Dr Liang Wang

In the rapidly evolving domain of vapor intrusion (VI) assessments, traditional methodologies encompass detailed groundwater and soil vapor sampling coupled with comprehensive laboratory measurements. These models, blending empirical data, theoretical equations, and site-specific parameters, evaluate VI risks by considering a spectrum of influential factors, from volatile organic compounds (VOC) concentrations in groundwater to nuanced soil attributes. However, the challenge of variability, influenced by dynamic ambient conditions and intricate soil properties, remains. Our study presents an advanced on-site gas sensing station geared towards real-time VOC flux monitoring, enriched with an array of ambient sensors, and spearheaded by the reliable PID sensor for VOC detection. Integrating this dynamic system with machine learning, we developed predictive models, notably the random forest regression, which boasts an R-squared value exceeding 79 % and mean relative error near 0.25, affirming its capability to predict trichloroethylene (TCE) concentrations in soil vapor accurately. By synergizing real-time monitoring and predictive insights, our methodology refines VI risk assessments, equipping communities with proactive, informed decision-making tools and bolstering environmental safety. Implementing these predictive models can simplify monitoring for residents, reducing dependence on specialized systems. Once proven effective, there's potential to repurpose monitoring stations to other VI-prone regions, expanding their reach and benefit. The developed model can leverage weather forecasting data to predict and provide alerts for future VOC events.

The application of portable chromatography¿mass spectrometer (GC¿MS) is restrained by its detection limits without the development of proper sample pre-concentration methods. The primary focus of this paper is to introduce a practical field measurement methodology for the analysis of volatile organic compounds (VOCs) in soil vapour and groundwater using a portable gas (GC¿MS)system for application to in situ assessment of vapour intrusion from VOC contamination. A solid-phase micro-extraction (SPME) technique was applied for sample pre-concentration before the GC¿MS¿ measurement. Practical in-field soil gas SPME sampling methods have been developed to optimise the SPME extraction efficiency to then ultimately improve the detection limits of portable GC¿MS. An Australian site impacted by a chlorinated VOC, trichloroethylene (TCE), was the subject of the case study. To rapidly assess soil vapour samples in subsurface soil, in-house-developed retractable soil vapour sampling probes (SVSPs) were installed at the site in clusters at depths of 1 m, 2 m and 3 m below ground level at each sampling location. Use of the SVSPs for sampling enabled the generation of a three-dimensional map and distribution contours for TCE concentrations using the in situ measurement results of a portable GC¿MS analysis for vapour intrusion investigation. The results of the portable GC¿MS¿ analysis were compared with the results from conventional USEPA methods, such as TO-15 and Method 8265 for soil vapour and groundwater samples, respectively. This work demonstrates that the developed methodology of using a portable GC¿MS system has the capability for in-field quantitative analysis of VOCs for rapid contaminated site vapour intrusion assessment.

Rhizoremediation potential of different wild plant species for total (aliphatic) petroleum hydrocarbon (TPH)-contaminated soils was investigated. Three-week-old seedlings of Acacia inaequilatera, Acacia pyrifolia, Acacia stellaticeps, Banksia seminuda, Chloris truncata, Hakea prostrata, Hardenbergia violacea, and Triodia wiseana were transplanted in a soil contaminated with diesel and engine oil as TPH at pollution levels of 4,370 (TPH1) and 7,500 (TPH2) mg kg-1, and an uncontaminated control (TPH0). After 150 days, the presence of TPH negatively affected the plant growth, but the growth inhibition effect varied between the plant species. Plant growth and associated root biomass influenced the activity of rhizo-microbiome. The presence of B. seminuda, C. truncata, and H. prostrata significantly increased the TPH removal rate (up to 30% compared to the unplanted treatment) due to the stimulation of rhizosphere microorganisms. No significant difference was observed between TPH1 and TPH2 regarding the plant tolerance and rhizoremediation potentials of the three plant species. The presence of TPH stimulated cluster root formation in B. seminuda and H. prostrata which was associated with enhanced TPH remediation of these two members of Proteaceae family. These results indicated that B. seminuda, C. truncata, and H. prostrata wild plant species could be suitable candidates for the rhizoremediation of TPH-contaminated soil.

Traditional contaminated site characterisation approaches are time-consuming, labour-intensive, and demand a high level of expertise. This case study provides a rapid field-based solution to investigating a VOC contaminated site and its vapour incursion by combining soil vapour and groundwater survey. To fully assess the volatile organic compound (VOC) distribution in a contaminated site, a number of self-developed soil vapour sampling probes (SVSPs) were placed vertically at different locations in a grid with different depths. Hence, 3D subsurface contour maps for VOC concentrations in soil vapour can be obtained and used to help identify hot spots and the migration patterns of VOCs. This SVSP is "easy-to-install" in the field and a cost-effective solution for rapid assessment of soil vapour samples. The SVSPs can be installed both vertically and horizontally. If there is a requirement to take soil vapour samples beneath an existing building from a potential contamination source zone, SVSPs can be horizontally installed beneath the building without compromising its structural integrity. In addition, to ascertain the correct groundwater channels that are likely to carry contaminants from a potential source zone, an electrical resistivity tomography technique was employed to provide the preliminary information for groundwater delineation in a complex groundwater channel network.

