CEH air sampler systems for environmental monitoring
DELTA® II system for measuring ammonia, ammonium, acid gases and aerosols
The CEH DELTA® (DEnuder for Long-Term Atmospheric sampling) 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-, SO42-, Cl-, Na+, Ca2+, Mg2+).
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 (ip 65) with clear lid/door. 2: Sample train holder. 3: Sample inlet (funnel as rain shield). 4: Plug-in mini-heater inside sample train holder to maintain temperature approx. 3 degrees Celsius above ambient. 5: G1.6 high sensitivity gas meter. 6: Rotameter. 7: Air pump (6v knf) and pcb (accepts voltage range of between 10 – 36v).
The DELTA® system is based on the concept of a coated single bore glass denuder. 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 and can be collected 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. A simple enclosure is used, which can be mounted easily in the desired location (typically 1.5 above ground for short grass). The DELTA® system can be run from mains power or using a solar panel/wind turbine and battery set-up for remote locations.
You can select which components you require on our order form and we will supply a quote. Details of what is available can be found below:
DELTA® components list
Low voltage (10-36v) DELTA® system
Mounting brackets fitted at the back of the enclosure as standard. The size used (size B) will fit over poles with an OD of 1 11/32 inch (~34.1mm). Other sizes can be mounted on request but additional charges may apply if they are more expensive. Two sample train holders are supplied with each DELTA system. *Denuder assembly (sample train) NOT included: see below for purchase detail.
Sample train components
All of these components are re-usable and represent a one-off purchase:
A. Denuder assembly for NH3 and NH4+ sampling (illustrated right)
Consisting of two component denuders, glass inlet, caps, one-stage filter pack and connecting silicone tubes. Minimum order 5.
B. Denuder assembly for sampling of NH3, acid gases + aerosol anions and cations
Consisting of four component denuders, 2.8cm Teflon inlet, caps, 2-stage filter pack and connecting silicone tubes. Minimum order 5.
C. Denuder assembly for sampling of NH3, acid gases (selective for HNO3) + aerosol anions and cations
Consisting of four component denuders, 2.8cm Teflon inlet, caps, 3-stage filter pack and connecting silicone tubes. Minimum order 5.
25mm diameter cellulose filter circles (used once and replaced). 500 per pack.
Manual and help videos
DocumentPDF - 1.11 MB
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