BIOGEOCHEMISTRY
Humus and vegetation has been used very successfully to discover buried mineralization.
The trees act as mini drills with their root structures sampling very large volumes of soil and in the case of phreatophytes the root structure searches out the water table and may extend hundreds of metres below the surface. The choice of package depends on the elements and detection limits required.
Humus (Decaying Surface Vegetation) – The material is dried below 60oC and then macerated with a cutting mill with a 1mm internal sieve. The ground material can be compressed into a briquette for INAA or ashed and analyzed by digestion and ICP or ICP-MS.
Ground humus samples weighing 6 to 15 g are compressed under 30 tons of pressure to form a briquette (smaller samples are weighed in vials). Smaller samples will be weighed into vials. Briquettes are stacked with flux wires and two internal standards (up to 28 samples) and irradiated along with flux wires at a thermal neutron flux of 7 x 10 12 ncm-2 s-1. After a 7-day period to allow Na-24 to decay the samples are counted on a high purity Ge detector with resolution of better than 1.7 KeV for the 1332 KeV Co-60 photopeak. Using the flux wires and control standards, the decay-corrected activities are compared to a calibration developed from multiple certified international reference materials. For values exceeding the upper limits, assays are recommended. Duplicates are analyzed when sample material is available.
Required Preparation: B1 (drying and blending humus)
Elements and Detection Limits (ppm)
| Element | Detection Limit |
|---|---|
| Ag | 2 |
| As | 1 |
| Au | 1 ppb |
| Ba | 100 |
| Br | 1 |
| Ca | 0.5% |
| Ce | 1 |
| Co | 1 |
| Cr | 1 |
| Element | Detection Limit |
|---|---|
| Cs | 0.5 |
| Eu | 0.2 |
| Fe | 0.05% |
| Hf | 0.5 |
| Hg | 0.5 |
| Ir | 5 ppb |
| La | 0.1 |
| Lu | 0.1 |
| Mo | 0.5 |
| Element | Detection Limit |
|---|---|
| Na | 100 |
| Nd | 3 |
| Ni | 10 |
| Rb | 20 |
| Sb | 0.1 |
| Sc | 0.1 |
| Se | 2 |
| Sm | 0.1 |
| Element | Detection Limit |
|---|---|
| Sr | 100 |
| Ta | 0.5 |
| Tb | 0.2 |
| Th | 0.5 |
| U | 0.1 |
| W | 1 |
| Yb | 0.1 |
| Zn | 20 |
Reference:
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.
Vegetation (dried and ground in a cutting mill to homogenize it. Then can be analyzed by compressing into a briquette, by ashing and analysis of ash, or analysis on unashed material.
Ground humus samples weighing 6 to 15 g are compressed under 30 tons of pressure to form a briquette (smaller samples are weighed in vials). Smaller samples will be weighed into vials. Briquettes are stacked with flux wires and two internal standards (up to 28 samples) and irradiated along with flux wires at a thermal neutron flux of 7 x 10 12 ncm-2 s-1. After a 7-day period to allow Na-24 to decay the samples are counted on a high purity Ge detector with resolution of better than 1.7 KeV for the 1332 KeV Co-60 photopeak. Using the flux wires and control standards, the decay-corrected activities are compared to a calibration developed from multiple certified international reference materials. For values exceeding the upper limits, assays are recommended. Duplicates are analyzed when sample material is available.
Required Preparation: B2 (drying and macerating vegetation in a Retsch mill with sieving to 1 mm)
Elements and Detection Limits (ppm)
| Element | Detection Limit |
|---|---|
| Ag | 0.3 |
| As | 0.01 |
| Au | 0.1 ppb |
| Ba | 5 |
| Br | 0.01 |
| Ca | 0.01% |
| Ce | 0.1 |
| Co | 0.1 |
| Cr | 0.3 |
| Element | Detection Limit |
|---|---|
| Cs | 0.05 |
| Eu | 0.05 |
| Fe | 0.01% |
| Hf | 0.05 |
| Hg | 0.05 |
| Ir | 0.1 ppb |
| K | 0.01% |
| La | 0.01 |
| Lu | 0.001 |
| Element | Detection Limit |
|---|---|
| Mo | 0.05 |
| Na | 1 |
| Nd | 0.3 |
| Ni | 2 |
| Rb | 1 |
| Sb | 0.005 |
| Sc | 0.01 |
| Se | 0.1 |
| Sm | 0.001 |
| Element | Detection Limit |
|---|---|
| Sr | 100 |
| Ta | 0.05 |
| Tb | 0.1 |
| Th | 0.1 |
| U | 0.01 |
| W | 0.05 |
| Yb | 0.005 |
| Zn | 2 |
Reference:
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.
