PNNL

Abstract

Particle-size analysis (PSA) is widely used in both soil science and geo-engineering. Soil classification schemes are built on PSA values while recent developments in pedotransfer functions rely on PSA to estimate soil hydraulic properties. Because PSA is method dependent, the standardization of experimental procedures is important for the comparison of reported results. A study was conducted to compare the American Society of Testing Materials (ASTM) hydrometer method (D422) for particle-size analysis with the hydrometer method published by the Soil Science Society of America (SSSA). Tests on soils ranging in texture from sand to a sandy clay loam were conducted at temperatures ranging from 20 C to 30 C. The main difference between methods is the temperature correction, with the ASTM method relying on an empirical correction and the SSSA method using a blank hydrometer reading. Identical texture estimates for all but one sample was observed between methods. Percent fines, silt, and clay demonstrated relatively consistent values between methods. D50 and D30 showed reasonable agreement between methods, with differences of less than 4 percent and 8 percent. For D10 values, the agreement was less satisfactory, with uncertainties of as much as 10 percent. The results suggest that ASTM and SSSA methods can be used interchangeably for textural analysis.