The Dirt on Dust

Rich Arimoto

Carlsbad Environmental Monitoring & Research Center New Mexico State University

2nd Mineral Dust Workshop10 -12 September 2003, Paris

Part I

Carlsbad (New Mexico) Studies

• Underground repository for transuranic waste

• Located in Chihuahuan Desert near Carlsbad, NM

• Disposal rooms 2150 feet underground in ancient salt caverns

WasteIsolationPilotPlant

WIPP-EM Aerosol Sampling Stations

On Site

Ambient Aerosol Sampling Schedule

Day

MondayTuesdayWednesdayThursdayFridaySaturdaySundayMondayTuesdayWednesdayThursdayFridaySaturdaySunday

Type of Sample

Ions

Radionuclides (4- 6 weeks)

Trace Elements

Ions

Trace Elements

Ions

Trace Elements

Week 1

Week 2

239,240Pu in aerosol (TSP) samples shows a strong seasonal cycle

Start Date of Sample Collection

Jan Jul Jan Jul Jan Jul Jan Jul Jan Jul Jan

Act

ivity

Con

cent

ratio

n, B

q m

-3

0

20x10-9

40x10-9

60x10-9

80x10-9

1998 1999 2000 2001 2002 | | | | | |

Cactus Flats Near Field Hobbs On Site

A seasonal cycle in 239,240Pu has been previously observed.*

But the causes for the seasonal cycles in the current vs. historical data are different.

*Perkins & Thomas, 1980

Alu

min

um,

g m

-3

0

1

2

3

4

5

6

Cactus FlatsNear FieldOn Site

Date of Sample Collection (Midpoint)

01/98 07/98 01/99 07/99 01/00 07/00 01/01 07/01 01/02 07/02

Alu

min

um,

g m

-3

0.0

0.5

1.0

1.5

Dichot--Coarse Fraction

Dichot--Fine Fraction

Current data suggests an association of 239,240Pu with aluminum, an indicator of mineral dust

239,240Pu activities are correlated with aluminum, and the 239,240Pu/Al relationships are similar at all sites

239,240Pu Activity Concentration, Bq m-3

0 20x10-9 40x10-9 60x10-9 80x10-9

Alu

min

um,

g m

-3

0

1

2

3

4

5

6

7

Cactus Flats Near Field On Site

Where does the 239,240Pu (and 241Am) come from?

Current 239,240Pu Levels in Soils (courtesy H. Beck)

Beck, H. L., and B. G. Bennett, Historical overview of atmospheric nuclear weapons testing and estimates of fallout in the continental United States, Health Physics, 82, 591-608.

Carlsbad is not a Pu hotspot—the Pu is probably associated with resuspended global fallout

Carlsbad

…but about half of the 239,240Pu activity is in the PM10 fraction, implying contributions from local sources

TSP 239,240Pu Activity Concentration (Bq m-3)

0 20x10-9 40x10-9 60x10-9 80x10-9

PM10

239,

240 P

u Act

ivity

Con

cent

ratio

n (Bq

m-3

)

0

20x10-9

40x10-9

60x10-9

80x10-9

Cactus FlatsNear Field

Intercept = -1.2 E-10Slope = 0.58R2 = 0.57

How strong is the radionuclide/dust link globally?

http://geography.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Fpubs.usgs.gov%2Fgip%2Fdeserts%2Fwhat%2Fworld.html

Atmospheric Nuclear Test Sites

(adapted from Beck & Bennett, 2002)

Non-Polar Arid Lands

Deserts sites were used for the atmospheric testing of nuclear weapons

Alamagordo

NTS(USA)

Johnston Is. Christmas Is.Malden Is.

Mururoa Fangataufa

(USA)

Reggane (FR)

• Kapustin Yar • Totsk

•

Semipalatinsk• Lop Nor

Monte Bello Is.

