@Article{PaulSJKMCMGDCNMP:2020:EvFiNa,
author = "Paul, Dipayan and Scheeren, Hubertus A. and Jensen, Henk G. and
Kers, Bert A. M. and Miller, John B. and Crotwell, Andrew M. and
Michel, Sylvia E. and Gatti, Luciana Vanni and Domingues, Lucas
Gatti and Correia, Caio Silvestre de Carvalho and Neves, Raiane
Aparecida Lopes and Meijer, Harro A. J. and Peters, Wouter",
affiliation = "{University of Groningen} and {University of Groningen} and
{University of Groningen} and {University of Groningen} and
{National Oceanic and Atmospheric Administration (NOAA)} and
{National Oceanic and Atmospheric Administration (NOAA)} and
{University of Colorado} and {Instituto Nacional de Pesquisas
Espaciais (INPE)} and {Instituto Nacional de Pesquisas Espaciais
(INPE)} and {Instituto Nacional de Pesquisas Espaciais (INPE)} and
{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Wageningen
University} and {University of Groningen}",
title = "Evaluation of a field-deployable Nafion™-based air-drying system
for collecting whole air samples and its application to stable
isotope measurements of CO2",
journal = "Atmospheric Measurement Techniques",
year = "2020",
volume = "13",
number = "7",
pages = "4051--4064",
month = "July",
abstract = "Atmospheric flask samples are either collected at atmospheric
pressure by opening a valve of a pre-evacuated flask or
pressurized with the help of a pump to a few bar above ambient
pressure. Under humid conditions, there is a risk that water vapor
in the sample leads to condensation on the walls of the flask,
notably at higher than ambient sampling pressures. Liquid water in
sample flasks is known to affect the C2 mixing ratios and also
alters the isotopic composition of oxygen (O-17 and O-18) in CO2
via isotopic equilibration. Hence, for accurate determination of
CO2 mole fractions and its stable isotopic composition, it is
vital to dry the air samples to a sufficiently low dew point
before they are pressurized in flasks to avoid condensation.
Moreover, the drying system itself should not influence the mixing
ratio and the isotopic composition of CO2 or that of the other
constituents under study. For the Airborne Stable Isotopes of
Carbon from the Amazon (ASICA) project focusing on accurate
measurements of CO2 and its singly substituted stable
isotopologues over the Amazon, an airdrying system capable of
removing water vapor from air sampled at a dew point lower than -2
degrees C, flow rates up to 12 L min(-1) and without the need for
electrical power was needed. Since to date no commercial
air-drying device that meets these requirements has been
available, we designed and built our own consumable-free,
power-free and portable drying system based on multitube Nafion
(TM) gas sample driers (Perma Pure, Lakewood, USA). The required
dry purge air is provided by feeding the exhaust flow of the flask
sampling system through a dry molecular sieve (type 3A) cartridge.
In this study we describe the systematic evaluation of our
NafionTm-based air sample dryer with emphasis on its performance
concerning the measurements of atmospheric CO2 mole fractions and
the three singly substituted isotopologues of CO2
((OCO)-O-16-C-13-O-16, (OCO)-O-16-C-12-O-17 and
(OCO)-O-16-C-12-O-18) as well as the trace gas species CH4, CO,
N2O and SF6. Experimental results simulating extreme tropical
conditions (saturated air at 33 degrees C) indicated that the
response of the air dryer is almost instantaneous and that
approximately 85L of air, containing up to 4 % water vapor, can be
processed staying below a -2 degrees C dew point temperature (at
275 kPa). We estimated that at least eight flasks can be sampled
(at an overpressure of 275 kPa) with a water vapor content below
-2 degrees C dew point temperature during a typical flight
sampling up to 5 km altitude over the Amazon, whereas the
remaining samples would stay well below 5 degrees C dew point
temperature (at 275 kPa). The performance of the air dryer on
measurements of CO2, CH4, CO, N2O, and SF6 and the CO2
isotopologues (OOO)-O-16-O-13-O-16 and (OCO)-O-16-C-12-O-18 was
tested in the laboratory sim- ulating real sampling conditions by
compressing humidified air from a calibrated cylinder, after being
dried by the air dryer, into sample flasks. We found that the mole
fraction and the isotopic composition difference between the
different test conditions (including the dryer) and the base
condition (dry air, without dryer) remained well within or very
close to, in the case of N2O, the World Meteorological
Organization recommended compatibility goals for independent
measurement programs, proving that the test condition induced no
significant bias on the sample measurements.",
doi = "10.5194/amt-13-4051-2020",
url = "http://dx.doi.org/10.5194/amt-13-4051-2020",
issn = "1867-1381",
language = "en",
targetfile = "paul_evaluation.pdf",
urlaccessdate = "27 abr. 2024"
}