̽��ֱ�� of Cambridge - pollutants

Sensors made from ‘frozen smoke’ can detect toxic formaldehyde in homes and offices

sc604 — Fri, 09 Feb 2024 19:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge, developed sensors made from highly porous materials known as aerogels. By precisely engineering the shape of the holes in the aerogels, the sensors were able to detect the fingerprint of formaldehyde, a common indoor air pollutant, at room temperature.

̽��ֱ��proof-of-concept sensors, which require minimal power, could be adapted to detect a wide range of hazardous gases, and could also be miniaturised for wearable and healthcare applications. ̽��ֱ��results are reported in the journal Science Advances.

Volatile organic compounds (VOCs) are a major source of indoor air pollution, causing watery eyes, burning in the eyes and throat, and difficulty breathing at elevated levels. High concentrations can trigger attacks in people with asthma, and prolonged exposure may cause certain cancers.

Formaldehyde is a common VOC and is emitted by household items including pressed wood products (such as MDF), wallpapers and paints, and some synthetic fabrics. For the most part, the levels of formaldehyde emitted by these items are low, but levels can build up over time, especially in garages where paints and other formaldehyde-emitting products are more likely to be stored.

According to a 2019 report from the campaign group Clean Air Day, a fifth of households in the UK showed notable concentrations of formaldehyde, with 13% of residences surpassing the recommended limit set by the World Health Organization (WHO).

“VOCs such as formaldehyde can lead to serious health problems with prolonged exposure even at low concentrations, but current sensors don’t have the sensitivity or selectivity to distinguish between VOCs that have different impacts on health,” said Professor Tawfique Hasan from the Cambridge Graphene Centre, who led the research.

“We wanted to develop a sensor that is small and doesn’t use much power, but can selectively detect formaldehyde at low concentrations,” said Zhuo Chen, the paper’s first author.

̽��ֱ��researchers based their sensors on aerogels: ultra-light materials sometimes referred to as ‘liquid smoke’, since they are more than 99% air by volume. ̽��ֱ��open structure of aerogels allows gases to easily move in and out. By precisely engineering the shape, or morphology, of the holes, the aerogels can act as highly effective sensors.

Working with colleagues at Warwick ̽��ֱ��, the Cambridge researchers optimised the composition and structure of the aerogels to increase their sensitivity to formaldehyde, making them into filaments about three times the width of a human hair. ̽��ֱ��researchers 3D printed lines of a paste made from graphene, a two-dimensional form of carbon, and then freeze-dried the graphene paste to form the holes in the final aerogel structure. ̽��ֱ��aerogels also incorporate tiny semiconductors known as quantum dots.

̽��ֱ��sensors they developed were able to detect formaldehyde at concentrations as low as eight parts per billion, which is 0.4 percent of the level deemed safe in UK workplaces. ̽��ֱ��sensors also work at room temperature, consuming very low power.

“Traditional gas sensors need to be heated up, but because of the way we’ve engineered the materials, our sensors work incredibly well at room temperature, so they use between 10 and 100 times less power than other sensors,” said Chen.

To improve selectivity, the researchers then incorporated machine learning algorithms into the sensors. ̽��ֱ��algorithms were trained to detect the ‘fingerprint’ of different gases, so that the sensor was able to distinguish the fingerprint of formaldehyde from other VOCs.

“Existing VOC detectors are blunt instruments – you only get one number for the overall concentration in the air,” said Hasan. “By building a sensor that can detect specific VOCs at very low concentrations in real time, it can give home and business owners a more accurate picture of air quality and any potential health risks.”

̽��ֱ��researchers say the same technique could be used to develop sensors to detect other VOCs. In theory, a device the size of a standard household carbon monoxide detector could incorporate multiple different sensors within it, providing real-time information about a range of different hazardous gases. “At Warwick, we're developing a low-cost multi-sensor platform that will incorporate these new aerogel materials and, coupled with AI algorithms, detect different VOCs,” said co-author Professor Julian Gardner from Warwick ̽��ֱ��.

