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New insights into the leaching of radioisotopes from nuclear wastes

27 Oct 2015

The sites of underground repositories for radioactive waste need to be selected, designed and built adequately. This requires an in-depth understanding of the geochemical processes governing the release and transport of radionuclides from the waste to the surrounding environment. In this study published in Environmental Science: Processes & Impacts, researchers describe a technique that will improve our knowledge of potential leaching of radionuclides in these environments.

Many countries around the world now meet a substantial fraction of their energy demand through nuclear power. A key environmental issue, therefore facing these nations, is how to ensure the safe and responsible disposal of radioactive wastes. The International Atomic Energy Agency outlines a number of different potential methods for disposing of radioactive wastes and discusses the approach of different nations.

Careful burial in well-engineered ‘repositories’ at various depths below the land surface – so-called ‘geological disposal’ – is now the preferred option for the final storage of nuclear waste for most countries with advanced nuclear programmes, including the UK, Canada, Finland, France, Sweden, Switzerland, Japan and the USA. Indeed, a 2004 European Commission Report on radioactive wastes states that:

“Burial at several hundreds of metres depth in stable rock environments is the option for disposal of the most hazardous radioactive wastes because it will provide permanent safety – not just for ourselves, but for future times very much longer than the whole of past human history.”

However, in order to ensure that this statement is true, it is essential to assess to what extent radionuclides could be released to the environment. Therefore, it is of great importance to understand how long-lived radionuclides (such as 79Se, 129I, 14C or 36Cl) are chemically bound in the radioactive waste matrix. The challenge for researchers and practitioners is to provide reliable safety assessments for such nuclear waste repository sites that provide reliable long-term predictions on the release of radionuclides in waste repositories as the waste undergoes geochemical transformations in ground waters.

Radiocative wastes are typically a highly heterogeneous material made up of the fuel matrix with 3–6% fission products and minor actinides dispersed among different phases. Long-lived isotopes like 79Se, 135Cs, 129I and 36Cl are of interest because they are easily soluble in water and sorb only weakly on mineral surfaces, implying that, once dissolved, under repository conditions they will migrate through the sub-surface environment very rapidly. These compounds are therefore major contributors to the overall radiological dose calculated in risk assessments of nuclear waste repositories.

The properties and behaviour of radionuclides like 79Se in nuclear wastes are not well understood due to the technical difficulty of obtaining sound experimental data on such highly radioactive materials. This insufficient knowledge is usually compensated by conservatism in the choice of parameter values for safety assessment calculations. For example, it has previously been assumed that a significant fraction of 79Se is rapidly released from the spent fuel waste on contact with aqueous solutions and is highly mobile. This is due to the observation that selenium has an appreciable volatility under reactor operation conditions and the high solubility of oxidized Se species in water.

However, recent experiments have indicated that less than 1% of the Se in a geological disposal repository is released to aqueous solution after 1 year leaching, suggesting only a small fraction is actually leachable. This demonstrates the need to further investigate the geochemical nature and behaviour of long-lived radionuclides such as 79Se in radioactive wastes and the interaction of these isotopes with spent UO2 fuel.

This work is the result of a collaboration between Swiss, Swedish, French and American research institutes, investigating radionuclide release of 79Se from radioactive waste in a deep water-saturated repository. In the study, X-ray Absorption Near Edge Spectroscopy (XANES) measurements were made on samples from the Leibstadt Boiling Water Reactor in Switzerland.

Their results offer a mechanistic explanation why Se appears to be much less soluble in short-term aqueous leaching experiments, compared to other radionuclides like I and Ce. It was shown that these results were corroborated by a simple thermodynamic analysis, showing that selenide is the stable form of Se under reactor operation conditions.

This study provides a technique that helps improve our understanding of the geochemical transformation and transport of radioactive nuclides in wastes disposed in geological formations. Investigations like this are required to reduce conservatism and improve reliability in carrying out safety assessment calculations. This work is therefore integral to the future selection and design of potential nuclear waste repository sites.

To read more about this research, download a copy of the manuscript for free* by clicking the link below.

Characterization of selenium in UO2 spent nuclear fuel by micro X-ray absorption spectroscopy and its thermodynamic stability
E. Curti, A. Puranen, D. Grolimund, D. Jädernas,D. Sheptyakov and A. Mesbah
Environ. Sci.: Processes Impacts, 2015,17, 1760-1768
DOI: 10.1039/C5EM00275C

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About the webwriter

Ian Keyte is currently a Science Policy Intern at the Royal Society. He previously gained a PhD at the University of Birmingham investigating atmospheric pollution, and has a BSc in Environmental Chemistry from Lancaster University.

