The laboratory is equipped with a high resolution Micromeritics Saturn DigiSizer 5200 laser particle size analyzer and auto-sampler, a Perkin-Elmer 2400 CHNS/O elemental analyzer, an IL 941 AA/AE spectrophotometer for metals analysis, a Lachat QuikChem 8000 FIA nutrient analyzer, a Shimadzu total carbon analyzer, an Antek 9000 Total N analyzer, a Decagon WP4 PoteniaMeter, and CX-2 water activity meter.

Sample preparatory equipment includes a Quantachrome Sieving Riffler, Sampletek 200 vial rotator, SPEX 8000 Ball Mill, precision analytical balances, high speed/high capacity centrifuges, and shaking tables. The laboratory is further equipped with specialized mechanical nested-sieve shakers, Chittick carbonate content analyzer, stereo- and petrographic microscopes, pressure extractor plates, and a Thermolyne 1400 muffle furnace.

Laser Particle Size Analysis

The Saturn Digisizer

The laser particle size analysis (LPSA) procedure is used to determine the percentage of size-class fractions in soil or sediment samples. The procedure is based on ASTM C 1070–01 to determine particle size distribution analysis (PSDA) of alumina and quartz powders by laser light scatter (ASTM, 2000). Laser-light scattering is based on the Mie theory of light scattering by a spherical particle using the Micromeretics Saturn DigiSizer 5200®. The DigiSizer is capable of analyzer particles in the range of 0.05 to 1000 micrometers.

The sample is internally dispersed using ultra-sonication in an aqueous medium of 0.005% surfactant (sodium?metaphosphate) and circulated through the path of the laser light beam. As the particles pass through the laser beam, the light scatters at angles inversely proportional to particle size and with intensity directly proportional to particle size. A 45° rotational charge-coupled device collects the scattered light intensity, which is converted to electrical signals and analyzed in a microprocessor. Data reduction consists of a mathematical convolution based on scattering model sets, each calculated from the general Mie theory for narrow distributions of isotropic spheres having a specific index of refraction and suspended in a liquid having a specific index of refraction. Data reported by the Saturn DigiSizer relates directly to an equivalent Mie sphere. The Mie theory consists of a "real" refractive index (1.550 for soils) and an "imaginary" refractive index (0.100 for soils) determined by Micromeretics Laboratories. The predictive model error (weighted residual) is proportional to the measure of the calculated Mie theory model to predictions of the observed laser-light scattering pattern.

Prior to LPSA, samples may be either 1) externally dispersed, sieved to remove the entire sand fractions (> 62.5 micrometers) and analyzing the fine fraction (typical for soils), or 2) dry sieved to remove the coarse sand particles >1 mm and internally dispersed with ultra-sonication. Method 1 has the advantage of added resolution to the fine end by removing larger sand-sized particles, thereby reducing multiple light scatter. Method 2 has the advantage of the entire sample being presented enabling the ability to determine a mean, mode and kurtosis of entire particle size distribution. However, coarse sand particles >1 mm must be sieved to assure the sample falls within instrument size range.

Quantachrome Sieving Riffler

Representative sampling prior to soil analysis accomplished with a Quantachrome Sieving Riffler. The unit consists of three basic components: A cylindrical vibrating hopper which is amplitude-variable and controls the delivery rate of the powder, a rotating sample collector which is divided into eight stainless steel compartments, and two nested sieves used to first remove gravel (>2mm) and particle in excess of the DigiSizer’s detection range (>1 mm).

Lachat QuickChem 8000 FIA

Nutrient analysis, soluble salt chemistry and tracer recovery of soil extracts is accomplished using a Lachat’s QuikChem® 8000 Flow Injection Analysis System features high sample throughput and simple but rapid method changeover. The Soil Characterization Lab is currently equipped with a 4 channel analyzer for various nutrients (PO 4, NO 3, and NH 4), anions common to desert soils (Cl and SO 4), as well as environmental tracers (Br).

This equipment was made possible by the National Science Foundation (MRI grant #DBI-0216553).

Perkin Elmer 2400 Series CHNS/O Analyzer

Total carbon, hydrogen and nitrogen in soil and plant material is determined using a Perkin-Elmer 2400 CHN Analyzer. Samples are oxidized at 1000 ° C, and analyzed by thermal conductivity detectors.

The Sampletek Model 200 Vial Rotator

Chemical analysis is typically conducted on ground soil sample. Grinding homogenizes the sample allowing for very small subsamples to be removed for metal extractions or total CHN analysis. The Soil Characterization laboratory is equipped with a Sampletek Vial Rotator which used rotational energy to crush sample to a fine talc. The unit can accommodate nearly 100 scintillation vials.

Antek Total N/S 9000 Series Analyzer

Nitrogen is an important measure of the level of ecosystem health and contamination in groundwater, waste water and freshwater streams. Quantification of total N in these samples has traditionally been accomplished by using the time-consuming Kjeldahl method. The Antek 9000 analyzer provides a quick, reliable method with a very wide detection range form ppb to percent level of aqueous samples.

This equipment was made possible by the National Science Foundation (MRI grant #DBI-0216553).