ALPHA® and DELTA® network
A new network of 25 ammonia (NH3) monitoring sites implementing the UKCEH ALPHA® method (ALPHA® network) and 4 reactive gases and aerosols monitoring sites implementing the UKCEH DELTA® method (DELTA® network) was established in spring 2019 across Northern Ireland.
The ALPHA® sites were selected to provide representative coverage of i) the range of modelled concentrations from FRAME (using the most recent 5 km NH3 emissions data for 2016), (ii) each of seven major dominant emission source classifications: cattle (beef and dairy), pigs & poultry, sheep, mixed, non-agricultural, fertiliser and background (very low emission density, < 1 kg N ha-1 yr-1), and (iii) spatial coverage across Northern Ireland.
The aims of the measurements are to (i) explore spatial and temporal patterns in NH3 concentrations, (ii) compare results with the FRAME atmospheric transport model and for verification of UK NAEI emissions inventory and FRAME model, (iii) monitor and assess relationship between NH3 and interacting gases (HNO3, SO2) and inorganic particulate phase composition.
Measurement data over the same period from existing UK long-term national network sites (Coleraine, Hillsborough, Lough Navar), and from the Ballynahone Bog project in Northern Ireland are also included in the report, to complement the network data.
All measurements are made through monthly time-integrated sampling, which is cost-efficient for providing annual means while permitting detection of seasonal trends in the data.
The first measurements in the ALPHA® and DELTA® networks started in early March 2019. The first full year of ratified monthly ALPHA® and DELTA® data for the period March 2019 – February 2020 are presented in this report.
Calibration of ALPHA® NH3 data
An annual field calibrated ALPHA® uptake rate is derived for each calendar year from the regression of passive ALPHA® versus active DELTA® measurements at nine inter-comparison sites in the UK National Ammonia Monitoring Network. The calibration is usually carried out in April each year, based on a full year of data from the preceding year. The updated uptake rate is then applied retrospectively to ALPHA® data for the year of calibration. Calibrated uptake rates derived from the UK national network are applied to the Northern Ireland ALPHA® network data. These were 0.0031665 m3 h-1 and 0.0031277 m3 h-1, for 2019 and 2020, respectively.
At AFBI25 Hillsborough, ALPHA® and DELTA® measurement are co-located with parallel measurements
