Archive for the ‘Hot Articles’ Category

Can nanotubes affect how polyaromatic hydrocarbons behave in soil?

Determining the fate of compounds once they’re released into the environment is a complex issue. However such study is vital in order to assess the persistence of a compound as well as its bioavailability.  

It is well-established that polyaromatic hydrocarbons (PAHs) bind to organic complexes through hydrophobic interactions and that this can occur within soils to matter such as humus and soot etc.  So how does the presence of multi-walled carbon nanotubes (MWNTs) impact this?  Particularly given they are organic particles with relatively high surface areas available for adsorption.  Given the increasing interest in MWNTs there is now an elevated risk of ‘traditional’ organic pollution being released into an environment where MWNTs are already present, co-released with them or for MWNTs to be released onto existing polluted soil.

Li et al. used batch equilibrium experiments to assess the relationship between soil types, MWNTs and PAHs.  The MWNTs used were 1-3 µm long, 11 nm diameter with relatively little bundling providing a high surface area.  The group assessed three soil types: sand, sandy loam and silt loam with 2 mg g-1 of MWNTs.  The compounds and concentrations of PAHs assessed were naphthalene 0.18–7.94 mg L-1, fluorine 0.16–1.62 mg L-1 and phenanthrene 0.1–0.91 mg L-1.  Sorption tests (HPLC-fluorescence) were carried out after 5 days, at which point the aqueous solution was removed and replaced with fresh and left for 24hrs under the same conditions to assess desorption.

The results confirmed that the sorption of these compounds increased with increasing organic content of the soil. However, the presence of MWNTs did not appear to influence this adsorption, even at these relatively high concentrations of MWNTs.  Desorption was minimal in all cases.

In addition, the group derived equations based on the ‘rule of mixtures’ capable of predicting the sorption coefficients of composite sorbents.  They found good correlations between predicted and experimental data using these equations despite limitations of the model, such as assuming no void spaces. 

This HOT article would be of interest to anyone carrying out batch equilibrium experiments, or is interested in the sorption of PAH and/or the fate of MWNTs.  You can access it from the website for free for the next 4 weeks*!

Polyaromatic hydrocarbons (PAHs) sorption behavior unaffected by the presence of multi-walled carbon nanotubes (MWNTs) in a natural soil system.
Shibin Li, Todd A. Anderson, Micah J. Green, Jonathan D. Maul and Jaclyn E. Cañas-Carrell
DOI: 10.1039/C3EM00099K

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How can you assess the impact of multiple methane sources to the environment?

In this HOT article, collaborators in Australia and California devise methods of assessing contributions of landfill and natural gas methane to mixtures in soil gas and groundwater. They use half-lives and concentration ratios to evaluate the age of release.

The group at URS Australia Pty Ltd, Geosyntec Consultants and Redwood Waste Management California, focus on the problem of methane from landfill gas migrating away underneath the surface of landfill sites. It is a particular problem due to methane’s flammable nature. Landfill gas is not the only source of migrating methane. Sources include natural organic matter decomposition, natural gas in supply lines, degradation of petroleum products and underground reservoirs of natural gas. There are many indicators used to determine the source of natural gas, such as the presence of CO2 being a marker for biodegradation. Carbon and hydrogen isotope composition is also used.

These researchers argue that using multiples of these indicators is the most reliable way to understand sources and migration pathways. This paper introduces a methodology to assess all of these different indicators at a complex site with multiple methane sources. Knowing the age of landfill gas using VOCs concentrations is a helpful parameter when assessing migration distance and time. This methodology using methane radioisotope data can distinguish on-going release from an inactive source and determine relative contributions of landfill gas and thermogenic methane to the environment. The theoretical basis for estimating landfill gas age is described in detail and applied to a case study at a municipal solid waste disposal facility in California.

As always, we’ve made this fascinating HOT research free to access for 4 weeks*!

Evaluation of the age of landfill gas methane in landfill gas–natural gas mixtures using co-occurring constituents
Henry B. Kerfoot, Benjamin Hagedorn and Mark Verwiel 
DOI: 10.1039/C3EM30971A

*Free access to individuals is provided through an RSC Publishing personal account. Registration is quick, free and simple

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HOT article! Hydrological and landscape factors affecting nutrient flux

J. Abell and colleagues at the University of Waikato and National Institute of Water and Atmospheric Research, New Zealand, have quantified nutrient and sediment inputs to a large eutrophic lake. They draw conclusions on how hydrological and landscape factors interact to produce pollutant flux.

