospheric models.

The UKEAP concentration measurements allow assessments to be made of pollutant deposition to the UK surface by provision of the measurements to the Defra-funded UK pollutant modelling and mapping projects. From this, derived critical level and critical load maps for UK ecosystems allow environmental impact assessments to be undertaken by local authorities and government agencies at both local and national scales. Data from rural NAMN, AGANet and some Precip-Net sites are submitted to EMEP, OSPAR and other databases as required by international UK obligations.

The United Kingdom contribution to the EMEP monitoring strategy is based on two Level II "supersites", one in the north of the UK (at our Auchencorth Moss monitoring site), and one in the south (Harwell), at which additional measurements are made to qualify as an EMEP Level III site.

Hourly gas and particulate composition data are provided for UK compliance purposes. Data from these sites at hourly or daily frequency are supplemented by long-term integrating measurements from other existing Defra-funded monitoring networks. Information regarding the measurements being made can be found at the EMEP website. Both sites are long-term monitoring sites for concentrations and Auchencorth is used for long-term flux monitoring of pollutant gases (SO2, NOx and O3).

Further details on Auchencorth are available here

Project partners and contacts

Co-funders: Defra and UKCEH
Joint contractors: Ricardo-Energy and Environment
Contract duration: 2012-2016
Project website: UKEAP

UKCEH contact details

Project contact email: Dr Marsailidh Twigg
UKCEH Project Directors Dr Eiko Nemitz and Prof Mark Sutton
CEH Project Manager and lead for NAMN and AGANet: Ms Sim Tang
Auchencorth Supersite Operations: Dr Marsailidh Twigg and Dr Matt Jones

Principal Investigator

2012–present: Atmospheric Chemist in the Atmospheric Chemistry and Effects Science Area at UKCEH Edinburgh
2007–2012: Research Associate, University of Edinburgh (Visiting Scientist at CEH)
2006–2007: Research scientist at CEH Edinburgh
2002–2006: PhD University of Ulster / CEH Edinburgh: Application of Tunable Diode Laser (TDL) Absorption Spectroscopy for the Investigation of Surface/Atmosphere Exchange of Ammonia