Environmental Science: Processes & Impacts blog

We are delighted to share with you a hand-picked selection of papers recently published in Environmental Science: Processes & Impacts (ESPI).

HOT papers – as recommended by our referees

A global atmospheric chemistry model for the fate and transport of PFCAs and their precursors
Colin P. Thackray et al.

Trichloroacetyl chloride, CCl₃COCl, as an alternative Cl atom precursor for laboratory use and determination of Cl atom rate coefficients for n-CH₂=CH(CH₂)_xCN (x = 3–4)
Sofie Askjær Hass et al.

Geochemical and isotope analysis of produced water from the Utica/Point Pleasant Shale, Appalachian Basin
T.L. Tasker et al.

Read more HOT papers at rsc.li/espi-hot

Reviews & Perspectives – timely overviews of key topics in environmental science

Quantifying the efficiency and selectivity of organohalide dechlorination by zerovalent iron
Feng He and Paul G. Tratnyek et al.

Potential risks of antibiotic resistant bacteria and genes in bioremediation of petroleum hydrocarbon contaminated soils
Maria S. Kuyukina et al.

How the 2010 Deepwater Horizon spill reshaped our understanding of crude oil photochemical weathering at sea: a past, present, and future perspective
Collin P. Ward and Edward B. Overton

Read more Reviews at rsc.li/espi-reviews

Open Access – read for free!

A geospatially resolved database of hydraulic fracturing wells for chemical transformation assessment
Andrew J. Sumner and Desiree L. Plata

Comparing non-targeted chemical persistence assessed using an unspiked OECD 309 test to field measurements
Zhe Li and Michael S. McLachlan

The importance of aromaticity to describe the interactions of organic matter with carbonaceous materials depends on molecular weight and sorbent geometry
Thilo Hofmann et al.

Read more Open Access content at rsc.li/espi-oa

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About ESPI
Published on a not-for-profit basis by the Royal Society of Chemistry and led by Editor-in-Chief Professor Kris McNeill (ETH Zurich), ESPI publishes high quality papers in all areas of the environmental chemical sciences, including chemistry of the air, water, soil and sediment. With a team of expert Associate Editors providing a first decision on submissions in just 38 days*, ESPI is committed to providing you with efficient and attentive service throughout the publication process. Furthermore, our flexible article types with no page or word count restrictions allow you to disseminate your research in a format that best suits you. More about the journal can be found at rsc.li/espi

Meet the ESPI team

*Average time from receipt to first decision for peer reviewed manuscripts in 2019

Find out more about the advantages of publishing in a Royal Society of Chemistry journal including our Open Access options

ESPI is complemented by our sister journals, Environmental Science: Nano, Environmental Science: Water Research & Technology and Environmental Science: Atmospheres; find out more about the these journals at rsc.li/envsci

We are delighted to share with you a hand-picked selection of papers recently published in Environmental Science: Processes & Impacts (ESPI).

HOT papers – as recommended by our referees

Evidence for a kinetically controlled burying mechanism for growth of high viscosity secondary organic aerosol
Barbara J. Finlayson-Pitts et al

Predicting Cr(VI) adsorption on soils: the role of the competition of soil organic matter
Zhenqing Shi et al

Risk-based water quality thresholds for coliphages in surface waters: effect of temperature and contamination aging
Alexandria B. Boehm

Read more HOT papers at rsc.li/espi-hot

Reviews & Perspectives – timely overviews of key topics in environmental science

The concept of essential use for determining when uses of PFASs can be phased out
Ian T. Cousins et al

Photochemistry of iron in aquatic environments
Caroline Schmidt et al

Positive matrix factorization on source apportionment for typical pollutants in different environmental media: a review
Fengwen Wang et al

Read more Reviews at rsc.li/espi-reviews

Open Access – read for free!

Comprehensive screening of quaternary ammonium surfactants and ionic liquids in wastewater effluents and lake sediments
Sarah G. Pati and William A. Arnold

Emerging investigator series: use of behavioural endpoints in the regulation of chemicals
Marlene Ågerstrand et al

The molecular interactions of organic compounds with tire crumb materials differ substantially from those with other microplastics
Thorsten Hüffer, Maren Wehrhahn and Thilo Hofmann

Read more Open Access content at rsc.li/espi-oa

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We hope you enjoy reading these papers, and we welcome your future submissions to the journal.