Once petroleum hydrocarbons (PHs) are released into the soil, the interaction between PHs and soil media is dependent not only upon the soil properties but also on the characteristics of PHs. In this study, the key factors influencing the interactions between PHs and soil media are discussed. The key factors include: 1) the characteristics of PHs, such as volatility and viscosity; and 2) soil properties, such as porosity, hydraulic properties and water status, and organic matter; and 3) atmospheric circumstances, such as humidity and temperature. These key factors can be measured either ex-situ using conventional laboratory methods, or in situ using portable or handheld instruments. This study overviews the current ex/in situ techniques for measuring the listed key factors for PH contaminated site assessments. It is a tendency to apply in situ methods for PH contaminated site characterisation. Furthermore, handheld/portable Fourier transform infrared spectroscopy (FTIR) instrument provides tremendous opportunities for in-field PH contaminated site assessment. This study also reviewed the non-destructive FTIR spectroscopy analysis coupling with handheld FTIR for in-field PH contaminated site characterisation, including determining the concentration of total PH, dominant PH fractions and soil key properties for PH transport modelling.

Arsenic (As) and zinc (Zn) are common co-contaminants in mining impacted soils. Their interaction on solubility and toxicity when present concurrently is not well understood in natural systems. The aim of this study was to observe their interaction in solubility (soil-solution), bioaccumulation (shoot uptake) and toxicity to cucumber (Cucumis sativa L) conducting 4 weeks pot study in 5 different soils spiked with As (0, 2, 4, 8 to 1024 mg kg-1) individually and with Zn at two phytotoxic doses. The As pore-water concentration was significantly reduced (df = 289, Adjusted R2 = 0.84, p < 0.01) in the presence of Zn in the whole dataset, whereas Zn and Zn2+ activity in pore-water was reduced significantly only in the two alkaline soils. This outcome may be due to adsorption/surface precipitation or tertiary bridging complexation. No homogenous precipitation of zinc arsenate could be established using electron microscopy, XRD or even equilibrium calculations. For bioaccumulation phase, no significant effect of Zn on As uptake was observed except acidic MG soil whereas, Zn uptake was significantly reduced (p < 0.05) by As in whole dataset. However, an additive response was observed mostly except acidic MG soil. The synergistic response (more than additive) was predominant in this soil for a wide range of inhibition concentration (0¿80%) at both Zn EC10 and EC50 levels. Since additive response is mostly considered in risk assessment for mixtures, precautions should be implemented for assessment of toxicity for As-Zn mixture in acidic soil due to their synergistic response in some soils.

Work reported in this manuscript takes into consideration the possible use of NH3 gas by terrorists and the potential for an effective and rapid removal of such toxic substance from air using a modified clay material. In this study, a series of clay/polymer composites were synthesised for ammonia gas (NH3) adsorption. The adsorbents were prepared by polymerisation of acrylic acid with N,N'-methylenebisacrylamide (MBA) as cross-linker in the presence of a large amount of highly dispersed clay nanoparticles, followed by interaction with copper ions (Cu2+). Two kinds of clays were used. One was an acid-treated bentonite that had a specific surface area (SSA) of 395 m2/g and the other was natural palygorskite with a SSA of 87 m2/g. The materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption and Fourier transform infrared spectroscopy (FTIR). The materials' ability to remove NH3 was investigated using NH3 breakthrough dynamic test while the strength of NH3 retention was characterised by Thermogravimetric Analysis (TGA) coupled with FTIR. The results indicate that clay/poly-acrylic acid composites are highly efficient adsorbents of NH3 after binding with Cu2+. Trapping NH3 on such adsorbents can lead to colour change and this makes it possible to predict the lifetime of the adsorption bed visually. In addition, the result of NH3 release from the material following adsorption showed that majority of the adsorbed NH3 desorbed at temperature above 180°C. The clay/polymer composites can potentially be used in air filters. They may provide an effective and cheap way for removing NH3 from contaminated air.

This study introduced a patented novel methodological system for automatically analysis of Fourier Transform Infrared Spectrometer (FTIR) spectrum data located at 'fingerprint' region (wavenumber 670-800 cm-1), to simultaneously determinate multiple petroleum hydrocarbons (PHs) in real mixture samples. This system includes: an object oriented baseline correction; Band decomposition (curve fitting) method with mathematical optimization; and Artificial Neural Network (ANN) for determination, which is suitable for the characteristics of this IR regions, where the spectra are normally with low signal to noise ratio and high density of peaks. BTEX components are potentially lethal carcinogens and contained in many petroleum products. As a case study, six BTEX components were determinate automatically and simultaneously in mixture vapor samples. The robustness of the BTEX determination was validated using real petroleum samples, and the prediction results were compared with gas chromatography-mass spectrometry (GC-MS).