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 HCl, @ 60 oC for 12-14 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

Trace elements coprecipitated with secondary soil

minerals and soil organic matter (SOM)

Fe and Al oxides B, P, V, Mn, Ni, Cu, Zn, Mo, As, SeMn oxides P, Fe, Co, Ni, Zn, Mo, As, Se, PbCa carbonates P, V, Mn, Fe, Co, CdIllites B, V, Ni, Co, Cr, Cu, Zn, Mo, As, Se, PbSmectites B, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, PbVermiculites Ti, Mn, FeOrganic matter Al, V, Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, P, N

Solid Coprecipitated trace elements

Carmichael Creek, MT

0

0.05

0.1

0.15

0.2

0.25

0.3

0 1 2 3 4 5

Total Organic Carbon (wt%)

P2O

5 (w

t. %

)

CCSnorth-facing

CCNsouth-facing

1A

1A

2A

2A

3A4A

3A4A

X-ray fluorescence (XRF)

The technology was developed in the 1950’s.

www.niton.com/.../primary-x-ray-radiation.jpg

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.

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.

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.

Bragg’s Lawnλ= 2d * sinΘ

http://en.wikipedia.org/wiki/X-ray_fluorescence

Schematic arrangement of a wavelength-dispersive (WD) X-ray fluorescence (XRF) spectrometer

B.

A.

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.

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.

Lithium metaborate flux + sample in a 7:1 proportion

Fusion in Pt crucible> 750 oC

Fused glass disk from gold or brass mould

Fused Glass DiskFor Major Oxide Analysis

Sample PreparationTypical Composition of Grinding Units

MaterialMajor

ElementsMinor

ElementsHardness (Mohs)

Resistance to Abrasion Durability

Hardened Steel Fe Cr, Si, Mn, C 5.5-6 Moderate HighStainless Steel Fe, Cr Ni, Mn, S, Si 5-5.5 Moderate HighCr-free Steel Fe C, Mn, Si, Mo 5-5.5 Moderate HighTungsten Carbide W, C, Co Ta, Ti, Nb 8.5 + High Long-wearing, but brittleAlumina Ceramic Al Si, Ca, Mg 9 Very High Long-wearing, but brittle

Agate SiAl, Na, Fe, K,

Ca, Mg 8.5Extremely

High Very long-wearing, but brittle

Zirconia Zr Hf, Mg 8.5Extremely

High Very long-wearingSilicon Nitride Si Y, Al, Fe, Ca 8.5 +

Extremely High Very long-wearing

Plastic C -- 1.5 Low Low, but disposableAvailable in the Department

Major OxidesDetection limit 0.02 %:

Al2O3 CaOFe2O3 K2OP2O5 Na2OMnO MgOTiO2 SiO2

Loss On Ignition (LOI) is carried out at 1000oC. Removes volatiles including carbon, sulfur and nitrogen compounds, and structural and adsorbed water (H2O).Detection limit 0.02 %: LOI wt.% = (sample weight - residue weight) * 100 sample weight

Trace ElementsDetection limit 2 ppm:

Zr Sr Rb Cr NbPb Ni Y Zn Co

Detection limit 5 ppm:

Cu W Mo ThDetection limit 10 ppm:

U VDetection limit 50 ppm:

Ba

Laboratory Bench-top Models

Field Hand-held Models

Mo Regression

y = 28.399x

R2 = 0.98940

20406080

100120140160

0 1 2 3 4 5

intensity Mo

Mo

(ppm

)

Nb Regression

y = 17.083x

R2 = 0.9959

0

50

100

150

200

250

300

0 5 10 15 20

intensity Nb

Nb

(ppm

)

Zr Regression

y = 16.189x

R2 = 0.9875

0200400600800

100012001400

0 20 40 60 80

intensity Zr

Zr

(ppm

)

Sr Regression

y = 0.0399x

R2 = 0.9348

05

101520253035

0 200 400 600 800

intensity Sr

Sr (

ppm

)

Linear Regressions for Select Trace Elementsusing Standard Reference Materials (SRMs)

PD Soil ProfileCore #1

Major Oxide Concentrations (wt.%)

Profi

le H

oriz

ons

Trace Elements Concentrations (ppm)

0 5 10 15 20

Al2O3

Fe2O3

Na2O

MgO

100 200 300 400 5000

Zr

Sr

V

A

AB

Bt

Bxta

Bxtb

II Bt

II Bx

II Bx2

PD Soil ProfileCore #1

Major Oxide Concentrations (wt.%)

Profi

le H

oriz

ons

Trace Elements Concentrations (ppm)

0 5 10 15 20

Al2O3

Fe2O3

Na2O

MgO

100 200 300 400 5000

Zr

Sr

V

A

AB

Bt

Bxta

Bxtb

II Bt

II Bx

II Bx2