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Re-use or miss-use? The risks and rewards of reclaimed waste water for crop irrigation

25 Sep 2015

The re-use of waste waters for crop irrigation is becoming an increasingly popular practice, particularly in arid, water-stressed regions of the world. A new study by researchers from the U.S. Salinity Laboratory and the Institute of Soil and Environmental Sciences at the University of Agriculture in Faisalabad, Pakistan, investigates the potential agronomic and environmental impacts this can have on farmlands, shedding light on the challenges for long-term management of water usage and crop production.

Depletion of freshwater resources is one of the most important issues facing future global development. Finite water resources are becoming increasingly stressed by an ever-growing world population and associated demand for food production. Furthermore, the increased frequency of drought in many areas resulting from climate change and resource degradation due to pollution make the task of ensuring the global population have access to enough clean water increasingly difficult. The United Nations have warned that, under existing climate change scenarios, almost half the world’s population will be living in areas of high water stress by 2030.

An increasingly popular option to cope with increased water demand for agriculture is to re-use waste water or degraded water for crop irrigation. For example, dairy lagoon wastewater has been proposed as an alternate water resource in agriculture, as this can be a plentiful source of essential nutrients and organic matter. Indeed, the Food and Agriculture Organization (FAO) produced a report presenting “an economic framework for the assessment of the use of reclaimed water in agriculture”. This could also have the additional benefit of alleviating the need for the costly and difficult storage, treatment and disposal of large volumes of waste water.

Crop irrigation system (http://www.access-irrigation.co.uk)

However, degraded water will also contain contaminants, particularly salts and heavy metals such as zinc (Zn), copper (Cu), nickel (Ni), arsenic (As), cadmium (Cd), and lead (Pb). This could mean the benefits of using wastewater could be offset due to increasing soil salinity and accumulation of potentially bioaccumulative toxins, which could have a negative impact on crop yield and quality, as well as wider reaching environmental problems. There is therefore a need for a greater understanding of how using dairy lagoon wastewater could impact the quality of agricultural land and the surrounding environment.

While the physical, chemical, and biological characteristics of degraded waters are generally well studied, the impact of its reuse on agricultural lands over long timescales is not well understood. In this study by Dennis Corwin and Hamaad Raza Ahmad, a field-scale impact investigation of dairy lagoon water reuse on agricultural soil characteristics was carried out. This represents the first study of this kind to be conducted at this spatial or temporal scale.

In the study, soil samples were collected at locations identified from apparent soil electrical conductivity (EC) measurements, a property of soil that reflects several soil physical and chemical properties (including soil salinity, texture, water content, bulk density, organic matter, and cation exchange capacity). Samples were taken at a number of different depth increments in an agricultural area in San Jacinto, California, first in 2007 and again in 2011, to establish the effect of using dairy lagoon water blended with recycled or well water on agricultural land over a 4 year irrigation period.

Chemical analyses of soil samples were carried out to determine key characteristics of the soil. This included the salinity, pH, SAR (sodium adsorption ratio), trace elements (As, B, Mo, Se), and heavy metals (Cd, Cu, Mn, Ni, Zn). The authors note that, from an agronomic perspective, the salinity, SAR, and B are of greatest concern, while from an environmental perspective, the salinity and Cu present the greatest potential effect upon groundwater safety.

The results suggest the reuse of dairy lagoon water presented very little detrimental environmental or agronomic impacts over the 4 years of the study duration. However, there were a number of potential long-term concerns that the study raises. For example, the pH values at all soil depths were shown to decrease. Additionally, potential long-term agronomic effect of salinity, SAR, and B levels, and the long-term environmental threat of salinity and Cu was highlighted. The accumulation of Cd, Mn, and Ni in the soil profile was also observed, raising concerns over the potential for metal contaminants such as these to leach from the soil in the future.

The authors note that, while the results demonstrated the short-term (4 year) viability of dairy lagoon water reuse as an alternative water resource for agriculture, the longer-term sustainability of dairy lagoon water reuse as a viable alternative for crop irrigation requires regular monitoring of soil properties to allow adequate site-specific management.

