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Ideas towards the eradication of diarrheal diseases in poor countries

Diarrheal disease is the second leading cause of death in children under five years, killing almost 800,000 children every year. A combination of different causes, such as poor hygiene conditions and malnutrition, make low and middle income countries more susceptible to the disease. In recent years, there has been a successful campaign to decrease this high mortality rate, from almost 2.5 million deaths in the year 2000, representing a decrease of 70 to 80%. However, the amount of diarrheal episodes, or morbidity, is still very high. Taking into consideration the problems in decreasing the morbidity, Timothy R. Julian brings a perspective emphasizing the interventions that would be most effective at reducing the burden of diarrheal disease.

The vast majority of diarrheal episodes is caused by pathogens, notably rotavirus, norovirus, E. coli, Shighella spp and Cryptosporidium spp. These present different dose-response relationship, with some being more likely to infect a child after exposure (Figure 1).  According to these estimates, a great decrease in exposure is often need to reduce the probability of infection and therefore interventions should focus on minimising children exposure to the pathogens.

Figure 1. Median estimates for dose-relationship for common diarrheal pathogens.

As data regarding quantitative pathogen and human-environment interaction data is sparse, scientists often use proxy measures, like human feces equivalents, to estimate exposure risks. For example, probability of infection is calculated using the HID50 (the pathogen dose at which there is a 50% likelihood of infection) and the shedding rate (eq. 1). Estimates for environmental contamination is also presented (eq. 2).

Diarrheal disease pathogens – E. coli organisms are usually divided into two categories: enterotoxigenic (ETEC) and enteropathogenic (EPEC). Infectivity is usually strain specific and it is in general relatively low, with HID50s ranging from 105 to 108 cells for ETEC and 105 to 107 cells for EPEC, corresponding to 0.001 to 10 g and 0.01 to 1 g of feces of an infected person, respectively. Despite being similar to E. Coli, Shigella spp are more infective, presenting an HID50 of around 103 cells, which corresponds to 0.01 to 1 g of infected feces. The protozoal pathogens Cryptosporidium spp are highly infective, with an HID50 as low as 9 oocysts (10-1 to 10-5 of the amount of feces shed in a day during infection). With high shedding and high infectivity rates, rotavirus is arguably the most important enteric pathogen: the HID50 is 6 focus-forming units (FFU), equivalent to only 10-3 to 10-9 g feces of an infected person. Different from rotavirus (endemic), norovirus is characterised by its role in epidemic outbreaks. Its HID50 is 1320 genome equivalents for susceptible people (some people are naturally resistant), which corresponds to 10-4 to 10-5 g of infected feces.

Environmental transmission – The routes of transmission can be explained using the F-diagram (Figure 2). The diagram connects six environmental reservoirs for the pathogens. Interactions between infected feces and these reservoirs (through human, animal and natural processes) and subsequent interactions between the reservoirs and susceptible people result in infections.

Figure 2. The F-diagram showing the complex transmission pathways of diarrheal diseases.

With 23% of the global population using unsafe water, this reservoir is arguably the most important route of exposure to the most important pathogens (all of them have been detected in stored drinking water in LMICs), especially for rotavirus, norovirus and Cryptosporidium spp, due to the high infectivity of these.

Food is also an efficient transmission pathway, especially for bacterial pathogens that can grow in these environments. Fecal bacterial is frequently detected on hands on LMICs, posing both a direct and indirect route of transmission. Flies are important due to their interactions with both feces and food. Fields (referring to crops and soil) are primarily an intermediate reservoir, but also play a role in copraphagy and geophagy in some regions. Finally, fomites are extensively contaminated with infected feces in LMICs, contributing to the ubiquity of the pathogens throughout a household and other environments.

