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Measurement of Carbonate Minerals in Aerosol Samples- A Preliminary Study. Johann Engelbrecht Desert 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.
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Measurement of Carbonate Minerals in Aerosol Samples- A Preliminary Study Johann Engelbrecht Desert 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) Scan RS611-38 µm
X-ray Diffraction (XRD) Scan RS611-PM10
X-ray Diffraction (XRD) Scan RS611-PM 2.5
X-ray Diffraction (XRD) Scan RS667-µm
X-ray Diffraction (XRD) Scan RS667-PM10
X-ray Diffraction (XRD) Scan RS646-38µm
X-ray Diffraction (XRD) Scan RS646-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]
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