This study demonstrates that EC-directed soil sampling can be used to monitor spatial and temporal changes in the chemical characteristics of agricultural soils due to degraded water reuse. This could help pave the way for studies over wider spatial and longer temporal scales and can help producers optimise crop yields while at the same time mitigating detrimental environmental impacts. Based on their observations, the authors provide a number of specific recommendations for achieving this most effectively. This method has clearly delivered an extensive spatio-temporal dataset, which highlights many of the challenges for successfully managing agricultural land irrigated by degraded wastewater.

The authors highlight the broad geographical relevance and impact of this research as it concerns the viability of degraded water reuse on irrigated, agricultural lands in arid regions throughout the world (e.g. northeast China, Middle East, North and Eastern Africa, Eastern Australia, India and Pakistan), where the reuse of degraded water is a major supplemental source of irrigation water.

To read more about this research, download a copy of the manuscript for free* by clicking the link below.

Spatio-temporal impacts of dairy lagoon water reuse on soil: heavy metals and salinity
Dennis L. Corwin and Hamaad Raza Ahmad
Environ. Sci.: Processes Impacts, 2015, Advance Article
DOI: 10.1039/c5em00196j

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About the webwriter Ian Keyte

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

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* Access is free until 22/10/2015 through a registered RSC account.

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Going deep: investigating the physical and chemical properties of humic substances in groundwater

21 Aug 2015

Humic substances play an important role in the speciation of metal ions in the aquatic environment. Understanding these processes is important to ensure the safety of drinking water. In this study, Japanese researchers reveal how physiochemical properties and ion-binding behaviour of HSs can differ between surface water and groundwater environments.

Groundwater constitutes the largest reservoir of freshwater in the world, accounting for over 97% (excluding glaciers and ice caps) of all available freshwater on the planet. It is estimated that about 75% of EU inhabitants depend on groundwater for their water supply. Groundwater also plays an integral role in the hydrological cycle, crucial to the maintenance of wetlands and river flows. Maintaining the quality of groundwater resources is therefore of major environmental, social and economic importance. This requires a good understanding of the physical and chemical processes that may influence groundwater environments.

For future use of deep underground space it is necessary to monitor and protect the quality of deep groundwater. The World Health Organisation (WHO) acknowledges the importance of groundwater resources and the potential risks that poor quality groundwater can cause to human health. Indeed, the WHO has produced a guidance document, “analysing hazards to groundwater quality, assessing the risk they may cause for a specific supply, setting priorities in addressing these, and developing management strategies for their control.”

Humic substances (HSs) are a class of natural organic molecules, ubiquitous in various environments including surface and ground water, oceans, soils, and the atmosphere. HSs are known to play an important role in freshwater systems. For example HSs can effectively capture inorganic and organic contaminants due to the tendency of protons and metal ions to readily bind to the functional groups of HS ligands e.g., carboxylic and phenolic groups and to a lesser extent amine- and sulphur-containing groups. This process can therefore alter the reactivity, bioavailability, and mobility of chemical constituents in fresh water.

The physical and chemical nature of HSs is likely to differ between deep underground and surface aquatic systems, due to slower water movement and more prolonged contact with underlying rocks and dissolved/suspended components, low oxygen, and lack of sunlight. However, while some characteristics of groundwater HSs are understood, their ion binding properties over a wide range of conditions is largely unknown. Given that in many areas, deep underground space may be used in the future for such uses as geological disposal of nuclear wastes, the potential deterioration of groundwater quality, the ion binding properties of deep groundwater HSs need to be studied carefully, and mechanistic models developed to describe these processes.

This study by Takumi Saito and co-workers investigates the physicochemical and binding properties of HSs isolated from deep groundwater in a sedimentary rock formation in the Horonobe Underground Research Laboratory of the Japan Atomic Energy Agency (JAEA). Binding isotherms of protons (H⁺) and copper (Cu²⁺) were measured over a wide range of conditions by potentiometric titration and were fitted to the NICA-Donnan model and the obtained parameters were compared with average parameters for HSs from surface environments. The oxidation state and local coordination environment of Cu²⁺ bound to the HA fraction of the HSs were also assessed by X-ray absorption spectroscopy (XAS).

The results clearly indicate distinctive physical and chemical characteristics for the HSs from surface and groundwater environments. It is found that the deep ground HSs were characterised by high aliphaticity and sulphur (S) content and relatively small sizes. Differences in the binding behaviours of H⁺ and Cu²⁺ with the HSs in deepwater and surface water were also observed.

