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Borrower: ERA 

Lending String: *CON,COV,NBU,WYU,OLA 

Patron: Michael A. Flagg 

Journal Title: need article 'from;Paleoclimatology 

and paleometeorology ; modern and past patterns 

of global atmospheric transport / 

Volume: Issue: 

MonthlYear: Pages: 133?165 

Article Author: Leinen, Margaret,; Sarnthein, M.; 

NATO Advanced Research Workshop on 

Paleoclimatology and Paleometeo 

Article Title: W.G. Nickling and J.A. Gillies, 

Emission of fine-grained particulate from desert 

soils 

. 

Il

. 

:J Imprint: Dordrecht;, Boston; Kluwer Academic 

Pu 

ILL Number: §~;§.§;O~21

1111I111111111111111111111111111111111111111111111 

Call #: QC981.8.C5 N37 1987 

Location: Branch Books 

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Charge 

Maxcost: $151EM 

Shipping Address: 

Region 9 Library, ILL 

U.S. Environmental Protection Agency 

75 Hawthorne Street 

San Francisco, CA 94105 

Fax: 415-947-3553 

Ariel: 
ile convective activity 

the country. Indian 

recasting Manual, part 

lnderstorms on 23 March 

C Meteorology and 

~e of dust haze over 

In May 13, 1963.' Indian 

::s, 20: 56- 5 7 • 

EMISSION OF FINE-GRAINED PARTICULATE

W. G. NICKLING & J. A. GILLIES
 

Department of Geography
 

University of Guelph
 

Guelph, Ontario
 

CANADA, N1G 2W1
 

1. INTRODUCTION 

During the past decade, considerable intere

emission, transport, deposition and climatologic

anthropogenic aerosols (e.g. Gillette, et al., 1982; 

Pewe, 1981). Several studies have also considere

concentration on light extinction (Pilat and Enso

Brazel, 1974)/ human health hazards (Leathers, 

and Gillette, 1977b) and ambient air quality (Hag

addition, a large volume of literature has been d

atmospheric, textural and surface conditions wh

atmospheric aerosols. 

Despite this, few studies have attempted to 

quantitative manner) the relative aerosol produ

and anthropogenic surfaces. As part of a long-r

dust emissions in the Southwestern U.S./ an init

carried out in Arizona to determine the relative 

potential of selected surface types. A total of 13 

were selected for the evaluation of dust emission 

designed, portable field wind tunnel. Informati

to understand total suspended particulate loadin

as the U.S. Southwest, Africa, and the Middle Ea

frequencies and total suspended particulate (T.S

high (Nickling and Brazel, 1984; Brazel and Nick

particulate loadings in these areas have frequent

environmental and human health hazards. For 

133 

M. Leinen and M. Samlhem (eds.), Paleoclimatology and PaleOfneteorolo

Atmospheric Transport, 133-165.
 

© 1989 by Kluwer Academic Publishers.
 
troversy has arisen over the sources of high 

ons (Nick1ing and Brazel, 1984). Various 

luding government agencies, have disputed the 

t concentrations. Potential sources have 

major construction sites, natural desert 

ll as stack and vehicle exhaust emissions. 

oversies, little quantitative data is presently 

efute most arguments. 

alth of information exists on the horizontal 

udies have been carried out on the vertical flux 

m natural surfaces. Chepil and Woodruff (1957) 

ata on the variation of sediment concentration 

ms in Colorado and Kansas. More recent 

uxes have been carried out in the High Plains of 

in Texas and Nevada by Shinn, et al. (1976). 

e also been undertaken in Canada by Complin 

m mill tailings and on undisturbed natural 

). The results of Shinn, et al. (1976) are not 

resent work because their investigation focused 

e sediment was entrained. In contrast, the 

 emission rate from different surface types. 

ormation on the vertical fluxes of aerosols from 

cts the logistical problems associated with 

all the above studies, particulate concentration 

wind erosion events using various types of 

nstrumentation placed on towers at selected 

s derived from such long-term field studies 

 degrees of success by other authors to produce 

sites. 

the U.S. Environmental Protection Agency to 

ndards to a limitation based on particulates 

namic diameter <10 IJ.IIl has necessitated a more 

e potential sources and land use activities 

 fluxes so that appropriate environmental 

 

2.	 FIELD SITES 

The thirteen sites selected: 

potential represent a range of su 

local environmental officials of 

dust concentrations in Southern 

basis of their soil textural charac 

degree of anthropogenic disturb 

agricu1turallands, abandoned a, 

construction sites and mine tailJ 

Figure 1 and a brief description 

characteristics is given in Table 

3.	 FIELD MEASUREMENT a 

A fundamental problem ill 

production potential of surfaces 

sediment loss under a wide ran, 

However, direct field observatil 

(~g. Gillette, 1977; Nick1ing, 197 

several serious drawbacks: 

, 1),	 they are extremely costly i: 

logistical support necessaI') 

2)	 field studies are very mud 

and as a result, one often s 

weather or surface conditi< 

quality and quantity of dab 

3)	 data obtained in such studi 

the lack of control on the r 

involved in the wind erosi 

The Portable Field Wind: 

In order to overcome somE 

'bs monitoring under natural' 

tunnel was designed and const! 

isimilar in design, although con: 
unents. 

:ion exists on the horizontal 

carried out on the vertical flux 

$. Chepil and Woodruff (1957) 

ltion of sediment concentration 

and Kansas. More recent 

carried out in the High Plains of 

'vada by Shinn, et ai. (1976). 

ertaken in Canada by Complin 

and on undisturbed natural 

: Shinn, et ai. (1976) are not 

ause their investigation focused 

entrained. In contrast, the 

~om different surface types. 

vertical fluxes of aerosols from 

problems associated with 

Lldies, particulate concentration 

~nts using various types of 

placed on towers at selected 

such long-term field studies 

:ess by other authors to produce 

unental Protection Agency to 

,tation based on particulates 

<10 IJll1 has necessitated a more 

ces and land use activities 

lppropriate environmental 

g

degree of anthropogenic disturbance. The surface 

agricultural lands, abandoned agricultural fields, 

construction sites and mine tailings. The locatio

Figure 1 and a brief description of each site's surf

characteristics is given in Table 1. 