“By using highly porous materials as the sensing element, we’re opening up whole new ways of detecting hazardous materials in our environment,” said Chen.

̽��ֱ��research was supported in part by the Henry Royce Institute, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Tawfique Hasan is a Fellow of Churchill College, Cambridge.

Reference:
Zhuo Chen et al. ‘Real-time, noise and drift resilient formaldehyde sensing at room temperature with aerogel filaments.’ Science Advances (2024). DOI: 10.1126/sciadv.adk6856

Researchers have developed a sensor made from ‘frozen smoke’ that uses artificial intelligence techniques to detect formaldehyde in real time at concentrations as low as eight parts per billion, far beyond the sensitivity of most indoor air quality sensors.

NASA/JPL-Caltech

Silica aerogel

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Scientists urge global action to preserve water supplies for billions worldwide

bjb42 — Tue, 19 May 2009 00:00:00 +0000

Melting glaciers, weakening monsoon rains, less mountain snowpack and other effects of a warmer climate will lead to significant disruptions in the supply of water to highly populated regions of the world, according to an international group of scientists convened by ̽��ֱ�� of California San Diego and the ̽��ֱ�� of Cambridge.

This will especially be the case near the Himalayas in Asia and the Sierra Nevada Mountains of the western United States.

More than two dozen international water experts participated in the "Ice, Snow, and Water: Impacts of Climate Change on California and Himalayan Asia" workshop held at UC San Diego.

They noted heavy rains in Indian deserts, a recent drought in what is typically one of the wettest place on earth along the foot of the Himalayas, and other extreme weather events in recent decades.

Major rivers in both regions, like China's Yellow River and the Colorado River in the southwestern United States, routinely fail to reach the ocean now.

These extremes are signs of the climate- and societally-induced stresses that will be exacerbated in the future under continuing climate changes, threatening massive and progressive disruptions in the availability of drinking water to more than a billion people in the two regions.

̽��ֱ��workshop seeks to use the intellectual resources amassed at these and other universities - ranging from climate change research at Scripps to the computing power of the California Institute of Telecommunications and Information Technology (Calit2), and bringing social sciences together with physical and biological sciences - to promote solutions to the world's most pressing sustainability issues.

"Solutions to immense problems have small beginnings and we began here," said Sustainability Solutions Institute Senior Strategist Charles Kennel. "I continue to be impressed by what a small group of dedicated people can achieve."

Workshop leaders plan to present the declaration at the 2009 Forum on Science and Technology in Society in Kyoto, Japan, taking place in October. Additionally, the ̽��ֱ�� of Cambridge will continue the discussion of the global water crisis when it hosts in September a companion workshop focused on African water problems.

Research performed at Scripps and at other research centers around the world have indicated that global warming and particulate air pollution, especially in the form of black carbon (essentially soot), are already disrupting natural supplies of water by raising air temperatures and by increasing the light absorption of snow and ice as pollutants darken the frozen surfaces.

Workshop experts represented the United Nations World Climate Research Program, the Chinese Academy of Sciences, the Indian Space Research Organization, the British Antarctic Survey, the California Department of Water Resources as well as several American universities.

̽��ֱ��workshop was coordinated by UC San Diego's Sustainability Solutions Institute (SSI) and Cambridge Centre for Energy Studies (CCES) based at Judge Business School.

More information at the links above right.

Chinese, Indian, American and British scientists have released a conference declaration urging a region-by-region response to increased water scarcity and heightened hazards.

Solutions to immense problems have small beginnings and we began here.

Charles Kennel

Burning Image from Flickr

every drop counts

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Unclouding uncertainty in climate modelling

bjb42 — Fri, 01 May 2009 00:00:00 +0000

Our climate is the net result of many complex processes that transfer and redistribute the Sun’s energy through the Earth’s atmosphere, oceans, land and ecosystems. Because these processes are basically nonlinear, their interaction unavoidably leads to chaotic variability of climate and weather on various time scales, and we rely on climate models to achieve some sense of the dynamics of weather and to predict future climate. Currently, one of the greatest sources of uncertainty in climate modelling is posed by clouds, which are not resolved individually but instead are averaged. Professor Hans-F. Graf’s group, based in the Department of Geography and part of the Centre for Atmospheric Science (see panel), is developing a new technique for global and regional climate modelling that moves beyond treating clouds as ‘one-size-fits-all’.