Perspective – Having in mind the multiple factors involved in the transmission of diarrheal pathogens (for example, etiology, infectivity, fecal shedding rate, reservoirs, human-reservoirs-nature interactions and sanitation) and that these are most likely region/site/country specific, it is important to combine interventions to interrupt simultaneously all the relevant transmission routes. For bacterial agents, reducing geophagy, prevention of growth in food and fly control could be effective in reducing exposure and therefore infection. Cryptosporidium spp and norovirus are more difficult to control due to high shedding and infectivity rates. A combination of fecal management, water and hygiene control and limited contact with infected people would be necessary. Unfortunately, rotavirus is almost impossible to control, with vaccination, nutrition and health care being the current focus to delay infection until after the first year of the child, when the mortality is reduced.

With multiple and specific interventions is therefore possible to successfully achieve great reductions in the burden of diarrheal diseases in LMICs and maybe reach eradication in the future.

To read the full Open Access article, click the link below:
Environmental transmission of diarrheal pathogens in low and middle income countries
Timothy R. Julian
Environ. Sci.: Processes Impacts, 2016,18, 944-955
DOI: 10.1039/C6EM00222F

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About the webwriter

Luiza Cruz is a PhD student in the Barrett Group at Imperial College London. Her work is towards the development of new medicines, using medicinal and natural products chemistry.

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Amines in Shanghai – a new quantitative analysis

Amines are (usually smelly) organic compounds that contain a basic nitrogen atom bearing a lone electron pair. They are often used in solvents and reagents, which causes them to be released to the atmosphere. Atmospheric amines may be dangerous for several reasons;

  • Oxidation of amines can result in some highly carcinogenic compounds
  • The release of amines to the air can alter the nitrogen cycle
  • Amines can contribute to chemical processes, including nucleation and the formation of aerosols, which can affect the water cycle by generating rain in unexpected locations

Structure of ethylamine (image by @moleculd, http://twitter.com/moleculd)

Thus, it is important that we can rely on effective ways of measuring the concentration of amines in the atmosphere. In this paper developed by chemists and engineers at Fudan University in Shanghai, China, the authors optimize a new quantitative analysis of aliphatic amines found in urban samples. To do so, these researchers have created a novel on-line derivatization of amines that transforms them into highly fluorescent molecules that can be separated and analyzed by HPLC.

This new method simplifies the experimental efforts normally required by offline derivatizations. The authors also demonstrated, using different concentrations of certified standards, that the method is statistically accurate. In addition, the procedure is very sensitive, reaching detection limits of 1 microgram per liter (ppb) for all the aliphatic amines that were analyzed.

Pollution over Shanghai (picture by Peter Dowley, https://www.flickr.com/people/40271931@N00)

Finally, it is worth highlighting that, using their own novel method, the authors have been the first to detect and quantify the seasonal variation of aliphatic amines in the pollution-fog over Shanghai. They have proved that these organic molecules are more abundant during the summer. Could this have any implications on local weather?

Interested in this research? Click on the link below to read the full article for free*

Quantitative analysis of aliphatic amines in urban aerosols based on online derivatization and high performance liquid chromatography.
X. Huang, C. Deng, G. Zhuang, J. Lin, and M. Xiao.
Environ. Sci.: Processes Impacts, 2016, Advance Article
DOI: 10.1039/C6EM00197A

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About the webwriter

Fernando Gomollón-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 12/07/2016 through a registered publishing personal account.

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Between a rock and a hard place: greenhouse gas storage and natural resource extraction

Humans are continuing to release increasing amounts of greenhouse gases to the atmosphere that have been implicated as key contributors to climate change. One major greenhouse gas is CO2. It is estimated that geological storage could result in a 17% reduction in atmospheric CO2 by 2050. Such projects aim to use sedimentary basins as they are believed to be the safest option for long-term storage of CO2 and other greenhouse gases. However, sedimentary basins are also valued for a range of extractable natural resources such as groundwater, oil and gas, and geothermal energy. Thus, there is a need to understand the potential interactions between these resources and subsurface storage of CO2 when targeting a particular site for CO2 storage.

A recently published study involving researchers from various institutes in Western Australia explain the potential risks involved with geological CO2 storage. Considering all the potential interactions between basin resource use and CO2 storage, the authors outline a Framework for Basin Resource Management Strategy (FBRMS) for optimizing interactions that may occur during the management of sedimentary basins.