3. FIELD MEASUREMENT OF AEROSOL FLU

A fundamental problem in identifying and 

production potential of surfaces is the need for t

sediment loss under a wide range of atmospheric 

However, direct field observations using special

<e.g. Gillette, 1977; Nickling, 1978; 1983), despite 

several serious drawbacks: 

1) they are extremely costly in terms of the in

logistical support necessary to investigate se

2) field studies are very much dependent on th

and as a result, one often spends considerab

weather or surface conditions that in the en

quality and quantity of data obtained; and 

3) data obtained in such studies are often extre

the lack of control on the many atmospheric 

involved in the wind erosion process. 

3.1 The Portable Field Wind Tunnel 

In order to overcome some of the limitation

loss monitoring under natural wind conditions, a 

tunnel was designed and constructed for in situ 

similar in design, although considerably larger th

reported by Wooding (1968) and Gillette (1978). T

12.0 m open-floored working section constructed 
.... 

C1'I 

/-... t:b ....., 

,J ..­ c..C'--.... eJ 

1, ."-""\ .... ';" r, 

TE CHARACI'ERISTICS 

getation or surface trash; double disked 2 days prior to 

vering the surface 

egetation or surface trash; secondary tillage operations 

ge clods of varying size covered the surface 

eeetation or surface trash: surface was loose and friable 
'

c:l o 2' 

• 

• 

"" () 

(

_ 

[ 8 ..<.., J 

... 

-

TABLE 1. Site Surface and Textural Chara

SITE 

Mesa, Arizona Flat, laser levele

(agriculatural land) testing; large clo

Maricopa, Arizona Flat, laser levele

(agricultural land) in preparation fo

Yuma, Arizona Flat, laser levele

(agricultural land) with few large c

Casa Grande, Arizona Flat, smooth, las

(abandoned agricultural grasses; weakly 

land) 

Glendale, Arizona Flat, smooth, ma

(construction site) earthmoving ma

vehicular traffic 

Tucson, Arizona Very flat, 

(construction site) by earthmoving

Ajo, Arizona Extremely flat, e

(mine tailings) sediment with s

Hayden, Arizona Extremely flat c

(mine tailings) lengths greater t

Algodones, California Relatively flat, e

(dune flats) vegetation cover

vehicles 
 

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plexiglass viewing/access windo 

t,"!~ dimensional, molded fiberglass i 

;:i~$ straightener and a conical fibergl ",I<

~f is provided by a 95 em centrifugl: 

,;~£1';The fan and engine are transport 

~< pickup truck and connected to tl 

'\1 flexible hosing. The inlet bell, lo'.l 

~i{ on a 8 m flatbed trailer. 

;!~, 3.2 Testing Procedures ~~:j

~;:,-.-:"

j;:' At each test site the wind tl 

'tifundisturbed surface and the wiI1 

tJnstalled into the test section. VI 

&:pitot tubes connected to magneh 

'i;';; tubes were positioned above the ~_c"

if Suspended sediment was CI 

_samplers mounted downwind at 

'.:.,~ ..•.. ..••," above the surface (F~g. 3). The s

,'ti\vacuum pump. Sediment was 0 

t~iisokinetically through preweighi 

~~.:(O.1 JlIIl pore diameter) held in ( 

~.f;'~within the samplers. Isokinetic: 

'~tained during each test by l 

!in~rporated into each vacuum 

.. Sediment transported in sal 

';(1941) type catcher installed alor 

'}:)ehind the suspended sediment 

Following installation of tt 

,el was slowly raised until n 

ers positioned at the plexi 

,hold test was completed, a 

hold was established in the 

Izzle flow rate set to the cente: 

,ear velocity was determined f 

,ing the Prandtl equation: 

u= 
flexible hosing. The inlet bell, working sections 

on a 8 m flatbed trailer. 

3.2 Testing Procedures 

At each test site the wind tunnel was caref

undisturbed surface and the wind velocity sens

installed into the test section. Velocity was mea

pitot tubes connected to magnehe1ic differential 

tubes were positioned above the soil surface at h

Suspended sediment was collected in two 

samplers mounted downwind and to either side 

above the surface (Fig. 3). The samplers were c

vacuum pump. Sediment was collected during 

isokinetica1ly through preweighed 3.7 em diam

(0.1 J.1ffi pore diameter) held in commercially av

within the samplers. Isokinetic flow through th

maintained during each test by means of a need

incorporated into each vacuum line. 

Sediment transported in saltation and cree

(1941) type catcher installed along the center lin

behind the suspended sediment collectors (Fig. 

Following installation of the instrumentat

tunnel was slowly raised until movement of par

observers positioned at the plexiglass viewing w

threshold test was completed, a predetermined 

threshold was established in the wind tunnel a

nozzle flow rate set to the center line velocity a

Shear velocity was determined from the wind v

using the Prandtl equation: 

u = ~* In k Zo 
...

a5 

...­
Figure 2: Th

tes

Figure 3:	 Susp

trap 

50 em 
•.I

ngth z, Zo is roughness length of the surface and 

 (0.4). 

dual test was dependent on the amount of 

as longer for surfaces with lower flux rates. 

ranged from 10 to 30 minutes. At the 

the sediment samples were removed from the 

d for subsequent weighing and grain-size 

~~<b 

m~

i 

! 

O'lt-.: 

Net) 

\()~

ay become depleted of erodible grains during 

move the tunnel to a new location for each 

 locations were normally within 10 m of the 

xis of the tunnel parallel to the initial 

 tunnel was repositioned, the threshold 

surements were repeated. In general, five or six 

ities above threshold were carried out at each of 

~~

~~

~~{/)Q 

~~

-IS

,:. -IS

,:. 

_ et) 

t'i et) et) 

~(!!;:

C'i(t')1 

pended sediment collected during each run was 

 image analyzing computer following the 

(1973). In this technique, a small portion of an 

mple is placed on a gelatin-coated microscope 

ter is quickly absorbed by the gelatin, leaving the 

and cemented on the slide. The slide is then 

roscope of the Quantimet 720. By setting class 

e programmed to measure the total particle area 

f the given limits. In using this technique, the 

 diameter of a circle with an equivalent area. In 

than 1 percent can be obtained when the 

than 5 percent of the viewing area (Peach and 

e suspended sediment samples analyzed, over 

 each slide. Results of the grain-size analysis for 

0, 1.0-2.5,2.5-10.0 and 10.0 /lIn are shown in 

.§

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cu 

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tTl 0 I 

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ooc - 10 C

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lfnc; 

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9 §;

p.. 0 a li6 Ef re g. 

