The 2023 terahertz science and technology roadmap

Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz–∼30 THz). Within its frequency boundaries exist a broad variety of scientific disciplines that have presented, and continue to present, technical challenges to researchers. During the past 50 years, for instance, the demands of the scientific community have substantially evolved and with a need for advanced instrumentation to support radio astronomy, Earth observation, weather forecasting, security imaging, telecommunications, non-destructive device testing and much more. Furthermore, applications have required an emergence of technology from the laboratory environment to production-scale supply and in-the-field deployments ranging from harsh ground-based locations to deep space. In addressing these requirements, the research and development community has advanced related technology and bridged the transition between electronics and photonics that high frequency operation demands. The multidisciplinary nature of THz work was our stimulus for creating the 2017 THz Science and Technology Roadmap (Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001). As one might envisage, though, there remains much to explore both scientifically and technically and the field has continued to develop and expand rapidly. It is timely, therefore, to revise our previous roadmap and in this 2023 version we both provide an update on key developments in established technical areas that have important scientific and public benefit, and highlight new and emerging areas that show particular promise. The developments that we describe thus span from fundamental scientific research, such as THz astronomy and the emergent area of THz quantum optics, to highly applied and commercially and societally impactful subjects that include 6G THz communications, medical imaging, and climate monitoring and prediction. Our Roadmap vision draws upon the expertise and perspective of multiple international specialists that together provide an overview of past developments and the likely challenges facing the field of THz science and technology in future decades. The document is written in a form that is accessible to policy makers who wish to gain an overview of the current state of the THz art, and for the non-specialist and curious who wish to understand available technology and challenges. A such, our experts deliver a 'snapshot' introduction to the current status of the field and provide suggestions for exciting future technical development directions. Ultimately, we intend the Roadmap to portray the advantages and benefits of the THz domain and to stimulate further exploration of the field in support of scientific research and commercial realisation

Assessing and communicating risk with communities living on contaminated land.

The U.K. government has emphasized redeveloping derelict land for housing. As a result, tools for assessing brownfield sites are well developed. However, there are many potentially contaminated sites on which people live, often not to the people's knowledge. For these situations, statutory guidance for risk communication is underdeveloped and, in certain situations, inadequate. This paper illustrates limitations of current methods using a heavily populated site where levels of specific contaminants exceed statutory limits. The authors describe how residents were involved in the site assessment process and how the process may be improved, and propose a framework to incorporate risk communication into the contaminated-land use strategy

Evaluating fugacity models for trace components in landfill gas.

A fugacity approach was evaluated to reconcile loadings of vinyl chloride (chloroethene), benzene, 1,3-butadiene and trichloroethylene in waste with concentrations observed in landfill gas monitoring studies. An evaluative environment derived from fictitious but realistic properties such as volume, composition, and temperature, constructed with data from the Brogborough landfill (UK) test cells was used to test a fugacity approach to generating the source term for use in landfill gas risk assessment models (e.g. GasSim). SOILVE, a dynamic Level II model adapted here for landfills, showed greatest utility for benzene and 1,3-butadiene, modelled under anaerobic conditions over a 10 year simulation. Modelled concentrations of these components (95 300 μg m−3; 43 μg m−3) fell within measured ranges observed in gas from landfills (24 300–180 000 μg m−3; 20–70 μg m−3). This study highlights the need (i) for representative and time-referenced biotransformation data; (ii) to evaluate the partitioning characteristics of organic matter within waste systems and (iii) for a better understanding of the role that gas extraction rate (flux) plays in producing trace component concentration

Identifying source correlation parameters for hydrocarbon wastes using compound- specific isotope analysis.

A preliminary evaluation of compound-specific isotope analysis (CSIA) as a novel, alternative method for identifying source correlation compounds in soils contaminated with residual heavy or weathered petroleum wastes is presented. Oil-contaminated soil microcosms were established using soil (sandy-loam, non- carbonaceous gley) amended with ballast-, crude- or No.6 fuel oil. Microcosms were periodically sampled over 256 days and δ13C values (which express the ratio of 13C to 12C) determined at each time point for five n-alkanes and the isoprenoid norpristane using gas chromatography–isotope ratio mass spectrometry (GC-IRMS). Although some temporal variation was observed, no significant temporal shifts in the δ13C values for the five n-alkanes were measured in all three oils. Isoprenoid isotope ratios (δ13C) appeared to be least affected by biotransformation, especially in the No.6 fuel oil. The research suggests that the δ13C of isoprenoids such as norpristane, may be of use as source correlation parameters. Compound-specific isotope analysis (CSIA) is a promising method for identifying source correlation compounds in soils contaminated with heavy or weathered petroleum

Assessing potential risk of heavy metal exposure from consumption of home-produced vegetables by urban populations

