Potentially toxic elements (PTEs) in soils pose severe threats to the environment and human health. It is therefore imperative to have access to simple, rapid, portable and accurate methods for their detection in soils. In this regards, the review introduces recent progresses made in the development and applications of spectroscopic methods for in-situ semi-quantitative and quantitative detection of PTEs in soil and critically compares them to standard analytical methods. The advantages and limitations of these methods are discussed together with recent advances in chemometrics and data mining techniques allowing to extract useful information based on spectral data. Furthermore, the factors influencing soil spectra and data analysis are discussed and recommendations on how to reduce or eliminate their influences are provided. Future research and development needs for spectroscopy techniques are emphasized, and an analytical framework based on technology integration and data fusion is proposed to improve the measurement accuracy of PTEs in soil.

For containment and water exclusion purposes, cement-bentonite (CB) barrier walls are usually built, with certain design criteria specified for the wall to fulfill intended purposes. While permeability is believed to be the most important criterion, it can be impacted by the stress-strain properties of the wall, which define the strength and stiffness. This study investigates the influence of curing time, confinement, rate of axial deformation, and quantity of cement (mix of Portland cement (PC) and ground granulated blast furnace slag (GGBS)) on the stress-strain properties of CB slurry walls. An unconfined compressive test supported by (i.e. UCT) undrained triaxial (UUT) tests were carried out on specimens prepared from two mix-designs (differentiated by the proportion of GGBS in the cement component) and cured 7, 14, 28, 60, and 90 days. Two rates of deformation (1.0mm/min and 1.2mm/min) were examined, using a range of confining pressure (i.e., 50 - 200 kPa) in the UUT. The results reveal that varying rates of deformation and the range of confining pressures have no clear influence on the mechanical properties (e.g., deviator stress, shear strength, and stiffness) of the CB mix-designs. However, increased curing time, and the proportion of GGBS significantly improved these properties. An increased proportion of GGBS enhances early strength. Thus, further work needs to be done to establish a balance between adequate strength and adequate flexibility of CB walls in order to not compromise permeability.

Potentially toxic elements (PTEs) contamination in soils threats human wellbeing and ecological health because of their toxicity and bioaccumulation. This research presents a portable Olympus Delta Premium 6000 Series XRF Analyser (Olympus, USA) as a rapid measurement tool (RMT) for PTEs: Cr, Cu, Fe, Pb, Mn, and Zn in contaminated soils in the Niger Delta, Nigeria. A total of 45 crude oil-contaminated soils were collected from three genuinely oil spill sites. The range of measured PTEs concentrations (mg/kg) in the study sites are as follows: Site 1: chromium (Cr) 54–75, copper (Cu) 5.4–16.6, iron (Fe) 14,841–23,404, lead (Pb) 13.5–21.4, manganese (Mn) 158–555, and zinc (Zn) 32.6–47.2; Site 2: (35–66), (5–16.1), (10166–20,967), (12–17.8), (209–440), (17.6–33.6); and Site 3: (32–115), (6.5–20.8), (7538–22,800), (12–135), (98–338), (19.9–177). The trend of PTEs across the three sites follows the same order: Fe > Mn > Cr > Zn > Pb > Cu. The average concentration values of PTEs in all the 3 sites were higher than background concentration values. Thus, crude oil spill spiked the PTEs concentrations. XRF spectroscopy is recommended as a cost-effective and RMT for PTEs in soils.