Soil Characterization and Quaternary Pedology Laboratory
The DRI Soil Characterization and Quaternary Pedology Laboratory offers expertise in field and lab-based characterization of soils and sediment to support client needs. The Soils Lab supports academic, industry, and government clients who seek analytical services for a variety of applications. The lab is outfitted with instrumentation to facilitate a wide range of analytical capabilities, and offers standardized methods specified by ASTM International (ATSM), the Environmental Protection Agency (EPA), the US Department of Agriculture (USDA), and more. The Soils Lab is also certified by the USDA to receive and process both domestic and foreign soil samples.
Click on any of the drop down tabs below for more information on the analyses we offer. To submit samples to the Soils Lab and view our analysis rates click here. Additional questions may be directed to email@example.com.
(does not display)
Your content goes here. Edit or remove this text inline or in the module Content settings. You can also style every aspect of this content in the module Design settings and even apply custom CSS to this text in the module Advanced settings.
Moisture and Gravel Content
Moisture and gravel contents of soil and sediment samples may be requested as standalone analyses, but are commonly required as sample pretreatment steps for most of our services. Moisture content is determined gravimetrically by drying bulk soil samples for 24 hours at 105°C (110°C for foreign soils). Thoroughly dried soil samples are sieved to quantitatively separate the >2 mm (gravel) fraction. Additional analyses are commonly conducted on the <2 mm “fine-earth” fraction.
Organic Matter/Carbonate Removal
Removal of soil constituents that may impact our ability to characterize the mineral fraction of soil and sediment samples is commonly recommended as a pretreatment step. The presence of organic materials or soluble salts influence a sample’s particle size distribution. Organic matter and soluble salts (chiefly calcium carbonate) are selectively removed via dissolution during sample pretreatment. See our list of Chemical Analytical services for quantitative determination of these constituents. Organic matter removal is achieved during sample pretreatment by addition of a 30% hydrogen peroxide solution to the sample. Calcium carbonate removal is achieved during sample pretreatment by leaching the sample in an acetic acid solution.
Milling, Crushing, Grinding, Splitting
The Soils Lab is fully equipped with a rock crushing and milling facility. As needed, whole rock samples are crushed and milled to a target particle size range. Soil and sediment samples may also be milled to powder for select chemical analyses. See our list of Chemical Analytical services for sample requirements. All laboratory samples are properly split using a Gilson splitter so that a representative portion is used for subsequent analyses.
Particle Size Distribution Analyses
PSDA – Optical Method
We routinely carry out laser particle size analysis (LPSA) of soil, sediment, and suspended sediment samples. Laser diffraction is used to measure the particle size distribution when a laser beam passes through a dispersed sample. The laser light scatters at angles inversely proportional to the particle’s size. The laboratory is equipped with a Malvern Mastersizer 3000, which can measure particle size ranging from 3.5 mm to 0.01 µm. Sample pretreatment for this analysis commonly includes gravel removal (>2 mm fraction), removal of organic matter and carbonate, and dispersion.
PSDA – Stacked Sieve Method
The Soils Lab offers stacked sieve analysis using a RO-TAP sieve shaker machine and sieves with various mesh sizes ranging from 3” to 44 µm. Sieves are stacked in order of coarse (top) to fine (bottom) and shaken with the RO-TAP. The mass retained in each sieve is recorded and provides the percent of sample in the specified size range. This approach is used when continuous size distributions are not required. Several methods are utilized in the Soils Lab, including ASTM D6913. Sample pretreatment for this analysis commonly includes gravel removal (>2 mm fraction), removal of organic matter and carbonate, and dispersion.
PSDA – Pipette Method
The pipette method relies on particle settling velocities to determine the percentage of sand, silt, and clay in a soil or sediment sample. This procedure is based on Stoke’s Law, which states that spherical particles settle in a fluid rate proportional to their radius and mass. Methodology for this analysis is based on Gee and Or, 2002. Pretreatment for pipette commonly includes gravel removal (>2 mm), organic matter and carbonate removal, dispersion, wet sieving to separate coarse (sand) fraction, and dry sieving of sand fraction.
