Environmental Science: Processes & Impacts blog

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.

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.

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.

We use fluorescence to identify counterfeit money. Could we use a very similar technique to assess the quality of fresh water? K. Khamis and colleagues suggest tryptophan-like fluorometers to do so. In their paper, they discuss a novel way of measuring pollutants thanks to this procedure, and also propose novel mathematical models to better conduct in situ experiments, thus avoiding the storage and transportation of samples.

When water is polluted with sewage or farm waste, the amount of dissolved organic matter (DOM) increases. Organic matter contains sugars, lipids, nucleic acids and proteins. The latter are biomolecules which have a very interesting property: fluorescence. Folded proteins are fluorescent, mainly because of the tryptophan residues, and they can absorb and emit light at 280 nm and 350 nm, respectively. As a consequence, fluorescence may be directly correlated with the quantity of organic waste dissolved in water.

However, very few fluorescence sensors have been developed to measure OM in freshwater, mostly because freshwater systems are quite dynamic in space and time. Moreover, certain factors such as temperature or suspended inorganic particles often alter the measurements. Temperature allows electrons to return to their ground-energy state without emitting any fluorescence. Additionally, soil particles can scatter light and reduce the fluorescence signal by up to 80%.

But Khamis and his team did not see a problem in this. On the contrary, they saw this fact as an opportunity to develop new tryptophan-like sensors and state-of-the art algorithms to minimize the effect of quenchers like temperature or soil particles. Researchers located in situ detectors near Birmingham to study urban streams and near Nottingham to study groundwater; they also took a wide set of samples which were analyzed in the lab.

The data obtained from these analyses was then compared to the in situ measurements. Using these two different groups of data, they elaborated mathematical models to compensate the effect of quenchers. These algorithms were fundamental to ensure the accuracy of the quantifications. When the corrections were applied, in situ and lab results appeared to correlate much better.

Thanks to these amazing results, scientists may soon be able to develop cheap, small sized, highly accurate tryptophan-like pollution sensors for freshwater. These detectors could be easily used in the field, hence completely eliminating the need to collect, preserve, store and carry around thousands of samples.

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

In situ tryptophan-like fluorometers: assessing turbidity and temperature effects for freshwater applications
K. Khamis, J. P. R. Sorensen, C. Bradley, D. M. Hannah, D. J. Lapworthc and R. Stevens
Environ. Sci.: Processes Impacts, 2015, 17, 740-752
DOI: 10.1039/C5EM00030K

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About the webwriter

Fernando Gomollon-Bel is a PhD Student at the ISQCH (CSIC–University of Zaragoza). His research focuses on asymmetric organic synthesis using sugars as chiral-pool starting materials towards the production of fungical transglycosidase inhibitors.

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* Access is free until 14/06/2015 through a registered RSC account.

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.

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