A modified TOP assay to detect per- and polyfluoroalkyl substances in aqueous film-forming foams (AFFF) and soil.

Total oxidisable precursor (TOP) assay can oxidise some per- and polyfluoroalkyl substances (PFASs) and their precursors, most of which cannot be quantitatively detected so far, and convert them to detectable PFASs, such as perfluoroalkyl acids (PFAAs). However, the conversion is constrained by the complexity of the target samples, including co-existent organics, unknown PFAS precursors, and background. In this study, the TOP assay is modified to increase the oxidation and conversion efficiency by changing the initial concentration of target sample, increasing oxidising doses, time, temperature, etc.

Thermal kinetics of PFAS and precursors in soil: Experiment and surface simulation in temperature-time plane.

Per- and polyfluoroalkyl substances (PFAS) are chemically and thermally stable due to the presence of carbon-fluorine (C-F) bond in their molecular structures, hence have been previously formulated as firefighting ingredients. During the firefighting process, however, owing to the high temperature, PFAS can be potentially degraded, particularly for PFAS precursors that contain non-C-F bonds, which is studied herein by exposing PFAS-contaminated soil in a muffle furnace oven. Different temperatures and time intervals are applied to the real soil sample to mimic the firing process and to evaluate the degradation and conversion of PFAS.

Ultrasound-enhanced Magnéli phase TiO anodic oxidation of per- and polyfluoroalkyl substances (PFAS) towards remediation of aqueous film forming foams (AFFF).

Per-and polyfluoroalkyl substances (PFAS) remediation is still a challenge. In this study, we propose a hybrid system that combines electrochemical treatment with ultrasound irradiation, aiming for an enhanced degradation of PFAS. Equipped with a titanium suboxide (TiO) anode, the electrochemical cell is able to remove perfluorooctanoic acid (PFOA) effectively.

Identification and visualisation of microplastics via PCA to decode Raman spectrum matrix towards imaging.

To visualise microplastics and nanoplastics via Raman imaging, we need to scan the sample surface over a pixel array to collect Raman spectra as a matrix. The challenge is how to decode this spectrum matrix to map accurate and meaningful Raman images. This study compares two decoding approaches.

Aging of nickel added to soils as predicted by soil pH and time.

Although aging processes are important in risk assessment for metals in soils, the aging of Ni added to soils has not been studied in detail. In this study, after addition of water soluble Ni to soils, the changes over time in isotopic exchangeability, total concentrations and free Ni(2+) activity in soil pore water, were investigated in 16 European soils incubated outdoors for 18 months. The results showed that after Ni addition, concentrations of Ni in soil pore water and isotopic exchangeability of Ni in soils initially decreased rapidly.

Speciation and isotopic exchangeability of nickel in soil solution.

Knowledge of trace metal speciation in soil pore waters is important in addressing metal bioavailability and risk assessment of contaminated soils. In this study, free Ni(2+) activities were determined in pore waters of long-term Ni-contaminated soils using a Donnan dialysis membrane technique. The pore water free Ni(2+) concentration as a percentage of total soluble Ni ranged from 21 to 80% (average 53%), and the average amount of Ni bound to dissolved organic matter estimated by Windermere Humic Aqueous Model VI was < or = 17%.

Long-term aging of copper added to soils.

Aging refers to the processes by which the mobility and bioavailability/toxicity of metals added to soil decline with time. Although long-term aging is a key process that needs to be considered in the risk assessment of metals in field soils, the long-term aging of Cu added to soils has not been studied in detail. In this study, the effects of aging on Cu isotopic exchangeability, total Cu in soil pore water, pore water free Cu2+ activity, and "available" Cu measured by the technique of diffusive gradient in thin film (DGT-Cu) were investigated in 19 European soils at two total Cu concentrations shown to inhibit plant (tomato) growth by 10 and 90%.

Stable isotope techniques for assessing labile Cu in soils: development of an L-value procedure, its application, and reconciliation with E values.

