In situ observation of dust involved photochemistry over southern China

中国酸雨沉降机制、输送态势及调控原理第三课题 2005CB422203

In situ observation of dust involved photochemistry over

southern China

LIFE+ PhotoPaq conference 2014 16 April 2014

Wei Nie1, Aijun Ding1, Tao Wang2, Christian George3

1Institute for Climate and Global Change Research/School of Atmospheric Sciences, Nanjing University2Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong

Kong, China3CNRS, UMR5256, IRCELYON, Institut de Recherches sur la Catalyse et l’Environnement de Lyon,

Villeurbanne, F-69626, France

BackgroundHealth effect

Dust aerosols

Global climate change

IPCC 2007

Atmospheric chemistry

Ocean ecosystem


Roles in photochemistry• Light extinction (scattering and absorbing)

• Scavenge reactive gaseous

• Scavenge molecular clusters

• Direct uptake and decomposition oxidant, e.g. O3 and OH


• Introduction to the campaign

• Roles of dust in new particle formation

• Roles of dusts in HONO chemistry

• Causes of the observed heterogeneous

photochemistry

Contents


Site location

Mt Heng

Mar to May 2009 ， 1269m a.s.l.


Duration ： 2009. 3. 14 – 6. 1Measurements ：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

Introduction to the campaign


Overall results


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.






photochemistry

Contents


New particle formation and growthWea

k dust

Strong

dust

NPF can co-exist with dusts, even under very heavy particle loadings!


New particle formation and growth

The formation rates and growth rates were significantly enhanced during dust episodes!

DateJ15

(cm-3 S-1)

GR(15-30)(nm h-1)

GR(30-50)(nm h-1)

Q(cm-3 s-1)

PM10**

(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


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.


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




• Causes of the observe heterogeneous

photochemistry

Contents


HONO production

Nitrite formation was significantly enhanced in the daytime of dust episode!


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)


SamplesFine particles

(µg/m3)Coarse particles

(µg/m3)NO2

- Ti NO3- NO2

- Ti* NO3-

25/04 daytime 0.68 0.58 2.0 2.02 1.61 18.2

26/04 daytime 1.5 0.42 1.0 4.49 1.12 10.7

HONO formation






photochemistry

Contents


Possible causes-mixture with anthropogenic pollution


Possible causes-mixture with anthropogenic pollution

0

5

10

15

20

25

30

35

0.1 1 10 100

dc/d

logD

p (µ

g/m

3 )

Diameter (µm)

25 April

Sulfate

Nitrate

• 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.LIFE+ PhotoPaq conference 2014 16 April 2014

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.


中国酸雨沉降机制、输送态势及调控原理第三课题 2005CB422203

谢谢！Thanks！LIFE+ PhotoPaq conference 2014 16 April 2014

HONO formationDust

episodePhotochemic

al episodeNitrite(µg/m3) 2.5 0.6

Nitrate(µg/m3) 15.6 20.1

BC (µg/m3) 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.


In situ observation of dust involved photochemistry over southern China

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