Potential impacts of CO2 geological storage on other basin resources (reproduced from K. Michael
et al., EAGE Third Sustainable Earth Sciences 2015 Conference, DOI: 10.3997/2214-4609.201414262)

The initial stage of the FBRMS is an assessment of potential basins for CO2 storage based on containment potential of the subsurface. Optimal conditions include thick layers of low permeability rocks such as shales and anhydrites that can effectively cap the CO2. Lateral containment should be provided by lateral decreases in permeability, low permeability faults, or, in the absence of physical barriers, residual trapping, dissolution into water and mineral formation via reactions with the subsurface matrix. In addition to geologic characterization, modelling, monitoring and risk assessment are crucial for verifying long-term CO2 containment.

Also considered in the FBRMS are the two general means by which CO2 storage can affect other basin resources: migration and increasing basin pressure. Vertical or horizontal migration may result in contamination of natural gas or another currently used or potentially extractable resource.

Once CO2 is present in the subsurface, the future potential use of the injected area is instantly limited. An important concern associated with using shale basins is that shale may be used as an unconventional gas resource in future, and the methods for utilizing this resource negate its effectiveness as a long-term cap for CO2 storage. Though the probability is extremely low, increasing subsurface pressure from CO2 injection could also force saline water upwards along a wellbore or through existing fractures into groundwater resources, or may even cause fractures. Regardless of the likelihood, identifying all of these risks is an important facet of the FBRMS, presumably leading to relevant monitoring activities. On the other hand, increased pressure could also be beneficial in counteracting reduced pressure in mature oil or gas fields, low groundwater levels, or subsidence.

The FBRMS integrates all of these concerns to evaluate the likelihood of various basin resource-storage interactions, how beneficial or detrimental the interactions would be, and to determine how best to manage these interactions. It is intended to be used by various project stakeholders throughout the lifetime of a project, and may require intensive data collection or expert risk assessment depending on the individual project being assessed.


To read the full paper for free*, click the link below:

Framework for the assessment of interaction between CO2 geological storage and other sedimentary basin resources
K. Michael, S. Whittaker, S. Varma, E. Bekele, L. Langhi, J. Hodgkinson, and B. Harris
Environ. Sci.: Processes Impacts,
2016, 18, 164-175
DOI: 10.1039/C5EM00539F

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About the webwriter

Abha Parajulee is a Ph.D. student at the University of Toronto Scarborough. She is interested in water resources and the behavior of organic contaminants in urban environments.

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* Access is free until 01/06/2016 through a registered RSC account.

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Are we eating flame retardants?

Most of the materials we use nowadays are impregnated with several chemicals to make them fireproof and meet fire safety regulations. These are classically halogenated compounds such as polybrominated diphenyl ethers (PBDEs). Recently, the food safety authorities in the EU banned PBDEs because several studies linked them to hepatic damage and perturbations in metabolism.

Environ. Sci.: Processes Impacts

Hence, chemists developed a new kind of fire retardants known as hexabromocyclododecanes (HBCDs). Manufacturers of goods such as plastics, textiles and electronic equipment, are increasingly using these compounds. However, HBCDs may not be an ideal solution: recent studies found them in dust, air, sediments, and sewage in areas surrounding electronic waste (or e-waste) processing plants. And what is worse, the presence of HBCDs has also been reported in eggs, while researchers have confirmed human exposure from eating food sourced near the e-waste treatment plants. These are concerning issues, since these chemical are potentially toxic, persistent and bioaccumulative.

In this article published in Environmental Science: Processes & Impacts, Dr. Fang Tao and co-workers investigated the presence of HBCDs and other fire retardants in fish, pigs and free-range chickens reared in areas that could have been polluted by e-waste plants in Bui Dau, Vietnam. In addition to this, the team also took samples from supposedly non-contaminated zones both in Vietnam and Japan and analysed them.