Isotopic techniques have become a valuable tool for assessing the lability or potential availability of elements in soil. Until now, work on soil Cu has been limited to E-value methods where soil solution extracts are obtained by physical means due to the very short (12.4 h) half-life of the radio isotope 64Cu.

Short-term natural attenuation of copper in soils: effects of time, temperature, and soil characteristics.

Natural attenuation of metals added to soils refers to the processes by which the mobility and bioavailability/toxicity of the added metals decline with time. In this paper, we used isotopic dilution techniques to investigate the short-term (30 d) natural attenuation of Cu added to 19 European soils at two effective concentrations shown to inhibit plant (tomato) growth by 10 and 90%. The results showed that the lability of Cu added to soils rapidly decreased after addition, especially in the soils with pH > 6.

Performance of a mixed binding layer for measuring anions and cations in a single assay using the diffusive gradients in thin films technique.

The performance of a mixed binding layer (MBL) for use in diffusive gradients in thin films (DGT) was investigated. The MBL consisted of ferrihydrite and Chelex-100 cation-exchange resin combined together in a binding gel in an attempt to allow measurement of anions and cations in a single assay. Results from the MBL were compared to experiments performed using individual Chelex gels and ferrihydrite gels that have been shown to work successfully for DGT methodology.

Prediction of zinc, cadmium, lead, and copper availability to wheat in contaminated soils using chemical speciation, diffusive gradients in thin films, extraction, and isotopic dilution techniques.

To predict the availability of metals to plants, it is important to understand both solution- and solid-phase processes in the soil, including the kinetics of metal release from its binding agent (ligand and/or particle). The present study examined the speciation and availability of Zn, Cd, Pb, and Cu in a range of well-equilibrated metal-contaminated soils from diverse sources using several techniques as a basis for predicting metal uptake by plants. Wheat (Triticum aestivum L.

Effect of toxic cations on copper rhizotoxicity in wheat seedlings.

Copper pollution may occur in acidic soils where the low pH leads to release of Al and Mn in soil solution, which could interact with Cu toxicity. Very little information exists regarding the influence of toxic cations on the phytotoxicity of Cu. In this study, we tested the hypothesis that phytotoxicity of Cu2+ may be overestimated in acidic soils due to synergism between Al or Mn and Cu toxicity.

Measurement of labile Cu in soil using stable isotope dilution and isotope ratio analysis by ICP-MS.

Isotope dilution is a useful technique to measure the labile metal pool, which is the amount of metal in soil in rapid equilibrium (<7 days) with the soil solution. This is normally performed by equilibrating soil with a metal isotope, and sampling the labile metal pool by using an extraction (E value), or by growing plants (L value). For Cu, this procedure is problematic for E values, and impossible for L values, due to the short half-life of the 64Cu radioisotope (12.

Coupling speciation and isotope dilution techniques to study arsenic mobilization in the environment.

We have developed an approach to isolate mechanisms controlling mobility and speciation of As in soil-water systems. The approach uses a combination of isotopic exchange and chromatographic/mass spectrometric As speciation techniques. We used this approach to identify mechanisms responsible for changes in the concentration of soluble As in two contaminated soils (Eaglehawk and Tavistock) subjected to different redox conditions and microbial activity.

Chemical speciation of Zn, Cd, Cu, and Pb in pore waters of agricultural and contaminated soils using Donnan dialysis.

Knowledge of trace metal speciation in soil pore waters is important in addressing metal bioavailability and risk assessment of contaminated soils. Numerous analytical methods have been utilized for determining trace metal speciation in aqueous environmental matrixes; however, most of these methods suffer from significant interferences. The Donnan dialysis membrane technique minimizes these interferences and has been used in this study to determine free Zn2+, Cd2+, Cu2+, and Pb2+ activities in pore waters from 15 agricultural and 12 long-term contaminated soils.