| Use: | Sampling of soil pore liquids in the vadose zone. |
Description:
The following is a description of the most common soil water extraction methods. Several other methods such as the membrane filter, hollow filter, ceramic tube sampler, and capillary wick sampler have been utilized for this procedure, but their use is relatively uncommon in the field.
| Vacuum-Type Porous Cup: | A porous cup attached to a small diameter tube is placed in the soil. A one-hole rubber plug is placed in the other end of the tube and small diameter tubing beginning at the base of the ceramic cup runs through the hole to the surface. A vacuum is applied to the small tubing, and the soil solution is drawn into a small flask. |
| Vacuum-Pressure Type Porous Cup: | Similar to the vacuum-type porous cup, except that a second line is placed in the porous-cup-tipped tube, which ends just below the stopper. The shorter line is connected to a pressure-vacuum source. When the unit is in place, a vacuum is applied to draw soil water into the sampler and push the sample into the flask. |
| Vacuum-Plate Sampler: | Operates in a similar fashion to the vacuum-type porous cup except that a plate (4.3 to 25.4 centimeters in diameter) is used in place of the cup. |
Soil core samples can be collected and soil water extracted using one of several field methods, which allow the vertical profiles of concentrations of specific pollutants to be obtained:
Analytes:
| 1. Non-Halogenated VOCs | 5. PAHs | 9. Inorganics |
| 2. Non-Halogenated SVOCs | 6. Pesticides/Herbicides | 10. Explosives |
| 3. Halogenated VOCs | 7. Metals | 11. TPHs |
| 4. Halogenated SVOCs | 8. Radionuclides |
Media:
| Soil: | Ground Water: | Surface Water: | Gas/Air: |
| MINIMUM | MAXIMUM | MAXIMUM | Not Applicable |
When evaluating sample quality, user must take into account relationships between pore sequences, water quality, and drainage rates.
| Maximum Depth: | Up to 100 feet. Vacuum-pressure method required for depths greater than 6 feet. |
| Production Rate: | Sample is available after an extended wait. |
| Investigation Derived Waste Volume: | Small volume of waste. |
| Technology Status: | Commercially available technology with moderate field experience. |
| Certification/Verification: | Technology has not participated in CalEPA certification and/or CSCT verification program. |
| Relative Cost per Sample: | Mid-range expense. |
Limitations:
Vacuum methods:
Solids sampling with soil water extraction:
ASTM Standards:
| D 2325 - 68 | Test Method for Capillary-Moisture Relationship for Course- and Medium-Textured Soils by Porous-Plate Apparatus (Soil Water Retention). |
| D 4696 - 92 | Pore-Liquid Sampling from the Vadose Zone. |
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