Tuesday, November 6, 2007
197-1

Particle Size Analysis of Gypsic Soils.

Justin Riggs, New Mexico State University, MSC 3Q, Las Cruces, NM 88003, H. Curtis Monger, PO Box 30003 Dept. 3Q, New Mexico State University, New Mexico State University, Plant & Environmental Sciences Dept., Las Cruces, NM 88003-8003, Mei Wang, Plant & Environmental Sciences, New Mexico State University, MSC 3Q, Las Cruces, NM 88003, and Rebecca Kraimer, USDA-NRCS, Las Cruces, NM 88011-7222.

Gypsum is a common mineral in many dryland soils throughout the world. It is a relatively soft mineral that consists of calcium sulfate dihydrate (CaSO4•2H2O). The chemical makeup of this mineral poses many problems that affect the physical properties of soils (i.e., pH, EC., etc.) and field/laboratory analysis (i.e. Particle Size Analysis). The most problematic aspect of gypsum is its solubility. Gypsum can be easily dissolved in water, thereby, affecting the soil texture when using the pipette method to determine particle size. This research effort will quantify the dissolution rates of gypsum while conducting the pipette method to determine soil texture. This investigation will explore different solutions other than deionized water, such as low viscosity oil and brine water, in an attempt to prevent dissolution of gypsum grains. Preliminary data suggests that brine water and low viscosity oil will reduce the amount of gypsum dissolved, thus, increasing the accuracy of the particle size analysis. Although these mediums will suffice in reducing the dissolution of gypsum, the latter poses economic and environmental issues such as expense and waste disposal.