R. A. McBride

This laboratory study investigated the susceptibility of subsurface archaeological ecofacts/artefacts to incidental damage from utility construction activities, as it pertains to the cultural heritage aspects of environmental impact assessment and municipal planning. The research objective was to use X‐ray microcomputed tomography (micro‐CT) imaging to non‐destructively determine the nature and extent of any damage inflicted on a range of ecofact and artefact types (authentic and replica) embedded in repacked, plastic clay soil by pure soil strain at variable levels of static load compactive effort up to 600 kPa. Uniaxial soil compression testing and micro‐CT imaging were combined procedurally to meet this objective. It was concluded that lithic artefacts were largely immune to damage from stresses up to 600 kPa due to their high strength properties, while moderately fragile ecofacts (replica charred maize kernels) exhibited evidence of dimensional distortion, but not of breakage. Very fragile ecofacts (unionid freshwater clam shells) showed dimensional distortion and minor structural damage at lower stresses (50 and 100 kPa), but significant breakage and fragmentation at higher stresses (300 and 600 kPa). Overall, the micro‐CT technique was shown to be useful in monitoring and describing any breakage or morphometric distortion in a wide range of test ecofacts/artefacts compressed in a clay‐rich soil matrix. However, earthen artefacts, such as terra cotta pottery sherds, were found to be problematic using the micro‐CT imaging technique for this application due to similarities in the densities of the ceramic sherds and the surrounding compressed soil matrix. Copyright © 2011 John Wiley & Sons, Ltd.

The objective of this study was to develop a statistically based function for the estimation of particle density of texturally diverse soils sampled from a reasonably large geographic area (∼12,000 km ² ) to enhance further development of pedotransfer functions with regional application. Available soil physical property data were assembled for soil series mapped during five municipal‐level soil inventory upgrades in southwestern Ontario, Canada. A total of 282 soil horizons from 91 soil profiles were identified that had the requisite measured data for particle density (water pycnometer method), soil organic carbon content (wet oxidation method), and particle‐size distribution (pipette method). Both linear and nonlinear regression procedures were used to relate particle density to soil organic matter content. Plausible estimates of particle density for the mineral component (2.65 Mg m ⁻³ ), and particularly for the humic component (1.23 Mg m ⁻³ ), were obtained ( r ² = 0.208, RMSE = 0.11 Mg m ⁻³ , P < 0.0001) even though the calibration data set had a limited range of soil organic matter content (<12%). The particle density of different mineral particle‐size fractions (e.g., clay) could also be distinguished statistically. The predictive capability of regression equations originating from soil inventory data sets encompassing large geographic areas are likely to be influenced by the soil taxonomic range sampled and the general data quality.