The authors reported that HBCDs, as well as other emerging fire retardants, are found in chicken, fish and pork samples collected near the e-waste processing plant in Bui Dau. According to these data, locals may be ingesting dangerous amounts of toxic, accumulative chemicals. Although the dangers of some of these compounds are not completely defined yet, the researchers suggest to keep studying this phenomenon: the quantity of these contaminants in the environment may rise soon.

Interested in this research? Click on the link below to read the full article for free*

Emerging halogenated flame retardants and hexabromocyclododecanes in food samples from an e-waste processing area in Vietnam
Fang Tao, Hidenori Matsukami, Go Suzuki, Nguyen Minh Tue, Pham Hung Viet, Hidetaka Takigami and Stuart Harrad.
Environmental Science: Processes and Impacts, 2016, Advance Article
DOI: 10.1039/C5EM00593K

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About the webwriter

Fernando Gomollón-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 11/04/2016 through a registered RSC account.

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The dangers of mercury in solid waste landfills

The (Mad) Hatter from Carroll's Alice in Wonderland (Illustration by John Tenniel - Public Domain)

The Hatter in Alice in Wonderland may not have been mad after all. He might have suffered from mercury poisoning! Thankfully, nowadays we know mercury is a dangerous element in almost all its forms. Organomercury compounds such as monomethylmercury (MMHg) and dimethylmercury (DMHg) are especially hazardous: not only because of their extreme toxicity but also because they can be bio-magnified in the food web. Moreover, mercury can travel the biosphere through air, water and soil, increasing the danger.

Even if we have stopped using mercury thermometers, a big number of household and industrial products still use this liquid metal. A lot of these products end up in landfills where they are treated as conventional waste, and may liberate dangerous amounts of this toxic metal to the atmosphere and soil.

In this critical review published in Environmental Science: Processes & Impacts, scientists analyze solid waste management in landfills and the chemistry of mercury, as well as the release of this metal into the environment and the possible bio and geological transformations it may suffer. As a conclusion, researchers review a series of studies that should be considered in depth in order to understand the problem of mercury release and to, eventually, find a solution.

As described in this work, landfills –mainly when they undergo the so-called anaerobic phase– present the ideal conditions (pH, redox, organic matter) for mercury to be speciated and transformed, then dissolved, mobilized and disseminated within the biosphere. It is mostly released as Hg(0) in gas form, but other species like MMHg and DMHg may also be produced and incorporated to soil and water reservoirs.

Whether you are a specialist in mercury or not, this review will surely captivate you. Landfills may seem boring, but the chemistry underneath is fascinating, like the liquid metal that fascinated alchemists for centuries. Remember, mercury was the prima materia from which all metals were formed!


Interested in this research? Click on the link below to read the full article for free*:

Biogeochemical transformations of mercury in solid waste landfills and pathways for release
Sung-Woo Lee, Gregory V. Lowry and Heileen Hsu-Kim.
Environmental Science: Processes & Impacts 2016, 18, 176-189
DOI: 10.139/C5EM00561B

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About the webwriter

Fernando Gomollón-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 18/03/2016 through a registered RSC account.

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Sun, wind, and a crowd: Tough days in the life of a passive sampler?

Passive air samplers (PAS) have found great utility in monitoring environmental concentrations of semivolatile organic contaminants (SVOCs) all over the world. They provide a picture of longer-term average air concentrations of SVOCs while being relatively portable, low-cost and extremely low-maintenance. Knowing the deployment time, the amount of chemical accumulated in the passive sampling medium (PSM), and the sampling rate derived when a PAS is first calibrated before widespread use, a time-averaged volumetric air concentration can be calculated.

Graphical Abstract

A key assumption underlying the calculation of PAS-derived air concentrations is that the passive sampling medium takes up chemicals uniformly. But this assumption has not been thoroughly tested so far and studies to date have indicated that the sampling rates of some commonly used PSM can differ with position inside a sampler housing. For example, sampling rates decreased with increasing distance from the opening at the bottom of a cylindrical sampler housing for the commonly used styrene-divinylbenzene copolymer or “XAD” resin.