Cloudy issues

Climate models consist of a set of coupled differential equations based on first principles of physics that are solved numerically by dividing the planet into a three-dimensional grid. Available computer power dictates that each grid is typically 100–300 km in size. Unfortunately, any processes that are smaller cannot be explicitly resolved and have to be ‘parameterised’ as an average. Among these are clouds: the standard approach has been to create an average cloud that has to mimic all the effects of the cloud spectrum of different-sized convective clouds. Of course, in nature, the cloud spectrum is highly variable depending on the actual weather situation and location, and clouds can range from a few hundred metres to a few kilometres in scale.

Clouds are extremely important for realistic model simulations since they are the ultimate drivers of the global atmospheric circulation. Water vapour carrying latent heat is transported upwards by convection or in large weather systems (fronts), where it cools and eventually forms clouds; precipitation as rain then releases the latent heat. This convection is strongest in the tropics, where the vapour-laden trade winds from both hemispheres converge, forming deep, rain-producing convective clouds. It is here that the atmosphere receives the energy that drives the whole global circulation.

Clouds are also highly relevant to changes in climate that result from human activities. Changes in land use affect reflectivity and evaporation from soil and vegetation, and hence the transfer of energy to the atmosphere; fossil fuel burning and industrial processes increase aerosols that reflect sunlight or absorb solar and terrestrial radiation. Both land use change and aerosols have an effect on cloudiness and precipitation at both the local and the micro scale.

Predator–prey

̽��ֱ��innovative approach adopted by Professor Graf’s group has been to simulate the behaviour and microphysics of convective clouds using a concept more familiar within population dynamics: they treat clouds as individuals that compete for food.

This technique allows the separation of individual clouds from a larger set of clouds that can potentially evolve under a given weather situation (that is, at a specific time and in a specific grid cell of the model). ̽��ֱ��system is based on the solution of a set of Lotka–Volterra-type differential equations, also known as predator–prey equations from their use for describing biological systems: the clouds (the ‘predators’) have a limited ‘food’ supply of convective available potential energy (the ‘prey’, this being the amount of energy available for convection), for which clouds of different characteristics (size, depth) are competing.

By capturing the variations of cloud spectra in a statistical sense, cloud microphysics can be treated explicitly and it is now possible to determine in-cloud vertical velocities, interactions with aerosols, convective transport, rainfall intensity and radiation effects.

Forest fires and volcanic ash

̽��ֱ��team has been focusing on a variety of different types of cloud – most notably the effects of smoke on clouds and precipitation over Amazonia and Indonesia. Initially funded by the European Union, the project is now contributing to the Danum-OP3 consortium that spans eight UK institutions and is funded by the Natural Environment Research Council (NERC) to investigate the effects of the replacement of pristine rain forest by oil palm plantations in northern Borneo. Recently published data show how the smoke from the extreme peat fires that plagued Indonesia and surrounding countries for months during 1997–8 reduced the amounts of rainfall in the area. ̽��ֱ��reduced rainfall, in turn, increased the residence time of the smoke particles in the atmosphere, thus aggravating the situation.

A second focus has been the development and application of the Active Tracer High-resolution Atmospheric Model (ATHAM). ̽��ֱ��development of this high-resolving model started immediately after the eruption of the Mount Pinatubo volcano on the Philippines in the early 1990s, when Professor Graf was at the Max Planck Institute for Meteorology in Hamburg. ̽��ֱ��model simulates convective plumes at resolutions down to a few tens of metres and was initially used to understand the dynamic, microphysical and chemical processes within volcanic eruption plumes. An important question was whether these vigorous convective systems could effectively transport magmatic halogen compounds into the stratosphere, where they could harm the ozone layer. ̽��ֱ��model has also been used successfully to simulate big fire storms induced by wild fires, and the results have proved that pollutants from these fires are introduced into the lower stratosphere.