The authors discuss the differences in chemical binding behaviour with reference to the unique chemical nature of the functional groups of groundwater HSs compared with those of surface waters and how the binding sites and binding mode can change with changes in conditions (e.g. pH). X-ray absorption spectroscopy also revealed that Cu²⁺ binds to O/N containing functional groups and to a lesser extent S containing functional groups.

The study therefore demonstrates how HSs could influence freshwater resources differently in deep-ground and surface environments. Although the HSs in this study were derived from a single groundwater source, the authors suggest the outcomes can be applied or be a good starting point to estimate the degree of metal binding to HSs in sedimentary groundwater in general.

The authors also suggest these results should be examined in the future by performing similar investigations for HSs isolated from a range of different groundwater samples and for a wider range of metal ions. This would allow accurate and realistic parameter sets applicable for groundwater HSs to be developed for further modelling for a more extensive range of chemical species.

To read more about this research, download a copy of the manuscript for free* by clicking the link below.

Physicochemical and ion-binding properties of highly aliphatic humic substances extracted from deep sedimentary groundwater
Takumi Saito, Motoki Terashima, Noboru Aoyagi, Seiya Nagao, Nobuhide Fujitake and Toshihiko Ohnuki
Environ. Sci.: Processes Impacts, 2015,17, 1386-1395
DOI: 10.1039/C5EM00176E

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Ian Keyte

About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

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* Access is free until 20/09/2015 through a registered RSC account.

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Getting to the chiral centre of aquatic pollution

30 Jul 2015

The chemical behaviour of pollutants in the aquatic environment requires careful monitoring in order for us to understand the toxicity different compounds will exert on natural ecosystems. Researchers from Israel describe a new modelling approach that may provide an exciting new technique to address a specific aspect of the chemical and environmental behaviour of pollutants.

The term ‘chiral’ is given to molecules that exhibit identical composition, but where the components of the molecule are arranged in a non-superimposable mirror image composition, centred around an asymmetric carbon atom. The two ‘mirror images’ of a chiral molecule are termed enantiomers. The study of the enantiomer-specific properties and how these vary between different molecules is of major interest within the broad fields of inorganic, organic, physical, biological and environmental chemistry.

Many anthropogenic chemicals of environmental concern, such as pesticides, are chiral molecules. These compounds can potentially be major threat to aquatic ecosystems. For example, the molecular structures and environmental implications of many chiral pesticides have been discussed in a review by the USEPA. It is important, therefore, to have means of accurately tracing the alteration of these compounds in the environment, particularly with reference to their enantiomer-specific environmental toxicity.

Researchers have previously proposed an enantiomeric enrichment factor (EEF), to describe the enantiomeric enrichment – conversion relationship of chiral compounds, derived using the Rayleigh equation, which describes the relationship between changes in the isotopic composition against the contaminant concentration during the degradation process. The EEF can therefore be used as an identifying tool for a specific enzymatic reaction of different molecules.

Developing models to describe enantio-selective biodegradation can alleviate the need for laborious practical work. To achieve this, there is a need to improve our understanding of the mechanisms of biodegradation, to classify chemicals according to their relative biodegradability, and to develop reliable biodegradation estimation methods for new chemicals. Quantitative structure–activity relationship (QSAR) models are typically derived based on the correlation between experimental data and physical properties (e.g. lipophilicity, steric and electronic parameters) and can be used to identify bioavailability, toxicity and biological activities of compounds as dependent variables.

This study, conducted by researchers from The Institute of Chemistry at The Hebrew University of Jerusalem and The Geological Survey of Israel, develops a QSAR model to describe the dependence of the enantiomeric enrichment factor on molecular structures and uses this method to evaluate EEF values for unstudied chiral compounds. The authors used the multiple linear regression (MLR) method to build the QSAR based on the Linear Hansch model. The enantioselective hydrolysis of 16 derivatives of 2-(phenoxy)propionate (PPMs) (some of which are common herbicides) using three different lipase enzymes was analysed.

The study provides a demonstration of the predictive power of QSAR and Hansch modeling for analysis of the structural dependence of the EEF, with the model shown to effectively correlate biological activity with key physicochemical properties. More importantly, at times, the QSAR of EEF values was shown to be a much better predictive tool than the QSAR of just the underlying individual kinetic parameters, clearly indicating this method could mark the way forward for research in this field.

