Environmental Science: Processes & Impacts blog

Understanding the transport of microorganisms in soil is key to evaluating the impact of releasing them into the environment through such processes as contaminated wastewater effluents. This article by Jean Martins et al. at Domaine Universitaire, Grenoble, France, looks at the mobility of E. coli, as a substitute for pathogenic cells, in undisturbed natural soil in conditions that simulate land effluent application.

Most interesting is the study of E. coli cell transport using repeated injections of bacterial suspension. The majority of cells injected were recovered in the resulting effluent and the leaching of the cells from the soil occurred very quickly post-injection. The cells did not reach the whole volume of the soil. The study revealed a dual mode of fast and slow transport, the slow transport being dominant, indicating that the soil structure was gradually affected during the flow giving preferred flow pathways of bacteria. The pore network was hydrodynamically active, changing over time. The fast component of the transport appears to cancel out the effect that high salinity usually has on bacterial of aggregation as the cells didn’t aggregate, no matter what the ionic strength, and most were isolated in the soil.

It is the dominance of the hydrodynamic properties of the soil that is the important conclusion from this work. Undisturbed natural soil is recommended in experiments studying bacteria mobility if natural media is to be used due to the unstable nature of the pore structure compared to model porous media. The effects that usually dominate in model media may be overshadowed in natural media by the influence of hydrodynamics.

All of our HOT articles are free to access for 4 weeks*, so why not have a read now?

Role of macropore flow in the transport of Escherichia coli cells in undisturbed cores of a brown leached soil
Jean M. F. Martins ,  Samer Majdalani ,  Elsa Vitorge ,  Aurélien Desaunay ,  Aline Navel ,  Véronique Guiné ,  Jean François Daïan ,  Erwann Vince ,  Hervé Denis and Jean Paul Gaudet
DOI: 10.1039/C2EM30586K

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

Choosing how we get to work is often based on money, time and local infrastructure; however Kam et al. have studied how this choice may also impact commuter’s exposure to pollutants and potential health risks.

This paper looks at the concentrations of a variety of particulate matter including metals and trace elements, using inductively coupled plasma mass spectrometry, and polyaromatic hydrocarbons (PAHs), via gas chromatography.  All of the compounds studied have been linked to life threatening conditions such as cancer, cardiovascular diseases and neurodegenerative disorders.

The sampling regime takes account of a variety of commuting methods in Los Angeles such as the subway, surface ‘light’ railway and a variety vehicular routes including a freeway, a surface-level street and a route used frequently by heavy duty vehicles (HDVs).

The compound profiles identified in the study fitted well with those predicted for each transport mode.  For example iron, associated with stainless steel and mechanical wear, was highest in the subway, lead and other elements associated with fuel use and vehicular traffic were higher in the road samples and elements which are greatly influenced by the environment, e.g. sodium, did not differ between the modes.  However the results also point to a more complex picture than this suggests with the season, location of the transportation and other transport users also playing significant roles in the exposure model.

Kam et al. also compared the relative potencies and unit risk factors of each individual PAH to estimate the cancer risk for commuters.  Road users were at greater risk from this pathway, particularly users of roads which have a higher HDV use.

This highly detailed study not only provides an insight into the potential long term health risks which may be associated with commuting, but is relevant to any group who lives near, works in or is routinely using these transport modes.  It also highlights the complexity involved in carrying out studies of this kind and interpreting environmental exposures.  It’s free to access* on our site for the next four weeks, so why not download the paper here:

A comparative assessment of PM2.5 exposures in lightrail, subway, freeway, and surface street environments in Los Angeles and estimated lung cancer risk
Winnie Kam, Ralph J. Delfino, James J. Schauer and C. Sioutas
DOI: 10.1039/c2em30495c

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

Published on behalf of Sian Evans, Environmental Science: Processes and Impacts web science writer. Sian is a PhD student based in Bath, United Kingdom

Sewage contains a myriad of potentially life threatening chemical and biological matter.  This paper shows studying sewage is crucial to understanding its threat, but it can also unlock potential epidemiological information.

Disposing of sewage appropriately is one of the most important life-saving technologies that exist, however processing such waste poses health risks.  Some of the hazards associated with sewage are from adenoviruses, which can be infectious through direct contact, ingestion and aerosol exposure; a particular concern as solid material from sewage plants is often disposed of as agricultural fertiliser.  Previous studies have focussed on single adenovirus species or grouped them together; however the seven main species all possess unique symptoms when contracted.  Bibby and Peccia have therefore used PCR and primers able to distinguish between the species to amplify DNA from samples of sewage influent and effluent.

The results revealed that the adenovirus-C was most abundant, responsible for respiratory symptoms, followed by adenovirus-B, also associated with respiratory illnesses as well as urinary infections.  It should be noted though that increased virus abundance does not necessarily correlate with increased infectious risk.  Interestingly, wastewater treatment had no impact on the virus numbers, showing treated solid waste, spread on agricultural land, poses an equal risk as raw influent from adenoviruses.