Pollutant concentrations after a rain event such as a storm vary greatly and therefore high-frequency sampling is needed.  The amount of pollutant must be measured as a function of the stream discharge. The relationship between the two parameters can provide insights into sources and transport mechanisms in a catchment area. A catchment area can act as a filter, regulating downstream transport.  Therefore changes over time that occur after a rain event give insights into upstream hydrological and landscape factors.

The team looked at two streams flowing into a large eutrophic lake, focusing on levels of suspended sediment, nitrogen and phosphorus over a range of discharge values. One stream flowed through a mainly forested area, the other through pasture land. They conducted high frequency sampling over two years for both streams, taking over 900 samples. Comparison of two streams allowed spatial conclusions to be drawn.

This article includes an in-depth discussion of the factors related to suspended sediment and nutrient levels of the two streams, and how all of these factors contribute to the eutrophic nature of the lake. The researchers examine how these results could to lead to improved management of lake water quality.

Free to access for 4 weeks*, read the detailed discussion here:

Quantifying temporal and spatial variations in sediment, nitrogen and phosphorus transport in stream inflows to a large eutrophic lake
J. M. Abell, D. P. Hamilton and J. C. Rutherford
DOI: 10.1039/C3EM00083D

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Issue 5 online! Bridging data gaps and sampling particulates, E-waste and radiocarbon analysis

A HOT article from a team at the US Naval Research Laboratory is featured on this month’s eye-catching outside front cover, which was recently featured on the ESPI blog. In this work, CO2 radiocarbon analysis is demonstrated as a tool to review remediation efficiency by differentiating between CO2 produced by degrading fuel contaminant and that produced naturally by organic matter. Free to access for 6 weeks*!

Radiocarbon-depleted CO2 evidence for fuel biodegradation at the Naval Air Station North Island (USA) fuel farm site
Thomas J. Boyd, Michael J. Pound, Daniel Lohr and Richard B. Coffin
DOI: 10.1039/C3EM00008G


 

Issue 5 contains two Perspective articles. The first written by Darrah Sleeth at University of Utah, USA, assesses the current air sampling techniques available for sampling beryllium particulates and outlines the components of the ideal aerosol sampler.

The impact of particle size selective sampling methods on occupational assessment of airborne beryllium particulates
Darrah K. Sleeth 
DOI: 10.1039/C3EM30877D


 

The second Perspective from Richard Brown et al. at the National Physical Laboratory, UK, follows on from their excellent HOT article featured on the front cover of Issue 3 in February. This Perspective article discusses the consequences of incomplete data coverage and evaluates strategies for making up for such data loss. The authors’ aim is to provoke debate about the best ways to address this problem, so have a read and let us know what you think by commenting below.

Improved strategies for calculating annual averages of ambient air pollutants in cases of incomplete data coverage
Richard J. C. Brown, Peter M. Harris and Maurice G. Cox
DOI: 10.1039/C3EM00039G


 

Issue 5 contains more HOT research, such as this article on E-waste which was highlighted on the blog last week:

Heavy metals and organic compounds contamination in soil from an e-waste region in South China
Ming Liu, Bo Huang, Xinhui Bi, Zhaofang Ren, Guoying Sheng and Jiamo Fu
DOI: 10.1039/C3EM00043E

Discover the full contents of Issue 5 here!

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HOT article: The impact of e-waste recycling in China

The dumping of e-waste is an ever-increasing environmental problem. Individuals and organisations are changing their mobile phones and computers at faster and faster rates to keep up to date with the latest technological innovations. 80% of the world’s e-waste is exported to Asia, with the vast majority ending up in China where the environmental regulations are softer and the cost of labour is lower.

The recycling of e-waste in China often involves environmentally unfriendly processes. Now mostly banned from use, PCBs are still prevalent in the majority of older electronic equipment, which is now e-waste. PBDEs are also used as flame retardants in electronics. These chemicals and heavy metals are released into the environment during e-waste recycling

Researchers at the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, China, describe an extensive study into the soil contamination levels in an e-waste region of Southern China. They identify which recycling activities emit which pollutants and look at the links between contamination levels in recycling sites and in local agricultural soils.

They find that local paddy and vegetable field soils are contaminated with the same heavy metals found at the recycling sites and this contamination may have been distributed via ponds and streams. This work will inform the reform of e-waste recycling policies and the team plan to investigate the mobility and toxicity of the contaminants in detail.

This HOT article on the processes of an important modern environmental issue is now free to access for the next 4 weeks*!