The authors note that the use of the QSAR modelling technique used in this study may serve as a powerful tracer tool in environmental studies, assisting in source tracking the enantio-selective conversion of both known and unstudied chiral compounds in aquatic ecosystems.

To read more about this study, download a copy for free* by clicking the link below.
Quantitative structure–activity relationship correlation between molecular structure and the Rayleigh enantiomeric enrichment factor
S. Jammer, D. Rizkov, F. Gelman and O. Lev
Environ. Sci.: Processes Impacts, 2015, Advance Article
DOI: 10.1039/c5em00084j

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About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

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* Access is free until 30/08/2015 through a registered RSC account.

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Slick research: reviewing available technologies for tackling oils spills

03 Jul 2015

Oil spills can cause widespread environmental damage. The production, refining, storage and distribution of oil are all potential sources of pollution of marine and terrestrial ecosystems. Recent high-profile accidents on offshore oil platforms such as the Deepwater Horizon incident in 2010 give the public clear insight into the effect large-scale oil spills can have. However, as dramatic as these pollution events are, these incidents represent less than 10% of total petroleum hydrocarbon discharges to the environment. The vast majority of pollution results from relatively low-level routine releases on a more local scale. The challenge is therefore to ensure safety of oil production as a whole rather than simply the prevention of large-scale incidents.

As existing oil reserves become increasingly depleted, exploration and drilling is spreading into deeper waters and more remote, fragile environments, such as the Arctic. Since oil production from newly explored or depleted reservoirs is more difficult, the risk of accidental oil spills in the future is likely to increase. Indeed, it is estimated that, for an average platform, each 30 metres of added depth increases the probability of an accident by 8.5%. There is clearly a need for clear and coherent strategies to be in place to help prevent and/or clean up accidental oil spills and to this end, there has been considerable world-wide effort has gone into strategies for minimising accidental spills and the design of new remedial technologies.

the Deepwater Horizon Oil Spill in the Gulf of Mexico caused a major ecological hazard

Deep Water Horizon Oil Spill - US Coast Guard Photo by Petty Officer First Class John Masson (courtesy of Chemistry World)

This critical review is the result of collaboration between the Institute of Ecology and Genetics of Microorganisms in the Russian Academy of Sciences, Perm State University in Russia, The Scottish Environmental Technology Network at the University of Strathclyde in Glasgow, UK, The University of Louisville in Kentucky, USA and the OECD Directorate for Science, Technology and Industry in Paris, France. The paper provides a summary of new knowledge as well as research and technology gaps essential for developing appropriate decision-making tools in actual oil-spill scenarios. The review will therefore be of interest to a wide range of stakeholders, including the oil industry, the scientific community and the public.

The review provides a clear comparison between the behaviour and environmental effects of marine and terrestrial oil spills (e.g. the nature of the spread of oil and size of affected area). The differences in appropriate response strategy for marine and terrestrial spills are clearly defined. The importance of ‘window-of-opportunity’ technology in combating oil spills is highlighted, i.e. the integration of different types of scientific information to allow rapid decision making on the best available strategy to achieve optimal environmental and cost benefits. The authors note that effective response to oil spills will require a) adequate data oil weathering over time; b) real-time remote sensing; c) analysis of response strategy performance. The review discusses the technological advances and challenges involving the multi-media modelling approaches to generating and analysing this information.

An in-depth review of different available technologies is provided and the authors use specific case studies to illustrate their effectiveness. For the marine environment this includes a discussion of chemical treatments (e.g. dispersants, emulsion breakers); in-situ burning; mechanical recovery (e.g. booms, skimmers, adsorbants etc) and bioremediation. In relation to the terrestrial environment, the review discusses the methods to prevent oil spills both on land and into ground/surface waters as well as more advanced clean-up technologies such as thermal desorption, soil vapour extraction, pump and treat technologies and solidification/stabilisation and bioremediation. The review also discusses the details, limitations and environmental effects of on-land containment and control technologies such as diversion/containment measures, trenches, sorbent or viscous liquid barriers.

