1. Measurement of Carbonate Minerals in Aerosol Samples- A Preliminary Study Johann Engelbrecht Desert Research Institute

2. X-ray Diffraction (XRD) XRD measures the presence and concentration of crystalline compounds (phases) such as minerals It does not record chemical concentrations

3. X-ray Diffraction (XRD) Scan RS611-38 µm

4. X-ray Diffraction (XRD) Scan RS611-PM 10

5. X-ray Diffraction (XRD) Scan RS611-PM 2.5

6. X-ray Diffraction (XRD) Scan RS667-µm

7. X-ray Diffraction (XRD) Scan RS667-PM 10

8. X-ray Diffraction (XRD) Scan RS646-38µm

9. X-ray Diffraction (XRD) Scan RS646-PM 10

10. Minerals Identified in 20 Re-suspended Aerosol Filter Samples Quartz [SiO 2 ] (common) Carbonate Minerals –Calcite [CaCO 3 ] –Aragonite [CaCO 3 ] –Dolomite [CaMg(CO 3 ) 2 ] Layered Silicates –Micas such as Muscovite –Vermiculite –Clays such as Dickite, Kaolinite & Montmorillonite –Chlorite

11. Minerals Identified in 20 Re-suspended Aerosol Filter Samples Feldspar Minerals –Anorthite –Microcline Oxides –Rutile Gypsum [CaSO 4.2H 2 O]

12. Chemical vs Mineralogical Ratios

14. Soluble Ca vs Total Ca

15. Carbonate vs Soluble Ca

16. OC4 vs Soluble Ca

17. Carbonate vs Total Ca

18. OC3 vs Total Ca

19. OC4 vs Total Ca

20. OC4 vs Carbonate

21. Chemical vs Mineralogical Ratios

22. Mineralogical Reactions CaCO 3 + SiO 2 = CaSiO 2 + CO 2 calcite + quartz wollastonite 490 – 550 o C

23. Mineralogical Reactions CaMg(CO 3 ) 2 + 4SiO 2 + H 2 0 = dolomite + quartz + water Mg 3 SiO 4 O 10 (OH) 2 + 3CaCO 3 + CO 2 talc + calcite 150 – 250 o C

24. Question With the current TOR method, are we quantitatively measuring all the carbonate in the aerosol samples?

25. 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