Greg Davis

This study examines PFAS leaching behavior from concrete contaminated by the historical use of aqueous film-forming foams at an Australian Defence site, highlighting the long-term environmental implications of contaminated infrastructure.

Biodegradation and biotransformation of contaminants in groundwater commonly occurs naturally. However, natural biodegradation rates can be slow leading to elongated contaminant plumes and prolonged risks that demand greater remedial intervention. Enhancement of the biodegradation of contaminants in groundwater can be induced by the addition of amendments to change the geochemical conditions to those that are more favorable for indigenous or added biota. Enhancing biodegradation requires collocation of the contaminant of concern with the ‘right’ microbial communities under the ‘right’ geochemical conditions, so that the microbiota thrive and bio-transform, degrade or lock up the contaminant of interest. This is most easily achievable at laboratory or bench scale where mixing is easily performed, and mass transfer limitations are minimized. However, inducing such changes at field scale in aquifers is non-trivial - amendments do not easily mix into groundwater because it is a laminar (non-turbulent) and low-energy flow environment. Bioaugmentation of cultured or genetically modified organisms have also been considered to add to groundwater to enhance contaminant degradation rates. Here we provide an overview of research studies over approximately 40 years that highlight the progression of understanding from natural biodegradation of plumes in groundwater to active bioremediation efforts that have been variably successful at field scale. Investigated contaminants providing insights include petroleum hydrocarbons, chlorinated and brominated hydrocarbons, ammonium, metals, munition compounds, atrazine and per- and polyfluorinated alkyl substances. The redox and electron acceptor/donor conditions that are inducive to biodegradation for a range of contaminants are highlighted. Biodegradation is challenged by the availability of electron donors/acceptors in the core of plumes and on plume fringes. Cases for bioaugmentation are identified. A long history of investigations provides examples of the importance of amendment delivery mechanisms, scale-up from laboratory to field, and field-scale demonstration of the effectiveness of groundwater bioremediation technologies. Advantages and disadvantages of remedial approaches are tabulated. The value and contributions of integrative modelling advances are identified. The literature review and example cases provide a deep understanding of what scale of bioremediation might be achievable for groundwater plumes. Limitations to bioremediation strategies outlined here will help direct future efforts. Addressing the sources of groundwater plumes as well as bioremediation of the plume itself will achieve more effective outcomes. Twelve ‘lessons learnt’ are synthesized from the review.

Objective: Safety and efficacy of the NEUROMARK® system for treating chronic rhinitis.Methods: A prospective, single‐arm, multicenter study was performed on adults with chronic rhinitis who underwent radiofrequency ablation to the posterior nasal nerves. Primary endpoints were device‐related serious adverse events (SAEs) at 1 month and change from baseline in visual analog scale nasal symptom scale (VAS NSS) for rhinorrhea and nasal congestion at 3 months. Total nasal symptom score (rTNSS) and mini Rhinoconjunctivitis Quality of Life Questionnaire (mini RQLQ) score were also evaluated.Results: Thirty‐six participants were enrolled and completed follow‐up at 1 and 3 months. Mean VAS NSS scores for rhinorrhea and nasal congestion demonstrated significant improvement at 3 months (both p < .0001). The mean percent changes from baseline in VAS rhinorrhea and nasal congestion were 53% and 55%, respectively. Total scores and all individual rTNSS items significantly improved (all p < .001) over the measured interval. Percent responder rate (≥30% reduction from baseline in total rTNSS) at 3 months was 78%. The total mean mini RQLQ scores, as well as all subdomains, improved significantly (all p < .0001). At 3 months, 89% of participants reported a minimal clinically important difference of ≥0.4 point improvement in the mini RQLQ score. No SAEs occurred during the study.Conclusions: The NEUROMARK System is a novel radiofrequency ablation device that provides safe and effective treatment to the posterior nasal nerves for patients with chronic rhinitis. Study participants experienced statistically significant and clinically meaningful improvement in symptoms and quality of life assessments at 3 months post‐procedure.Trial Registration: The study is registered at www.clinicaltrials.gov with the unique identifier of NCT05324397.Level of Evidence: 4.

Can we hope for autonomous (self-contained in situ) sensing of subsurface soil and groundwater pollutants to satisfy relevant regulatory criteria? Global advances in sensors, communications, digital technologies, and computational capacity offer this potential. Here we review past efforts to advance subsurface investigation techniques and technologies, and computational efforts to create a digital twin (representation) of subsurface processes. In the context of the potential to link measurement and sensing to a digital twin computation platform, we outline five criteria that might make it possible. Significant advances in sensors based on passive measurement devices are proposed. As an example of what might be achievable, using the five criteria, we describe the deployment of online real-time sensors and simulations for a case study of a petroleum site where natural source zone depletion (NSZD) is underway as a potential biodegradation management option, and where a high-quality conceptual site model is available. Multiple sensors targeting parameters (major gases and temperature influenced by soil moisture) relevant to the subsurface NSZD biodegradation processes are shown to offer the potential to map subsurface processes spatially and temporally and provide continuous estimates of degradation rates for management decisions, constrained by a computational platform of the key processes. Current limitations and gaps in technologies and knowledge are highlighted specific to the case study. More generally, additional key advances required to achieve autonomous sensing of subsurface soil and groundwater pollutants are outlined.

This paper describes the proceedings of a Special Session on Natural Source Zone Depletion (NSZD) at the AquaConSoil conference, held virtually in June 2021. It spans research across Europe, the United States of America and Australia. NSZD has been described as the ‘combination of processes that reduce the mass of LNAPL light non-aqueous phase liquid) in the subsurface’. LNAPL NSZD research and investigations have been focused on a range of hydrocarbon products, such as gasoline, diesel, jet fuel, as well as crude oil. Key NSZD processes include aerobic biodegradation, fermentation and methanogenesis of LNAPL constituents, dissolution of LNAPL constituents into groundwater and volatilization of LNAPL constituents into the unsaturated zone. In turn the generated methane, carbon dioxide and dissolved/volatilized constituents can be cycled and biodegraded in the unsaturated and saturated zones. Importantly these physical, chemical, and biological processes can act without human intervention to reduce the NAPL mass and toxicity. Over time NSZD can both reduce LNAPL mass, and change its chemical composition resulting in risk reduction, and ultimately source depletion. Methanogenesis of organic materials has long been recognized in municipal landfills and natural anoxic environments, such as peat and wetlands. Recognition of similar processes in LNAPL source zones in the past decade along with high rates of aerobic biodegradation observed in unsaturated zones above LNAPL-impacted areas, has significantly revised the conceptual model of LNAPL source zone behaviour and persistence. Several NSZD monitoring approaches have been developed and are being applied in field studies. While the quantitative NSZD rates derived can vary between techniques, they all demonstrate that NSZD LNAPL removal can exceed that delivered by engineered LNAPL recovery techniques, particularly for mature LNAPL bodies.