Bisphenol A (BPA) is one of the most used industrial chemicals worldwide. Since its introduction in the market in 1959, BPA production has increased steadily and it is forecasted to reach 7.3 million tons by the end of 2023.¹ BPA is used for a range of applications: from dental sealants to internal can coatings, electronic equipment and supermarket receipts.² “In the past years, concerns have been raised over the use of this compound due to its estrogenic effects that can be observed also at low BPA concentration, such as the ones found in the natural environment.^2,3 Thus, investigation of natural attenuation processes might help us developing strategies to reduce human exposure to this widespread chemical.

Several literature studies showed that manganese oxides (MnO_x)-mediated oxidation represents the main PBA degradation pathway in anoxic conditions.² This process produces a series of degradation products, including radicals that might couple to dissolved organic matter to form the so-called “bound residues”, unknown high molecular weight products whose long-term environmental risks are still debated.⁴ A detailed knowledge of the reaction mechanism will therefore allow to predict, and ideally prevent, the formation of degradation products that might be more hazardous than the parent compound.

In this context, Balgooyen et al. used stirred flow reactors to investigate the effect of influent concentrations on BPA degradation mechanism via birnessite (δ-MnO₂) oxidation. This research question was motivated by the hypothesis that higher influent concentrations might lead to a higher formation of bound residues. The results of this work are directly relevant for engineered water treatment systems that use MnO_x-coated sand,⁵ where contaminant inflow concentrations might change during time.

As a unique feature of this work, the authors used a combined approach based on the detection of both organic and inorganic reaction products. Specifically, they followed the formation of both hydroxycumil alcohol (HCA) and aqueous Mn(II). HCA is the main PBA oxidation product and is considered a proxy for bound residues formation, while Mn(II) is a reaction byproduct released in solution upon reduction of birnessite.

Unexpectedly, the two approaches gave opposite results: HCA yields were constant for the influent concentration range investigated, while Mn(II) yields decreased as the influent concentration increased. In order to explain their results, the authors hypothesized that Mn(II) was not an accurate proxy, as comproportionation and disproportionation reactions occurring at the mineral surface might alter aqueous Mn(II) concentrations. Using an elegant series of sorption and desorption experiments, Balgooyen et al. were able to confirm this hypothesis, leading to the conclusion that BPA oxidation mechanism in stirred-flow reactors is indeed independent from the influent concentration.

In addition to providing a valuable new piece of information for the complex puzzle of BPA cycling in anoxic conditions, the work of Balgooyen et al. teaches us something that has little to do with micropollutants or flow-through reactors: for a throughout study of a chemical mechanism, all reaction partners must be considered – no matter how many different analytical techniques you will have to use.

To download the full article for free*, click the link below:

Impact of bisphenol A influent concentration and reaction time on MnO2 transformation in a stirred flow reactor

Sarah Balgooyen, Gabrielle Campagnola, Christina K. Remucal and Matthew Ginder-Vogel

Environ. Sci.: Processes Impacts, 2019, 21, 19

DOI: 10.1039/c8em00451j

About the Webwriter:

Rachele Ossola is a PhD student in the Environmental Chemistry group at ETH Zurich. Her research focuses on photochemistry of dissolved organic matter in the natural environment.

Additional references

(1)        The Global Bisphenol A Market, https://www.researchandmarkets.com/reports/4665281/the-global-bisphenol-a-market (accessed May 26, 2019).

(2)        Im and Löffler, Environ. Sci. Technol. 2016, 50 (16), 8403–8416.

(3)        vom Saal and Hughes, Environ. Health Perspect. 2005, 113 (8), 926–933.

(4)        Barraclough et al. Environ. Pollut. 2005, 133 (1), 85–90.

(5)        Charbonnet et al., Environ. Sci. Technol. 2018, 52 (18), 10728–10736.

*Article free to access until the 30th June 2019

Polychlorinated biphenyls (PBCs) are a wide class of compounds with numerous everyday applications such as electrical insulators, cooling fluids, plasticizers and flame retardants – just to name a few. However,  back in the 1970s evidence started accumulating on their environmental persistency and on their toxicity as human carcinogens. In 1978, PBCs production was terminated and an international ban followed their inclusion in the Stockholm convention of Persistent Organic Pollutants. Interestingly though, PBCs are still present in our houses and schools today. A recent study conducted in rural and urban schools in the US measured indoor PBCs concentrations one to two orders of magnitude higher than outdoor values.¹ Another study measured PBCs in residential homes and found kitchen cabinets to act as an indoor source of these semivolatile compounds.² Considering their adverse health effects and their widespread occurrence, non-invasive, easy-to-use and cheap detectors are needed to monitor indoor PBCs levels.

