Rapid evaluation of arsenic contamination in paddy soils using field portable X-ray fluorescence spectrometry

Portable X-ray fluorescence (pXRF) analysis of heavy metal contamination in church graveyards with contrasting soil types

Human remains have been interred in burial grounds since historic times. Although the re-use of graveyards differs from one country, region or time period to another, over time, graveyard soil may become contaminated or enriched with heavy metal elements. This paper presents heavy metal element soil analysis from two UK church graveyard study sites with contrasting necrosols, but similar burial densities and known burial ages dating back to the sixteenth century and some possibly older than 1,000 years. Portable X-ray fluorescence element laboratory-based analyses were undertaken on surface and near-surface soil pellets. Results show elevated levels of Fe, Pb, Mn, Cr, Cu, Zn and Ca in both necrosols when compared with background values. Element concentration anomalies remained consistently higher than background samples down to 2 m, but reduced with distance away from church buildings. Element concentration anomalies are higher in the clay-rich necrosol than in sandy necrosol. Study result implications suggest that long-used necrosols are likely to be more contaminated with heavy metal elements than similar soil outside graveyards with implications for burial grounds management, adjacent populations and where burial grounds have been deconsecrated and turned to residential dwellings.

A Green Approach Based on Micro-X-ray Fluorescence for Arsenic, Micro- and Macronutrients Detection in Pteris vittata

In this study, benchtop micro-X-ray fluorescence spectrometry (µXRF) was evaluated as a green and cost-effective multielemental analytical technique for P. vittata. Here, we compare the arsenic (As) content values obtained from the same samples by µXRF and inductively coupled plasma-optical emissions spectrometry (ICP–OES). To obtain samples with different As concentrations, fronds at different growth time points were collected from P. vittata plants grown on two natural As-rich soils with either high or moderate As (750 and 58 mg/kg). Dried samples were evaluated using multielement-µXRF analysis and processed by PCA. The same samples were then analysed for multielement concentrations by ICP–OES. We show that As concentrations detected by ICP–OES, ranging from 0 to 3300 mg/kg, were comparable to those obtained by µXRF. Similar reliability was obtained for micro- and macronutrient concentrations. A positive correlation between As and potassium (K) contents and a negative correlation between As and iron (Fe), calcium (Ca) and manganese (Mn) contents were found at both high and moderate As. In conclusion, we demonstrate that this methodological approach based on μXRF analysis is suitable for monitoring the As and element contents in dried plant tissues without any chemical treatment of samples and that changes in most nutrient concentrations can be strictly related to the As content in plant tissue.

The use of portable XRF as a forensic geoscience non-destructive trace evidence tool for environmental and criminal investigations

Hand-held, portable X-Ray fluorescence instruments (pXRF) provide a means of rapid, in-situ chemical characterisation that has considerable application as a rapid trace evidence characterisation tool in forensic geoscience. This study presents both a control test study which demonstrates optimisation of the data collection process, alongside a range of individual forensic case studies, including heavy metal contamination, conflict archaeology, forensic soil characterisation, and verification of human remains, which together validate the technique and provide some comparison between field-based and laboratory-based pXRF applications. Results highlight the time-efficiency and cost-effectiveness of in-situ, field-based pXRF analyses for material characterisation when compared with other trace evidence methods. Analytical precision of various analytes during in-situ analysis was sufficient to demonstrate considerable application of field-based pXRF as a tool for rapid identification of specific areas of interest to be further investigated. Laboratory-based pXRF analyses yielded greater accuracy which could provide an efficient compromise between field-based pXRF and traditional laboratory-based analytical techniques (e.g. WD-XRF, ICP-MS). Further studies should collect more advanced datasets in more diverse locations to further validate the techniques capability to rapidly conduct geochemical surveys in a range of environments.

Fast and efficient aqueous arsenic removal by functionalized MIL-100(Fe)/rGO/δ-MnO2 ternary composites: Adsorption performance and mechanism

Because of its significant toxicological effects on the environment and human health, arsenic (As) is a major global issue. In this study, an Fe-based metal-organic framework (MOF) (Materials of Institut Lavoisier: MIL-100 (Fe)) which was impregnated with reduced graphene oxide (rGO) by using a simple hydrothermal method and coated with birnessite-type manganese oxide (δ-MnO₂) using the one-pot reaction process (MIL-100(Fe)/rGO/δ-MnO₂ nanocomposites) was synthesized and applied successfully in As removal. The removal efficiency was rapid, the equilibrium was achieved in 40 min and 120 min for As(III) and As(V), respectively, at a level of 5 mg/L. The maximum adsorption capacities of As(III) and As(V) at pH 2 were 192.67 mg/g and 162.07 mg/g, respectively. The adsorbent revealed high stability in pH range 2-9 and saturated adsorbent can be fully regenerated at least five runs. The adsorption process can be described by the pseudo-second-order kinetic model and Langmuir monolayer adsorption. The adsorption mechanisms consisted of electrostatic interaction, oxidation and inner sphere surface complexation.

Construction of Rutile-TiO2 Nanoarray Homojuction for Non-Contact Sensing of TATP under Natural Light

Triacetone triperoxide (TATP) is a new terrorist explosive, and most nitrogen-based sensors fail to detect TATP. Herein, a sea urchin-like TiO2-covered TiO2 nanoarray is constructed as a TATP-sensitive homojunction (HJ) by one step hydrothermal method. By taking fluorine-doped tin oxide (FTO) and indium tin oxide (ITO) conducting glass as the substrate, the conducting glass is horizontally and vertically put in the reactor to epitaxially grow TiO2–FTO, TiO2–ITO, TiO2–FTO–HJ and TiO2–ITO–HJ. TiO2–FTO–HJ shows a broad absorption band edge in the visible region and high sensitivity to TATP under the simulating natural light compared with TiO2–FTO, TiO2–ITO, and TiO2–ITO–HJ. E-field intensity distribution simulation reveals that constructing homojunctions between the urchin-shaped TiO2 nanosphere and TiO2 nanoarrays can enhance the localized electromagnetic field intensity at the interface of junctions, which may provide photocatalysis active sites to reduce TATP molecules by promoting charge separation. Moreover, the TiO2–FTO–HJ shows high selectivity to TATP among ammonium nitrate, urea and sulfur, which are common homemade explosive raw materials.