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

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Richard Brown from the National Physical Laboratory, UK, discusses the causes and effects of data loss in environmental air sampling and proposes a modelling method for overcoming data loss for benzo(a)pyrene (BaP) concentrations.

If levels of a pollutant are not measured every day of every year, there will be inevitable gaps in the data. Often, it is not viable or necessary to sample every day and in the European Union there are minimum limits set on the time coverage (33% of the year) and data capture (90% of this time must result in valid data), and a maximum uncertainty of 50%. Such data should be obtained evenly over the year. Add to this the possibility for equipment breaking down, poor weather and quality control, this can mean significant gaps.

This is more of a problem when the concentration of the pollutant in question varies considerably with the season. BaP fits this category in urban and rural environments, but is more stable at industrial sites. The National Physical Laboratory is responsible for operating the UK PAH Monitoring network and Richard Brown here explores the effects of losing one month’s data for BaP and compares it against nickel in PM₁₀, which varies relatively little over the year.

He concludes that there could be a maximum underestimation of 13.5% in January and an underestimation of up to 7.1% in July with industrial stations included, which have consistent emission rates. Removing industrial sites gives -16.0% and +7.6%. The annual average is therefore biased. In contrast, losing 6 consecutive months of data for Ni still only gives discrepancies of around +/-5%.

Brown shows that for urban and rural BaP levels, the data fits a quadratic function very well and therefore this can be used to predict missing data fragments. He tests this on a data set with a month’s data removed, comparing the calculated annual average from the full data set and the data set with predictions filling in the missing month. This works well, with exceptions in months where the conditions are significantly different to the average (for example, being much colder than previous years). Therefore, he suggests taking measured ambient temperature data into consideration in future. This method is quicker and less complex than using dispersion modelling approaches and improves annual average result accuracy for highly seasonal pollutants with a block of missing data.

Read the interesting discussion of this intricate problem now, as this article is free to access for the next 4 weeks*:

Data loss from time series of pollutants in ambient air exhibiting seasonality: consequences and strategies for data prediction
Richard J. C. Brown
DOI: 10.1039/C3EM30918E

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The assessment and quantification of occupational exposure to volatile organic compounds is important, as such compounds are often carcinogenic and cause a range of chronic health problems.

In this HOT article, a research team at University of Minnesota calculates the health risk of the 8 VOCs most likely to be produced from swine production buildings. They calculate a probability distribution of the risk using Monte Carlo simulation.

The study tested the farrowing room, the office, the nursery and the gestation room. There were significantly higher levels of VOCs in the farrowing room. Notably, these concentrations did not exceed recommended exposure limits, but concentrations of p-cresol and benzene were above preliminary remediation goals (PRGs).

They also measured the emission rates of the VOCs from each room, with the highest rates coming from the gestation room. The nursery had the lowest emission rates for some compounds, with little difference between the nursery and farrowing rooms in terms of emissions. However, the farrowing room had the highest emission rates per head.

Monte Carlo simulations were used to calculate the health risks to workers in the different rooms. It was found that the cancer risk values for ethylbenzene of all workers exceeded the EPA’s target of one per million. The highest cumulative cancer risk was found for the worker who spent the day in the farrowing room. In terms of hazard risk, benzene had the highest risk and four of the VOCs had higher than acceptable risk values. Again, the worker in the farrowing barn had the highest risk.

The researchers conclude that around 1.13% of workers in farrowing barns are likely to develop chronic health problems; bearing in mind that this study only looked at 8 VOCs this figure could be higher. Rotating tasks may be a good way to reduce the risk.

Read this important occupational health study now, as this article is free to access for the next 4 weeks*:

Health risk assessment of occupational exposure to hazardous volatile organic compounds in swine gestation, farrowing and nursery barns
Neslihan Akdeniz, Larry D. Jacobson and Brian P. Hetchler
DOI: 10.1039/C2EM30722G

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The aerosol compositions generated by industrial processes such as welding have been found to contain metal fumes, including those of manganese. Such fumes are potentially harmful and have been known to cause neurological and psychological problems.

The bioaccessibility of the particles is a determinant of how much is taken up by the lungs into the bloodstreams of workers. The solubility of the particles that contain the metal may help to clarify the level of the health risk associated with exposure to manganese. This particle solubility may be different for different industrial processes as different formation mechanisms take place and particles develop differing chemical complexity and size. For example, higher fluorine content in welding fumes increases particle solubility.

Researchers from the National Institute of Occupational Health, Norway, and the Northwest Public Health Research Centre, Russia, have collaborated to test the bioavailability of manganese in welders. They cross-referenced results from blood, serum and urine samples with the results of solubility tests of personally collected aerosol samples. The researchers used a simulated lung lining fluid to test the pulmonary solubility of the aerosol samples.

They found statistically significant correlations between the manganese concentrations in the biological fluids of welders and their aerosol samples, whereas this was a non-significant relationship with the non-welder group and in former welders. They conclude that manganese in urine may be a better biomarker for immediate exposure than that in blood or serum. Manganese in the blood is associated with cumulative exposure over a number of years, but that it is not necessarily a good measure of such exposure as there may also be internal deposits in tissues.

Overall, this study shows that the fraction of manganese in welding fumes that is bioaccessible is low. Despite the correlation between soluble manganese and the amount in the biological samples, the background levels of manganese meant that the welders could not be distinguished from the non-welder group.

Read the full discussion of these interesting results in full, as this article is free to access for the next 4 weeks*, by clicking on the link below:

The bioavailability of manganese in welders in relation to its solubility in welding fumes
Dag G. Ellingsen, Evgenij Zibarev, Zarina Kusraeva, Balazs Berlinger, Maxim Chashchin, Rita Bast-Pettersen, Valery Chashchin and Yngvar Thomassen
DOI: 10.1039/C2EM30750B

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