Maralinga• Emu

• Bikini

Enewetak

Novaya Zemlya

• • •

•

• •

•

•

(USA)• •

• •

•

•

Recent trends of plutonium fallout observed in Japan: plutonium as a proxy for desertification

K. Hirose , Y. Igarashi , Michio Aoyama , C. K. Kim , C. S. Kim and B. W. Chang  Abstract: Plutonium in monthly deposition samples collected in Tsukuba (the Meteorological Research Institute), Japan from 1990 to end of 2001 is reported, together with monthly plutonium deposition in Nagasaki and Yonaguni in 2000. The annual deposition of 239,240Pu during the period from 1990 to 2001 shows no systematic inter-annual variation. However, monthly 239,240Pu depositions show a typical seasonal variation with a maximum in spring season (March to April), which corresponds to seasonal cycle of soil dusts originating from the East Asian arid area. Plutonium isotopic ratios in the deposition samples suggest that significant amounts of the recent 239,240Pu deposition observed in Japan are attributed to the resuspension of plutonium-bearing surface soil particles; resuspended plutonium originates from the East Asian arid areas. The recent increased tendency of 239,240Pu content in residues in deposition samples may reflect desertification in the East Asian continent.

 J. Environ. Monit., 2003, 5 (2), 302 - 307

A recent study indicates that Asian dust also is contaminated with plutonium!

Part I I

ACE- Asia Studies

Chemical Composition of Atmospheric Aerosols from Zhenbeitai, People’s Republic of China, and Gosan, South Korea, during ACE-Asia

 R. Arimoto, X. Zhang, B. J. Huebert, C.H. Kang, J. M. Prospero, D. Savoie, S. Sage, C. A. Schloesslin, and H. Khaing

Rishiri

Sado

Hachijo

Chichijima

Seoul

GosanGosan

Amami

30oN

40oN

20oN

10oN

50oN

60oN

160oE100oE 140oE120oE 180o

Midway

ACE-Asia Ground Station Network

Fukue

Tango

Lan-yuHong Kong

Beijing

Qingdao

Linan

ZhenbeitaZhenbeitaiiDunhuang

Wan-li

Sampling & Analyses

Zhenbeitai IMPROVE-type sampler (PM2.5) IC & ICP-MS at CEMRC TSP sampler IC at UH, PIXE at IEE/BNUGosan High-volume bulk sampler IC & ICP/MS at CEMRC (Same sampler used for PEM-West)

Concentration (g m-3) Ion

Type of

Sample

Number of

Samples Mean Standard Deviation

Correlation with Al (r)

PM2.5 9 6.0 4.2 0.87 WS Ca2+

TSP 56 14.0 16.8 0.85

PM2.5 8 0.51 0.29 0.57 WS K+

TSP 56 0.32 0.33 0.68

PM2.5 9 0.38 0.1.2 0.81 WS Mg2+

TSP 56 0.48 0.43 0.85

PM2.5 9 0.99 1.1 0.89 WS Na+

TSP 56 1.07 1.02 0.74

Water Soluble (WS) Cations in Aerosol Samples from Zhenbeitai (ZBT): Concentrations and Relationships to Aluminum

Cations are correlated with aluminumAt Zhenbeitai

ACE-Asia

Al Ca WS Ca2+ K WS K+ Mg WS Mg2+ Na WS Na+

Al 58 54 64 53 63 54 63 53

Ca 0.93 50 58 50 58 50 59 46

WS Ca2+ 0.64 0.72 54 53 54 55 55 51

K 0.87 0.94 0.54 53 63 54 63 52

WS K+ 0.71 0.72 0.76 0.64 52 53 53 50

Mg 0.82 0.83 0.38 0.89 0.58 54 63 51

WS Mg+ 0.58 0.61 0.68 0.57 0.82 0.65 55 51

Na 0.31 0.37 0.59 0.43 51

WS Na+ 0.64 0.67 0.47 0.63 0.77 0.72 0.82 0.55

Correlations (r-values) Bold, p < 0.01Plain, p < 0.05, Blanks , ns.