Vegetation Ash
A 1g aliquot is encapsulated in a polyethylene vial and irradiated along with flux wires at a thermal neutron flux of 7 x 10 12 ncm-2 s-1. After a 7-day period to allow Na-24 to decay the samples are counted on a high purity Ge detector with resolution of better than 1.7 KeV for the 1332 KeV Co-60 photopeak. Using the flux wires and control standards, the decay-corrected activities are compared to a calibration developed from multiple certified international reference materials. For values exceeding the upper limits, assays are recommended. One standard is run for every 11 samples. One blank is analyzed per work order. Duplicates are analyzed when sample material is available.
Required Preparation: B3 (ashing of vegetation in dedicated kilns at 475°C for 18-24 hours)
Vegetation Ash-INAA Elements and Detection Limits (ppm)
| Element | Detection Limit |
|---|---|
| Ag | 2 |
| As | 0.5 |
| Au | 5 ppb |
| Ba | 50 |
| Br | 1 |
| Ca | 0.20% |
| Ce | 3 |
| Co | 1 |
| Cr | 1 |
| Element | Detection Limit |
|---|---|
| Cs | 0.5 |
| Eu | 0.01 |
| Fe | 0.05% |
| Hf | 0.5 |
| Hg | 1 |
| Ir | 2 ppb |
| K | 0.05% |
| La | 0.1 |
| Lu | 0.05 |
| Element | Detection Limit |
|---|---|
| Mo | 2 |
| Na | 10 |
| Nd | 5 |
| Ni | 50 |
| Rb | 5 |
| Sb | 0.1 |
| Sc | 0.1 |
| Se | 2 |
| Sm | 0.1 |
| Element | Detection Limit |
|---|---|
| Sr | 300 |
| Ta | 0.5 |
| Tb | 0.5 |
| Th | 0.1 |
| U | 0.1 |
| W | 1 |
| Yb | 0.05 |
| Zn | 50 |
Reference:
Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.
2 grams of vegetation samples are ashed at 475°C. The ash sample is digested with aqua regia for 2 hours at 95°C and analyzed by ICP. Ashing is included in this package.
Required Preparation: B3 (ashing of vegetation in dedicated kilns at 475°C for 18-24 hours)
Vegetation Ash-ICP Elements and Detection Limits (ppm)
| Element | Detection Limit | Upper Limit |
|---|---|---|
| Ag | 0.2 | 100 |
| Cu | 1 | 10,000 |
| Mn | 1 | - |
| Mo | 1 | 10,000 |
| Ni | 1 | 10,000 |
| Pb | 1 | 5,000 |
| Zn | 1 | 10,000 |
Vegetation samples are ashed at 475°C over a 36 hour period. A proprietary acid digestion is used on the ash. Digested ash samples are diluted and analyzed by ICP-MS. A matrix blank and digested blank are each run every 35 samples. Two digested standards are run every 35 samples. Instrument is recalibrated every 70 samples. Duplicates are digested and analyzed every 14 samples. Results are reported on an ash weight basis. If Au, Pd, Pt are required please use Code 2E.