In a study recently published in Environmental Science: Processes & Impacts, Zhang and co-workers at the University of Toronto Scarborough have put their XAD PAS to the test once more to determine if exposure to sunlight, wind, and the presence of multiple units of XAD-filled mesh cylinders in one PAS housing caused differential chemical uptake across the length of a single cylinder.

The chemicals of interest in this series of experiments, polychlorinated biphenyls (PCBs), were chosen because their environmental partitioning properties are inclusive of a range of SVOCs commonly measured in the environment. One indoor experiment included axially segmented PAS at four indoor locations, one of which also used fans to simulate the effect of wind. At one of the indoor locations, a similar experiment was conducted outdoors, where the effect of heat conduction resulting from sunshine was also tested. This involved using PAS with regular housings, housings painted black to enhance heat absorption, and housings shaded by a steel cover.

Two additional experiments varied the number of mesh cylinders inside each housing. One experiment deployed a pair of PAS containing one and four mesh cylinders at one outdoor and one indoor location. A final outdoor experiment attempted to incorporate a variety of temperatures and wind speeds by deploying PAS at nine locations on the Big Island of Hawaii. Each site had one PAS containing one XAD-filled mesh cylinder and another containing two.

Environmental Science: Processes & Impacts front cover image highlighting the article

In the first indoor experiment, the total amount of PCBs accumulated in all segments was not significantly different from the amount accumulated in a mesh cylinder that had not been segmented. In those cylinders that were axially segmented, the amount of PCBs accumulated in the bottom segments was significantly higher than in the upper two segments in office and storage areas, and assumed to have little activity and therefore air turbulence. But this difference was not significant in the mesh cylinder placed in a cargo-loading area, presumably because of the relatively higher level of activity and therefore air turbulence. Similarly, gradients within PAS deployed outdoors were also not as strong, and the samplers exposed to fans indoors showed no significant gradients – strong indications that increased air turbulence allows for more uniform uptake across the length of the sampler.

The effect of heat convection on total accumulation and axial distribution of PCBs was determined to be minor, as was the presence of multiple mesh cylinders within one housing, but only outdoors. Indoors, the amount of PCB accumulated per sampler was significantly lower in those PAS with four mesh cylinders, and the gradient was also steeper.

The final outdoor deployment across varying temperature and wind conditions in Hawaii, which measured accumulation of PCBs, pesticides, polycyclic aromatic hydrocarbons, and polybrominated diphenyl ethers, showed no significant difference in chemical accumulation in PAS with one versus two XAD-filled mesh cylinders. The finding that uptake of SVOCs by XAD PAS is affected very little by the presence of multiple mesh cylinders in one housing in a variety of outdoor conditions means that fewer housings can be used during a given sampling campaign that uses XAD PAS. This augments the low-maintenance nature of this monitoring method, and thus the value of this particular PAS as a tool for monitoring SVOCs in the environment.


To read the full Open Access article, click the link below:

Exploring the role of the sampler housing in limiting uptake of semivolatile organic compounds in passive air sampler
Xianming Zhang, Michelle Hoang, Ying D. Lei, and Frank Wania
Environ. Sci.: Processes Impacts,
2015, 17, 2006-2012
DOI: 10.1039/C5EM00447K

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About the webwriter

Abha Parajulee is a Ph.D. student at the University of Toronto Scarborough. She is interested in water resources and the behavior of organic contaminants in urban environments.

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Naphthalene-eating bacteria

Most petroleum hydrocarbons are dangerous for the environment and are known to be toxic. These chemicals can cause severe respiratory problems, mutations and cancer. A very particular type of hydrocarbons, known as polycyclic aromatic hydrocarbons (PAHs), represents a serious environmental threat. PAHs can obviously be dangerous when directly inhaled, but they are especially harmful since they can accumulate in water, sediments and soil, taking decades to decompose and thus polluting ecosystems for generations.

