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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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

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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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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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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

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David Cwiertny holds a BS in Environmental Engineering Science with a minor in Chemistry from the University of California, Berkeley awarded in 2000. He then received his PhD in Environmental Engineering from Johns Hopkins University (Baltimore, Maryland, USA) in 2005. After completing his doctoral work, he served as a post-doctoral research associate at the University of Iowa in joint appointment between the Departments of Civil and Environmental Engineering and Chemistry. In the Fall of 2011, he returned to the University of Iowa as an Assistant Professor in the Department of Civil and Environmental Engineering after serving four years in the same capacity at the University of California, Riverside. His research program broadly focuses on pollutant fate in natural and engineered systems, with a particular emphasis on the development of materials-based treatment technologies that promote water sustainability. This includes projects on the transformation of emerging contaminant classes (e.g., synthetic hormones and pharmaceuticals) in natural aquatic systems, and the development of nanomaterial-enabled technologies for advanced chemical treatment of water and wastewater. At the University of Iowa, he is a core faculty member in the campus-wide Water Sustainability Initiative, developing interdisciplinary research, outreach and education programs intended to increase water awareness at the University and across the state of Iowa.

Here David presents his research vision. Click “Read more” below to find out more!

                  

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

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Young-Shin Jun is an Assistant Professor of Energy, Environmental & Chemical Engineering at Washington University (St. Louis, USA), where she leads the Environmental NanoChemistry Laboratory. She is a 2011 U. S. National Science Foundation CAREER award recipient. Her research focuses on interfacial reactions in complex aqueous systems. Her research group’s projects include elucidating physicochemical reaction mechanisms occurring during water reuse through aquifer storage, treatment, and recovery to secure underground sources for drinking water; improving our understanding of the fate and transport of contaminants and nanoparticles; and providing more environmentally sustainable CO₂ sequestration strategies. Prior to her position at Washington University, she conducted postdoctoral research in Nanogeoscience at the University of California at Berkeley/Lawrence Berkeley National Laboratory, Berkeley, USA. She holds an S.M. and Ph.D. in Environmental Chemistry from Harvard University (Cambridge, USA). She received her B.S. and M.S. in Environmental Science and Engineering at Ewha Womans University (Seoul, Korea).

                  

This recently published article from Jing-Fu Liu et al. takes a critical view of the current investigations into the effects that silver nanoparticles have on the environment. It was published in January’s

Appropriate sampling, separation and analytical methods are vital, particularly for analysis of silver nanoparticles in complex environmental samples. This review covers: 

1. A brief history of silver colloids in the environment
2. Beneficial properties versus environmental concerns
3. Analytical techniques, including combinations of different methods, and the different sample sources, such as aerosols and soil
4. Factors and processes influencing fate and transport of AgNPs
5. Environmental transformation
6. Toxicity of silver nanoparticles and different silver species

Each of the above mentioned topics are interesting in themselves, but this article pulls the information together to give one wide perspective of the flow of silver nanoparticles through our environment and ways we can detect and analyse their effects. It highlights how much is still unknown and how complex such investigation will continue to be.

Silver nanoparticles in the environment
Su-juan Yu, Yong-guang Yin and Jing-fu Liu
DOI: 10.1039/C2EM30595J

                  

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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