Control technologies to prevent or tackle accidental oil spills

Technologies to prevent, control or tackle accidental oil spills

The authors emphasise that, because every spill is unique, there is no ‘one size fits all’ technology that will be suitable. The environmental impact and sustainability of remedial technologies vary widely so a suite of remedial technologies is required, and this should be part of the ‘risk-based remedial design’ strategy. The review highlights bioremediation methods as sustainable, cost-effective clean-up solutions and to achieve greater penetration of these techniques into the market depends on the harmonisation of environment legislation and application of innovative laboratory techniques e.g. ecogenomics to improve the predictability of bioremediation. However, it is also stressed that prevention is far less expensive than cure, and oil spill prevention should continue to be the focus for the industry.

This paper is a comprehensive and timely review of oil spill prevention and remediation methods, providing an invaluable summary of available technologies for remediation to increase awareness that a hierarchy of remedial technologies exists. Furthermore, it demonstrates that that there is a need for further development of both “soft” technologies, such as contingency planning, and “hard” engineering solutions for spill prevention. It is stressed that ultimately an integrated approach to prevention and remediation is needed and that greater international cooperation in contingency planning and spill response would probably lead to higher safety standards and fewer accidents.

To access the full article and read more about the technologies and strategies of tackling oil spills, download a copy for free* by clicking the link below.

Oil spill problems and sustainable response strategies through new technologies
Irena B. Ivshina, Maria S. Kuyukina,Anastasiya V. Krivoruchko, Andrey A. Elkin,Sergey O. Makarov,Colin J. Cunningham,Tatyana A. Peshkur,Ronald M. Atlasand James C. Philp
Environ. Sci.: Processes Impacts, 2015, Advance Article
DOI: 10.1039/C5EM00070J

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About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

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* Access is free until 18/08/2015 through a registered RSC account.

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Breaking the mould: assessing microbial pollution in the indoor environment

11 Jun 2015

Understanding the levels and behaviour of mould and fungal particles in the indoor environment is essential in order to carry out more comprehensive exposure assessments and analysis of their associated health effects. Researchers at Korea University and the National Institute of Environmental Research in Seoul present a study, describing a valuable method to achieve this.

Microbial pollution (for example from bacteria and fungi) can present a serious public health risk. A particular concern has been raised regarding filamentous fungi (better known as mould). Indoor mould is primarily caused by excess moisture, for example due to leaking pipes, rising damp or rain seepage. The World Health Organisation warns that mould is a key element of indoor pollution, linked with triggering and exacerbating allergic symptoms and diseases such as asthma and other respiratory illnesses.

Children are particularly sensitive to allergen exposure and, because they spend considerable time indoors, they could be vulnerable to these serious health effects if the indoor environment is not well maintained. Elementary (primary) school children spend upwards of six hours a day in school, mostly in one classroom. This emphasises the importance of minimising the risk of developing or increasing allergic diseases due to pollutants in the school environment. While there has been considerable interest in assessing the problem of mould in school classrooms, as yet few comprehensive assessments have been performed.

Mould in the indoor environment can be a major source of microbial pollution and associated health effects

Household mould - a cause of indoor microbial pollution (Source: http://www.yourlocalguardian.co.uk)

Traditionally, studies of microbial pollution from mould involve making spore counts by culturing from collected samples due to ease of sampling and analysis. However, this method does not allow adequate evaluation of the exposure to mould due to the different growth rates of different types of mould. Therefore, assessment of spore concentration is not adequate on its own to fully investigate fungal exposure to humans.

More recently, the measurement of (1,3)-β -D-glucan has been proposed as a new tool to determine microbial pollution. This compound exists in fungal cell walls and is more common in airborne spores, so it is proposed that analysis of (1,3)-β -D-glucan in small-scale fungal fragments could be applied for an exposure assessment of mould and associated health effects in the school environment. This research by SungChul Seo and co-workers presents the first study of its kind to apply this approach to a relatively large-scale assessment of actual classrooms.

In the study, the levels of small-size (submicron) fungal fragments as well as airborne moulds, bacteria, and particulate matter (PM₁₀), were evaluated in both indoor and outdoor areas of 70 classrooms in 8 elementary schools and the variation in the concentrations before and after the rainy season (May and July) were investigated. The concentrations of (1,3)-β -D-glucan in submicron fungal fragments, airborne mould and bacteria, and PM10 were measured simultaneously and the association of these levels with physical factors (i.e. temperature and relative humidity) wasalso compared and analysed.

The results indicate that the indoor/outdoor ratios of (1,3)-β -D-glucan concentrations were greater than 1 in every school. It was also shown that in the sampling period after the rainy season, the (1,3)-β -D-glucan concentrations decreased by about 35%, and similar significant decreases in the concentrations of airborne mould, bacteria and PM₁₀ were observed as well. A negative association between the concentration of submicron fungal fragments and relative humidity was also observed.