A few years ago, some scientists observed that certain species of bacteria had developed, by the means of natural selection, the ability to degrade molecules like hydrocarbons or polymers. Some of these species have evolved to degrade PAHs such as naphthalene, phenanthrene or pyrene, which means that they can be used to treat the waste of certain chemical plants, lowering the amount of these dangerous products released in to the environment.

Using tools like artificial selection or genetic engineering could enhance the efficacy of these bacteria. Moreover, the influence of some external factors may be optimized to improve the conversion of pollutants to non-toxic substances. In this article, recently published in Environmental Science: Processes & Impacts, Professor Mutai Bao and his team studied the effects of supporting bacteria on biodegradable, porous, low-cost materials like semi-coke, walnut shells and activated carbon. Immobilization methods are widely used and accepted by the scientific community because they are versatile and straightforward. Moreover, these systems can be easily cleaned and reused.

Before performing the experiment, scientists had to choose the right species of bacteria. They also had to let them adapt until they were able to properly digest PAHs. To facilitate this, bacteria were fed small amounts of classic carbon sources: glucose, lactose, starch or urea. The ones that received the combination of lactose and PAHs gave the best biodegradation results and were used for the optimization.

After a series of experiments, the authors concluded that immobilized bacteria degrade up to 47% more PAHs than free microbes. Semi-coke was the best support for these microorganisms, followed by walnut shell and activated carbon. In addition to this, they found bacteria to be adaptable to a broad range of pH and salinity. These biodegradation systems could be used in real-life situations such as oil spills in the ocean, where usually other techniques are less productive.

Interested in this research? Click on the link below to read the full article for free*

Biodegradation of different petroleum hydrocarbons by free and immobilized microbial consortia
Tiantian Shen, Yongrui Pi, Mutai Bao, Nana Xu, Yiming Li and Jinren Lu
Environ. Sci.: Processes Impacts, 2015, 17, 2022-2033
DOI: 10.1039/C5EM00318K

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About the webwriter

Fernando Gomollón-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 18/02/2016 through a registered RSC account.

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Charcoal from summer barbecuing to soil remediation?

Well, not quite. But in recent years researchers have been exploring the potential of using “biochar” to remediate soil contaminated with organic chemicals. Similar to but definitely not the charcoal commonly used during barbecue season, biochar is made by heating biomass such as fruit peels in oxygen-limited conditions. Its physical and chemical characteristics impart an exceptional ability to sorb chemicals, especially organic chemicals, and reduce their bioavailability in soil.

A new study by Xu and co-workers at Peking University and the Chinese Academy of Agricultural Sciences focuses on two widespread organic chemicals: bisphenol A (BPA) and 17α-ethylyneestradiol (EE2). BPA is used for manufacturing polycarbonate plastics and epoxy resins. Thus, it is found in a multitude of commonly used products such as cars, food storage containers, and electronic equipment. EE2 is a synthetic estrogen most commonly used as an ingredient in birth control pills.

Both of these chemicals have been found to be endocrine disrupters, and can be transported to soils via wastewater irrigation, sludge fertilizers and landfill leachates. As both chemicals are quite hydrophobic, Xu et al. hypothesized that biochar added to soil would significantly sorb BPA and EE2, and as a result would also affect leaching and dissipation of the chemicals.

The researchers tested this hypothesis by adding biochar derived from corn stalks to soil in a series of lab experiments. First, sorption studies involved adding biochar at a level of 4 wt% to soils spiked with 0.01 or 0.1 mg/L of both BPA and EE2, and measuring the amount of the chemicals in both the soil solids and the soil water after equilibrium was established in about 7 days.

They found that the soils containing biochar increased the solid-water distribution coefficients by at least 200% for BPA and EE2 respectively, relative to the soils with no biochar. Next, leaching experiments meant to simulate repeated rainfall events compared biochar-free soils to those with 1, 2 and 4 wt% of biochar, all of which were spiked with BPA and EE2 at levels reflective of environmentally contaminated soils. Biochar-amended soils decreased the amount of leached BPA by 19 to 53% and EE2 by 42 to 77%.

