Air sampler systems for environmental monitoring

Change Note

Due to the ALPHA^® membrane material being discontinued we are supplying a new style of membrane from October 2020. This new membrane has been selected based on excellent results of intercomparison testing with the old style of membrane.

ALPHA^® PTFE1020 will have a slightly different product specification to the old style and as such the uptake rate will be different. UKCEH currently recommends using the value: 0.0035891 which has been determined by calibration of ALPHA^® PTFE1020 against the old membrane in early field trials. UKCEH recommends using one type of membrane for an entire network, project, experiment or study and not mixing the membranes.

An experiment to determine a UK annual calibrated uptake rate for ALPHA^® PTFE1020 will be conducted in 2020 and the results available in April 202. We then expect this experiment to be repeated annually to give an annual UK calibrated uptake rate for ALPHA^® PTFE1020. This value will be published in the ALPHA^® manual and on the UKCEH website. We will also continue to provide a UK annual calibrated uptake rate for the old membrane style until at least 2022.

If you have any questions or want more information regarding this change please get in touch with us by email.

Additional information for analysis projects

Information on the membrane style to be used will be clearly provided at the quoting stage or in email to the project lead if a change is required within a project duration. Changes of membrane style will be avoided within project durations to the best of our ability.

Enquiries and Orders

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Ammonia and air quality background

Ammonia is a highly reactive gas, an excess of which can lead to eutrophication and acidification of terrestrial and freshwater ecosystems, biodiversity loss and the formation of secondary particulate matter. It originates from both natural and anthropogenic sources, including agricultural related emissions such as manures, slurries and fertiliser application.

Ambient ammonia monitoring can be carried out with two UKCEH products:

• ALPHA^®
• DELTA^®

The DELTA^® system can also be used to actively sample a wider range of atmospheric species.

ALPHA^®

The UKCEH ALPHA^® (Adapted Low-cost Passive High Absorption) sampler is a system designed for the measurement of the concentration of ammonia (NH₃) in air. It has been used for over 10 years on the UK national ammonia monitoring network and designed for ecosystem impact assessment studies. It is a simple to use, low cost method which does not require electricity. It is useful as a complementary method for assessing spatial differences in source areas where NH₃ concentrations may vary hugely. It does not sample ammonium aerosol.

Suitable range of ammonia concentrations:

Monthly monitoring = 0.03 - 100 ug NH₃ m^-3
Weekly monitoring = 0.05 - 400 ug NH₃ m^-3

Above: Outline diagram of a single ALPHA^® sampler and components.

All of the plastic components of the ALPHA^® samplers, including the PTFE membranes, can be cleaned and reused. The only component that is single use is the filter paper.

UKCEH can provide parts for the samplers, which you can prepare and coat yourself, or costings for our laboratory service offering and science advice which includes prepared samplers. Use the ALPHA^®/DELTA^® order form.

Sampler Background

The passive sampling system consists of three replicate ALPHA^® samplers attached to the underside of a shelter at about 1.5m height above ground. The samplers operate on the principle of diffusion with an acid-coated filter which serves to capture the ammonia. Replicate tubes are used in order to give more reliable results.

Exposed samples are stored at 4˚C until analysis. The chemical of interest captured on the filter paper or denuder tube is extracted, usually into deionised water, which is then analysed. At UKCEH we use the SEAL AA3 for ammonium analysis or Ion chromatography for other chemicals of interest. We use a set of standards and quality control samples to ensure accurate results.

Download a short version of the manual

DELTA^®

The UKCEH DELTA^® system is a low-volume denuder air sampling method for long-term sampling of ammonia and ammonium in the atmosphere. The system can also be extended to sample acid gases (NH₃, HNO₃, HCl, SO₂) and aerosols (NH₄⁺, NO₃^-, SO₄^2-, Cl^-, Na⁺, Ca²⁺, Mg²⁺). It requires power (wind solar systems available) and a user with a good foundation in scientific instrumentation to operate correctly.

Above: Detail of components in the monitoring enclosure of the low voltage DELTA^® system. An example installation of the low voltage DELTA^® system powered by wind and solar in the field is shown on the right. 1: Durable plastic enclosure 2: Sample train holder. 3: Sample inlet 4: Plug-in for sample train heater 5: Gas meter. 6: Rotameter. 7: Pump box

DELTA systems and parts can be purchased from UK CEH and in 2021 we will have a limited number of instruments available for short term (<1 year) hire. Link to form

Background to the DELTA® system

When a laminar air stream passes through the coated denuder, gases of interest react with and are captured by the coating. The coating is later extracted and analysed in a laboratory. Aerosols pass through the coated tube uncollected and are captured by coated filters placed downstream of the denuder. The separation of aerosol from gaseous components is achieved due to the much more rapid diffusion of gaseous species to the tube wall compared with that of particles.

