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Issue 5, 2001
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Comparison of low cost measurement techniques for long-term monitoring of atmospheric ammonia

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Abstract

An inter-comparison of techniques for long-term sampling of atmospheric ammonia (NH3) was conducted with a view to establishing a national network with >50 sites. Key requirements were for: a low cost system, simplicity and durability to enable a postal exchange with local site operators, a precision of <±20% for monthly sampling at expected NH3 concentrations of 1–2 µg m−3, a detection limit sufficient to resolve the small NH3 concentrations (<0.2 µg m−3) expected in remote parts of the UK, and a quantitative means to establish quality control. Five sampling methods were compared: A, a commercially available membrane diffusion tube (exposed in triplicate), with membranes removed immediately after sampling; B, the above method, with the membranes left in place until analysis; C, open-ended diffusion tubes (exposed with 4 replicates); D, a new active sampling diffusion denuder system; and E, an active sampling bubbler system. Method D consisted of two 0.1 m acid coated glass denuders in series with sampling at ≈0.3 l min−1. These methods were deployed at 6 locations in the UK and the Netherlands and compared against reference estimates. Method D was the most precise and sensitive of the techniques compared, with a detection limit of <0.1 µg m−3. The bubbler provided a less precise estimate of NH3 concentration, and also suffered several practical drawbacks. The diffusion tubes were found to correlate with the reference at high concentrations (>3 µg m−3), but were less precise and overestimated NH3 at smaller concentrations. Of the passive methods, A was the most precise and C the least precise. On the basis of the results, method D has been implemented in the national network, together with application of method A to explore spatial variability in regions with expected high NH3 concentrations.

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Publication details

The article was received on 12 Mar 2001, accepted on 01 Aug 2001 and first published on 13 Sep 2001


Article type: Paper
DOI: 10.1039/B102303A
J. Environ. Monit., 2001,3, 446-453

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    Comparison of low cost measurement techniques for long-term monitoring of atmospheric ammonia

    M. A. Sutton, B. Miners, Y. S. Tang, C. Milford, G. P. Wyers, J. H. Duyzer and D. Fowler, J. Environ. Monit., 2001, 3, 446
    DOI: 10.1039/B102303A

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