Heavy metals and organic compounds contamination in soil from an e-waste region in South China
Ming Liu, Bo Huang, Xinhui Bi, Zhaofang Ren, Guoying Sheng and Jiamo Fu  
DOI: 10.1039/C3EM00043E

 *Free access to individuals is provided through an RSC Publishing personal account. Registration is quick, free and simple

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HOT article: Radiocarbon for remediation analysis

In remediation of hydrocarbon contamination, it is vital to be able to monitor the levels of the desired relatively harmless end-product CO2. There are a large number of different ways to check hydrocarbon degradation varying in cost and complexity.

Differentiating naturally derived CO2 from contaminant-derived CO2 for accurate measurements is often a problem. Carbon isotope ratios of the contaminant versus the product environment can be used. Radiocarbon analysis can monitor CO2 very effectively as fossil fuel sources are radiocarbon-free and can be compared against carbon from plants and soil from photosynthesis. Enhanced radiocarbon-depleted CO2 relative to a background measurement indicates fossil fuel degradation.

In this HOT article, soil gas and groundwater CO2 radiocarbon analysis is used to assess whether fuel hydrocarbons at a US Navy facility are being removed naturally. Using a two end-member isotopic mixing model the researchers determine how much of the CO2 comes from fossil fuel. The model includes two components are the fossil fuel-derived and the natural organic matter-derived CO2 analysed using the one tracer, radiocarbon. The fraction of CO2 from fossil fuel was 93% at the fuel contaminated site.

This is further demonstrating of radiocarbon as an on-site tool for initial or ongoing analysis to assess remediation method efficiency. This HOT article as chosen by the referees is free to access for the next 4 weeks*:

Radiocarbon-depleted CO2 evidence for fuel biodegradation at the Naval Air Station North Island (USA) fuel farm site
Thomas J. Boyd, Michael J. Pound, Daniel Lohr and Richard B. Coffin   
DOI: 10.1039/C3EM00008G

*Free access to individuals is provided through an RSC Publishing personal account. Registration is quick, free and simple

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Antibiotics in swine wastewater

There has been recent concern that antibiotics in the environment may increase bacterial resistance, potentially having consequences on their efficacy.  The use of antibiotics on livestock has greatly increased in recent years, estimated by over 50% between 2007 and 2010, resulting in a proportional increase in the amount excreted into wastewater as active compounds.

antibiotics, farming

Ben et al. surveyed 41 swine wastewaters from 21 concentrated animal feeding operation sites in the Shandong Province, China, in both the summer and winter.  The group targeted 5 sulfonamides, 3 tetracyclines and a macrolide analysing both the liquid and solid fractions of the wastewater.  The sample preparation in brief included ultrasonication (for the solid samples) and Solid Phase Extraction (SPE) followed by LC-MS.

Results in brief showed that all antibiotics, apart from one, were found at concentrations which were largely comparable to other data within this field, although occasionally up to 2.02 mg L-1, with concentrations generally higher during the winter.  The concentrations of antibiotics added to food was proportional to the size of the site, whereas those given at times of disease were much more variable.  Partitioning coefficients for each antibiotic were calculated and reported; the antibiotics were largely present in the liquid, although significant proportions were adsorbed to solid matrices, with adsorption vary between seasons.

This paper would be of interest to anyone interested in antibiotic resistance, analytical techniques to detect antibiotics and agricultural practices with regard to antibiotic use.  You can download the paper here, free for the next 4 weeks*.

Occurrence and partition of antibiotics in the liquid and solid phases of swine wastewater from concentrated animal feeding operations in Shandong Province, China
Weiwei Ben ,  Xun Pan and Zhimin Qiang
DOI: 10.1039/C3EM30845F

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Issue 4 online today! On-site porewater analysis, reviewing PBDE toxicity and xenobiotics in wastewater

The beautiful image on the outside front cover highlights important research from Beat Müller et al. This research conducted in Switzerland combines convenient technologies to develop a method for speedy, portable sediment porewater sampling and on-site analysis. This article was featured on the blog last week and you can browse the blog or read the post here. As a cover article, it’s also now free to access for 6 weeks*!

Sediment porewater extraction and analysis combining filter tube samplers and capillary electrophoresis
Natascha T. Torres, Peter C. Hauser, Gerhard Furrer, Helmut Brandl and Beat Müller
DOI: 10.1039/C3EM00068K

An interesting Frontier review from Xiao-Min Ren and ES: P&I Editorial Board member Liang-Hong Guo on the likely impact of PBDE toxicity on the body, specifically looking at what is known about the molecular mechanism of PBDE in disruption of hormone receptor pathways and how PBDE toxicity is being investigated.