I-l..... :i 0 ;:I. (/l 9 (/

;. go ;. (/ls, e; 

o £l)!» 

"'0 =' Qq 

§ [Qq !..2 2: ? 

I»!::' 

(/l"" 

I <:< ;:;0.,.,. 0 $ 

,., (/l .... I» ::r < .... (/

o N-\J \J ,.,. 

§ re ;. a..0' g. 

=' eo p.. g. O'.Qq 

0 a. 

=' !»;. I» :

... p.. 

g ::s I» 

TABLE 2. Grain Size Characteristics of Sus

GRAIN SIZE DISTR

AEROSOLS (% FR

1.0 • 

SITE < 1.0 JlDt 2.5 JlDt 10

Mesa,AZ 1 24.81 40.88 

(agricultural) 2 33.32 34.61 

3 28.96 35.09 

4 48.24 27.20 

5 44.95 31.41 

6 36.78 26.63 

Glendale, AZ 

(construction) 

1 

2 

42.00 

32.16 

31.68 

37.13 

3 65.53 30.65 

4 17.48 21.33 

Maricopa, AZ 1 14.21 23.31 

(agricultural) 2 24.76 24.92 

3 19.68 27.30 

4 21.46 17.64 

5 27.12 32.68 

Yuma,AZ 1 10.88 15.75 

(disturbed 2 14.28 16.79 

desert) 3 9.49 21.62 

4 9.42 13.11 

5 14.36 23.81 
MEAN STANDARD SHEAR 

SIZE DEVIATION VELOCITY 

LD1. (J.Lm) (J.Lm) (em/sec) 

 5.21 3.37 29.6 

 4.89 3.12 31.9 

 5.50 3.31 34.6 

 5.44 3.16 57.0 

 5.89 3.21 51.7 

 4.91 3.67 26.7 

 5.67 3.41 34.3 

 5.04 3.04 50.4 

 4.19 3.11 49.7 

 3.87 3.37 48.7 

 6.62 3.27 40.4 

 4.37 3.91 SO.5 

 4.04 3.72 40.4 

 5.62 3.32 41.3 

 4.69 3.35 46.7 

 4.13 3.47 21.4 

 3.77 3.39 30.8 

 4.27 3.41 41.7 

 6.53 2.97 34.5  5.76 3.10 18.9 

 5.97 3.16 35.1 

MEAN STANDARD SHEAR 

SIZE DEVIATION VELOCITY 

D1. (J.Lm) (J.Lm) (em/sed 

 

 

 

 

3.47 

5.82 

4.94 

5.59 

2.92 

3.26 

3.64 

3.21 

18.5 

30.9 

30.4 

50.2 

 3.49 3.35 49.1 
Yuma, AZ 1 46.77 1.74 

(scrub desert) 2 31.09 30.12 

3 15.09 17.33 

4 23.00 21.33 

5 30.95 23.11 

Tucson, AZ 1 31.75 29.12 

(Santa Cruz 2 26.99 24.99 

river terrrace) 3 6.88 13.31 

4 9.48 20.47 

5 10.78 16.51 

TABLE 2. (Continued) 

GRAIN SIZE DISTR

AEROSOLS (% FR

1.0- 

SITE < 1.0 fJJIl 2.5 fJJIl 10

Tucson, AZ 1 26.70 36.49 

(construction) 2 12.36 17.87 

3 22.07 23.80 

4 13.43 18.56 

5 36.71 27.44 

Ajo,AZ 1 22.15 23.02 

(mine tailings) 2 28.68 20.02 

3 16.85 22.75 

4 31.05 27.33 

Hayden, AZ 1 15.85 22.99 

(mine tailings) 2 27.90 22.37 

3 15.64 14.98 

4 14.66 15.33 

5 30.02 26.79 

6 30.35 30.90 

Mesa, AZ 1 23.07 10.98 

(salt river) 2 13.36 16.65 

3 30.05 26.67 

4 9.59 18.62 

5 28.17 24.83 

Casa Grande, AZ 1 25.25 43.73 

(abandoned 2 32.82 28.19 

agricultural) 3 12.16 16.64 

4 9.31 20.18 
ty !J 00 (f) It)

~. to-: 00 N (f) .... 

es for the sampled surfaces vary markedly and .. A 

 (Table 3). These values are similar to threshold 

l. (1980) for a variety of undisturbed and Ji 

oq \C) t"! 

Mojave Desert. ara 'U I- \Q .... 00 ..c .... N Q ~~ fg 

3 are the associated 10m wind velocities tj ].~.- q \C)

motion and the mean vertical aerosol fluxes (F). II 

-< 'U -= 6 .... ::1. § 

mputed using the Prandtl equation (Eq. 1) and J!~­ .... .... .... II)

 during the wind tunnel tests. Although there :J 

(I) 

cu 

een the threshold .values of the undisturbed c:: .!::I o (f) \C) .. (1)'-

rbed surfaces in general have considerably cu.5 6 g 0\ N 

6"::1. .... $ 

. This finding is also consistent with the data tb

'U 

:x 

q. 

.... 

o 6.... .... 6 6.... 

cities indicate that wind erosion could be )( )( )( )(

~a to... o 00 to... 

ost normally occurring natural wind cu u N 0) oq 0)

6~ to-: .... N

latively high threshold values found at the 

d the three active agricultural sites would 

sion events would be relatively infrequent oS 

N~ .... 8 

urally occurring wind velocities. o o o o 

~'2 N 0'1 

te, et al. (1980) have shown a general increase in ..,(1) oq It} 

Lri (f) \C) to... 

h an increase in the modal size of the surface :)! .... .... .... 

t should be noted, however, that the empirical 

e authors are relatively weak and demonstrate 'U -cu 0'1 N ~~ 

atural sediments. Results from the wind • II)

~! d ~~ 

 relationship between mean grain size and 

for the 13 Arizona sites. This most likely i 

f modal diameters for the sampled sites and the ] ] ] N'~ 

surface parameters, such as vegetation and ..!!l ..!!l ..!!l < Cl 

not evaluated in a simple bivariate relationship. jg~jg !is ala 

NE .. ENE]J: 

the 0.1 confidence level, however, was found to <a B..a <a ~~ 

r velocity and the percentage of aggregates "'C S'C ""C OJ: 

tlSbC'CbC§bCl}Ji 

tIS tIS _tIS tIS _tq Cl 

least squares relationship is: ~-~ >o-u ... 

