Liquefaction Assessment Using the CPT and Accounting for Soil Ageing

Due to its continuous data recording capability, excellent repeatability and accuracy, relatively low cost and simplicity of operation, the cone penetration test (CPT) offers enhanced liquefaction assessment over its predecessor the standard penetration test (SPT). However, soil ageing, which influences the cyclic resistance ratio (CRR), is difficult, if not impossible, to be detected by the CPT due to disturbance during the test. This situation may lead to excessively conservative estimation of CRR values which result in conservative assessment of liquefaction potential. This paper presents and discusses liquefaction assessment using the CPT and methods for accounting for soil ageing. A field study, conducted at Gillman, South Australia, is presented and the study site is assessed for liquefaction potential. This paper also explores the influence of soil ageing on the subsequent liquefaction assessment.

Changes in functional traits of the terricolous lichen Peltigera aphthosa across a retrogressive boreal forest chronosequence

Changes in the functional traits of the terricolous lichen Peltigera aphthosa with declining soil fertility during ecosystem retrogression were investigated. A well-documented retrogressive chronosequence of 28 forested islands in northern Sweden that differ greatly in fire history and which spans 5000 years was used. The abundance of cephalodia increased, indicative of higher N2-fixation rates resulting from lower N availability. Thallus δ13C values increased with ageing soils, in line with declining δ13C values of the humus substratum along this gradient. However, δ13C values were also driven by variation in factors that were at least partly independent of soil ageing. As such, δ13C values were mostly related to specific thallus mass (STM), possibly because a higher STM gives a thicker cortical layer and thus greater resistance to CO2 diffusion, leading to higher δ13C values. STM and other measured traits (i.e. thallus N, P, secondary compounds and water-holding capacity) were unresponsive to the gradient, despite these traits being very responsive to the same gradient in epiphytic lichen species.

Use of bentonite to control the release of copper from contaminated soils

A decrease in release and availability of heavy metals in soil has been of worldwide interest in recent years. Bentonite is a type of expandable montmorillonite clay, and has strong sorption for heavy metals. In this work, the control of amended bentonite on the release of copper (Cu2+) from spiked soils was investigated using a batch equilibrium technique. Sorption of Cu by bentonite was pH-dependent, and could be well described using the Langmiur model. Maximum sorption capacity of the bentonite used in this study was 5.4 mg/g, which was much greater than soils reported in the literature. The extent of Cu2+ release from spiked soils was correlated with slurry concentrations, pH, and soil ageing process. In all cases, the amendment of bentonite was observed to effectively decrease the release of Cu2+ from soils. The apparent aqueous concentrations of Cu2+ released from soils devoid of bentonite treatment were 113–1160% higher than those from the soils amended with bentonite. Moreover, the magnitude of Cu2+ release decreased with increasing amount of bentonite added to soils. The bentonite added was more effective in retaining Cu2+ in sorbents for aged contaminated soils. Such enhanced retention resulting from the presence of bentonite was observed within a wide pH range from 2.5 to 7.0. Bentonite, as one of the most abundant minerals in soils, is regarded to improve the soil overall quality. The results obtained from this work provide useful information on utilisation of bentonite to control the release of heavy metals from contaminated soils.