At Gosan Alkali/alkaline earths, major cations and Al are generally correlated

Correlation Matrix

Numbers of sample pairs

ACE-Asia

Aluminum, g m-3

10-1 100 101 102 103

Calci

um or

WS

Calci

um,

g m-3

10-1

100

101

102

103

0.331

Calcium, PM2.5

Calcium, TSP (North)

WS Calcium, PM2.5

WS Calcium, TSP (North)

water-soluble calcium is about equal to total calcium

At Zhenbeitai both WS and total Ca are correlated with aluminum

Aluminum, g m-3

10-2 10-1 100 101 102 103

Calci

um or

WS

Calci

um,

g m-3

10-1

100

101

102

103

0.10.331WS Calcium, TSPCalcium, TSP

Ca & Al concentrations are lower

At Gosan (compared with Zhenbeitai)

a smaller percentage of Ca is water soluble both WS and total Ca are correlated with Al, but the ratios to Al are lower

TSP, North Winds TSP, South Winds PM2.5

Zhenbeitai: large particle sulfate sometimes accompanies the dust

Aluminum vs Sulfate

50 0.67

8 0.11

N r

TSP (North)PM2.5

Feb Mar Apr May Jun

Sul

fate

, g

m-3

0

10

20

30

40

50

Date of Sample Collection (2001)

Feb Mar Apr May Jun

Sol

uble

Cal

cium

, g

m-3

0

20

40

60

80

100

120

140

160

Al & sulfate are correlated in TSP samples, but not PM2.5

Soluble Calcium, g m-3

0 20 40 60 80 100 120 140

Sul

fate

to S

olub

le C

alci

um(M

olar

Rat

io)

0.001

0.01

0.1

1

10

100

Soluble Calcium, g m-3

0 20 40 60 80 100 120 140

Nitr

ate

to S

olub

le C

alci

um

(Mol

ar R

atio

)

0.001

0.01

0.1

1

10

100

Sulfate/WS Ca2+ molar ratio averages 0.090 ± 0.035 Nitrate/WS Ca2+ molar ratio averages 0.015 ± 0.005

At Zhenbeitai during high dust events (> 40 µg m‑3 soluble Ca)

Sulfate and nitrate in dust prior to mixing?

TSP, North Winds

TSP, South Winds

PM2.5

the sulfate/WS Ca2+ molar ratio is about 5 to 10X higher than at ZBT the correlation between sulfate and Al is lower than at ZBT (r = 0.35),

but still significant Daily Multi-day

At Gosan

Soluble Calcium, g m-3

0 2 4 6 8

Sul

fate

to S

olub

le C

alci

um(M

olar

Rat

io)

0.01

0.1

1

10

100

ACE-Asia

Observations and Possible Explanations

The sources for dust at ZBT and GOS are different

Calcium and especially WS Ca2+ are preferentially removed relative to Al during transport

Pollution sources mix non-crustal proportions of Ca, Al and sulfate with the dust

Differences in Ca and WS(Ca2+) concentrations at ZBT & GOS

Higher percentage of WS(Ca2+) at ZBT

Higher sulfate/WS(Ca2+) ratio at GOSSulfate/Al correlation lower at GOS

Summary: There’s (probably) dirt on that dust!

Dust from Carlsbad, NM is contaminated with transuranic radionuclidesAsian dust/major ion relationships

Al vs. cation relationships demonstrated

Al & sulfate tend to be correlated, but there’s a need to better constrain element/ion relationships in source materials

Ca results are perplexing--need to evaluate source differences vs. differential removal vs. weathering reactions

,1

;n

t dW VT V t

Wind threshold-distance

(Wt,d) is the sum of the products of the wind velocities (V) above the threshold (t) and duration (T)

Wt,d measures wind travel and has units of meters

Relationship between 239,240Pu and wind speed

Relationships between wind threshold-distance and 239,240Pu activity vary as a function of threshold velocity

Threshold Velocity (m sec-1)0 2 4 6 8 10 12 14 16

Corr

elatio

n Coe

fficie

nt (r

)

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6