0.202 

aggregates >0.84 mm) (2) 
Lriety of undisturbed and .~.... C"i

.... 

.... oq 

00 

O'l 

00 

lted 10m wind velocities 

mean vertical aerosol fluxes (F). 

! Prandtl equation (Eq. 1) and 

ld tunnel tests. Although there 

ld values of the undisturbed 

l general have considerably 

ls also consistent with the data 

o g

.... 

o 

.... 

.... 

lQN

.... 

0\ o.... o

.... 

hat wind erosion could be 

curring natural wind 

reshold values found at the 

e agricultural sites would 

lId be relatively infrequent 

; wind velocities. 

.... 

a 

o 

cp o

.... 

)( 

.... 

cp o

.... 

)( 

cp o

.... 

)( 

t-. 

O'l 

N 

6.... 

)( 

It') 

-q 

It') 

.... 

0\ 

q 

o b.... 

)( 

Cf') 

oq

.... 

.... 

q 

o 

..

..

q 

o 

lave shown a general increase in 

the modal size of the surface 

ed, however, that the empirical 

.atively weak and demonstrate 

,. Results from the wind 

tween mean grain size and 

lna sites. This most likely 

rs for the sampled sites and the 

ters, such as vegetation and 

a simple bivariate relationship. 

ce level, however, was found to 

le percentage of aggregates 

ationship is: 

Cf') 

-q 

It')

.... 

00 

-q 

\0 

..

..

a

mm) 0.202 

r = 0.58 

(2) 

n= 13 
l

Chepil (1951) and Gillette, 

... 

CD 

"~ ... J:I a: '" CD 2 C "D 

u 2 8 Iii Ii U) u C C.~'"

IlIll1a -8a:l' E~rJa>.!::1ll

o 

o o

.... 

relationships between soil erod 

agricultural and natural desert 

tion of large particles or aggreg 

velocity in at least two ways. F 

too large to be transported at a 

~~'=:.t~~tJ and absorb a large proportion ( 

O¢4l<.O. This effect is noticeable even v 

t: 

t;{ I s C • C ._ a:{ . 

Z ~~ !.~ a1~ O:{.aC«a - "Dullllll"D I- Ii C"i: E E & « QJ.!! IlI :::J:::J_ 

U :::El':::E)-)-« o 

...J ileO ... <J_ 

0

.... E 

E 

-5 

.~

Bagnold (1941), from thee 

observations, found that threst 

can be defined by: 

units is relatively small (ChepiJ 

tend to shield smaller, more ea 

Consequently as the concentra 

threshold shear velocity also it 

'<:t 

'-" 

= 0 

/\ .... c u 

N 

(I) 

w u 

o 

Cl 

N 

0 

'VO 

S 

III=

CD 

!5l

III =

(7) 

0 IX) 

« 

(.:J 

w 

a: 

(.:J 

(.:J 

« 

M 

(oj • 

Q) e ~e

:g~ o . 

.t:: 0 

where (J and p are the particle a 

acceleration due to gravity, Dp 

empirical coefficient equal to a 

Reynolds numbers (B) > 3.5 (B 

of air). 

0 

N 0 

II II

.- ... :::J 

M 

.... 

II 

C 

.t::~ .... (oj 

Q)bO

bOQ)

(oj M M bO Q)bO 

(oj

..... ..... 0 

o Q) 

Although the Bagnold eql 

threshold velocity of well sortE 

" less satisfactory in the predicti 

, soils (Gillette, et al., 1980; Nick 

; no Platter how well sorted, USl 

iii. iii 'i i 

.... It- ci 

~bO

ojg 

',tj 

(oj Q) .... u 

M 

>~

including clays that cause sigr 

',Moreover, non-erodible rough 

and boulders) decrease the me 

, particles thereby increasing thl 

Al13013/\ H'V3HS 010HS3HHl 

0 

.... Similarly, other surface effects 

, residues and clay crusts tend tl 

. (Gillette, et al., 1980; 1982 and 1 

;j 

bO.... 
II 

c 

0 

& 

<i: 

• 

0

.... E 

E 

o:t 

0 

/\ 

U) 

w 

.... 

« 

c:J 

w 

ex:: 

c:J 

c:J 

« 

*-

.... 

M

.... 

II 

- C 

.... -~-~ci

10HS3l:1Hl 

This effect is noticeable even when the concen

units is relatively small (Chepil, 1951). Second

tend to shield smaller, more easily entrained p

Consequently as the concentration of non-erod

threshold shear velocity also increases. 

Bagnold (1941), from theoretical considera

observations, found that threshold shear veloci

can be defined by: 

0' _ P 

U.t=A -p- .g.

( 

where (J and p are the particle and air densities, 

acceleration due to gravity, Dp - the mean pa

empirical coefficient equal to approximately 0.1 

Reynolds numbers (B) > 3.5 (B = 

u .. Dp / y, whe

of air). 

Although the Bagnold equation is quite re

threshold velocity of well sorted sands >0.1 mm 

less satisfactory in the prediction of thresholds 

soils (Gillette, et al., 1980; Nickling, 1984). Natu

no iIlatter how well sorted, usually contain a w

including clays that cause significant variation 

Moreover, non-erodible roughness elements (s

and boulders) decrease the momentum transfe

particles thereby increasing the shear velocity r

Similarly, other surface effects such as moisture

residues and clay crusts tend to stabilize the su

(Gillette, et al., 1980; 1982 and Nick1ing, 1984). 
 10.6 

s by several investigators have shown that the 

sediment over eroding surfaces decreases as a 

ith exponents ranging from approximately -0.25 

odruff, 1957; Shinn, et al., 1976; Gillette, 1977 and 

nship can be expressed by: 

dn=p!!.

dz z (4) 

ation at height z and P is the average slope of 

ight relationship (- -0.3). 

d Shinn, et al. (1976) suggest that the established 

nd in the concentration profiles allows the 

scribed by: 

dn F=K dz (5) 

ity. Under neutral stability conditions, 

K=u.kz (6) 

d k is von Karman's Constant (- 0.4). 

centration follows a power law distribution 

equations 4, 5, and 6, the vertical aerosol flux (F) 10-9 

an be estimated by: 

F=kPu.n (7)

nt concentration (n, J.1g/m3) at the 50 em 

 tunnel during each test run was calculated by: 

W 

n=Rt 10.10 I 

(8) 

10 20 

J1g) of sediment collected on the membrane Shear 
• • 

(4) 

and P is the average slope of 

(- -0.3). 

