Environmental Science: Processes & Impacts blog

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

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 Environmental Science :Processes & Impacts 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.

In 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

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Reported removal efficiencies of micropollutants at wastewater treatment plants vary a great deal for the same substance, with negative removal efficiencies even being reported and simply averaged out.

Often, to reduce cost and effort, sampling studies are very short at one to two days. The efficiency is then based on a calculation of mass balancing the sample loads in influent and effluent, using the flawed assumptions that the volume of each is equal and that micropollutant concentrations are in steady-state conditions at all times.

Researchers at the Resource Center for Environmental Technologies in Luxembourg saw this need to systematically examine this method and the accuracy of it with regard to the sampling method and conditions. This HOT article describes the application of hydraulic modeling to match up the influent and effluent loads, reducing uncertainties.

Hydraulic residence times are often used in chemical engineering but not in evaluation of wastewater treatment sampling. In previous modeling work, the team has concluded that the load carried by an effluent sample taken over the course of one day is made up of influent load from the days before. This study takes this and attempts to calculate how much of one day’s micropollutant influent load ends up in a day’s effluent sample. The number of influent sampling days was gradually increased until 80% of the effluent sample was accounted for.

They provide a model that can be adapted for use in other wastewater treatment plants and recommend best practice for taking inevitable errors ranges into account. This article is free to access for the next 4 weeks* so you can read it now at:

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

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Julie Fox et al. tackle the problem of how different studies of exhaled breath condensate (EBC) sampling can be directly compared in this HOT article dedicated to the late Dr Alison Geyh. This requires standardisation of the method and equipment used, which are both highly dependent on the nature of the biomarker being assessed and the population studied.

The group concentrate on the assessment of metals, as elemental biomarkers that are not affected by degradation through the analysis process. The researchers based at University of Washington, Johns Hopkins Bloomeberg School of Public Health and ICF International, USA, incorporated a number of quality control aspects meaning the method can be used for different EBC sample types.

The instrument used was the commercially available Rtube, with a polypropylene condensing surface and an aluminium sleeve that is chilled to condense the EBC. This is a cheaper, more portable option with no temperature control during sampling. They add a spirometer for recording ventilation and subjects were trained to use a visual incentive spirometer to keep their breathing consistent during sampling. A HEPA filter reduces exposure to airborne particles and the modified Rtube is also able to connect up to a temperature-controlled device, the EcoVent, as needed.

The found that is vital to evaluate any possible sources of contamination prior to the experiment. The group measured a number of collection parameters and recommend detailed description of these for all experiments.

The method was validated by measurements of Mn, Cd, Ni and Cr in an unexposed population on a small scale, with a focus on Mn. Wider conclusions about the general population cannot be made from this small study, however this HOT article presents a methodology and protocol recommendations for future EBC studies that is portable, economical and widely applicable.

This article is now free to access for the next 4 weeks*, so you can read the detail of the parameters measured and the example study now:

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

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