In this respect, passive samplers represent a valid alternative to conventional sampling techniques. They consist of a disc of polymeric material placed into a protective shell. After the sampler is deployed in the environment, semivolatile compounds diffuse into the chamber and get absorbed onto the polymer. After a certain exposure time, the passive sampler is withdrawn from the field, and the absorbed compounds are extracted and quantified. The “on-the-sampler” concentration (C_sampler) is then used to obtain environmental exposure values.

However, using passive samplers in an accurate and reliable manner is challenging. One of the most critical but elusive parameters is the sampling rate (R_s), which represents the volume of air sampled per unit of time and is required to correctly convert C_sampler into exposure data. In outdoor applications the sampling rate is commonly measured using a “depuration compound”, an isotopically-labelled version of the species of interest that is adsorbed onto the polymeric disc before deploying the sampler in the field. The sampling rate is simply estimated from the loss of the depuration compound. This technique is effective, but the toxicity of these reference molecules makes it unsuitable for indoor applications. Another possibility involves the calibration of the passive sampler before its use, but this approach is time consuming and requires the use of an additional independent sampling method (for instance, an active air sampler).

Alternatively, R_s can be estimated with mathematical models. These models have already been developed for outdoor applications and allow the estimation of R_s from the wind speed data. Starting from this point, Herkert and Hornbuckle in their most recent publication hypothesized that these same models, if adjusted appropriately, can provide R_s from the indoor airflow data. To test their ideas, they set out a two-phase study with the final aim of providing practical recommendations for an accurate use of passive samplers in indoor environments.

In the first phase, they measured the sampling rate of thirty-eight PBCs congeners in a school room using a combination of passive and active samplers, and compared the results with the modelled values. The predicted R_s values were obtained from the room-averaged wind speed, a parameter that can be easily measured with an anemometer. Their results showed that the difference between the empirical and the simulated values was on overall less than 25%, demonstrating that mathematical models represent a reasonably good method to access sampling rates.

In a second phase, they investigated how the position of the passive sampler within the room influenced the value of the sampling rate. They observed that location did matter, as different zones of the room experienced different air flow. Specifically, fluid dynamics simulation of a typical room showed that samples placed close to the walls (< 30 cm), the ceiling (< 30 cm), the air diffuser (< 50 cm) or placed on surfaces experience unrepresentative wind speeds, while open or closed doors seem to have a minimal effect. They thus concluded that R_s can be modelled accurately if the passive samplers are placed appropriately, opening up this technology for use in indoor settings.

To download the full article for free*, click the link below:

Effects of room airflow on accurate determination of PUF-PAS sampling rates in the indoor environment

Nicholas J. Herkert and Keri C. Hornbuckle

Environ. Sci.: Processes Impacts, 2018, 20, 757

DOI: 10.1039/c8em00082d

About the Webwriter:

Rachele Ossola is a PhD student in the Environmental Chemistry group at ETH Zurich. Her research focuses on photochemistry of dissolved organic matter in the natural environment.

References in article:

(1)        Marek et al., Environ. Sci. Technol. 2017, 51 (14), 7853–7860.

(2)        Herkert et al., Environ. Sci. Technol. 2018, 52 (9), 5154–5160.

*Article free to access until the 1st of January 2019

Heavy metals are toxic, but sometimes their organometallic compounds are worse. In this respect, methylmercury (MeHg⁺) represents an excellent example: the detrimental health and environmental effects associated with mercury (Hg) pollution are in fact caused by MeHg⁺, and not by the metal itself. Methylmercury is produced in the aquatic environment by archea and anoxic bacteria, which use inorganic mercury as a starting substrate. Once produced, MeHg⁺ enters the food-web and accumulates in organisms such as fish and seafood, which represents the main methylmercury exposure pathway for the human beings.

Due to its high neurotoxicity, many efforts have been devoted to improve our knowledge on the environmental fate of methylmercury. In this context, identify and characterize MeHg⁺ degradation mechanisms represent an important step, as the degradation processes will directly affect methylmercury concentrations in the environment, thus the dose at which we are exposed.

So far, four different MeHg⁺ degradation pathways have been identified. The so-called oxidative demethylation involves the degradation of MeHg⁺ to inorganic mercury and carbon dioxide by anaerobic bacteria. Differently from the other three processes, which are relatively well understood, many doubts still remain on the details of this pathway despite almost 30 years of scientific investigations. So many, in fact, to bring some researchers back to the literature with a big question to be answered: is oxidative demethylation a real process, or it is just an experimental artifact?

