Measurement of Carbonate Minerals in Aerosol Samples- A

Preliminary Study

Johann EngelbrechtDesert Research

Institute

X-ray Diffraction (XRD)• XRD measures the presence

and concentration of crystalline compounds (phases) such as minerals

• It does not record chemical concentrations

X-ray Diffraction (XRD) ScanRS611-38 µm

X-ray Diffraction (XRD) ScanRS611-PM10

X-ray Diffraction (XRD) ScanRS611-PM 2.5

X-ray Diffraction (XRD) ScanRS667-µm

X-ray Diffraction (XRD) ScanRS667-PM10

X-ray Diffraction (XRD) ScanRS646-38µm

X-ray Diffraction (XRD) ScanRS646-PM10

Minerals Identified in 20Re-suspended Aerosol Filter

Samples• Quartz [SiO2] (common)• Carbonate Minerals

– Calcite [CaCO3]– Aragonite [CaCO3]– Dolomite [CaMg(CO3)2]

• Layered Silicates– Micas such as Muscovite– Vermiculite– Clays such as Dickite, Kaolinite &

Montmorillonite– Chlorite

Minerals Identified in 20 Re-suspended Aerosol Filter

Samples• Feldspar Minerals

– Anorthite– Microcline

• Oxides– Rutile

• Gypsum [CaSO4.2H2O]

Chemical vs Mineralogical Ratios

CAXC/SIXC vs Carbonate/Quartz

y = 0.5305x - 4.3187R2 = 0.7639

0

100

200

300

0 100 200 300Carbonate/Quartz, XRD

CAXC

/SIX

C, C

hem

ical

Chemical vs Mineralogical Ratios

CAAC/SIXC vs Carbonate/Quartz

y = 0.4333x - 3.741R2 = 0.7315

0

100

200

300

0 100 200 300Carbonate/Quartz, XRD

CAAC

/SIX

C, C

hem

ical

Soluble Ca vs Total CaCAAC vs CAXC

y = 0.8566x - 0.4067R2 = 0.9007

0

4

8

12

16

20

0 4 8 12 16 20Calcium % by XRF

Solu

ble

Calc

ium

% b

y AA

MeasuredAll SolubleLinear (Measured)Linear (All Soluble)

Carbonate vs Soluble Ca

Carbonate vs CAAC

y = 0.9286x + 1.2187R2 = 0.7327

0

8

16

24

32

0 8 16 24Soluble Calcium by AA

Car

bona

te %

by

TOR

MeasuredTheoreticalLinear (Measured)

Linear (Theoretical)

OC4 vs Soluble CaO4TC vs Soluble Calcium

y = 0.2006x + 0.0487R2 = 0.3959

0

1

2

3

4

5

0 4 8 12 16 20 24Soluble Calcium % by AA

O4T

C %

Carbonate vs Total Ca

Carbonate vs Calcium by XRF

y = 0.7552x + 1.1622R2 = 0.5948

0

8

16

24

32

0 8 16 24Total Calcium % by XRF

Car

bona

te %

by

TOR

MeasuredTheoreticalLinear (Measured)Linear (Theoretical)

OC3 vs Total CaO3TC vs Total Calcium

y = 0.0244x + 0.894R2 = 0.0574

0.0

0.4

0.8

1.2

1.6

2.0

0 4 8 12 16 20 24Total Calcium % by XRF

O3T

C %

OC4 vs Total CaO4TC vs Total Calcium

y = 0.2118x - 0.3516R2 = 0.5418

0

1

2

3

4

5

0 4 8 12 16 20Total Calcium % by XRF

O4T

C %

OC4 vs CarbonateO4TC vs C3TC

y = 0.1131x + 0.5249R2 = 0.1481

0

1

2

3

4

5

0 8 16 24 32C3TC % by TOR

O4T

C %

Chemical vs Mineralogical Ratios

Carbonate by TOR/SIXC vs Carbonate/Quartz

y = 0.3775x + 6.3167R2 = 0.5755

0

100

200

300

0 100 200 300Carbonate/Quartz, XRD

Carb

onat

e by

TO

R/SI

XC

Mineralogical Reactions

CaCO3 + SiO2 = CaSiO2 + CO2

calcite + quartz wollastonite

490 – 550 oC

Mineralogical Reactions

CaMg(CO3)2 + 4SiO2 + H20 = dolomite + quartz + water

Mg3SiO4O10(OH)2 + 3CaCO3 + CO2

talc + calcite

150 – 250 oC

Question• With the current TOR

method, are we quantitatively measuring all the carbonate in the aerosol samples?

Conclusions• Minerals can play an important

role in aerosol samples which contain a significant amount of soil dust

• XRD is an appropriate analytical tool for identifying & quantifying minerals on filter samples, but does require research

• The TOR method for the measurement of mineral carbonate should be reviewed