Journal of Geophysical research
Supporting Information for
The first UK measurements of nitryl chloride using a chemical ionisation mass
spectrometer in central London in the summer of 2012, and an investigation of the
role of Cl atom oxidation.
Thomas J. Bannan1, A. Murray Booth1, Asan Bacak1, Jennifer B. A. Muller1, Kimberley E.
Leather1, Michael Le Breton1, Benjamin Jones1, Dominique Young1, Hugh Coe1, James
Allan1,2, Suzanne Visser3, Jay G. Slowik3, Markus Furger3, André S.H. Prévôt3, James
Lee4, Rachael Holmes4, James R Hopkins4,5, Jacqueline F Hamilton4, Alastair C Lewis4,5,
Lisa K. Whalley6,7, Thomas Sharp6, Daniel Stone6, Dwayne E. Heard6,7, Zoë L. Fleming8,
Roland Leigh9, Dudley E. Shallcross10 and Carl J. Percival1
1 Centre for Atmospheric Science, School of Earth, Atmospheric and Environmental Science, University of
Manchester, Oxford Road, Manchester, M13 9PL, UK, 2National Centre for Atmospheric Science, University
of Manchester, 3Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen PSI, 5232, CH, 4
Wolfson Atmospheric Chemistry Laboratories, University of York, Heslington, York, YO10 5DD, UK, 5
National Centre for Atmospheric Science, University of York, Heslington, York, YO10 5DD, UK, 6School of
Chemistry, University of Leeds, Leeds, LS2 9TJ, UK, 7 National Centre for Atmospheric Science, School of
Chemistry, University of Leeds, Leeds, LS2 9JT, 8National Centre for Atmospheric Science, Department of
Chemistry, University of Leicester, Leicester LE32BQ, 9Department of Physics and Astronomy, University of
Leicester, Leicester, LE1 7RH, 10Biogeochemistry Research Centre, School of Chemistry, University of
Bristol, Cantock’s Close, Bristol, BS8 1TS, UK
Contents of this file
Text S1
Tables S1 to S2
Introduction
Text S1 shows extended explanation of the marine and continental regimes as well as a
more detailed description of the UK Met Office’s Numerical Atmospheric-dispersion
Modelling Environment (NAME) model used to define these regimes.
Table S1 gives detailed descriptions of the relationship between ClNO2 and N2O5 on
each night of the campaign as well as the definition of the marine and continental
regimes. Table S2 shows rate coefficients for reactions included in the MCM.
1
Text S1
As described in the paper dispersion modelling was carried out using the UK Met
Office’s NAME dispersion model to produce 3 hourly averaged air mass footprints that
track the air mass origins during the previous 24 hours. This dispersion modelling only
tracks when the air arriving at the site comes into contact with the surface (0- 100m). For
this modelling 10,000 particles were released backwards from the site and tracked for a
period of 24 hours prior to arriving at the station. A count of particle concentration was
taken every 15 minutes during the 24 hour period and summed together to create a
probability footprint, highlighting the number of particles travelling through pre-defined
regions that reach the measurement site.
To quantify the extent of the marine influence during each 3 hourly period, the Atlantic
Ocean, the Channel and the North Sea were combined resulting in a % marine influence
as shown in figure 3 in the paper. This represents the amount of time the air mass has
spent over marine areas, irrespective of which continental regions it has also passed
over before or after the marine surface. Throughout the campaign all air masses have at
least some marine influence but the extent of the marine influence varies significantly
between periods, affecting the gas phase measurements and Na and Cl concentrations.
The 28th of July has the lowest marine influence and is the only day during the summer
campaign where the marine influence is negligible at 0.3%, as defined by NAME
trajectory analysis. Other days where the marine influence is insignificant include the
30th of July, 9th and 10th of August NAME marine scores being 5.8, 3.5 and 6.0%
respectively. Increased concentrations of Na and Cl occur mainly with winds from the
SW to W and air masses having travelled over the Atlantic Ocean, e.g. 1st August
midday until 6th August midday.
Using gas phase and aerosol data, as well as NAME dispersion modelling it is therefore
possible to separate the time series into two different regimes; marine and continental. A
classification of either a continental or marine dominance defined in table 1. Marine
dominated air masses are predominantly associated with high Na and Cl (figure3) and in
this study we will define a marine influenced air mass as being above 15% marine, as it
is at this level where a general enhancement of Na and Cl is observed in the RDI
analysis. Other air masses (<15 % marine) are defined as continental.
The 22nd to the 25th of July showed different characteristics to other periods above the
15% threshold defined by the name modelling with no enhancement in Na and Cl being
observed. Na, an indicator of a marine influence, from 22nd to the 25th July was on
average 168 ng m-3 and did not exceed 250 ng m-3 during this period, suggesting no
significant marine influence at these times. For the purposes of this study this period will
be defined as a continental regime despite NAME modelling suggesting otherwise.
On the 29th of July despite the marine influence exceeding 15% (reaching over 40%), it
is still however classified as a day defined by a continental regime. This is due to the
peak in marine influence being at 12 noon, a time when no ClNO2 would be expected, or
was measured. At 6 pm the percentage of trajectories with a marine influence had
reduced to 1.1% and after sunset at 9 pm when ClNO2 would begin to be produced the
percentage had further reduced to 0.27%.
2
Table S1. Relationship between ClNO2, N2O5 and meteorological conditions.
ClNO2:N2O5 (average values) calculated using average values when
concentrations exceed that of the LOD, generally between 8 pm and 10 am.