We performed a risk assessment of metal exposure to population subgroups living on, and growing food on, urban sites. We modeled uptake of cadmium, copper, nickel, lead, and zinc for a selection of commonly grown allotment and garden vegetables. Generalized linear cross-validation showed that final predictions of Cd, Cu, Ni, and Zn content of food crops were satisfactory, whereas the Pb uptake models were less robust. We used predicted concentrations of metals in the vegetables to assess the risk of exposure to human populations from homegrown food sources. Risks from other exposure pathways (consumption of commercially produced foodstuffs, dust inhalation, and soil ingestion) were also estimated. These models were applied to a geochemical database of an urban conurbation in the West Midlands, United Kingdom. Risk, defined as a "hazard index," was mapped for three population subgroups: average person, highly exposed person, and the highly exposed infant (assumed to be a 2-year-old child). The results showed that food grown on 92% of the urban area presented minimal risk to the average person subgroup. However, more vulnerable population subgroups (highly exposed person and the highly exposed infant) were subject to hazard index values greater than unity. This study highlights the importance of site-specific risk assessment and the "suitable for use" approach to urban redevelopment

A review of the abundance, behaviour and detection of clostridial pathogens in agricultural soils.

The soil is a reservoir for various clostridial pathogens, with agricultural soils representing a major source of contamination for overlying crops and grazing livestock. Understanding the prevalence and behaviour of pathogens in these soils is fundamental to ascertaining and mitigating the risk of disease from agroecosystems. This article reviews research pertaining to the overall distribution and abundance of clostridial pathogens in the soil while identifying possible environmental and soil factors influencing their behaviour. Large-scale soil screens have identified pathogens across the globe, although some Clostridium botulinum toxinotypes are more prevalent in certain geographic regions. Faecal inputs and organic waste amendments to the soil can elevate the levels of enteric clostridial pathogens in the soil and the subsequent disease risk, as highlighted by case–control studies. The ability of Clostridia to sporulate results in their long-term persistence post-introduction, increasing the time period for disease transmission. Regularly or permanently saturated soils may also enhance survival, or potentially facilitate the regrowth of some indigenous or introduced Clostridia. This is supported by the high prevalence of Clostridia in paddy soils, greater detection of pathogens in flooded soils, and the higher onset of some clostridial diseases in regions with poorly drained soils. Future research should elucidate soil types and environmental conditions which can enhance pathogen survival/regrowth. The adoption of molecular and sequencing technologies for future diagnostics can facilitate more sensitive detection and a higher resolution of pathogen typing, allowing a better understanding of pathogen population dynamics in farm soils and disease epidemiology

Optimising the biopiling of weathered hydrocarbons within a risk management framework.

Thirty years of research into petroleum microbiology and bioremediation have bypassed an important observation – that many hydrocarbon contaminated sites posing potential risks to human health harbour weathered, ‘mid-distillate’ or heavy oils rather than ‘fresh product’ (Pollard, 2003). Ex-situ biopiling is an important technology for treating soils contaminated with weathered hydrocarbons. However, its performance continues to be represented by reference to reductions in the hydrocarbon ‘load’ in the soils being treated, rather than reductions in the risks posed by the hydrocarbon contamination (Owens and Bourgouin, 2003; Tien et al., 1999). The absence of ‘risk’ from the vocabulary of many operators and remediation projects reduces stakeholder (regulatory, investor, landowner, and public) confidence in remediation technologies, and subsequently limits the market potential of these technologies. Stakeholder confidence in the biopiling of weathered hydrocarbons may be improved by demonstrating process optimisation within a validated risk ma

Exercise, Urban Food Production, Preparation and Consumption: Implications, Benefits and Risks to Grow-Your-Own (GYO) Gardeners

This study is the first to consider, and estimate, the influence of gardening routines on exposures to both health benefits and health risks. This holistic approach helped to contrast the healthy lifestyle of gardening with health risks from exposures to potentially toxic elements such as Cd and Pb in urban environments. A total of 120 participants who grew their own produce in an urban setting were recruited to the study. A detailed questionnaire was developed that included sections on gardening activity, cultivation and consumption of produce, consumption of commercially grown produce, and other lifestyle factors. Administered alongside the questionnaire was the Short Form 36 (v2) as a standardised tool for measuring physical and mental health. Fruit and vegetable consumption was found to be correlated with the amount of gardening individuals did in autumn/winter and was greater than fruit and vegetable consumption, on average, in the UK general population. Levels of physical activity were also found to be higher in our study than regional averages, whilst BMI was lower than average. This is the first study to find a relationship between gardening more regularly (in autumn/winter) and the physical component of the Short Form 36, and this relationship was elevated compared to non-gardening populations. The physical component scores from this study were also significantly higher for older participants, compared to means from a Western population. This finding supports studies suggesting that gardening may be more beneficial for the elderly generation. These benefits were assessed in the context of potential exposures estimated from the type and frequency of produce being consumed. The benefit of maintaining a healthy lifestyle is likely to outweigh the health risks of gardening on soils mildly contaminated with Cd and Pb but requires formal consideration within a risk management framework