Ef f ects of Sol ubl e Surf actants on
Parti cl e Properti es
Lui s A . Cuadra-Rodríguez
Prof . G. Barney El l i son
Uni versi ty of Col orado at Boul der
GREF Fel l ow
D r. A l l a Zel enyuk
PN N L-EM SL
CGEP End-of -Summer
A ugust 17th , 2010
OUTLI N E
• Introduction to Marine Aerosol Model
– Ongoing work and highlights
• Background on hygroscopic (Inorganic) particles
• Experimental Approach
• Results
• Conclusions
M ari ne A erosol M odel
(Ellison,Tuck,Vaida. J.Geo.Phys.Res. (1999))
• “Inverted” micelle
• Water core (1010) surrounded by
surfactants (107) for a 1µm aerosol
• Poor CCN
• Atmospheric oxidants make them
good CCN
• Accounts for C mass on atm
M ari ne A erosol M odel (cont…)
• Gill et al. proposed the same model 1983
• Donaldson & Vaida (Chem. Rev. 2006, 106,
1445-1461)
–
–
–
–
–
–
Soluble vs Insoluble surfactants
Equilibrium vs surface partition
Photochemistry
Role of water
Transport
Chemistry
water/Na+NO3–
Inorganic
salt
M ari ne A erosol M odel (cont…)
• Thorton group (University of Washington)
• McNeill et al. Atmos. Chem. Phys., 6, 1635–
1644, 2006
• Sodium Dodecyl Sulfate (SDS)
NaCl
Inorganic Particles’ Properties
• Physical and Chemical properties
• Efflorescence  relative humidity at w hich
particles lose all the w ater and crystallized.
(liquidsolid)
• Deliquescence  relative humidity at w hich
particles gain w ater and become a droplet.
(solidliquid)
• Grow th Factors (GFs)
Sub-micron-size Particles Properties
Sodium Chloride, N a+Cl -
Efflorescence ~ 42% RH
Deliquescence ~78% RH
A mmonium Choride, (N H 4+ )2SO42-
Efflorescence ~ 37-40% RH
Deliquescence ~80% RH
Tang,I.N .; M unkelw itz,H .R. J Geophys. Res-Atmos 1994, 99(D9): 18801-18808
Tang, I.N .; Tridico, A .C.; Fung, K.H . J Geophys. Res-Atmos 1994, 102(D19): 23269-23275
M icron-sized Particles Properties
(N H 4+)2SO42-
aw = 1.00 + ∑ Ci wf i
RH = 100aw
ρ = 1.00 + ∑ Ai wf i
d
3
ve
 ( wf ) ρ p
=
 ρ
salt

d ve =
3
d ve
=3
dm
 3

 dm

 ( wf ) ρ p

 ρ
salt



 dm

 ( wf ) ρ p

 ρ
salt





Tang,I.N .; M unkelw itz,H .R. J Geophys. Res-Atmos 1994, 99(D9): 18801-18808
Tang, I.N .; Tridico, A .C.; Fung, K.H . J Geophys. Res-Atmos 1994, 102(D19): 23269-23275
• A large fraction of atmospheric particles are composed of
common hygroscopic inorganic salts (sulfates, nitrates,
sea salts) that are mixed w ith a variety of organics.
• Surfactants – coat particle’s surface, alter particles’
interactions w ith the atmosphere (gas species, w ater
vapor), CCN activity, change size and optical properties
as a function of RH .
• It is important to quantitatively characterize these
particles’ behavior as a function of RH
A pproach
Na+
Na+
NO3-
NO3-
Drop
No shape factor
Inorganic
salt
Dry particle
CH 3 (CH 2 )11 SO −4 Na +
(SDS)
Na+
Cl-
Na+
Shape factor
Cl-
Experimental (Density)
Diffusion
dryers
A tomizer
D ry D M A
Salt/ SDS solution
dm mobility diam.
dva aerodynamic diam.
distributions
Experimental (GFs)
D ry D M A
A tomizer
Diffusion
dryers
RH meter
Salt/ SDS solution
H umidifier
dm,dry dry mobility
diameter
CPC
Wet D M A
dm,wet wet mobility
diameter
Density
GFs
d va
ρ p = ρ0
dm
d m , wet
d va ρ p 1 Cc (d va χ ρ 0 ρ p )
ρ eff ≡ =
d m ρ0 χ 2
Cc ( d m )
1
χ
2
ρ eff
= 1.094
− 0.096
ρp
GFm =
d m ,dry
d m, wet
d ve, wet
GFm =
=
d m, dry d ve, dry χ DMA Cc (d m, dry ) Cc (d ve, dry )
(
GF = ε O GF + ε IN GF
3
O
ZSR model
)
3 1/ 3
IN
SN / SDS density
ρ SDS = 0.24 - 3.61 × 10 -3 WF + 3.94WF 2 - 5.19WF 3 + 2.14WF 4
SN / SDS d va distributions
SN / SDS GFs
(
GF = ε O GF + ε IN GF
3
O
)
3 1/ 3
IN
SN / SDS GFs
(
GF = ε O GF + ε IN GF
3
O
)
3 1/ 3
IN
N aCl/ SDS d va distributions
N aCl/ SDS effective density
ρ SDS = 0.381 + 0.226WF - 1.95WF 2 + 5.01WF 3 - 2.47WF 4 - 0.0554WF 5
DSF = 1.10 - 0.467WF + 0.944WF 2 - 1.09WF 3 + 0.687WF 4 - 0.181WF 5
N aCl/ SDS GFs
d m, wet
d ve, wet
GFm =
=
d m, dry d ve, dry χ DMA Cc (d m, dry ) Cc (d ve, dry )
N aCl/ SDS
w f = 9.8 x 10-3
w f = 9 x 10-2
w f = 0.37
Conclusions
• Quantitatively described the physical
properties of SN and N aCl using
multidimensional analysis w here
independent measurements are coupled and
fit.
• Behavior is complex (composition, RH ,
shape).
• These data (or method) could be used in
prediction models and ambient sampling of
organic aerosols.
Spectrometer Overview
90º def l ector
Ei nzel l ens
Cryo pump
D ri f t Regi on
PM Ts f or green
scattered l i ght
Quadrupol e
M ass Fi l ter
10-30 mJ/ 10 ns pul se-1
2.94 µm f ocused to 1 mm
50 mW
532 nm di odes
Capi l l ary i nl et
Ø = 0.5mm x 10 cm
Gracias
• GCEP-GREF (M ilton Constantin,
Jeff Gaffney, N ancy M arley, Rick
Petty, Staff)
• Dr. A lla Zelenyuk (PN N L-EM SL)
• B. Ellison and Ellison’s group
• DOE-Basic Science
Surfactant effects-Previous w ork
• Growth Factors (GFs) – H TDM A w ork show ed that the
addition of organics to inorganics does N OT prevent
w ater uptake or loss but the amount gained or loss.
(H ansson et al. (1999), Chen & Grace (1999 & 2001)
– Larger organic fraction  low er GFs
– Deliquescence points are low er compare to pure salt.
• CCN activity – surfactants did “ alter” (N H 4)2SO4 particle
activation, did N OT inhibit it, except for estearic acid.