The effect of triclosan on microbial community structure in three soils

The application of sewage sludge to land can expose soils to a range of associated chemical toxicants. In this paper we explore the effects of the broad spectrum anti-microbial compound triclosan on the phenotypic composition of the microbial communities of three soils of contrasting texture (loamy sand, sandy loam and clay) using phospholipid fatty-acid (PLFA) analysis. Each soil type was dosed and subsequently re-dosed 6 weeks later with triclosan at five nominal concentrations in microcosms (10, 100, 500, 1000 mg kg⁻¹ and a zero-dose control). PLFA profiles were analysed using multivariate statistics focussing on changes in the soil phenotypic community structure. Additionally, ratios of fungal:bacterial PLFA indicators and cyclo:mono-unsaturated PLFAs (a common stress indicator) were calculated. It was hypothesised that triclosan addition would alter the community structure in each soil with a particular effect on the fungal:bacterial ratio, since bacteria are likely to be more susceptible to triclosan than fungi. It was also hypothesised that the PLFA response to re-dosing would be suppressed due to acclimation. Although the microbial community structure changed over the course of the experiment, the response was complex. Soil type and time emerged as the most important explanatory factors. Principal component analysis was used to detect phenotypic responses to different doses of triclosan in each soil. As expected, there was a significant increase in the fungal:bacterial ratio with triclosan dose especially in treatments with the highest nominal concentrations. Furthermore, the PLFA response to re-dosing was negligible in all soils confirming the acclimation hypothesis.     

Toxicity of silver nanoparticles to rainbow trout: A toxicogenomic approach

Silver (Ag) nanoparticles are used as antimicrobial adjuvant in various products such as clothes and medical devices where the release of nano-Ag could contaminate the environment and harm wildlife. The purpose of this study was to examine the sublethal effects of nano-Ag and dissolved Ag on Oncorhynchus mykiss rainbow trout. Hepatic Ag contents and changes in gene expression were monitored to provide insights on bioavailability and mode of action of both forms of silver. Fish were exposed to increasing concentrations (0.06, 0.6 and 6 μg L⁻¹) of nano-Ag (20 nm) and silver nitrate (AgNO₃) for 96 h at 15 °C. A gene expression analysis was performed in the liver using a DNA microarray of 207 stress-related genes followed by a quantitative polymerase chain reaction on a selection of genes for validation. The biochemical markers consisted of the determination of labile zinc, metallothioneins, DNA strand breaks, lipid peroxidation (LPO) and vitellogenin-like proteins. The analysis of total Ag in the aquarium water revealed that nano-Ag was mostly aggregated, with 1% of the total Ag being dissolved. Nevertheless, hepatic Ag content was significantly increased in exposed fish. Indeed, dissolved Ag was significantly more bioavailable than nano-Ag only at the highest concentration with 38 ± 10 and 11 ± 3 ng Ag mg⁻¹ proteins for dissolved and nano-Ag respectively. Exposure to both forms of Ag led to significant changes in gene expression for 13% of tested gene targets. About 12% of genes responded specifically to nano-Ag, while 10% of total gene targets responded specifically to dissolved Ag. The levels of vitellogenin-like proteins and DNA strand breaks were significantly reduced by both forms of Ag, but DNA break levels were lower with nano-Ag and could not be explained by the presence of ionic Ag. Labile zinc and the oxidized fraction of metallothioneins were increased by both forms of Ag, but LPO was significantly induced by nano-Ag only. A discriminant function analysis revealed that the responses obtained by biochemical markers and a selection of ten target genes were able to discriminate completely (100%) the effects of both forms of Ag. Exposure to nano-Ag involved genes in inflammation and dissolved Ag involved oxidative stress and protein stability. Hence, the toxicity of Ag will differ depending on the presence of Ag nanoparticles and aggregates.     