Biochar created by pyrolysis. Image: Wikipedia.org

A final set of incubation experiments used soils spiked in a similar manner to those used in the leaching experiments. All soils, including a biochar-free control, were left outdoors at ambient temperatures for three months. Portions of the soils were sampled at 1, 30 and 90 days, and analyzed for their total and bioavailable BPA and EE2 content. The results showed no significant effect on the dissipation of the two chemicals in soil, but large reductions in the bioavailable fractions of BPA and EE2 in soil.

In addition to holding much promise for removing various organic residues from soil, other benefits of biochar in soil include carbon sequestration, reducing greenhouse gas emissions, and improving crop production. The long-term stability of biochar in soil further highlights the multi-faceted potential of biochar as a soil amendment.



To read more about Xu and co-workers’ investigation into biochar’s ability to reduce the mobility of two widespread organic contaminants, download a copy of the full article for free*:

Influence of biochar on sorption, leaching and dissipation of bisphenol A and 17α-ethynylestradiol in soil
N Xu, B Zhang, G Tan, J Li and H Wang
Environ. Sci.: Processes Impacts, 2015, 17, 1722-1730
DOI: 10.1039/C5EM00190K

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About the webwriter

Abha Parajulee is a Ph.D. student at the University of Toronto Scarborough. She is interested in water resources and the behavior of organic contaminants in urban environments.

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* Access is free until 01/12/2016 through a registered RSC account.

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Tracking down europium

We have used nuclear energy for a while now. It is a clean form of energy, except for one little thing: what happens with radioactive waste? Scientists think the best solution is burying it deep in the ground and labelling it clearly enough so that future generations (or aliens!) will not dare to look inside. However, is this really the best solution? What happens with radioactive nuclei once they are inside the nuclear graveyard?

DOI C5EM00412H

Scientists need to study the interactions of radioactive elements with the environment that surrounds them in the ground. But using radioactive elements is tricky: they can be dangerous and unstable, and most of them tend to decay in a few seconds (minutes, if you are lucky). Hence, researchers have determined to use models that mimic the behaviour of elements such as americium, curium or plutonium. Right in the row above actinides we find lanthanides, which have very similar oxidation states and comportment.

Image from Wikipedia

Source: Wikipedia.org

Scientists dig into europium. Not only because of its stability, but also because of its high fluorescence. This makes europium easy to track down in the lab. Outside the lab, europium is also very useful: the European Central Bank (ECB) uses europium as a fluorescent marker to fight counterfeit banknotes. Rumour has it the ECB intended the euro pun when choosing this particular element.

A group of researchers in China have studied the interactions of europium with alumina and humic acid (HA). These two substances represented the average inorganic and organic components of soil. In previous studies, they investigated the effect of reaction time, pH or ionic strength. In this paper, recently published in Environmental Science: Processes & Impacts, researchers examined the influence of temperature in the interactions of europium. And temperature is important when it comes to radioactive wastes: nuclear debris can keep temperatures of up to 100ºC during at least 1000 years, due to exothermic radioactive effects such as decomposition.

Luckily, the results were quite positive. Apparently, at high temperatures the formation of very stable structures is favoured, and the sorption of europium in alumina and alumina/HA systems is slightly increased with temperature. Nonetheless, trivalent cations are not the only substances present in nuclear waste. The interactions between soil-like substances (like alumina or HA) and other type of nuclei remain to be studied in depth.


Click on the link below to read the full article for free*

Sequestration and speciation of Eu(III) on gamma alumina: role of temperature and contact order
Yawen Cai, Xuemei Ren, Yue Lang, Zhiyong Liu, Pengfei Zong, Xiangke Wanga and Shitong Yang
Environ. Sci.: Processes Impacts, 2015, 17, 1904-1914
DOI: 10.1039/C5EM00412H

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About the webwriter

Fernando Gomollón-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 20/12/2015 through a registered RSC account.

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New insights into the leaching of radioisotopes from nuclear wastes

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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* Access is free until 24/11/2015 through a registered RSC account.

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