Required Preparation: B3 (drying and ashing at 475°C in dedicated kilns)
(Vegetation Ash-ICP/MS) Elements and Detection Limits (ppm)
| Element | Detection Limit |
|---|---|
| Ag | 0.2 |
| Al | 2 |
| As | 1 |
| B | 5 |
| Ba | 3 |
| Be | 0.005 |
| Bi | 0.05 |
| Ca | 0.10% |
| Cd | 0.01 |
| Ce | 0.01 |
| Co | 0.01 |
| Cr | 1 |
| Cs | 0.001 |
| Cu | 0.2 |
| Dy | 0.001 |
| Element | Detection Limit |
|---|---|
| Er | 0.001 |
| Eu | 0.001 |
| Fe | 0.01% |
| Ga | 0.1 |
| Gd | 0.01 |
| Ge | 0.1 |
| Hf | 0.01 |
| Ho | 0.001 |
| In | 1 ppb |
| K | 0.01% |
| La | 0.002 |
| Li | 0.5 |
| Lu | 0.001 |
| Mg | 0.01% |
| Mn | 0.1 |
| Element | Detection Limit |
|---|---|
| Mo | 0.1 |
| Na | 0.01% |
| Nb | 0.005 |
| Nd | 0.002 |
| Ni | 5 |
| Pb | 0.1 |
| Pr | 0.002 |
| Rb | 0.01 |
| Re | 0.1 ppb |
| Sb | 0.02 |
| Sc | 0.5 |
| Se | 1 |
| Si | 0.20% |
| Sm | 0.001 |
| Sr | 0.1 |
| Element | Detection Limit |
|---|---|
| Ta | 0.001 |
| Tb | 0.001 |
| Te | 0.01 |
| Th | 0.001 |
| Ti | 1 |
| Tl | 0.001 |
| Tm | 0.001 |
| U | 0.001 |
| V | 1 |
| W | 0.5 |
| Y | 0.001 |
| Yb | 0.001 |
| Zn | 1 |
| Zr | 0.5 |
Samples are ashed at low temperature in dedicated ovens at 475oC for 24 hours. 0.25g of ash is digested in aqua regia at 95oC for 2 hours. Digested ash samples are diluted and analyzed by ICP-MS. A blank is run every 69 samples. Two digested controls are analyzed every 69 samples. Duplicates are digested and analyzed every 14 samples. Instrument is recalibrated every 69 samples. Results are reported on an ash weight basis. On request results can be computed on a dry weight basis.
Required Preparation: B3 (dry and ash at 475°C in dedicated vegetation kilns)
Elements and Detection Limits (ppm)
| Element | Detection Limit |
|---|---|
| Ag | 0.2 |
| Al | 2 |
| As | 3 |
| Au | 5 ppb |
| B | 5 |
| Ba | 3 |
| Be | 0.08 |
| Bi | 0.05 |
| Ca | 0.10% |
| Cd | 0.01 |
| Ce | 0.01 |
| Co | 0.01 |
| Cr | 10 |
| Cs | 0.001 |
| Cu | 0.2 |
| Dy | 0.001 |
| Element | Detection Limit |
|---|---|
| Er | 0.001 |
| Eu | 0.001 |
| Fe | 0.01% |
| Ga | 0.1 |
| Gd | 0.01 |
| Ge | 0.1 |
| Hf | 0.01 |
| Ho | 0.001 |
| In | 1 ppb |
| K | 0.01% |
| La | 0.002 |
| Li | 0.5 |
| Lu | 0.001 |
| Mg | 0.01% |
| Mn | 0.1 |
| Mo | 0.1 |
| Element | Detection Limit |
|---|---|
| Na | 0.01% |
| Nb | 0.005 |
| Nd | 0.002 |
| Ni | 5 |
| Pb | 0.1 |
| Pd | 3 ppb |
| Pr | 0.002 |
| Pt | 2 ppb |
| Rb | 0.01 |
| Re | 0.1 ppb |
| Ru | 10 ppb |
| Sb | 0.02 |
| Sc | 0.5 |
| Se | 10 |
| Si | 0.20% |
| Sm | 0.001 |
| Element | Detection Limit |
|---|---|
| Sn | 1 |
| Sr | 0.1 |
| Ta | 0.001 |
| Tb | 0.001 |
| Te | 0.01 |
| Th | 0.001 |
| Ti | 1 |
| Tl | 0.001 |
| Tm | 0.001 |
| U | 0.001 |
| V | 10 |
| W | 0.5 |
| Y | 0.001 |
| Yb | 0.001 |
| Zn | 1 |
| Zr | 0.5 |
Vegetation Un-Ashed
Raw vegetation samples are digested in aqua regia at 95°C for 2 hours. Resultant sample solutions are diluted and analyzed by ICP-MS.