Seasonal and spatial variation of organic tracers for biomass burning in PM1 aerosols from highly insolated urban areas

PM₁ aerosol characterization on organic tracers for biomass burning (levoglucosan and its isomers and dehydroabietic acid) was conducted within the AERTRANS project. PM₁ filters (N?=?90) were sampled from 2010 to 2012 in busy streets in the urban centre of Madrid and Barcelona (Spain) at ground-level and at roof sites. In both urban areas, biomass burning was not expected to be an important local emission source, but regional emissions from wildfires, residential heating or biomass removal may influence the air quality in the cities. Although both areas are under influence of high solar radiation, Madrid is situated in the centre of the Iberian Peninsula, while Barcelona is located at the Mediterranean Coast and under influence of marine atmospheres. Two extraction methods were applied, i.e. Soxhlet and ASE, which showed equivalent results after GC-MS analyses. The ambient air concentrations of the organic tracers for biomass burning increased by an order of magnitude at both sites during winter compared to summer. An exception was observed during a PM event in summer 2012, when the atmosphere in Barcelona was directly affected by regional wildfire smoke and levels were four times higher as those observed in winter. Overall, there was little variation between the street and roof sites in both cities, suggesting that regional biomass burning sources influence the urban areas after atmospheric transport. Despite the different atmospheric characteristics in terms of air relative humidity, Madrid and Barcelona exhibit very similar composition and concentrations of biomass burning organic tracers. Nevertheless, levoglucosan and its isomers seem to be more suitable for source apportionment purposes than dehydroabietic acid. In both urban areas, biomass burning contributions to PM were generally low (2 %) in summer, except on the day when wildfire smoke arrive to the urban area. In the colder periods the contribution increase to around 30 %, indicating that regional biomass burning has a substantial influence on the urban air quality.     

Cytogenetic biomonitoring of primary school children exposed to air pollutants: micronuclei analysis of buccal epithelial cells

There is an increasing attempt in the world to determine the exposures of children to environmental chemicals. To analyze the genotoxic effect of air pollution, micronucleus (MN) assay was carried out in buccal epithelial cells (BECs) of children living in an urban city of Turkey. Children from two schools at urban-traffic and suburban sites were investigated in summer and winter seasons for the determination of BEC-MN frequency (per mille) and frequency of BEC with MN (per mille). The same children were also recruited for lung function measurements within a MATRA project (“Together Towards Clean Air in Eskisehir and Iskenderun”) Measured NO₂ and SO₂ concentrations did not exceed the European Union (EU) limit levels either in urban-traffic or suburban regions. Higher O₃ concentrations were measured in the suburban site especially in the summer period. Particulate matter (PM_2.5 and PM₁₀) levels which did not differ statistically between two regions were above the EU limits in general. Although BEC-MN frequencies of children living in the suburban sites were higher in general, the difference between two regions was not significant either in the summer or winter periods. BEC-MN frequencies of the urban-traffic children were found to be significantly higher in summer period (mean ± SD, 2.68?±?1.99) when compared to winter period (1.64?±?1.59; p?=?0.004). On the other hand, no seasonality was observed for the suburban children. Similar results have been obtained in the BEC frequency with MN in our study. In summer, BEC-MN frequencies were significantly increased with the decrease in pulmonary function levels based on forced expiratory flow between 25 and 75 % of vital capacity (FEF_25–75 %) levels (p?<?0.05). As a conclusion, children living in urban-traffic and suburban areas in the city of Eski?ehir exhibited similar genotoxicity. Seasonal variation in genotoxicity may be interpreted as relatively high ozone levels and increasing time spent at outdoors in the summer.     

SoilTrEC: a global initiative on critical zone research and integration

Soil is a complex natural resource that is considered non-renewable in policy frameworks, and it plays a key role in maintaining a variety of ecosystem services (ES) and life-sustaining material cycles within the Earth's Critical Zone (CZ). However, currently, the ability of soil to deliver these services is being drastically reduced in many locations, and global loss of soil ecosystem services is estimated to increase each year as a result of many different threats, such as erosion and soil carbon loss. The European Union Thematic Strategy for Soil Protection alerts policy makers of the need to protect soil and proposes measures to mitigate soil degradation. In this context, the European Commission-funded research project on Soil Transformations in European Catchments (SoilTrEC) aims to quantify the processes that deliver soil ecosystem services in the Earth's Critical Zone and to quantify the impacts of environmental change on key soil functions. This is achieved by integrating the research results into decision-support tools and applying methods of economic valuation to soil ecosystem services. In this paper, we provide an overview of the SoilTrEC project, its organization, partnerships and implementation.     