76) suggest that the established 

:ration profiles allows the 

(5) 

ral stability conditions, 

(6) 

an's Constant (- 0.4). 

s a power law distribution 

Ld 6, the vertical aerosol flux (F) 

by: 

(7) 

(n, Ilg/m3) at the 50 em 

ach test run was calculated by: 

(8) 

collected on the membrane 

unpler nozzle and t is the 

e mean concentration during 

lcentration values measured on 

+ 

10-7 • 

l:!.A •

A 

•

+ 

.~ 0 + 0 

u X 0' ott A 

G)

'" • 

0 N 

E 

u I. 

-

al 0 

U. 

>cO 

.= ·0 

i

u. 10.8 0 

• 0 

Gl « 0

-;;

iii 

u .-* G) •

.+ > 

, 

10.9 

F = 2.33 x 10- 11 u .. 

r = 0.42 

0 n = 67 

10 .104------,..........--...,.....----r"_...,......----r_-

10 20 30 40 50 60 7

Shear Velocity u.. em/sec 

Figure 5: Variation of vertical aerosol flux (F) w

velocity (u..). 
10-6 

he wind tunnel for each test. In almost all cases 

measured concentrations were less than 10%, 

od reproducibility of the sampling technique. 

osol fluxes (F) measured at the thirteen selected 

The measured fluxes range from 1.0 x 10-9 to 6.5 x 

ide intersite variability. Shear velocities 

fluxes range from 17.7 to 80.1 em/sec. 

there is a general increase in the vertical flux 

ity. Although there is a considerable degree of 

 described by the following least squares 

ant at the 0.1 confidence level. 

 =2.33 x 10-11u~·889 (9) 

= 0.42 

=68 

n the data is not unexpected considering the 

ce characteristics such as soil texture, the absence 

st, and the type and percentage of vegetative 

is not a simple bivariate relationship between 

ear velocity but multivariate, with surface 

nd influencing the availability of particles for 

flux rates. 

he data shown in Figure 4 compares very 

ed by Gillette (1977) in terms of both the range of 

 the degree of data scatter. Gillette's data were 

ing a four-year period over nine agricultural 

 characteristics. 

er in the data set, it was partitioned on the basis 

 clay measured in the surface sediments (Figs. 6 

arity of surface morphology and land use. 

tical flux against u. for soils having a combined 

For these silty loams, a relatively high 

ncreasing vertical flux and u: 

'1 I 

LOCATI 

* Mesa 

• Glenc: 

o Marie {\, i I A Yumi 

6 Yum. 

10 7 -I I • Algae 

D Yumc 

it Santa u. 

x' ' Tucso 

::) X Ajo ..J 

u. • Haydl

O' o Salt R 

1 * Casa ( Ljllt .... 

W' E lOB 

est. u 

:'.J' -a. 

« 

to' 

i= 

ffi 

> 

(~,

10-9 

F =6.12 x 10-15 

r =0.75 

n =21 

10 10 , I 

SHE. 

Ftgw.e 6: Variation of vertica -F) ;, velocity (u.) for soil 
l 17.7 to 80.1 em/sec. 

"increase in the vertical flux 

~re is a considerable degree of 

:ollowing least squares 

fidence level. 

(9) 

lnexpected considering the 

;uch as soil texture, the absence 

ld percentage of vegetative 

variate relationship between 

lultivariate, with surface 

availability of particles for 

Figure 4 compares very 

7) in terms of both the range of 

"a scatter. Gillette's data were 

~riod over nine agricultural 

it was partitioned on the basis 

.the surface sediments (Figs. 6 

lorphology and land use. 

.1... for soils having a combined 

lInS, a relatively high 

flux and u...: 

u.. 

x· 

:::> 

-I 

u.. 

-I 

o u 

51 

a:: N' 

W E 10 8 

<t~

-I 01 

e::t: 

u 

Ia:: 

w 

> 

10 9 

10 10 

Figure 6: 

• Algodones 

o Yuma Scrub 

tt Santa Cruz River 

, Tucson Canst. 

X Ajo 

• Hayden

o Salt River 

* Casa Grande 

F = 6.12 x 10-15 u*4.271 

r = 0.75 

n = 21 

-Iy----,--.-.....-.........-TT";----

10 

SHEAR VELOCITY, U* 

Variation of vertical aerosol flux (F

velocity (u...) for soils with silt and c
= 6.12 x 10-15U:·271 (10) 

=0.75 

=21 

al flux with increasing u .. for the sandy soils (silt 

 Figure 7. The relatively poor relationship, 

ot, primarily results from the inclusion of the 

ata. This site, although similar in sand content 

considerably different in terms of surface 

he field on which tests were carried out had 

d and was characterized by well-defined ridges 

ion, the surface was covered with large clods 8-

sulted from ploughing under somewhat moist 

ds were not broken down by abrasion during the 

 acted as large non-erodible roughness elements 

ner soil fractions from deflation (Chepil and 

ts in a much less rapid increase in vertical flux 

ty than was observed at the other four sites. 

e omitted from the regression because of the 

he vertical aerosal flux for the sandy soils can be 

= 7.79 x 10-13u;·027 (11) 

=0.77 

= 19 

bove results, Gillette (1977) found a fairly 

 vertical particle flux with increasing shear 

 soils. He attributes this relatively good 

ty of the dry aggregate structure of the soils 

n contrast, the relationship between vertical flux 

 by Gillette (1977) for loamy soils showed great 

ed to the widely different dry aggregate 

is argument is similar to that used to account 

t the Maricopa agricultural site in this study. 

y not be readily available when estimating 

10.6 

.f, 10.7 -

r 

u.. 

L x· 

:::> 

..J 

u.. 

..J 

H~ u 

. 0 31. ,L D: N 

10 8 

5 .- ..J 01 

-- ct- i' (J 

.~

D: 

W 

> 

I; 

10-9 

10 10 

LOCATII 

* MesaJ 

• Glend 

o Marice 

• Yuma 

A Yuma 

• Algod 

C Yuma 

Santa 

, Tucsol 

X Ajo 

• Hayde 

¢ SaltR 

* Casa c: 

SHE. 