Based on the available literature on methylmercury chemistry and biogeochemistry, Kanzler et al. hypothesized that a simple abiotic process could be responsible for the MeHg⁺ degradation that have been observed in the presence of sulfate-reducing bacteria, the microorganisms that are believed to perform oxidative demethylation. The proposed reaction involves the formation of a binuclear complex, bis(methylmercury) sulphide ((MeHg)₂S), which can degrade to insoluble cinnabar (HgS) and dimethylmercury (Me₂Hg), a volatile compound.

2MeHg⁺ + HS^– ⇌ (MeHg)₂ S + H⁺→ Me₂Hg + HgS

Several factors influence the thermodynamics and the kinetics of this reaction, including the solution pH and the concentrations of the two precursors, methylmercury and hydrogen sulfide. Using a combination of experimental and computational approaches, Kanzler et al. developed a model that allows the prediction of both MeHg⁺ speciation (i.e., the position of the first equilibrium) and dimethylmercury formation rates as a function of the chemical composition of the medium.

Based on this model, the authors showed that the binuclear complex bis(methylmercury) sulphide is the dominant methylmercury species in the pure culture studies that previously investigated the oxidative demethylation pathway. In other words, the methylmercury loss was most likely associated to the abiotic formation of (MeHg)₂S, rather than to an enzymatic degradation process. Notably, these former microbiological studies lack abiotic control experiments that might undoubtedly prove or disprove Kanzler’s conclusions.

The model was also employed to investigate whether (MeHg)₂S decomposition might be a relevant dimethylmercury (Me₂Hg) formation pathway in the natural environment. Dimethylmercury represents almost half of the total mercury species in the open ocean, but so far very few explanations have been proposed regarding its formation mechanism. Despite being an appealing hypothesis, very slow Me₂Hg formation rates were anticipated in environmentally-relevant conditions, implying that (MeHg)₂S decomposition can be a relevant dimethylmercury formation process only in environments with long MeHg⁺ residence times, i.e. in the subsurface ocean.

In this study, Kanzler et al. cast new lights on aspects of the biogeochemical cycle of MeHg⁺ that are still poorly understood. New work is now needed to confirm the model’s prediction and to update our knowledge on the environmental fate of this neurotoxic compound.

To download the full article for free* click the link below:

Emerging investigator series: methylmercury speciation and dimethylmercury production in sulfidic solutions
Charlotte R. Kanzler, Peng Lian, Emma Leverich Trainer, Xiaoxuan Yang, Niranjan Govind, Jerry M. Parks and Andrew M. Graham
Environ. Sci. Process. Impacts, 2018, 20, 584–594
DOI: 10.1039/C7EM00533D

About the Webwriter:

Rachele Ossola is a PhD student in the Environmental Chemistry group at ETH Zurich. Her research focuses on photochemistry of dissolved organic matter in the natural environment.

*Free to read until 31st August 2018

Cyanotoxins are often found in surface waters worldwide. If contaminated water is consumed, they can bioaccumulate in the liver and cause death in high doses. They can also poison other animals and plants, causing a real threat to life and increasing the potential of disruption in drinking water supply in affected areas.  Among all cyanotoxins, microcystin (MC) is the most studied. Herein, Maghsoudi and colleagues report a new bacterium isolate that degrade these toxins and present a study on some factors involved on its biodegradation activity.

MCs are small cyclic toxins composed of seven peptides and, as a result of structural variation, 89 analogues have been identified to date. Their hepatotoxicity is due to the presence of the unique amino acid, Adda, in their structure. They are resistant to enzymatic and physico-chemical breakdown owing to their small cyclic structure. However, they can be biodegraded by a few genus of bacteria.

The majority of studies that have focused on MC degradation have identified Sphingomonas sp as the most common degrades.  Among these, the gene mlrA encodes the enzyme responsible for cleaving the peptide bond between arginine and Adda and, therefore, causing the breaking down of the cyclic structure. However, different peptides that do not carry the arginine-Adda bond are also degraded by bacteria from the genus Sphingomonas. This indicates that different pathways may be involved in biodegradation. Using modern sequencing methods, Maghsoudi and colleagues also sought to identify and determine the role of theses genes in different MC variants.

The group collected samples of water from the Missisquoi Bay, Quebec, Canada, where several cyanobacterial blooms have been observed. A total of 22 strains were isolated with the ability to degrade cyanotoxins and, among these, four were able to degrade all MC variants (MCLR, YR, LY, LW and LF). Moreover, sequencing analysis showed that one of the isolates (MB-E) demonstrated 99% identity with the Sphingopyxis genus.

