United Kingdom Eutrophying & Acidifying Network (UKEAP)

Introduction

The UK Eutrophying and Acidifying Pollutants (UKEAP) network project combines two Defra atmospheric pollutant monitoring projects, which have measured air pollutants at rural sites across the UK over the past two decades. This network provides information on deposition of acidifying compounds in the United Kingdom. Its main emphasis has always been the assessment of potential impacts on UK ecosystems. Other measurements including sulphur dioxide, nitrogen dioxide and particulate sulphate have also been made within the programme in order to provide a more complete understanding of precipitation chemistry in the United Kingdom.

What is measured?

Parameters Measured Monitoring sites and data
Acidity in precipitation
Acidity wet deposited
Ammonium as N aerosol (coarse)
Ammonium as N aerosol (fine)
Ammonium as N in precipitation
Ammonium as N wet deposited
Bicarbonate wet deposited
Calcium in precipitation
Calcium wet deposited
Chloride aerosol
Chloride aerosol (coarse)
Chloride aerosol (fine)
Chloride in precipitation
Chloride wet deposited
Conductivity
Fluorine
Magnesium in precipitation
Magnesium wet deposited
Nitrate as N aerosol (coarse)
Nitrate as N aerosol (fine)
Nitrate as N in precipitation
Nitrate as N wet deposited
Nitric acid gas as N
Nitrogen dioxide
Nitrogen dioxide as N
Non-marine sulphate as S in precipitation
Non-marine sulphate as S wet deposited
Particulate ammonium
Particulate nitrate
pH in precipitation
Phosphate as P in precipitation
Phosphate as P wet deposited
Potassium in precipitation
Potassium wet deposited
Rainfall
Sodium aerosol
Sodium aerosol (coarse)
Sodium aerosol (fine)
Sodium in precipitation
Sodium wet deposited
Strong acid in precipitation
Strong acid wet deposited
Sulphate as S aerosol
Sulphate as S aerosol (coarse)
Sulphate as S aerosol (fine)
Sulphate as S in precipitation
Sulphate as S wet deposited
Sulphur dioxide as S
Sum of ammonia and ammonium
Sum of nitric acid and nitrate
Current sites: 41
Total sites: 141
Data availability: 01/01/1973 to 22/11/2017

What is the purpose of the network?

The aims of the network are to provide a long-term dataset of monthly speciated measurements of acid gases and aerosols that will be used to:

  • Provide temporal and spatial patterns and trends, and compare results with dispersion models.
  • Facilitate Pollution Climate mapping and assessment of Acid Deposition Processes.
  • Contribute to mass closure from the measurements of several components of particulate matter (NO3-, SO42-, Cl-, Na+, Mg2+ and Ca2+) together with NH4+ from the closely integrated NAMN), which was one of the recommendations in the Department's Air Quality Expert Group's report on Particulate matter.
  • Calculate national and regional deposition budgets, especially in upland areas that are sensitive to acid deposition.

Also under the UNECE Gothenburg Protocol and the National Emissions Ceilings Directive of the EU, the target of both these agreements is that NH3 emissions should not exceed 297 kt as NH3 by 2010, with a particular focus on reducing the extent of critical loads exceedence for acidification and eutrophication effects. Abatement of NH3 emissions is also included in EU Integrated Pollution Prevention and Control (IPPC) for the intensive pig and poultry sectors.

The monitoring provides a baseline in reduced nitrogen (NHx) species, which is necessary for examining responses to changes in the agricultural sector and to verify compliance with targets set by international agreements. Data from the network are also used to test the performance of an atmospheric chemistry and transport model (FRAME) and to contribute to national Nitrogen (N) deposition estimates.

How is the network run?

The network is split into four components:

  1. UKEAP-Acid Gas and Aerosol Network (AGANet) consists of 30 sites. The network provides a long-term dataset of monthly speciated measurements of acid gases and aerosols that are used to provide temporal and spatial patterns and trends, and compared with results from dispersion models.
  2. UKEAP - National Ammonia Monitoring Network (NAMN) Gaseous ammonia (NH3) Monthly = 85 sites. The network is used to quantify temporal and spatial changes in air concentrations and deposition in NH3 and NH4+ on a long term basis. The monitoring provides a baseline in the reduced nitrogen species (NH3 + NH4+), which is necessary for examining responses to changes in the agricultural sector and to verify compliance with targets set by international agreements.
  3. UKEAP - NO2-diffusion tube Network (NO2-Net) Nitrogen Dioxide. The nitrogen dioxide measurements are made at 24 of the 38 PrecipNet composition sites. The nitrogen dioxide measurements made in this sampling programme provide valuable information regarding background concentrations of the gas.
  4. UKEAP - Precipitation Network (PrecipNet) PrecipNet consists of 38 sites in at which the chemical composition of precipitation (i.e. rainwater) is measured. The network allows estimates of wet deposition of sulphur and nitrogen chemicals. Samples are collected fortnightly at 38 sites and daily at 2 sites.

Monitoring Methods

Precipitation Composition
  • Rainwater sampling using a bulk collector on a fortnightly basis
  • Rainwater sampling using a bulk collector on a daily basis
  • Additional wet-only measurements on a daily basis
Nitrogen Dioxide
  • Diffusion tube measurements on a monthly basis
Nitric Acid, other acid gases and aerosol
  • Denuder (DELTA) measurements on a monthly basis

Data can be downloaded from the Defra Pollutant Deposition webpages and where available, dropdowns to direct data access are provided on the subpages to this section.




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