Variation of vertica 

velocity (u..) for soil 

Ag. site data are nc 
lts from the inclusion of the 

hough similar in sand content 

rent in terms of surface 

l tests were carried out had 

erized by well-defined ridges 

,as covered with large clods 8-

ghing under somewhat moist 

n down by abrasion during the 

In-erodible roughness elements 

from deflation (Chepil and 

rapid increase in vertical flux 

rved at the other four sites. 

Le regression because of the 

flux for the sandy soils can be 

7 

(11) 

~tte (1977) found a fairly 

flux with increasing shear 

tes this relatively good 

'egate structure of the soils 

ationship between vertical flux 

) for loamy soils showed great 

different dry aggregate 

nilar to that used to account 

;ricultural site in this study. 

vailable when estimating 

npt was made to partition the 

land use. Despite the limited 

10-7 

u.. 

x-

::J 

...J 

u.. 

...J 

o u en Q) 

o '" cc: N -

UJ E 10 8 

«~

...J Ol 

« 

u 

lcc: 

UJ 

> 

10-9 

Figure 7: 

6 YumaAg 

• Algodoneso YumaScrub 

tl Santa Cruz River 

, Tucson Const. 

X Ajo 

• Hayden o Salt River 

* casa Grande 

10 

SHEAR VELOCITY, U

Variation of vertical aerosol flux 

velocity (u..) for soils with silt and 

Ag. site data are not included in 
1

isturbed Desert Sites, 4) Mine Tailings 

d or Modified by Fluvial Processes, F= 

r = 

Sites, 

n= 

 and 

The wide data scatter and 

ites. for the agricultural sites is mos1 

parameters which are not acc01 

were derived. for all classes except agricultural .This is borne out by the fact the 

sions are typified by relatively high correlation individual sites except Maricop 

 useful for estimating emission rates from 

 are lacking. A great deal of cautipn must be Several authors have sugg 

e criteria on which the classes were based. is related to the amount of materi 

dlaracterize this relationship, t: 

j]ux (F) to horizontal soil flux, q 

nships derived for the morphological land use The horizontal soil flux (q') is c 

transport rate q (g/em sec) by tl 

(Gillette, 1977). 

urbed Desert Sites . Despite the data scatter a s 

fe1ationship can be described by F =7.99 x 10-13u;·99 (12) 

r = 0.76 (F/q'): 

n =10 

r =0. 

n= 6~

F =1.59 X 10-13u~·32 .. A somewhat clearer pictur (13) die basis of soil texture. The ml 

r = 0.61 ~o~ a significant increase in f] 

n =16 

(F/q'): 

s 

r = 0, 

F = 5.82 X 1O-15u~·24 n=21 (14) 

r =0.81 

: This result is very similar 

n= 10 found that the flux ratio increa: 

,pproximately 4.0. 
all classes except agricultural 

by relatively high correlation 

Lting emission rates from 

~eat deal of caution must be 

:h the classes were based is 

r the morphological land use 

99 

(12) 

32 

(13) 

Z4 

(14) 

The wide data scatter and the lack of a sig

for the agricultural sites is most likely related t

parameters which are not accounted for in a si

This is borne out by the fact that significant rel

individual sites except Maricopa. 

Several authors have suggested that the v

related to the amount of material transported i

characterize this relationship, the dimensionles

flux (F) to horizontal soil flux, q' (g/cm2 sec) ha

The horizontal soil flux (q') is calculated by div

transport rate q (g/em sec) by the height of the 

(Gillette, 1977). 

Despite the data scatter a statistically signif

relationship can be described by: 

fF/q'}= 3.14x 1O-10u;·8

r =0.54 

n=68 

A somewhat clear~r picture is obtained if t

the basis of soil texture. The more loamy textur

sho~ a significant increase in flux ratio with in

fF/q'l = 5.01 x 1O-12u~·0

r =0.63 

n=21 

This result is very similar to that presented 

found that the flux ratio increased with shear v

approximately 4.0. 

A similar, but somewhat weaker, relations

sandy textured soils (silt + clay <15%). 
•• 

0 

• 

•tr l:> 

l:>

 l:> • ., 

• 70 0 

rtr

• 

•

0 

I LOCATION 

X,. 0 ox. "'Ie • Mesa Ag. Site 

• Glendale Const. 

o Maricopa Ag. 

Xf- ... Yuma Dist. Desert 

• ...

• 

l:> YumaAg 

• -. • Algodones 

° Yuma Scrub 

0 tr Santa Cruz River 

, Tucson Const. 

X Ajo 

• Hayden 

o Salt River 

, • Casa Grande 

•

F/q' = 3.14 x 10.10 u.

2

.

85 

r=O.54 

n=68 

(F/q'): r = O. 

IJ.·~ n 

= 1~

,. The above relationships dl 

the emission of fine particulate 

produced more fine dust per u 

textured soils. The increase of 

,Je"centage of silt and clay also 

particulates at a much higher rc 

4.3 Aerosol Grain-Size Chara£ 

~.; Frequency size distributiol 

tUnnel tests are shown in Table 

of'both the aerosols and the ass 

In general, the aerosols art 

distributions with weak to moe 

grains). The most striking feat 

similarity. Almost all the dish 

15-10.0 J.1ID size range. The on 

agricultural site, which has strc 

. classes reflecting the relatively 

parent soil (Table 3). 

~~,

, .,. The mean size of the aero: 

l'emarkable uniformity of meat 

~th standard deviations rangi 

being from 3.25 to 3.55 J.1ID. n 

been reported by Gillette, et al. 

Nickling (1983). It is suggestee 

.fine-grained aerosols 0-20 J.1ffi 

.t:elocities of these particles. 

.-: Gillette (1974) suggests th 

i.mall and that their sedimenta 

~ost all eroding winds and' 
I 

LOCATION 

t Mesa Ag. Site 

• Glendale Const. 

J Maricopa Ag. 

.. Yuma Dist. Desert 

YumaAg 

• Algodones 

] Yuma Scrub 

:t Santa Cruz River 

• Tucson Const. 

( Ajo 

Hayden 

> Salt River 

, Casa Grande 

.85 

I 

00 

aerosol flux (F) to horizontal 

~p with increasing shear velocity. 

produced more fine dust Per unit horizontal so

textured soils. The increase of the exponent va

percentage of silt and clay also indicates that th

particulates at a much higher rate as shear velo

4.3 Aerosol Grain-Size Characteristics 

Frequency size distributions of the aerosol

tunnel tests are shown in Table 2. The mean si

of both the aerosols and the associated surface s

In general, the aerosols are characterized b

distributions with weak to moderate positive sk

grains). The most striking feature of the size di

similarity. Almost all the distributions have m

2.5-10.0 Jllll size range. The one major exceptio

agricultural site, which has strong modes in the 

classes reflecting the relatively high silt and cla

parent soil (Table 3). 

