4.particle.matter.10 - Particulate Matter in the...

Particulate Matter in the Environment

Introduction

Atmospheric Aerosols
Properties and Environmental Behavior

Aquatic Matter
Properties and Environmental Behavior

Summary and Conclusions

Definition: Aerosol is a suspension of tiny solid or liquid particles in gas .
(Commonly refer to the particulate component only)
•
Size:
2 nm < diameter < 20 μm
Fine particles = d
p
<2.5 μ m
•
Shape:
spherical & irregular
•
Concentration:
10
2
~ 10
5
#/cc
<1 ~ 100+ μ g m-
3
•
Phase:
solid, liquid, or complex
•
Composition:
highly variable
II. Atmospheric Aerosols
Aerosols = Particles = Particulate Matter (PM)

PM Sizes (aerodynamic diameter)
Nanoparticles 0.01 µm (10 nm) or smaller
Ultrafine particles 0.1 µm (100 nm) or smaller
PM 2.5 2.5 µm or smaller
PM 10 10 µm or smaller
Fine vs. coarse particle

H
2
O
s
H
2
O
2003 NARSTO Assessment
Atmospheric Aerosol Composition
Typical composition :
• Soil erosion, dust: metals/crustal
materials.
• Sea-salt: Na, Cl
-
• Fossil fuel / biomass combustion:
Black carbon
• Secondary inorganics: Sulfate,
nitrate, ammonium
• Organics: a complex mixture of
many individual organic
compounds
• H
2
O





Org
SO
4
2-
NO
3
-
NH
4
+
Fine Aerosol Composition
Zhang et al., Geophys. Res. Lett., 34, L13801, 2007.

•
Visibility reduction:
–
Visibility definition: “the farthest distance one can see a large black object against
the background sky.”
–
Influencing factors: aerosol loading, size, RH
–
Economical concerns (tourism)
2.5 -3 2.5 -3
Pittsburgh, USA
July 2, 2001 July 18, 2001
7/25/08
1 -3
8/31/08
1 -3
Beijing, China
Why do we care about aerosols?

Satellite image of ship track
over the ocean
Influence of aerosol on clouds
Ships burn high-sulfur fuel
 sulfate aerosols (CCN)
 clouds

Direct scattering
effect: Absorb and
scatter solar
radiation and
outgoing IR
radiation
Indirect cloud
effect:
Act as CCN
(cloud condensation