Molecular toxicology of polybrominated diphenyl ethers: nuclear hormone receptor mediated pathways
Xiao-Min Ren and Liang-Hong Guo
DOI: 10.1039/C3EM00023K

Issue 4 also contains HOT articles, two of which recently featured on the blog and both are still free to access* for the next couple of weeks:

Characterization of a portable method for the collection of exhaled breath condensate and subsequent analysis of metal content
Julie R. Fox, Ernst W. Spannhake, Kristin K. Macri, Christine M. Torrey, Jana N. Mihalic, Sorina E. Eftim, Peter S. J. Lees and Alison S. Geyh
DOI: 10.1039/C3EM30906A

Read the blog post here

A case-study on the accuracy of mass balances for xenobiotics in full-scale wastewater treatment plants
Marius Majewsky, Julien Farlin, Michael Bayerle and Tom Gallé
DOI: 10.1039/C3EM30884G

Read the blog post here

Curious to know more about Environmental Science: Processes & Impacts?

 View the full issue here today

 

*Free access to individuals is provided through an RSC Publishing personal account. Registration is quick, free and simple

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Stream water pollution – the importance of analysing multiple matrices

An extensive study by Gonzalez et al. investigating persistent organic pollutants (POPs) in the Argentinian Quequ´en Grande River watershed has emphasised the importance of analysing multiple matrices to gain a fuller picture of the contamination within an environment.

The group sampled water, suspended particulate material, fish muscle, local soil, plant roots, stems and leaves and river sediments.  Organochlorine pesticides, polychlorinated biphenyls and polybrominated diphenyl ethers were analysed by GC-ECD, in addition isotherm studies were carried out on the compounds.  PCA was carried out as part of the statistical analysis to determine patterns and groupings within the data.

In brief, the study is able to compare not only relative concentrations between the different types of pollutants but also differences in persistence and preferential degradation pathways in differing soil types.  Water samples, perhaps unsurprisingly, were more subject to variation depending on how recent any of the compounds had been applied locally. Roots were found to contain more than aerial parts of the plants and fish muscle was found to contain levels of all pollutants targeted, however at levels which were not deemed a risk to human health. 

This is an extensive study which incorporates a variety of matrices across an entire watershed and provides information on transformation and distribution of POPs within the catchment.  This paper would be of interest to anyone working in the fields of environmental sampling, water pollution, modelling or persistent pollutants.

Organic pollutant levels in an agricultural watershed: the importance of analyzing multiple matrices for assessing streamwater pollution
Mariana Gonzalez, Karina S. B. Miglioranza, Sebastián I. Grondona, Maria Florencia Silva Barni, Daniel E. Martinez and Aránzazu Peña
DOI: 10.1039/C3EM30882K

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Speedy, high-throughput sediment porewater extraction and analysis method

Collaborators at Eawag, the University of Basel, ETH Zurich and University of Zurich have come together to develop a faster, portable way to take sediment samples, extract porewater and analyse it in under 15 minutes.

Led by Beat Muller, the researchers combine a portable capillary electrophoresis instrument with MicroRhizon samplers in this ES:P&I paper.

MicroRhizon samplers are made of chemically inert microporous tubing connected to a syringe and are inexpensive, portable and simple to use. The difficulty in analysis is that only a small sample volume is collected, extra handling and sample preparation is required and there is a risk of contamination in transferring the sample for analysis.

The previously developed portable capillary electrophoresis device with contactless conductivity detection eliminates these concerns as it enables sensitive detection of ionic compounds in the field immediately after sampling.

porewater sampling, MicroRhizonIn this article, the team applies this combination to porewater sampling and analysis, giving high spatial resolution.

 The method is validated by sampling of sediment from a eutrophic lake, comparing the results to those from ion chromatography. They successfully separate out major inorganic ionic compounds in under 15 minutes. The disturbance of the sediment samples is minimal and zero-oxygen conditions were maintained without difficulty. No splitting, acidification or dilution of the sample is necessary.

Such speedy porewater analysis will be beneficial for the study of oxidizing agents and nutrients in organic matter. Read the full article here as it’s now free to access for the next 4 weeks*

Sediment porewater extraction and analysis combining filter tube samplers and capillary electrophoresis
Natascha T. Torres, Peter C. Hauser, Gerhard Furrer, Helmut Brandl and Beat Müller
DOI: 10.1039/C3EM00068K

 *Free access to individuals is provided through an RSC Publishing personal account. Registration is quick, free and simple

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