This study therefore provides valuable insights into the concentrations, behaviour and variability of microbial pollution associated with mould in the school environment. This clearly outlines some of the key practical considerations required to carry out assessments of fungal exposure and could pave the way for similar studies in different locations. The authors note that more comprehensive exposure assessments for smaller-sized fungal particles should be performed for better understanding of their health impact, particularly with regard to seasonal and temporal changes.

To access the full article, download a copy for free* by clicking the link below.

Submicron fungal fragments as another indoor biocontaminant in elementary schools
SungChul Seo, Yeong Gyu Ji, Young Yoo, Myung Hee Kwon and Ji Tae Choung
Environ. Sci.: Processes Impacts, Advance Article, 2015
DOI: 10.1039/c4em00702f

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About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behaviour and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

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Tracing the impact of the Fukushima nuclear accident

20 May 2015

Monitoring the environmental effects of major nuclear incidents is an essential but complex undertaking. The use of the iodine-129 isotope as a tracer for detecting nuclear pollution in the environment has been widely established. The present study, by researchers from the Horia Hulubei National Institute for Physics and Engineering in Bucharest, Romania, applies this method to assess the impact of radioactive releases after the 2011 Fukushima accident in Japan.

On March 11^th 2011, a magnitude 9.0 earthquake stuck 130 km off the east coast of Japan, causing a 15 m tsunami, which inundated about 560 sq km of land. In addition to causing a death toll of over 19,000 and destroying or damaging over a million coastal buildings, this tsunami also disabled the power supply and cooling of three nuclear reactors at the Fukushima Daiichi plant, causing a major nuclear accident. Over 100,000 people were evacuated from the area, and an exclusion zone of 20 km around the plant was established. A comprehensive account of the cause and effects of this Fukushima incident is provided by the World Nuclear Association.

exclusion zone at the site of the Fukushima nuclear incident

Fukushima exclusion zone. Source: Thom Davies (http://thomdavies.com/tag/fukushima/)

In the wake of the disaster, much research and discussion has been undertaken to assess its environmental impact and the future safety of nuclear energy generation. Experts estimate that the Fukushima incident caused the largest ever direct release of radioactive material, such as iodine-129 and caesium-137 isotopes into the Pacific Ocean. The nature and extent of how this nuclear material is transported and dispersed in the ocean requires careful consideration, in order to assess the full environmental impact of the accident.

There is considerable uncertainty regarding the eastward migration of this radioactive plume in the Pacific Ocean and efforts to locate and characterise its position and movement have been unsuccessful so far. Iodine-129 displays a long residence time (half-life of 15.7 million years) and relatively low bioavailability. In very small quantities, it can act as an effective sensitive tracer of the radioactive plume in ocean waters. As a consequence, this study by C. Stan-Sion and co-workers used iodine-129 to determine the nuclear plume impact on the West Coast of the USA, roughly two years after the Fukushima incident.

For this research, ocean water samples were collected in La Jolla, San Diego, California on the West Coast of the USA (approx. 8770 km east of Fukushima) between April and July of 2013. Accelerator Mass Spectrometry (AMS) was used to determine the iodine-129/ iodine-127 ratio in the collected samples. Its very high sensitivity for measuring such isotopes was the main reason why this analytical method was chosen.

The results showed two sudden increases of the iodine-129/ iodine-127 isotopic concentration in the ocean water during late spring of 2013. The isotopic iodine-129/ iodine-127 ratio was more than a 2.5 factor higher in USA West Coast water samples, compared with those measured 40 km offshore of Fukushima immediately after the accident.

Map of Fukushima study area

Also, compared with the pre-Fukushima background values, the results of this study show an isotopic ratio of about two orders of magnitude higher. Based on these results, the authors calculated that the plume travelled with an average speed of approximately 12 cm s^-1, which is consistent with the zonal current speed in the Pacific Ocean.

This investigation therefore demonstrates how the iodine-129/ iodine-127 isotopic ratios can be used to assess the impact of a certain nuclear accident in locations far removed from the accident site. Finally, the authors also coupled their iodine-129 results with the results of the Ka’imikai-O-Kanaloa international expedition in June 2011 to assess the activity of other radioactive isotopes such as hydrogen-3 and caesium-137, and the activity of these radio-isotopes were compliant with the international regulatory limits.