Further applications of ATHAM are under current investigation by Dr Michael Herzog in Professor Graf’s group, particularly in relation to aviation safety. Fine silicate ash from volcanic eruptions poses a severe risk for aeroplanes. Although ash clouds can be detected by satellite monitoring, they are often obscured by ice particles residing above the ash, and ATHAM can be used to predict whether ice is formed within a volcanic plume. Further plans with ATHAM are ongoing with support from a joint Chinese–German research project that will study the effects on weather and climate in Southeast Asia resulting from the dramatic changes of land use and ecology on the Tibetan plateau during the past 60 years.

For more information, please contact the author Professor Hans-F. Graf (hans.graf@geog.cam.ac.uk) at the Department of Geography.

New understanding of the physics of clouds is helping to model both climate change and the impact of volcanic eruptions and wild fires.

Professor Graf’s group has simulated the behaviour and microphysics of convective clouds using a concept more familiar within population dynamics: they treat clouds as individuals that compete for food.

Flickr - Marsha Jorgensen

Clouds 1 - free to use

Centre for Atmospheric Science

̽��ֱ��Centre for Atmospheric Science is one of the premier groups in the UK for atmospheric studies. It encompasses research in three departments:

Department of Chemistry: Numerical modelling of tropospheric and stratospheric chemistry/climate (Professor John Pyle), instruments and measurements (Professor Rod Jones), measurements of gas kinetics (Dr Tony Cox) and studies of atmospheric aerosols (Dr Markus Kalberer).
Department of Applied Mathematics and Theoretical Physics: Investigation of fundamental aspects of atmospheric dynamics and physical processes (Professors Peter Haynes and Michael McIntyre).
Department of Geography: Research on convection, modelling plumes and stratospheric dynamics (Professor Hans-F. Graf and Dr Michael Herzog).

̽��ֱ��Centre is co-directed by Professor John Pyle and Professor Peter Haynes. For more information, please contact Professor Haynes (P.H.Haynes@damtp.cam.ac.uk) or visit www.atm.ch.cam.ac.uk

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Putting metabolism on the eco-map

tdk25 — Fri, 01 Feb 2008 00:00:00 +0000

To what extent do living organisms absorb pollutants in our environment? Are particular ‘chemical cocktails’ more risky than others? Do current ecotoxicological risk assessment techniques adequately protect the environment? These are the sorts of questions that interest Drs Oliver Jones and Julian Griffin in the Department of Biochemistry, who are working as part of a Europe-wide integrated research project to develop better tools to evaluate the chemical risks we face in everyday life.

Ecotoxicology

It is generally acknowledged that many organisms in the environment are exposed to a large variety of pollutants during their lifetime; a fact borne out by advances in analytical technology. For example, many people will have heard of the effects on fish populations caused by endocrine-disrupting compounds in sewage, whereby some male fish living downstream of sewage treatment plants were found to have developed female characteristics, leading to a reduction in their ability to reproduce. In recent years, a plethora of other anthropogenic contaminants such as pharmaceuticals, personal care products, pesticides and flame retardants, and the potential for these man-made products to work their way into the food chain, have also begun to be of concern to environmental chemists.

However, the majority of these pollutants are present at extremely low concentrations and so it is difficult to ascertain whether or not they have an overall effect on ecosystem health, especially if outward effects are minimal. An added complication is the fact that the interaction between the environment and organism health is extremely complex, with chemical, biological, physical and geographical stressors each contributing to toxicological effects over time.

It’s important therefore to develop methods for assessing the cumulative risks for a range of species that are being exposed to mixtures of pollutants at non-lethal levels. In this way, steps can be taken both to improve safety in the environment and to safeguard ecological health.

Metabolomics

One technique that shows a great deal of promise in the area of ecotoxicology is metabolomics. This rapidly emerging discipline measures the thousands of naturally occurring small molecules (metabolites) such as sugars, organic acids, amino acids and lipids that are the products of cellular metabolism. An organism’s ‘metabolome’ is its full complement of metabolites, in the same way that its genome is its complete genetic content.