The mean size of the aerosols range from 1

remarkable uniformity of mean sizes. The aero

with standard deviations ranging from 1.69 to 3

being from 3.25 to 3.55 Jllll. The relatively poor 

been reported by Gillette, et al. (1972), Patterson 

Nickling (1983). It is suggested that the rather p

fine-grained aerosols (1-20 Jllll) results from th

velocities of these particles. 

Gillette (1974) suggests that particles less th

small and that their sedimentation velocities ar

almost all eroding winds and remain in suspen

Since all particles «20 Jllll) that are ejected into 

remain in suspension, the size distributions ten

(Le. poorly sorted) as a result of turbulent mixin

velocity or textural characteristics of the parent 
I

.

ed, there is a great similarity in the mean sizes of 

espite a considerable difference in the textural 

ce sediments from which the aerosols were 

nsistent relationship is evident between the mean 

 at which the suspended sediments were 

onsistent relationships between the mean size of 

ze range with shear velocity and textural 

nt soils has been noted by several authors. 

e (1977a), from their study of aerosols over eroding 

distributions are characterized by three distinct 

be present under a given set of conditions. The 

characteristic modes A, B and C. Mode A, which 

ticles having diameters between 2 and 20 J.1IIl, is 

ed aerosols but does not appear to be related to the 

ent soil. Mode B is centered between 20 and 

 of the particle size distribution of the parent soil. 

 under conditions of heavy to moderate dust 

red between 0.04 and 0.1 J.1IIl. In general, it is not 

 in composition or origin but is characteristic of a 

ntration related to the transient nuclei mode of 

). 

 (1974) suggest that mode B is characteristic of 

se soil aggregates, while mode A results from the 

he saltation process (sandblasting) and the 

aggregated material into the atmosphere. As the 

 the threshold for erosion, the first particles to be 

th diameters between 40 and 100 J.1IIl. The initial 

e to saltation in which the particles bounce along

 particles collide with other particles on the 

aggregating smaller particles which are injected 

roduce mode A. The larger particles which form 

ly settle out because of their high sedimentation 

latively narrow range of particle sizes is kept aloft 

cal velocity fluctuations. 

rt process, related to the turbulent nature of most 

or the narrow range of mean sizes and poorly 

DISCUSSION 

The collected data reveale 

. ~cluding the Algodones dune 

agricultural sites, have higher 

particulate fluxes than the othe: 

. iPSQciated with several importe 

resulting from the presence of I 

these soils from erosion for all 

lD\ount of vegetative cover pIa 

aerosol flux because of momeI1 

effects. Precipitation is also an 

~ticulate emissions from des. 

emissions by the simple wettin 

short lived because of the higt 

Of greater importance is the in, 

\Yegetation pattern and surface 

During periods of increa~

\when temperatures and evapol 

annual grasses may become est 

if these grasses do not survive 

stubble can persist for several 

,emission (Brazel and Nickling, 

The frequency and intensi 

fdevelopment and maintenanCE 

and redistributes clay particles 

sediment out during infiltratic 

rainfall events may break up S' 

effectiveness; thereby increasir 

(Gillette, et al., 1982). 

, A final consideration for 

tusruptions of the surface. Lo) 

deflation of erodible material c 

effectively armours the surfacl 

The stability of these soils can 

such as off-road vehicles or 0' 
y 

lted by several authors. 

r study of aerosols over eroding 

aracterized by three distinct 

. given set of conditions. The 

~s A, B and C. Mode A, which 

eters between 2 and 20 JlI11, is 

s not appear to be related to the 

:; centered between 20 and 

distribution of the parent soil. 

:>f heavy to moderate dust 

\d 0.1 JlI11. In general, it is not 

origin but is characteristic of a 

the transient nuclei mode of 

t mode B is characteristic of 

while mode A results from the 

i (sandblasting) and the 

at into the atmosphere. As the 

!rosion, the first particles to be 

~n 40 and 100 JlI11. The initial 

hich the particles bounce along 

rith other particles on the 

!r particles which are injected 

'he larger particles which form 

ie of their high sedimentation 

\ge of particle sizes is kept aloft 

tions. 

to the turbulent nature of most 

! of mean sizes and poorly 

:ollected during the wind 

associated with several important factors. The 

resulting from the presence of clay and natural 

these soils from erosion for all but extremely h

amount of vegetative cover plays a significant 

aerosol flux because of momentum partitionin

effects. Precipitation is also an extremely impo

particulate emissions from desert soils. Althou

emissions by the simple wetting of the surface, 

short lived because of the high evaporation ra

Of greater importance is the indirect effect prec

vegetation pattern and surface crusting. 

During periods of increased rainfall, parti

when temperatures and evaporation rates are l

annual grasses may become established thereby 

if these grasses do not survive subsequent sum

stubble can persist for several years acting as a

emission (Brazel and Nickling, 1986). 

The frequency and intensity of precipitatio

development and maintenance of surface crust

and redistributes clay particles and allows them 

sediment out during infiltration and evaporati

rainfall events may break up surface crusts, red

effectiveness; thereby increasing the susceptibil

(Gillette, et al., 1982). 

A final consideration for the desert soils i

disruptions of the surface. Long disturbance-fr

deflation of erodible material and the developm

effectively armours the surface; thereby reduci

The stability of these soils can be seriously affec

such as off-road vehicles or overgrazing, which 

erodible particles available for transport. In co

agricultural soils is related to their ridged surfa

which protect the finer soil fractions from defl

threshold shear velocity. 
eration in the determination of aerosol fluxes 

dressed is the decrease in flux through time as 

a lag of non-erodible grains develops at the 

study were measured in the order of minutes and 

ns the deflation of the fine-grained particulates 

. The surface then became stable as a lag of non

ed (>0.84 mm) which effectively sheltered the 

nsequently, the erosion system involves an 

The surface will not produce a given aerosol flux 

for an indefinite period of time. This relationship 

further research is necessary to examine the decay 

urfaces, soil textures and for the degree of 

d more light on the question of the relative 

rfaces in the production of atmospheric aerosols 

he variety of sites tested, it was apparent that 

riodic disturbance such as the river channels and 

 greatest potential for increased aerosol 

greater sediment supply and lower threshold 

ral desert sites, controlled construction sites, and 

reduced emission potential because of their 

ocities and lower flux values because sediment 

 such as progressive armouring, surface crusting 

. 

y indi~tes the usefulness of in situ testing using 

Previous to this research, the most detailed data 

ural surfaces was that presented by Gillette (1977). 

ace over a four-year period, with a limited range 

ontrast, data collection for the present study was 

ately eight weeks for a wide range of velocity and 

mparable results. 