Low, stable air sampling rates of 0.2-0.4 / min^-1 are achieved using small air pumps, with air volumes being measured by a high sensitivity dry gas meter. The low sampling rate means that short glass denuders can be used, which allows easy exchange of samples through the post.

Image above shows example sample train configuration for ammonia/ammonium measurements.

Download DELTA short manual [PDF]

Frequently Asked Questions

References and related publications

Martin Nicholas A, Ferracci Valerio, Cassidy Nathan, Hook Josh, Battersby Ross M, di Meane Elena Amico, Tang Yuk S, Stephens Amy C M, Leeson Sarah R, Jones Matthew R, Braban Christine F, Gates Linda, Hangartner Marcus, Stoll Jean-Marc, Sacco Paolo, Pagani, Diego, Hoffnagle John A, Seitler, Eva (2019). Validation of ammonia diffusive and pumped samplers in a controlled atmosphere test facility using traceable Primary Standard Gas Mixtures. Atmospheric Environment, 199. 453-462. DOI: 10.1016/j.atmosenv.2018.11.038

Tang Y Sim, Braban Christine F, Dragosits Ulrike, Simmons Ivan, Leaver David, van Dijk Netty, Poskitt Janet, Thacker Sarah, Patel Manisha, Carter Heather, Pereira M Gloria, Keenan Patrick O, Lawlor Alan, Connolly Christopher, Vincent Keith, Heal Mathew R, Sutton Mark A (2018). Acid gases and aerosol measurements in the UK (1999–2015): regional distributions and trends. Atmospheric Chemistry and Physics, 18 (22). 16293-16324. DOI:10.5194/acp-18-16293-2018

Tang Y S, Braban C F, Dragosits U, Dore A J, Simmons I, van Dijk N, Poskitt J, Pereira M G, Keenan P O, Conolly C, Vincent K, Smith R I, Heal M R and Sutton M A (2018). Drivers for spatial, temporal and long-term trends in atmospheric ammonia and ammonium in the UK, Atmospheric Chemistry and Physics, 18, 705-733, DOI: 10.5194/acp-18-705-2018.

Puchalski M A, Sather M E , Walker J T, Lehnmann C M B, Gay D A, Mathew J, Robarge, W P (2011). Passive ammonia monitoring in the United States: Comparing three different sampling devices. Journal of Environmental Monitoring, 13, 3156.

Sutton M A, Miners B, Tang Y S, Milford C, Wyers, G P, Duyzer, J H and Fowler, D (2001a) Comparison of low cost measurement techniques for long-term monitoring of atmospheric ammonia. J. Environ. Monit. 3, 446‑453.

Sutton M A, Tang Y S, Miners B and Fowler, D (2001b) A new diffusion denuder system for long-term, regional monitoring of atmospheric ammonia and ammonium.  Water, Air and Soil Pollution. Focus, 1, Part 5/6, 145‑156.

Tang Y S, Cape J N & Sutton M A (2001) Development and types of passive samplers for monitoring atmospheric NO2 and NH3 concentrations. In Proceedings of the International Symposium on Passive Sampling of Gaseous Pollutants in Ecological Research. TheScientificWorld, 1, 513-529.

Tang Y S, Simmons I, van Dijk N, Di Marco C, Nemitz E, Dämmgen U, Gilke K, Djuricic V, Vidic S, Gliha Z, Borovecki D, Mitosinkova M, Hanssen J E, Uggerud T H, Sanz M J, Sanz P, Chorda J V, Flechard C R, Fauvel Y, Ferm M, Perrino C & Sutton M A (2009) European scale application of atmospheric reactive nitrogen measurements in a low-cost approach to infer dry deposition fluxes. Agriculture, Ecosystems and Environment: NitroEurope Special issue. (133), 183-195.

Training courses

UKCEH have a selection of training courses which we run regularly. We can also run bespoke courses or specific dates so please contact us at cehairquality@ceh.ac.uk to ask about that.

We’ll also update/ advertise any upcoming courses with availability on our Twitter feed.

Example Course Titles:

• Ammonia as an air quality pollutant
• Ammonia: measurement planning
• ALPHA® and DELTA® local site operator (LSO) Training
• Laboratory skills for ALPHA® samplers
• Laboratory skills for DELTA® samplers
• ALPHA® site set up and choosing site locations
• DELTA® site set up and site servicing

We do provided logged training certificates to attendees of our training courses and you can contact us for an email to verify that you attended a particular course (in the last three years).