Presentation is loading. Please wait.

Presentation is loading. Please wait.

Total Carbon (TC) = Total Organic Carbon (TOC) + Total Inorganic Carbon (TIC) TOC preparation: ~0.25 g dry, powdered sample acidified in baked glass beaker.

Similar presentations


Presentation on theme: "Total Carbon (TC) = Total Organic Carbon (TOC) + Total Inorganic Carbon (TIC) TOC preparation: ~0.25 g dry, powdered sample acidified in baked glass beaker."— Presentation transcript:

1 Total Carbon (TC) = Total Organic Carbon (TOC) + Total Inorganic Carbon (TIC) TOC preparation: ~0.25 g dry, powdered sample acidified in baked glass beaker with 1N 60 o C for hours filtered with de-ionized water to flush out Cl- onto a baked glass fiber filter transferred to a crucible boat for drying and elemental analysis Calcite

2 Trace elements coprecipitated with secondary soil minerals and soil organic matter (SOM) Fe and Al oxidesB, P, V, Mn, Ni, Cu, Zn, Mo, As, Se Mn oxidesP, Fe, Co, Ni, Zn, Mo, As, Se, Pb Ca carbonatesP, V, Mn, Fe, Co, Cd IllitesB, V, Ni, Co, Cr, Cu, Zn, Mo, As, Se, Pb SmectitesB, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb VermiculitesTi, Mn, Fe Organic matterAl, V, Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, P, N SolidCoprecipitated trace elements

3 CCS north-facing CCN south-facing 1A 2A 3A 4A 3A 4A

4 X-ray fluorescence (XRF) The technology was developed in the 1950s.

5 X-ray fluorescence (XRF): The emission of characteristic "secondary", or fluorescent, X-rays from a material that has been excited by bombarding with high- energy X-rays or gamma rays.

6 Irradiating an atom with high-energy primary X-ray photons delivers sufficient energy for an electron to be ejected completely out of the atom. An outer shell L electron falls inward to fill the void created in the inner shell, and an X-ray characteristic of the atom's elements is emitted.

7 Schematic arrangement of wavelength dispersive spectrometer. X-ray fluorescence (XRF) spectrometers Schematic arrangement of energy dispersive spectrometer The dispersion and detection are a single operation. Proportional counters or various types of solid state detectors (PIN diode, Si(Li), Ge(Li), Silicon Drift Detector SDD) are used. Braggs Law nλ= 2d * sinΘ

8 Schematic arrangement of a wavelength-dispersive (WD) X-ray fluorescence (XRF) spectrometer B. A.

9 Various types of detectors most commonly gas flow proportional and scintillation are used to measure the intensity of the emitted beam on bench top models. Gas flow proportional counters are used mainly for detection of longer wavelengths (lighter elements). The gas is usually 90% argon, 10% methane ("P10"). The argon is ionized by incoming X-ray photons, and the electric field multiplies this charge into a measurable pulse. The methane suppresses the formation of fluorescent photons caused by recombination of the argon ions with stray electrons. Scintillation counters consist of a scintillating crystal (typically of sodium iodide doped with thallium) attached to a photomultiplier. The crystal must be protected with a relatively thick aluminum/beryllium foil window, which limits the use of the detector to wavelengths below 0.25 nm. Typically used for heavier elements. Scintillation - a flash of light produced in certain materials when they absorb ionizing radiation. B. A.

10 To obtain good XRF results using the pressed powder technique, control of particle size is absolutely critical. Pressed Powder Disks/Pellets Used primarily for trace elements and uniform samples compositions.

11 Lithium metaborate flux + sample in a 7:1 proportion Fusion in Pt crucible > 750 o C Fused glass disk from gold or brass mould Fused Glass Disk For Major Oxide Analysis

12 Sample Preparation Typical Composition of Grinding Units Material Major Elements Minor Elements Hardness (Mohs) Resistance to AbrasionDurability Hardened SteelFeCr, Si, Mn, C5.5-6ModerateHigh Stainless SteelFe, CrNi, Mn, S, Si5-5.5ModerateHigh Cr-free SteelFeC, Mn, Si, Mo5-5.5ModerateHigh Tungsten CarbideW, C, CoTa, Ti, Nb8.5 +HighLong-wearing, but brittle Alumina CeramicAlSi, Ca, Mg9Very HighLong-wearing, but brittle AgateSi Al, Na, Fe, K, Ca, Mg8.5 Extremely HighVery long-wearing, but brittle ZirconiaZrHf, Mg8.5 Extremely HighVery long-wearing Silicon NitrideSiY, Al, Fe, Ca8.5 + Extremely HighVery long-wearing PlasticC--1.5LowLow, but disposable Available in the Department

13 Major Oxides Detection limit 0.02 %: Al 2 O 3 CaO Fe 2 O 3 K 2 O P 2 O 5 Na 2 O MnOMgO TiO 2 SiO 2 Loss On Ignition (LOI) is carried out at 1000 o C. Removes volatiles including carbon, sulfur and nitrogen compounds, and structural and adsorbed water (H 2 O). Detection limit 0.02 %: LOI wt.% = (sample weight - residue weight) * 100 sample weight Trace Elements Detection limit 2 ppm: ZrSrRbCrNb PbNiY Zn Co Detection limit 5 ppm: CuWMoTh Detection limit 10 ppm: UV Detection limit 50 ppm: Ba

14 Laboratory Bench-top Models Field Hand-held Models

15 Linear Regressions for Select Trace Elements using Standard Reference Materials (SRMs)

16

17 PD Soil Profile Core #1 Major Oxide Concentrations (wt.%) Profile Horizons Trace Elements Concentrations (ppm) Al 2 O 3 Fe 2 O 3 Na 2 O MgO Zr Sr V A AB Bt Bxt a Bxt b II Bt II Bx II Bx2

18 PD Soil Profile Core #1 Major Oxide Concentrations (wt.%) Profile Horizons Trace Elements Concentrations (ppm) Al 2 O 3 Fe 2 O 3 Na 2 O MgO Zr Sr V A AB Bt Bxt a Bxt b II Bt II Bx II Bx2


Download ppt "Total Carbon (TC) = Total Organic Carbon (TOC) + Total Inorganic Carbon (TIC) TOC preparation: ~0.25 g dry, powdered sample acidified in baked glass beaker."

Similar presentations


Ads by Google