Establishing Regular Measurements of Halocarbons at Taunus Observatory Tanja Schuck, Fides Lefrancois, Franziska Gallmann, and Andreas Engel Goethe University Frankfurt, Institute for Atmospheric and Environmental Sciences
Taunus Observatory
NOAA ESRL Global Monitoring Annual Conference 23/24 May 2017 2
• Regular halocarbon measurements in Europe are made predominantly at clean air stations (NOAA and AGAGE network)
• Data from a semi-polluted site in central Europe will result in stronger constraints for emission estimates
Taunus Observatory
3 NOAA ESRL Global Monitoring Annual Conference 23/24 May 2017
• Taunus Observatory is located at Kleiner Feldberg at 50.22°N, 8.44°W at 825m altitude.
• The site is influenced by emissions from the densely populated Rhein-Main region.
• Long-range transport is mainly from westerly directions, including marine background air from the North Sea.
• Regular measurements of halocarbons started October 2013.
courtesy Dominik Brunner
Current Status
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• Samples collected weekly in stainless steel canisters • Analysis by GC-MS (Agilent 7980A) using a quadrupole MS
(Agilent 5975C) and a TOF-MS (ALMSCO/BenchTOF) in parallel • Sample drying with Mg(ClO4)2
• Cryo-trapping at -80°C (Stirling cooler), desorption at ≈ 200 °C • Data quality assessment by taking double samples and having
two analyses of each individual canisters
TOF-MS
gas chromatograph
preconcentration unit ASCEND
sample and stream selection Quadrupole-MS
calibration gas
Hoker et al., Atmos. Meas. Tech. 2015
Sample Collection at Mace Head - Comparison with NOAA HATS data
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75 80 85 90 95 100 10575
80
85
90
95
100
105
IAU
[ppt
]
NOAA [ppt]21 22 23 24 25
21
22
23
24
25
IAU
[ppt
]
NOAA [ppt]232 234 236 238 240
232
234
236
238
240
IAU
[ppt
]
NOAA [ppt]
480 520 560 600
480
520
560
600
IAU
[ppt
]
NOAA [ppt]24 25 26 27
24
25
26
27
IAU
[ppt
]
NOAA [ppt]3.0 3.5 4.0
3.0
3.5
4.0
IAU
[ppt
]
NOAA [ppt]
HCFC-142b r=0.84
methylchloroform r=0.98
HFC-134a r=0.60 (0.99)
chloromethane r=0.98
CFC-11 r=0.48
HCFC-141b r=0.66
• sample collection at Mace Head twice per month (when wind is from clean air sector)
• comparison with NOAA data set @ Mace Head (sample collection for us and NOAA is under background conditions within less than half an hour)
• our calibration is on AGAGE scales, scale conversion necessary for most substances
Time Series
6 NOAA ESRL Global Monitoring Annual Conference 23/24 May 2017
2011 2012 2013 2014 2015 2016 2017500
525
550
Taunus Observatory Mace Head AGAGE Global Mean
CFC
-12
[ppt
V]
2011 2012 2013 2014 2015 2016 20170
2
4
6
8
10
Taunus Observatory Mace Head AGAGE Global Mean
CH
3CC
l3 [p
ptV
]
2011 2012 2013 2014 2015 2016 201720
22
24
26
28
30
Taunus Observatory Mace Head AGAGE @ Mace Head
HC
FC-1
41b
[ppt
]
2011 2012 2013 2014 2015 2016 20170
10
20
30
40
50
60
Taunus Observatory Mace Head AGAGE @ Mace Head
HFC
_143
a [p
pt]
• mixing ratios at Mace Head nicely represent background • good agreement with AGAGE data at Mace Head • higher variability at Taunus Observatory with many
polluted samples (includes data from all wind sectors, whereas Mace Head is from clean air sector only)
2013 2014 2015 2016 20170
25
50
75
100
125
150
175
200
Taunus Observatory Mace Head
dich
loro
met
hane
[ppt
]
Seasonal Cycles
7 NOAA ESRL Global Monitoring Annual Conference 23/24 May 2017
2013 2014 2015 2016 20170
25
50
75
100
125
150
175
200
Taunus Observatory Mace Head
dich
loro
met
hane
[ppt
]
2011 2012 2013 2014 2015 2016 201720
22
24
26
28
30
Taunus Observatory Mace Head AGAGE @ Mace Head
HC
FC-1
41b
[ppt
]
Trajectory Analysis • Back trajectory calculations were
performed for every single sample using • HYSPLIT4 • 120 hours backward • 1° x 1° GDAS1 dataset
NOAA ESRL Global Monitoring Annual Conference 23/24 May 2017 8
Trajectory Analysis: CFC-11
• HYSPLIT trajectories (120 hours backward) for samples collected in 2015
• color coded by CFC-11 mixing ratio • elevated mixing ratios correlate with
air mass origin from southwest
2010 2011 2012 2013 2014 2015 2016 2017220
230
240
250
260
270
Taunus Observatory Mace Head AGAGE Global Mean
CFC
-11
[ppt
V]
• use of CFC-11 is regulated • atmospheric mixing ratios decrease • variability at Taunus Observatory is low
with few outliers
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Trajectory Analysis HCFC-142b
• HYSPLIT trajectories for samples collected in 2015
• color coded by HCFC-42b mixing ratio
• elevated mixing ratios correlate with air mass origin from southwest
2011 2012 2013 2014 2015 2016 201720
25
30
35
Taunus Observatory Mace Head AGAGE@ Mace Head
HC
FC-1
42b
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• used as replacement for CFCs • use is regulated • mixing ratios have stabilized and are
expected to decrease in the future • over our observation period atmospheric
mixing ratios have no significant trend • variability at Taunus Observatory is high
compared to Mace Head clean air samples
Trajectory Analysis • HYSPLIT trajectories (120h backward) for each individual sample are
grouped by the direction from with they approach Taunus Observatory (> 50% of time spent in respective sector)
• four main sectors were identified: northwest (slow and fast trajectories) west (slow and fast trajectories) southwest (slow trajectories) east (slow trajectories)
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Trajectory Analysis
• For most substances investigated highest mixing ratios are measured in air masses arriving from the southwest sector.