Ion Chromatography – Anion and Cation Suites
Ion chromatography (IC) measures concentrations of a variety of anions or cations in aqueous solutions. Sample solutions may be collected as aqueous samples or may be extracted from soil or sediment samples during a leaching procedure. Sample solutions are pumped through an anion- or cation-exchange column. A conductivity cell continuously measures the solution conductivity signal to produce a chromatogram. Peaks in the chromatogram are identified using calibration standard solutions that also provide conversions to solution concentration for each analyte. Anions commonly measured include fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate. Cations commonly measured include lithium, sodium, ammonium, potassium, magnesium, and calcium.
Fe Oxides – Cit-Dithionite and Hydroxylamine Methods
We measure iron oxides using the citrate-dithionate extraction method which is useful for dissolving nonsilicate iron in soils. We also offer the hydroxylamine method which is used for removing noncrystalline material from crystalline iron oxides.
The Soils Lab utilizes the Niton portable XRF to measure the elemental composition of a soil or sediment sample via x-ray fluorescence. Lab samples are powdered and packed into plastic cups prior to analysis and are measured against known standards. The GOLDD+ technology and optional helium atmosphere provide additional accuracy and sensitivity for lighter elements.
The pressure-calcimeter method is used to determine carbonate content of a soil or sediment sample (Horvath et al., 2005). Hydrochloric acid is added to sample vials and weighed standards containing calcium carbonate. The pressure created by the production of CO2 is then measured by a tensiometer to determine the carbonate content.
Electrical conductivity can be measured to determine the total soluble salts of a soil or sediment sample. Potassium chloride conductivity standards (1,000 µS/cm, 11.16 µS/cm) are used to calibrate the Accumet Excel XL 30 Conductivity Meter. Aqueous soil extracts are dispersed by mechanical shaking and then centrifuged and extracted for conductivity measurement.
Organic Matter Content
The lab is equipped to measure organic matter content using the loss-on-ignition method (ASTM D2974). Samples are pre-dried to a constant mass, then added to crucibles and placed in a muffle furnace at 400°C. Sample pretreatment may include moisture content and gravel removal.
The pH of soil is measured using a soil-aqueous matrix suspension using calcium chloride (CaCl2) solution. The Soils Lab utilizes the Accumet pH Meter 915 with pH 4.01 and 10.01 buffer solutions.
Soil Moisture Release Curves
The Soil Lab offers laboratory techniques for determination of hydraulic soil properties from soil moisture release curves. Soil moisture release curves are generated using the Wind/Schindler evaporation method. The lab is equipped with three METER HYPROP 2 stations for simultaneous measurement of soil or sediment samples and a METER WP4C dew point potentiometer to evaluate samples at high matric suction. The HYPROP 2 has two tensiometers at different levels within a sample to accurately measure water potentials up to ~800 hPa. The WP4C can measure water potentials up to -300 MPa to achieve a moisture release curve that covers the driest end member.
Atterberg Limits are engineering properties of soils that are used to find the critical water content of the fine-grained fraction of soils. This is done to determine the liquid and plastic limits of a soil sample. Atterberg Limits can be used to characterize different types of silt and clay, and the behavior of the soil when in solid, plastic, and liquid states. We routinely analyze soil and sediment samples to determine their Plasticity Index (Liquid Limit and Plastic Limit), also known as Atterberg Limits using ASTM Method D4318 and ASTM D2487 (USCS Soil Classification).
Bulk Density – Wax Peds
Bulk density of soil or sediment clods can be measured using the waxed ped method. An undisturbed sample clod is weighed, and its volume is then calculated by determining the volume of water it displaces after the sample is coated with paraffin wax and placed in a beaker of water.
Soil analyses are often important for understanding the environmental conditions (e.g. water content, bulk density) and the stratigraphic context of geochronology samples, which is critical for the interpretation of geochronology data. Since soil development can be used to indicate the relative ages of landforms, our joint services can provide a multi-pronged approach to answering Quaternary geochronology questions. For more information, contact Dr. Brad Sion.
Quality Assurance & Quality Control Practices
The Soil Characterization and Quaternary Pedology Laboratory follows strict standard operating procedures (SOPs) for all analyses. Known lab standards and reference materials are routinely analyzed with sample batches for accuracy. Blanks, sample duplicates, and standards are measured with all relevant analyses. All analytical scales and balances receive annual certified calibration and are checked weekly by laboratory personnel. All samples received are logged into the lab using a standardized chain of custody format. Analyses are only performed by laboratory personnel trained in the methods. To learn more about what ASTM, USDA, EPA, etc. methods we offer, navigate to any of our analyses on this page.