Following this finding, a next generation sequencing method was used for analysing the mlr gene cluster of the new strain. Results showed that organisation of mlr genes in this cluster is identical to those of several Sphingomonas strains that degrade MCs. Results also revealed that transcription of the mlrA gene is triggered by the presence of microcystin in the medium and that the same pathway is used in the biodegradation of all MC variants. This was the first time that this new sequencing method was used to characterise the genome of MC degraders.

Moreover, pH-dependent biodegradation is thought to be the determinant factor in the fate and disappearance of these toxins. However, limited information is known about the correlation of dynamic changes in pH and cyanotoxin degradation. Using MB-E, biodegradation was observed at pH values between 6.10 and 8.05. The highest biodegradation rate was observed at pH 7.22 and data showed that MB-E was not able to grow under basic conditions. Considering that cyanobacterial blooms are often associated with a high pH (between 8.5 and 11), MB-E may have had limited biodegradation activity in the bay. However, MB-E was still able to degrade toxins at pH 9.12, that is closer to the pH of drinking water during cyanobacterial blooms.

In summary, using new sequencing methods, Maghsoudi and colleagues proved that gene expression profile of a new isolate that exhibit microcystin biodegradation is identical to Sphingopyxis sp, a novel result. Moreover, further studies on dynamic pH changes during cyanobacterial blooms might be useful in providing insight into the persistence and biodegradation activity of MB-E in drinking waters.

To read the full article for free* click the link below:
Cyanotoxin degradation activity and mlr gene expression profiles of a Sphingopyxis sp. isolated from Lake Champlain, Canada
Ehsan Maghsoudi, Nathalie Fortin, Charles Greer, Christine Maynard, Antoine Pagé, Sung Vo Duy, Sébastien Sauvé, Michèle Prévost and Sarah Dorner
Environ. Sci.: Processes Impacts, 2016, 18, 1417-1426
DOI: 10.1039/C6EM00001K

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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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*Access is free until 08/02/2017 through a registered publishing personal account.

As the Paris climate deal takes legal effect, it is necessary to assess the technical aspects and challenges to limit the global temperature increase. Given the problems in completely eliminating greenhouse gases (GHGs) emissions from human activities, one of the possible solutions is using Negative Emission Technologies (NETs) as a way of compensating for those emissions. As the UK has recently stated a target of net zero emission, Smith and colleagues took on a preliminary assessment of land-based NETs in this country in order to estimate their potential and impact.

There are a number of ways negative emissions could compensate for CO₂ emissions:

1) Bioenergy with Carbon Capture and Storage (BECCS), using crops to extract CO₂ and then burning them for energy and sequestering the result emissions, thought to hold the most potential to bring down CO₂ levels

2) Direct Air Capture of CO₂ (DAC) from ambient air and either burying it underground or using it in chemical processes

3) Enhanced Weathering of minerals (EW), by spreading pulverised rocks onto soils to increase the natural weathering process that takes up CO₂

4) Afforestation and Reforestation (AR)

5) Soil Carbon Sequestration (SCS), which uses modern farming methods to reverse past losses of soil carbon and sequester CO₂

6) Biochar, that converts biomass into biochar for use as soil amendment

Smith and colleagues considered the use of UK land specifically and only technical aspects of these technologies. Other factors, e.g. of a socio-political nature, were not considered and are thought to lower the potential of the NETs considerably.

Regarding land availability, BECCS and AR use land that can no longer be used for food production, assumed to be 1.5 Mha. The same value is assumed for biochar, since growing feedstock for it cannot be done in the same land used for food. SCS and EW can be practised on land without changing its use, here assumed to be 8.5 Mha. Finally, DAC has no land footprint so it is not constrained by land availability.

Negative emission potential for BECCS, AR and biochar are 4.5‒18, 5.1 and 1.73‒11.25 Mt C eq. per year, respectively. SCS would deliver 0.255‒8.5 Mt C eq. per year and the combined potential for EW would be 22.5 Mt C per year. DAC is compared at the same level of BECCS, i.e. 4.5‒18 Mt C eq. per year.

In the UK, total emissions of GHGs are equal to an average of 153 Mt C eq. per year. Considering that not all NETs can be applied at the same time and assuming no interaction between practices, the maximum aggregate potential of land-based NETs is estimated to be 12‒49 Mt C eq. per year (BECCS plus SCS plus EW). This represents only 8‒32% of current UK GHGs emissions.  DAC, however, could increase this number further.

This maximum aggregate potential is limited by a number of factors, including cost, energy, environmental and socio-political constraints. More studies are needed to fully understand and hopefully overcome the barriers to implementation and reach the target of net zero emission.

To read the full article for free* click the link below:

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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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*Access is free until 23/12/2016 through a registered publishing personal account.

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 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.

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.