Download Heterogeneous photochemistry of polluted dust

In situ observation of dust involved
photochemistry over southern China
Wei Nie1, Aijun Ding1, Tao Wang2, Christian George3
1Institute
for Climate and Global Change Research/School of Atmospheric Sciences,
Nanjing University
2Department of Civil and Environmental Engineering, The Hong Kong Polytechnic
University, Hong Kong, China
3CNRS, UMR5256, IRCELYON, Institut de Recherches sur la Catalyse et
l’Environnement de Lyon, Villeurbanne, F-69626, France
中国酸雨沉降机制、输送态势及调控原理
LIFE+
PhotoPaq conference 2014
第三课题 2005CB422203
16 April 2014
Background
Global climate
change
Health effect
Dust aerosols
IPCC 2007
Ocean ecosystem
LIFE+ PhotoPaq conference 2014
Atmospheric chemistry
16 April 2014
Roles in photochemistry
• Light extinction (scattering and absorbing)
• Scavenge reactive gaseous
• Scavenge molecular clusters
• Direct uptake and decomposition oxidant,
e.g. O3 and OH
LIFE+ PhotoPaq conference 2014
16 April 2014
Contents
• Introduction to the campaign
• Roles of dust in new particle formation
• Roles of dusts in HONO chemistry
• Causes of the observed heterogeneous
photochemistry
LIFE+ PhotoPaq conference 2014
16 April 2014
Contents
• Introduction to the campaign
• Roles of dust in new particle formation
• Roles of dusts in HONO chemistry
• Causes of the observed heterogeneous
photochemistry
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16 April 2014
Site location
Mar to May 2009， 1269m a.s.l.
Mt Heng
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16 April 2014
Introduction to the campaign
Duration：2009. 3. 14 – 6. 1
Measurements：
Gaseous:
SO2, NOx, NOy, NH3, HNO3, HCl, CO, CO2, VOCs, O3
Aerosols:
PM2.5, PM10, BC, Bsp, WSIs, Size distribution, MOUDI, Filter samples
Cloud and fog:
pH, conductivity, WSIs, organic acids, heavy metals, HCHO, H2O2，
S(IV)，PAHs
Wet deposition:
pH, conductivity, WSIs, organic acids, heavy metals
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Overall results
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Overall results
1. CALIPSO measured vertical profiles of total attenuated backscatter
and aerosol subtype on 25 April.
2. MODIS true-color imagery of eastern China on 24 and 25 April 2009.
LIFE+ PhotoPaq conference 2014
16 April 2014
Contents
• Introduction to the campaign
• Roles of dust in new particle formation
• Roles of dusts in HONO chemistry
• Causes of the observed heterogeneous
photochemistry
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16 April 2014
New particle formation and growth
Weak
dust
Strong
dust
NPF can co-exist with dusts, even under very heavy
particle loadings!
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New particle formation and growth
Date
J15
GR(15-30) GR(30-50)
Q
PM10**
(cm-3 S-1)
(nm h-1)
(nm h-1)
(cm-3 s-1)
(μg m-3)
15-Mar
0.26
4.3
NA*
1.0e+06
-***
25-Mar
0.17
5.6
5.6
1.1e+06
56.3
7-Apr
0.27
7.7
11.4
1.9e+06
75.7
20-Apr
0.15
6.1
6.1
1.0e+06
82.0
22-Apr
0.20
4.9
19.3
1.5e+06
135.1
25-Apr
0.45
7.2
12
2.8e+06
668.6
26-Apr
0.26
7.4
22.4
2.8e+06
506.9
27-Apr
0.31
6.1
11.9
1.7e+06
75.3
4-May
0.17
4.6
3.5
1.3e+06
69.8
5-May
0.29
6.4
5.8
1.8e+06
54.6
The formation rates and growth rates were
significantly enhanced during dust episodes!
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16 April 2014
NPF- possibly additional H2SO4
•
•
•
Sulfuric acid proxy in DS episodes show different feature;
Sulfate was formed corresponded to NPF in the daytime;
Probably additional H2SO4 was produced related to dust.
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16 April 2014
NPF- possibly additional OVOCs
•Calculated VOCs was lower in DS episodes;
•Potentials of producing low-volatile organic vapors is also
lower;
•Probably additional low-volatile organic vapors were produced
related to dusts
Contents
• Introduction to the campaign
• Roles of dust in new particle formation
• Roles of dusts in HONO chemistry
• Causes of the observe heterogeneous
photochemistry
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16 April 2014
HONO production
Nitrite formation was significantly enhanced in the
daytime of dust episode!
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Possible related surface processes
1. Surface photolysis of HNO3(Zhou et al., 2003; Ramazan et al., 2004)
2. NO2 photo-conversion on the soot surface(Aubin and
Abbatt,2007)
3. Heterogonous photochemical process of NO2 on the
surface organic substance(George et al., 2005; Stemmler et al., 2006)
4. NO2 photo-catalyic on the surface of TiO2 (Gustafsson et
al.,2006; Ndour et al., 2008)
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HONO formation
Samples
25/04
daytime
26/04
daytime
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Fine particles
(µg/m3)
NO2- Ti
NO3-
Coarse particles
(µg/m3)
NO2Ti*
NO3-
0.68
0.58
2.0
2.02
1.61
18.2
1.5
0.42
1.0
4.49
1.12
10.7
16 April 2014
Contents
• Introduction to the campaign
• Roles of dust in new particle formation
• Roles of dusts in HONO chemistry
• Causes of the observed heterogeneous
photochemistry
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16 April 2014
Possible causes-mixture with anthropogenic pollution
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Possible causes-mixture with anthropogenic pollution
25 April
35
Sulfate
dc/dlogDp (µg/m3)
30
Nitrate
25
20
15
10
5
0
0.1
1
10
100
Diameter (µm)
•Anthropogenic pollutants, e.g. sulfate and BC were enhanced during DS;
•Evident secondary coating were formation on the surface of dust
particles;
•Sufficient solar radiation and RH even during heavy dust storms.
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Summary and implication
Summary and implication
• In-situ observed evidence for dust promoted
NPF and HONO production;
• Suggesting an un-expected roles of Asian dust
in the global climate change via influencing the
CCN budget;
• Indicating that aerosols have potentials to act as
oxidant (catalyst) via direct and indirect
pathways to enhance the atmospheric oxidation
capacity, and thus impact the atmospheric
chemistry in a more significant way.
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16 April 2014
谢谢！
Thanks！
中国酸雨沉降机制、输送态势及调控原理
LIFE+
PhotoPaq conference 2014
第三课题 2005CB422203
16 April 2014
HONO formation
Nitrite
(µg/m3)
Nitrate
(µg/m3)
BC
(µg/m3)
Dust episode
Photochemical
episode
2.5
0.6
15.6
20.1
3.2
3.5
Concentrations of nitrate and BC were higher in
photochemical episodes than those in dust storm, excluding the
possibility of first two processes.
LIFE+ PhotoPaq conference 2014
16 April 2014