Required Preparation: B2 (dry and macerate vegetation in a Retsch cutting mill with internal 1 mm sieve)
Elements and Detection Limits (ppb)
| Element | Detection Limit |
|---|---|
| Ag | 1 |
| As | 5 |
| Au | 0.1 |
| B | 200 |
| Ba | 1 ppm |
| Be | 0.1 |
| Bi | 1 |
| Ca | 2 ppm |
| Cd | 0.1 |
| Ce | 0.5 |
| Co | 0.5 |
| Cr | 10 |
| Cs | 0.1 |
| Cu | 20 |
| Dy | 0.05 |
| Er | 0.05 |
| Element | Detection Limit |
|---|---|
| Eu | 0.1 |
| Fe | 0.5 ppm |
| Ga | 0.5 |
| Gd | 1 |
| Ge | 10 |
| Hf | 2 |
| Hg | 5 |
| Ho | 0.01 |
| In | 0.1 |
| K | 10 ppm |
| La | 0.2 |
| Li | 5 |
| Lu | 0.2 |
| Mg | 0.5 ppm |
| Mn | 10 |
| Mo | 1 |
| Element | Detection Limit |
|---|---|
| Na | 10 ppm |
| Nb | 0.5 |
| Nd | 0.2 |
| Ni | 0.1 ppm |
| Pb | 10 |
| Pd | 2 |
| Pr | 0.5 |
| Pt | 0.1 |
| Rb | 10 |
| Re | 0.1 |
| Ru | 0.5 |
| Sb | 0.2 |
| Sc | 1 |
| Se | 0.2 ppm |
| Sm | 0.1 |
| Sn | 40 |
| Element | Detection Limit |
|---|---|
| Sr | 15 |
| Ta | 0.1 |
| Tb | 0.02 |
| Te | 1 |
| Th | 5 |
| Ti | 20 |
| Tl | 0.5 |
| Tm | 0.05 |
| U | 1 |
| V | 10 |
| W | 5 |
| Y | 0.2 |
| Yb | 0.4 |
| Zn | 0.2 ppm |
| Zr | 5 |
Raw vegetation samples are digested in aqua regia at 95°C for 2 hours. Resultant sample solutions are diluted and analyzed on a ICP-MS. A blank is run every 69 samples. Two digested controls are analyzed every 69 samples. Duplicates are digested and analyzed every 14 samples. Instrument is recalibrated every 69 samples.
Required Preparation: B2 (dry and macerate vegetation in a Retsch cutting mill with internal 1 mm sieve)
Elements and Detection Limits (ppb, except where noted)
| Element | Detection Limit |
|---|---|
| Ag | 3 |
| Al | 4 ppm |
| As | 10 |
| Au | 0.2 |
| B | 1 ppm |
| Ba | 100 |
| Be | 30 |
| Bi | 2 |
| Ca | 25 ppm |
| Cd | 6 |
| Ce | 15 |
| Co | 4 |
| Cr | 100 |
| Cs | 0.2 |
| Cu | 50 |
| Dy | 0.5 |
| Element | Detection Limit |
|---|---|
| Er | 0.4 |
| Eu | 0.2 |
| Fe | 3 ppm |
| Ga | 4 |
| Gd | 0.4 |
| Ge | 3 |
| Hf | 0.4 |
| Hg | 2 |
| Ho | 0.2 |
| In | 0.2 |
| K | 10 ppm |
| La | 10 |
| Li | 10 |
| Lu | 0.5 |
| Mg | 2 ppm |
| Mn | 100 |
| Element | Detection Limit |
|---|---|
| Mo | 10 |
| Na | 5 ppm |
| Nb | 2 |
| Nd | 5 |
| Ni | 50 |
| P | 4 ppm |
| Pb | 50 |
| Pd | 0.2 |
| Pr | 1 |
| Pt | 0.2 |
| Rb | 10 |
| Re | 0.2 |
| Sb | 10 |
| Se | 100 |
| Sm | 1 |
| Sn | 50 |
| Element | Detection Limit |
|---|---|
| Sr | 40 |
| Ta | 0.2 |
| Tb | 0.2 |
| Te | 8 |
| Th | 2 |
| Ti | 150 |
| Tl | 1 |
| Tm | 0.1 |
| U | 1 |
| V | 10 |
| W | 25 |
| Y | 2 |
| Yb | 0.4 |
| Zn | 400 |
| Zr | 20 |
