Kwaliteitscontrole interim meetnet ammoniak: een onderzoek naar de invloed van de temperatuur in de meetstations
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Series / Report no.
Open Access
Type
Report
Language
nl
Date
1995-03-31
Research Projects
Organizational Units
Journal Issue
Title
Kwaliteitscontrole interim meetnet ammoniak: een
onderzoek naar de invloed van de temperatuur in de
meetstations
Translated Title
Quality Control in the interim network for the
measurement of ammonia: an investigation of the influence of the temperature
inside the measurement stations
Published in
Abstract
I.v.m. aanwijzingen dat de temperatuurscorrectie voor
de meetapparatuur zoals in gebruik in het interim meetnet ammoniak niet
correct zou zijn is (opnieuw) onderzoek uitgevoerd naar de
temperatuurgevoeligheid van deze apparaten met zowel de 'oude' als de
'nieuwe', door de fabrikant aangegeven correctie. De 'oude'
correctiemethode is fout daar deze uitgaat van de verkeerde
referentietemperatuur terwijl de 'nieuwe' correctiemethode wel uitgaat van
de goede referentietemperatuur (20 graden C). Daarnaast is onderzocht wat
aanpassing (volgens de 'nieuwe' correctiemethode) van het bestaande bestand
aan ammoniakdata uit het interim meetnet voor gevolgen zou hebben voor
individuele uurwaarden, periodegemiddelde concentraties en het
periodegemiddelde dagverloop.Tevens is inzicht verkregen in de werkelijke
temperatuurrange in de geconditioneerde meetstations. Het
klimaatkameronderzoek naar de temperatuurgevoeligheid toont afwijkingen in
de 1-uursgemiddelde concentraties tot -25% bij 35 graden C (26 mug/m3,
'oude', huidige correctiemethode) resp. +20% bij 35 graden C (1.3 mug/m3,
'nieuwe' correctiemethode). Het onderzoek toont met name aan dat rekening
is te houden met een concentratieafhankelijkheid van de
temperatuurgevoeligheid. Gebeurd dit niet (zoals bij de 'nieuwe'
correctiemethode) dan kunnen bij lage concentraties (ca. 1 mug/m3) nog
significante afwijkingen optreden van -11% tot +20% bij temperaturen van 10
resp. 35 graden C ('nieuwe' correctiemethode). Onder dit
concentratieniveau wordt de absolute afwijking echter marginaal. De
temperatuur in de meetbehuizingen is in de winter 20 +-2 graden C. In de
zomer bij hoge buitenluchttemperaturen (30 graden C) blijkt de temperatuur
in de meethut rond 19.00 uur op te kunnen lopen tot zo'n 35 graden C. De
airconditioning is dus ondergedimensioneerd. Met de huidige 'oude'
temperatuurscorrectie worden bij deze hoge temperaturen uurgemiddelde
ammoniakconcentraties zo'n 25 % onderschat. Voor periodegemiddelde (2 tot 4
weken) concentraties blijft deze onderschatting beperkt tot ca.3 %. Dit
wordt veroorzaakt door de relatief lage frequentie van gelijktijdig
voorkomen van hoge temperaturen en hoge concentraties. Om diezelfde reden
wordt het periodegemiddelde dagprofiel van NH3 ook slechts marginaal
beinvloed. Aanbevolen wordt (na aanvullend onderzoek en indien praktisch
mogelijk) de temperatuurscorrectie concentratie afhankelijk te maken en/of
de temperatuurshuishouding in de meetbehuizingen beter te beheersen en/of
thermostatisering van de apparatuur.
Because of doubts concerning the correction method for temperature sensitivitiy of the instruments used in the interim network for the measurement of ammonia (NH3), this sensitivity was investigated again using two correction methods ("old" and "new") as proposed by the manufacturer. The "old" method is used in the interim network and turned out to be principally wrong because it does not use the correct reference temperature while the "new" method does, namely 20 degrees C. Also, the influence on 1-hour averages, period-averages and diurnal variations when using the "new" method for recalculating the excisting NH3 database, which was determined with the "old" correction method, was investigated. A deeper understanding was gathered about the real temperature range in the measurement cabins. The investigation in a climate chamber showed deviations in the 1-hour averaged concentrations up to -25% at 35 degrees C (26 mug/m3, "old" correction method) and +20% at 35 degrees C (1.3 mug/m3, "new" correction method) respectivily. Particularly, a concentration dependence was found for the temperature sensitivity. If no concentration depending correction is used, deviations of -11% up to +20% at temperatures of 10 and 35 degrees C respectively ("new" correction method) can still occur particularly with low concentrations (ca. 1 mug/m3). Below this value, the absolute deviation becomes small. During wintertime, the temperature in the cabins is 20 +-2 degrees C. In summer, at high ambient temperatures (30 degrees C), the temperature in the cabin can reach 35 degrees C at about 19.00 h. So, the air-conditioning is not dimensioned well. With the "old" correction method, which is now in use, one hour averaged ammonia concentrations are underestimated with about 25% at these high temperatures. Period averages (2 - 4 weeks) are underestimated less, namely about 3%. This is caused by the low frequency of simultaneous occurrence of high temperatures and high concentrations. For the same reason, diurnal variations are only marginally influenced. It is recommended (after additional investigation) to make the temperature correction concentration dependent, to improve the temperature-conditioning in the cabins or to thermostat future versions of the instrument itself.
Because of doubts concerning the correction method for temperature sensitivitiy of the instruments used in the interim network for the measurement of ammonia (NH3), this sensitivity was investigated again using two correction methods ("old" and "new") as proposed by the manufacturer. The "old" method is used in the interim network and turned out to be principally wrong because it does not use the correct reference temperature while the "new" method does, namely 20 degrees C. Also, the influence on 1-hour averages, period-averages and diurnal variations when using the "new" method for recalculating the excisting NH3 database, which was determined with the "old" correction method, was investigated. A deeper understanding was gathered about the real temperature range in the measurement cabins. The investigation in a climate chamber showed deviations in the 1-hour averaged concentrations up to -25% at 35 degrees C (26 mug/m3, "old" correction method) and +20% at 35 degrees C (1.3 mug/m3, "new" correction method) respectivily. Particularly, a concentration dependence was found for the temperature sensitivity. If no concentration depending correction is used, deviations of -11% up to +20% at temperatures of 10 and 35 degrees C respectively ("new" correction method) can still occur particularly with low concentrations (ca. 1 mug/m3). Below this value, the absolute deviation becomes small. During wintertime, the temperature in the cabins is 20 +-2 degrees C. In summer, at high ambient temperatures (30 degrees C), the temperature in the cabin can reach 35 degrees C at about 19.00 h. So, the air-conditioning is not dimensioned well. With the "old" correction method, which is now in use, one hour averaged ammonia concentrations are underestimated with about 25% at these high temperatures. Period averages (2 - 4 weeks) are underestimated less, namely about 3%. This is caused by the low frequency of simultaneous occurrence of high temperatures and high concentrations. For the same reason, diurnal variations are only marginally influenced. It is recommended (after additional investigation) to make the temperature correction concentration dependent, to improve the temperature-conditioning in the cabins or to thermostat future versions of the instrument itself.
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