Whilst providing information for risk assessments this data also lends support to the notion that sewage contains a great amount of information regarding its source population, negating the need for, and potential flaws in, medical data.  In this case, adenovirus C and B, the most abundant in the sewage, are also the most abundantly reported infections within the population. 

This work is of interest to a variety of people including those involved in human health risk assessments, gene amplification, sewage treatment and disposal and sewage epidemiology it’s free to access* on our site for the next four weeks, so why not download the paper here:

Prevalence of respiratory adenovirus species B and C in sewage sludge
Kyle Bibby and Jordan Peccia
DOI: 10.1039/c2em30831b

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

Published on behalf of Sian Evans, Environmental Science: Processes and Impacts web science writer. Sian is a PhD student based in Bath, United Kingdom

Water quality assessment is vital for identifying potential hazards to both the environment and human health.  This paper suggests a revolutionary  new approach to toxicity testing which would have significant implications for a wide range of industries and potentially the way in which water quality is measured.

The activation of toxicity pathways may be more sensitive than testing for toxicity endpoints.  This is the principle behind Tox21, a ground-breaking project examining chemicals using high throughput technology.  This same thinking has inspired Escher et al to use an assay to test surface, drinking and wastewater for indicators of oxidative stress and use this as a measure of water quality.

Escher et al used a sensitive cell line (AREc32) which, via luciferase expression, reports the activation of the antioxidant response element (ARE).  The ARE, being sensitive to a relatively wide range of stressors and highly conserved in all human cells is a good toxicity screening tool.

The cell line proved to be sensitive to a variety of the validation test chemicals used, with ARE activation often proving more sensitive than cytotoxicity to stress.

The examination of environmental grab samples provided interesting results suggesting that although water treatment generally reduced stressors which would lead to ARE activation, chlorination increased them.  However, this was reversed by the time the water had reached the drinking tap.

This paper reports the validation and methodology for using this cell line as an indicator for water quality.  Although the authors identified areas for development and improvement the technique has already provided data on an impressive range of samples, illustrating its potential use.  It’s free to access* on our site for the next four weeks, so why not download the paper here:

Water quality assessment using the AREc32 reporter gene assay indicative of the oxidative stress response pathway
Beate I. Escher, Mriga Dutt, Erin Maylin, Janet Y. M. Tang, Simon Toze, C. Roland Wolf and Matti Lang
DOI: 10.1039/C2EM30506B

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

Published on behalf of Sian Evans, Journal of Environmental Monitoring web science writer. Sian is a PhD student based in Bath, United Kingdom

In this HOT article from researchers in Canada, the authors investigate the possibility of using American kestrel and European starling eggs as bio-monitoring species for flame retardant contamination in terrestrial ecosystems.

Testing for for sixteen PBDE congeners and nineteen non-PBDE flame retardants, the authors were able to detect major components of commercial mixtures, and found point source influences for some geographical areas.

Flame retardants in eggs of American kestrels and European starlings from southern Lake Ontario region (North America)
Da Chen, Robert J. Letcher and Pamela Martin
DOI: 10.1039/C2EM30472D

In their critical review, researchers from the University of Hawaii have carried out an economic appraisal into the separation of human urine from other waste waters at the source, and the subsequent storage and treatment of this separated water.

They conclude that energy, water and nutrients could be saved using this approach, along with decreasing green house gas emissions.

An economic appraisal of using source separation of human urine to contain and treat endocrine disrupters in the USA
Krishna Lamichhane and Roger Babcock
DOI: 10.1039/C2EM30254C

All our HOT articles are free to access for 4 weeks following a simple registration.

This HOT article from Orsolya Klebercz and co-workers from Hungary and the UK discusses the ecotoxicity of fluvial sediments that resulted from the spillage of bauxite processing residue (red mud) in Ajka, Hungary.

The team carried out physico-chemical analyses on a number of samples taken from sites downstream of the spill. Biological characterisation and ecotoxicity testing was also carried out on a number of test species, including the Vibrio fischeri luminescence inhibition test, the Sinapis alba root and shoot growth inhibition test and the Heterocypris incongruens mortality test.

Adverse effects were recorded across a range of trophic levels at the different sample sites, although the microbial activity was shown to have increased. Lemna minor was shown to be a useful test species when assessing the impact of red mud contamination.

Read more about the study here – the paper is free to access for 4 weeks:

Ecotoxicity of fluvial sediments downstream of the Ajka red mud spill, Hungary
Orsolya Klebercz, William M. Mayes, Áron Dániel Anton, Viktória Feigl, Adam P. Jarvis and Katalin Gruiz
DOI: 10.1039/C2EM30155E