To access the full article, download a copy for free* by clicking the link below.

AMS analyses of I-129 from the Fukushima Daiichi nuclear accident in the Pacific Ocean waters of the Coast La Jolla – San Diego, USA
C. Stan-Sion, M. Enachescu and A. R. Petre
Environ. Sci.: Processes Impacts, 2015, 17, 932-938
DOI: 10.1039/c5em00124b

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About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the urban atmosphere.

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* Access is free until 21/06/2015 through a registered RSC account.

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Passive sampling for improved monitoring of indoor air quality

07 May 2015

Indoor air pollutants require careful and accurate monitoring in order to ensure people are not exposed to levels that could cause adverse health effects. This study, commissioned by the U.S. Department of Defense, demonstrates the usefulness of diffusive passive air samplers for this purpose.

People can potentially be exposed to dangerous levels of air pollutants indoors, either directly from indoor sources or from polluted air transported from outside. The WHO has acknowledged the threat of poor indoor air quality, identifying a number of specific pollutants of concern and providing guidance on health effects and recommended guideline exposure limits associated with these contaminants. One class of pollutants causing concern are volatile organic compounds (VOCs). The USEPA warn that VOCs have been linked with a number of adverse health effects including damage to the kidney, liver and central nervous system, as well as eye, nose and skin irritation, headaches and nausea.

Domestic combustion sources, such as heating and cooking, are known to be important sources of VOCs; however, an emerging source of interest is the intrusion of vapour from contaminated soil or groundwater into a building. Careful monitoring of VOCs is clearly needed to carry out appropriate risk assessment and identify the relative contribution of this intrusive source on total VOC concentration in the indoor environment. Conventional air sampling methods typically do not allow for monitoring for more than a 24 hour period. However, due to the temporal variability of some VOCs, longer sampling duration is needed to better represent the long-term average concentrations of VOCs.

Passive diffusive samplers are therefore well-suited to this application as they have the ability to detect relatively low concentrations of contaminants over relatively long sampling duration. Passive air samplers commonly use a sorbent material to trap VOCs, which reach the sampler via diffusive transfer from the surrounding atmosphere. A time-weighted average concentration can be calculated subsequently in the lab. Passive sampling has been used for indoor air quality monitoring in occupational settings for decades, but the application to monitoring subsurface vapour intrusion to indoor air requires further work to assess their capabilities and limitations for lower concentrations and longer exposure durations.

Air samplers

This article by Todd McAlary and co-workers, combining work of research laboratories in Canada, the USA, UK and Italy, describes laboratory testing of passive diffusive samplers for assessing indoor air concentrations of VOCs in order to demonstrate and validate their potential usefulness.

Four different passive samplers were tested, utilising different types of sorbent, under a wide range of controlled laboratory conditions (temperature, humidity, VOC concentration and sampling duration) with review from leading experts on each sampler type. 10 different VOCs were measured including aliphatic compounds such as alkenes and alkanes as well as aromatic compounds such as benzene and naphthalene, in order to assess compounds that cover a range of physiochemical properties and some compounds that pose a challenge to sampling.

The results demonstrate that passive samplers can potentially provide data that is more representative of long-term average indoor air concentrations than conventional methods that are limited to shorter sample durations. The results show the passive samplers proved data that meets a set of success criteria for most of the compounds tests, although some compounds were identified as being more problematic. The study provides a unique and valuable new body of data on indoor air quality monitoring. However, the authors also caution that passive sampling programs will need to be supplemented by quality assurance measures. For example, outdoor air samples should be taken simultaneously with indoor sampling to help ascertain the relative contributions of different pollution sources.

To access the full article, download a copy for free* by clicking the link below:

Passive sampling for volatile organic compounds in indoor air-controlled laboratory comparison of four sampler types
Todd McAlary, Hester Groenevelt, Stephen Disher, Jason Arnold, Suresh Seethapathy, Paolo Sacco, Derrick Crump, Brian Schumacher, Heidi Hayes, Paul Johnson and Tadeusz Góreckic
Environ. Sci.: Processes Impacts, 2015, Advance Article
DOI: 10.1039/c4em00560k

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About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

—————-

* Access is free until 07/06/2015 through a registered RSC account.

Comments Off on Passive sampling for improved monitoring of indoor air quality

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