Il'azel, A.J., and Nickling, W.G., 

dust storm generation in A 

'Chepil, W.S., 1951: Properties 0 

State of dry aggregate strucl 

Chepil, W.S., and Woodruff, N.F 

storms: IT, Visibility and dl 

Chepil, W.S., and Woodruff, N.F 

control, Advances in Agr~

Complin, P.G., and Piersol, P., 1 

emissions, Proceedings Thi 

Measurement and Control, 

Gillette, D.A., 1977: Fine partict 

ASA, 80: 890-897. 

Gillette, D.A., 1978: A wind tun 

of soil texture, sandblasting 

production, Atmos. Envir01 

tGillette, D.A., and Goodwin, P.A 

., soil aggregates eroded by \\ 

':Gillette, D.A., Blifford, I.H., Jr., a 

aerosol on land subject to , 

tGillette, D.A., Adams, J., Endo, .. 

velocities for input of soil I 

Res., 85: 5621-5630. 

Gillette, D.A., Adams, J., Muhs, 

, velocities and rupture mod 

; soil particles into air, J. Gee 

{'Leathers, C.R., 1981: Plant com] 

significance for man, In: Pl 

characteristics and effects on 
rosion system involves an 

lot produce a given aerosol flux, 

period of time. This relationship:; 

s necessary to examine the decay 

ll'es and for the degree of 

he question of the relative 

luction of atmospheric aerosols 

tested, it was apparent that 

e such as the river channels and 

I for increased aerosol 

supply and lower threshold 

mtrolled construction sites, and 

L potential because of their 

flux values because sediment 

:ive armouring, surface crusting 

efulness of in situ testing using 

'esearch, the most detailed data 

that presented by Gillette (1977). 

ar period, with a limited range 

:lion for the present study was 

for a wide range of velocity and 

;and and Desert Dunes, Morrow, 

p, , 

, , 

storms: IT, Visibility and dust concentratio

Chepil, W.S., and Woodruff, N.P., 1963: The ph

control, Advances in Agronomy, 15: 211

Complin, P.G., and Piersol, P., ~978: Uran~um 

emissions, Proceedings Third SympOSIum 

Measurement and Control, San Francisco, 

Gillette, D.A., 1977: Fine particulate emissions 

ASA, 80: 890-897. 

Gillette, D.A., 1978: A wind tunnel simulation 

of soil texture, sandblasting, wind speed an

production, Atmos. Environ., 12: 1735-174

Gillette, D.A., and Goodwin, P.A., 1974: Micros

soil aggregates eroded by wind, J. Geophys. 

Gillette, D.A., Blifford, I.H., Jr., and Fenster, D.R

aerosol on land subject to wind erosion, J. 

Gillette, D.A., Adams, J., Endo, A., Smith, D., an

velocities for input of soil particles into air 

Res., 85: 5621-5630. 

Gillette, D.A., Adams, J., Muhs, D., and Kihl, R

velocities and rupture moduli for crusted d

soil particles into air, J. Geophys. Res., 87: 9

Leathers, C.R., 1981: Plant components of deser

significance for man, In: Pewe, T. (Ed.), De

characteristics and effects on man, Geologic

Special Paper 186, p. 191. 
n sediment transport during dust storms: Slims 

erritory, Canada, Canad. ]. Earth Sci., 15: 

n size characteristics of sediment transported 

Sed. Pet., 53: 1011-1024. 

tabilizing role of bonding agents on the 

nt by wind, Sedimentology, 31: 111-117. 

A.J., 1984: Temporal and spatial characteristics 

s,]. Climatol.,4: 645-660. 

, D.A., 1977a: Commonalities in measured size 

ols having a soil-derived component, 

4-2082. 

, D.A., 1977b: Measurements of visibility vs. 

 airborne soil particles, Atmos. Environ., 11: 

, 1974: Grain-size distribution within glacial 

3-46. 

, 1973: Gelatin-coated microscope slides in 

sis,]. Sed. Pet., 43: 1174-1175. 

t: an overview, In: Pewe, T.L. (Ed.) Desert Dust: 

nd Effect on Man, Special Paper 186, The 

merica, BouJder, CO, pp. 1-10. 

1971: Comparison between the light extinction 

tion relationship of atmospheric and air 

osols, Atmos. Environ., 5: p. 209. 

ogische Anwendung der Stromungslehre, Beitr., 

XIX: 188-202. 

, J.H., Kennedy, J.C., Kova 

Observations of dust flux i.J 

nonsteady cases, Proceedil 

Particulate and Gaseous Po 

Washington, Energy Resec 

SYmposium Series CONF-'i 

Willeke, K., and Whitby, K.J., 1~

interpretation, ]. Air Poilu 

Wooding, R.A., 1968: A low-sp 

meteorology, 1, General {.; 

Ind. Res. Organ., Aust. Div. 

Paper 25, pp. 3-24. 
f bonding agents on the 

limentology, 31: 111-117. 

poral and spatial characteristics 

645-660. 

:omrnonalities in measured size 

•i1-derived component, 

~easurementsof visibility vs. 

•artic1es, Atmas. Environ., 11: 

ze distribution within glacial 

coated microscope slides in 

3: 1174-1175. 

,In: Pewe, T.L. (Ed.) Desert Dust: 

:n, Special Paper 186, The 

, CO, pp. 1-10. 

;on between the light extinction 

p of atmospheric and air 

nviron., 5: p. 209. 

Lung der Stromungslehre, Beitr., 

Willeke, K., and Whitby, K.J., 1975: Atmospheri

interpretation, ]. Air Pollution Control Ass

Wooding, R.A., 1968: A low-speed wind tunnel 

meteorology, 1, General design considerat

Ind. Res. Organ., Aust. Div. Plant Ind., Canb

Paper 25, pp. 3-24.