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Title:
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Characterisation of the regional concentration fields for ammonia:sampling and monitoring strategy
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Author(s):
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Published by:
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Publication date:
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ECN
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1996
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ECN report number:
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Document type:
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ECN-C--96-038
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ECN publication
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Number of pages:
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Full text:
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59
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Download PDF
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Abstract:
Five different samplers were tested as to their suitability fordetermining averaged monthly atmospheric ammonia concentrations in ambient
air. The samplers investigated were: an open diffusion tube of 7 cm long
(method A), a similar diffusion tube with a mesh grid fitted over the mouth
(method B), a diffusion tube of 3.5 cm long with its mouth covered by a
plastic membrane (methods C and D), a diffusion tube developed by Wageningen
Agricultural University (method E), and a low-volume denuder (method F). In
methods A, B and C the apparatus was placed in a plastic cylinder open at the
bottom to protect it from direct meteorological influences. In methods D, E
and F the apparatus was placed in the open air without such protection. The
measurements made with these samplers during 12 four-week periods were
compared with measurements made by a continuous flow denuder, as reference
method, at various sites. The influence of the meteorology on the
measurements was also investigated. Based on precision and the extent of
correspondence with the reference measurements (accuracy), it appears that
two types of passive sampler are very suitable for measuring month average
ammonia concentrations: a diffusion tube of 7 cm long with a stainless steel
mesh grid over the mouth (method B) and a diffusion tube of 3.5 cm long with
a plastic membrane fitted over the mouth (methods C and D). The decision was
taken to carry out a follow-up study, designed to characterise regional
ammonia concentration fields, using method D. In order to develop a
monitoring strategy for the characterisation of regional ammonia
concentration fields, the spatial variability of the ammonia concentrations
in two 5x5 km grid squares was investigated. The study showed that a minimum
of 8 monitoring sites are needed in each grid square in order to make a
representative estimate of the year average ammonia concentrations for the
area. 19 figs., 5 tabs.,10 refs.
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