• Background conditions are experienced when air mass transport towards the site is from the northwest.
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Future Development: in-situ GC-TOF-MS • In summer 2017, an in-situ GC-MS system will be
installed. • Measurements will be every 2h (following AGAGE
protocol) • The mass spectrometer to be deployed is a medium
resolution time-of-flight mass spectrometer • Large substance range: 90+ known species in the
chromatogram • High measurement precision:
0.2-1.5% typical (multiple species) 0.15% at best (CFC-12)
• Linear detector tested up to 5 ppb (25 ng) CFC-12 (~4 orders of magnitude)
• Open data format • Complete mass scan will allow retrospective
analysis (digital air archive)
NOAA ESRL Global Monitoring Annual Conference 23/24 May 2017 13 Obersteiner et al., Atmos. Meas. Tech. 2016
Summary
14 NOAA ESRL Global Monitoring Annual Conference 23/24 May 2017
• We started regular collection of air samples at Taunus Observatory in 2013 • Our measurement are linked to global networks through flask sampling at Mace Head
(Ireland) • Mace Head represents baseline for Taunus Observatory • Trajectory analysis shows a distinct polluted / clean air sector
• Data from a medium-polluted site have the potential to better constrain European emission estimates
• Data from Taunus Observatory will be used for inversion modelling
• In summer 2017, an in-situ GC-TOF-MS system will be installed – rapid growth of the dataset
• Measurements will be every 2h (following AGAGE protocol) – now we have one data point per week
• Complete mass scan of the TOF-MS will allow retrospective analysis (digital air archive)
Thank you for your attention!
Instrumentation: Stream Selection Unit
• sample selection with multiposition Valve (Valco) • stream selection (sample, blank, calibration gas) with pressure
operated on/off valves (Valco) • drying tube Mg(ClO4)2
• 2 x 2l reference volume for sample volume determination • mass flow controller for sample flow regulation (Bronkhorst)
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Instrumentation: Preconcentration Unit
• sample enrichment is done on a sample loop filled with HayeSep D
• sample loop is embedded into a cooled aluminium block • cooling works cryogen-free, based on a Stirling Cooler • trapping at -80°C (flow 150 ml/min) • desorption at ca. +200°C
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Instrumentation: Gas Chromatography
• column: 30m GasPro PLOT column (7.5m pre-column, 22.5m main column), inner diameter 0.32mm
• total duration: 17.95 min, backflush after 12.6 min • oven temperature 50 – 200°C • carrier gas: purified Helium 6.0
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Time Series
− mixing ratios of substances for which use is regulated decrease
− very similar mixing ratios at Mace Head and at Taunus Observatory
− low variability at Taunus Observatory with only few polluted samples (includes data from all wind sectors, whereas Mace Head is from clean air sector only)
2010 2011 2012 2013 2014 2015 2016 2017220
230
240
250
260
270
Taunus Observatory Mace Head AGAGE Global Mean
CFC
-11
[ppt
V]
2011 2012 2013 2014 2015 2016 2017500
525
550
Taunus Observatory Mace Head AGAGE Global Mean
CFC
-12
[ppt
V]
2011 2012 2013 2014 2015 2016 20170
2
4
6
8
10
Taunus Observatory Mace Head AGAGE Global Mean
CH
3CC
l3 [p
ptV]
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Time Series
2011 2012 2013 2014 2015 2016 20170
10
20
30
40
50
60
Taunus Observatory Mace Head AGAGE @ Mace Head
HFC
-143
a [p
pt]
− mixing ratios of substances still widely uses increase at Taunus Observatory
− mixing ratios at Mace Head represent background
− good agreement with AGAGE data at Mace Head
− high variability at Taunus Observatory with many polluted samples (includes data from all wind sectors, whereas Mace Head is from clean air sector only)
2011 2012 2013 2014 2015 2016 20170
20
40
60
80
100
120
140
160
180
200
Taunus Observatory Mace Head AGAGE @ Mace Head
HFC
-134
a [p
pt]
2011 2012 2013 2014 2015 2016 201720
22
24
26
28
30
Taunus Observatory Mace Head AGAGE @ Mace Head
HC
FC-1
41b
[ppt
]
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Time Series
2013 2014 2015 2016 20170
25
50
75
100
125
150
175
200
Taunus Observatory Mace Head
dich
loro
met
hane
[ppt
]
2013 2014 2015 2016 2017300
400
500
600
700 Taunus Observatory Mace Head
CO
S [p
pt]
2013 2014 2015 2016 2017400
450
500
550
600
650
700
750
800
Taunus Observatory Mace Head
chlo
rom
etha
ne [p
pt]
− similar seasonality of chloromethane and dichloromethane at Mace Head and Taunus Observatory
− higher variability at Taunus Observatory
− amplitude of seasonal cycle somewhat larger at Taunus Observatory
− lower mixing ratios of COS at Taunus Observatory
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