Environmental Science: Processes & Impacts blog

Algae are identified in variety of research fields and used as indicators of water quality.  Quantifying and identifying algae is often a laborious task and requires a high level of skill.  Although there are several automated techniques now available, commercial developments have been limited.  Several software techniques based on imaging have been previously presented, however they’re often limited to only a few algal types, so not applicable to field samples. 

This paper presents an innovative method which provides real time recognition of multiple algaes.  The software uses image segmentation, shape features i.e. contours, centroid spectrum calculations and pigmentation.  The set up uses relatively simple hardware and no sample processing or fixation.  Coltelli et al tested the method on both cultured strains and field samples with the method correctly identifing 96.6% of 24 different algal phyla from 3423 images.

This article would be of interest to anyone involved in algal identification, whether from lab based cultures or water samples from the field. 

Automatic and real time recognition of microalgae by means of pigment and shape
Primo Coltelli, Laura Barsanti, Evangelista, Anna Maria Frassanito, Vincenzo Passarelli and Paolo Gualtieri
DOI: 10.1039/C3EM00160A

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

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

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.

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

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

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