Why study metabolic changes? Well, these changes often happen much earlier in an organism than either tissue accumulation of pollutants or induced histopathological changes. ̽��ֱ��technique can be used to give a biochemical snapshot of a cell, tissue or indeed whole organism at a moment in time. When an organism is stressed or diseased, its metabolic pathways are perturbed. Advanced computer-assisted pattern recognition techniques can then be used to assess the differences in metabolic profiles between sample groups. Metabolomics therefore offers a particularly sensitive method to monitor changes in a biological system and is proving to be an outstanding tool for studying ecotoxicology.

No Miracle

̽��ֱ��environmental research in Dr Griffin’s group in the Department of Biochemistry is part of a European Union (EU) research project involving 38 laboratories spread across 16 countries and is known as NoMiracle (for ‘Novel Methods for Integrated Risk Assessment of Cumulative Stressors in Europe’). ̽��ֱ��project seeks to improve ecological and environmental risk assessment in the EU, and to help scientists gauge the impact of chemicals on the environment and human health.

̽��ֱ��Cambridge team are developing analytical techniques based on high-throughput analysis of metabolites from organisms at different positions in the food chain, such as earthworms, nematodes, slime moulds, marine mussels and water fleas. Being able to study such a broad set of experimental species has been possible because of long-term collaborations with the Centre for Ecology and Hydrology (part of the UK Natural Environment Research Council), King’s College London, the ̽��ֱ�� of Piemonte Orientale in Italy and the ̽��ֱ�� of Antwerp in Belgium, all developed as part of the NoMiracle project.

Using state-of-the-art nuclear magnetic resonance spectroscopy and gas chromatography mass spectrometry, long-term studies are being run to establish a basal metabolic profile for each of these species, as well as how these profiles change in response to toxic insult. By looking at the different patterns of metabolic profiles between organisms, a comprehensive description is being built up of how each of them responds to stress and toxicity. One important finding has been that biochemical effects are often observed at lower chemical concentrations than were previously thought to cause any effect when assessed using traditional toxicology testing techniques.

Assessing the risks

Why is there a need for improved risk assessment in ecotoxicology? In current toxicity tests, an organism is typically exposed to a single chemical in a strictly controlled laboratory setting, over a relatively short period of time (typically days or weeks). Yet, in the environment, organisms will clearly be exposed to many different pollutants possibly throughout their entire life. An accurate risk assessment must take into account cumulative effects rather than just direct effects and single factors. Organisms are also often likely to be stressed by other factors not present in a laboratory setting. For instance, work within the NoMiracle project has demonstrated that organisms can be affected by pollutants at much lower levels than those predicted from traditional toxicity tests if they are also stressed by other factors such as co-exposure to pollutants, temperature extremes or food restriction.

̽��ֱ��work in the Cambridge section of the NoMiracle project is moving into its third and final year. ̽��ֱ��research is showing that the accurate assessment of chemical mixtures is more complex than current testing regimes allow for and the aim now is to use these results to develop a new framework for assessing the effects of complex mixtures of pollutants. ̽��ֱ��ultimate goal of the NoMiracle partners is to change ecotoxicology policy in the whole of the EU, so that long-term, multi-stressor exposure testing is considered as standard. This will offer great improvements in understanding and mitigating the effects of cumulative pollution exposure on the health of our ecosystem.

For more information, please contact the authors Dr Oliver Jones (oahj2@mole.bio.cam.ac.uk) or Dr Julian Griffin (jlg40@mole.bio.cam.ac.uk) at the Department of Biochemistry.

One of the latest technologies to emerge - metabolomics - is being used to create a snapshot of how environmental chemicals affect living organisms.

An added complication is the fact that the interaction between the environment and organism health is extremely complex, with chemical, biological, physical and geographical stressors each contributing to toxicological effects over time.

Karolina Lada and Oliver-Jones

Tricarboxylic Acid (TCA) Cycle

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