ClNO2:N2O5 (peak values) calculated using highest night-time value of both
species. Sunset to sunrise slope, where y=ClNO2 and x=N2O5, calculated using
only data in the absence of solar radiation, with the positive or negative
relationship being determined by the gradient when steeper than ±0.3x.
Date
ClNO2:N2O5 ClNO2:N2O5 Sunset to
(Average
(Peak
sunrise slope
Values)
Values)
Sunset
to
sunrise
r2
Marine Vs
Continental
ClNO2:N2O5
relationship
21/7/12
0.32
0.63
y = 0.76x
0.14
Continental
Positive
22/7/12
0.24
0.21
y = 3.46x
0.87
Continental
Positive
23/7/12
0.10
0.23
y = 5.19x
0.71
Continental
Positive
24/7/12
0.02
0.04
y = -0.27x
0.00
Continental
25/7/12
0.04
0.06
y = 0.83x
0.01
Continental
Positive
26/7/12
0.76
0.48
y = -1.12x
0.64
Marine
Negative
27/7/12
0.12
0.15
y = 0.42x
0.01
Continental
Positive
28/7/12
0.10
0.27
y = 1.58x
0.09
Continental
Positive
29/7/12
0.31
0.34
y = 1.35x
0.35
Continental
Positive
30/7/12
0.23
0.18
y = 1.44x
0.09
Continental
Positive
31/7/12
0.94
0.98
y = -0.68x
0.85
Marine
Negative
01/8/12
0.61
0.46
y = -0.09x
0.07
Marine
Negative
02/8/12
1.02
1.93
y = -0.21x
0.49
Marine
Negative
03/8/12
1.48
2.05
y = -0.04x
0.06
Marine
Negative
04/8/12
2.41
3.55
y = -0.1x
0.54
Marine
Negative
05/8/12
0.97
0.89
y = 0.56x
0.75
Marine
Positive
3
06/8/12
Marine
07/8/12
0.35
0.40
y = -1.57x
0.60
Marine
Negative
08/8/12
0.12
0.44
y = -2.57x
0.33
Marine
Negative
09/8/12
Continental
10/8/12
0.36
0.51
y = -0.87x
0.28
Continental
Negative
11/8/12
0.43
1.37
y = -0.29x
0.72
Marine
Negative
12/8/12
0.48
0.33
y = -1.21x
0.45
Marine
Negative
13/8/12
0.49
0.72
y = 0.28x
0.11
Marine
Positive
14/8/12
0.66
1.17
y = -0.16x
0.14
Marine
Negative
15/8/12
0.39
0.47
y = -1.5x
0.65
Marine
Negative
16/8/12
0.43
0.77
y = 0.54x
0.71
Marine
Positive
17/8/12
0.02
0.04
y = 11.24x
0.63
Marine
Positive
Average
0.51
0.72
0.39
Table S2: Rate constants of the additional Cl atom reactions included in the MCM
Reaction
CH3CHO + CL = CH3CO3 + HCL ;
C2H4 + CL = RCLO2 ;
C3H6 + CL = RCLO2 ;
C2H2 + CL = RCLO2 ;
C4H6 + CL = RCLO2 ;
TPENt2ENE + CL = RCLO2;
PENT1ENE + CL = RCLO2;
C5H8 + CL = RCLO2;
BENZENE + CL = C6H5O2 + HCL;
TOLUENE + CL = C6H5CH2O2 + HCL;
EBENZ + CL = RCLO2;
MXYL + CL = RCLO2;
PXYL + CL = RCLO2;
k (298K)
7.61E-11
3.01E-10
2.71E-10
7.07E-11
2.51E-10
3.95E-10
3.97E-10
4.20E-10
1.76E-16
6.10E-11
1.15E-10
1.40E-10
1.50E-10
Reference
Atkinson et al., (1989)
Atkinson et al., (1992)
Kaiser and Wallington (1996)
Wallington et al., (1988)
Stutz et al., (1998)
Ezell et al., (2002)
Ezell et al., (2002)
Ragains et al., (1997)
Alecu et al., (2007)
Smith et al., (2002)
Anderson et al., (2007)
Shi and Bernhard (1997)
Shi and Bernhard (1997)
4
OXYL + CL = RCLO2;
MACR + CL = RCLO2;
MVK + CL = RCLO2;
CH3OH + CL = HCHO + HO2 + HCL;
CH3COCH3 + CL = CH3COCH2O2 + HCL ;
C2H5OH + CL = C2H5O + HCL;
NPROPOL + CL = HO1C3O2 + HCL;
NBUTOL + CL = NBUTOLBO2 + HCL;
TM123B + CL = RCLO2;
TM124B + CL = RCLO2;
TM135B + CL = RCLO2;
HCHO + CL = CO + HO2 + HCL;
1.50E-10
2.40E-10
2.20E-10
5.50E-11
3.50E-12
9.40E-11
1.50E-10
2.19E-10
1.50E-10
1.50E-10
1.50E-10
7.30E-11
Shi and Bernhard (1997)
Orlando et al., (2003)
Orlando et al., (2003)
Atkinson et al., (2001)
Atkinson et al., (2001)
Atkinson et al., (1997)
Atkinson et al., (1997)
Hurley et al., (2009)
Shi and Bernhard (1997)
Shi and Bernhard (1997)
Shi and Bernhard (1997)
Atkinson et al., (2001)
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6