Changes in the nature of dissolved organics during pulp and paper mill wastewater treatment: a multivariate statistical study combining data from three analytical techniques

The paper-making process can produce large amounts of wastewater (WW) with high particulate and dissolved organic loads. Generally, in developed countries, stringent international regulations for environmental protection require pulp and paper mill WW to be treated to reduce the organic load prior to discharge into the receiving environment. This can be achieved by primary and secondary treatments involving both chemical and biological processes. These processes result in complex changes in the nature of the organic material, as some components are mineralised and others are transformed. In this study, changes in the nature of organics through different stages of secondary treatment of pulp and paper mill WW were followed using three advanced characterisation techniques: solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy, pyrolysis-gas chromatography mass spectrometry (py-GCMS) and high-performance size-exclusion chromatography (HPSEC). Each technique provided a different perspective on the changes that occurred. To compare the different chemical perspectives in terms of the degree of similarity/difference between samples, we employed non-metric multidimensional scaling. Results indicate that NMR and HPSEC provided strongly correlated perspectives, with 86 % of the discrimination between the organic samples common to both techniques. Conversely, py-GCMS was found to provide a unique, and thus complementary, perspective.     

A chronic bioassay with the estuarine amphipod Corophium volutator: test method description and confounding factors

Methods of conducting a chronic sediment toxicity test with the estuarine amphipod Corophium volutator are described. They consist of a 49-day exposure, after which mortality, growth and reproduction are determined. Pilot experiments were used to optimize test design parameters such as temperature, duration, feeding and refreshing regimes, and effects of indigenous organisms. By way of further validation, the present study focused on the effects of four different parameters: oxygen saturation, salinity, ammonium and nitrite. These confounding factors might play an important role especially if the test is used for risk assessment of field-contaminated sediments. It is concluded that the present experimental design is well suited for chronic sediment exposures with C. volutator. The test can be performed at a broad range of salinity values, provided that controls are performed at the same salinity. Results further demonstrate that with the endpoints growth and reproduction this chronic test procedure is a factor 7-18 more sensitive to ammonium and nitrate than the standardized acute bioassay (endpoint mortality).     

Effects of oil sands process-affected waters and naphthenic acids on yellow perch (Perca flavescens) and Japanese medaka (Orizias latipes) embryonic development

Syncrude Canada Ltd. is currently developing environmentally acceptable oil sands process-affected water management methods as part of their land reclamation strategy. Surface waters of the “wet landscape” reclamation option characteristically have elevated concentrations of sodium sulphate and naphthenic acids (NAs), with low levels of PAHs. The following experiment compared early-life stage responses of yellow perch (Perca flavescens) to those of Japanese medaka (Oryzias latipes) when exposed to Mildred Lake settling basin (MLSB) surface water and a commercial sodium naphthenate (Na-NA) standard. Perch eggs were fertilized and incubated in: 100%, 50%, 20%, 4%, 0.8%, and 0.16% dilutions of MLSB water, as well as 20, 10, 5, 2.5, and 1.25 mg/l solutions of the commercial standard. Medaka embryos were exposed to the same treatments, post-fertilization. Both species demonstrated an increase in the incidence of deformity, and a decrease in length at hatch as NA concentrations increased. MLSB surface water contained higher levels of NAs than the commercial standard, however, showed consistently higher NA threshold effect concentrations for both species. Significant differences between the MLSB water and the Na-NA standard suggest that they contain NA congeners with different toxicity, or other compounds such as PAHs. Species differences in thresholds could be explained by the difference in developmental stage in which the exposures were initiated.     

Phytoremediation of contaminated soils and groundwater: lessons from the field

Background, aim, and scope

The use of plants and associated microorganisms to remove, contain, inactivate, or degrade harmful environmental contaminants (generally termed phytoremediation) and to revitalize contaminated sites is gaining more and more attention. In this review, prerequisites for a successful remediation will be discussed. The performance of phytoremediation as an environmental remediation technology indeed depends on several factors including the extent of soil contamination, the availability and accessibility of contaminants for rhizosphere microorganisms and uptake into roots (bioavailability), and the ability of the plant and its associated microorganisms to intercept, absorb, accumulate, and/or degrade the contaminants. The main aim is to provide an overview of existing field experience in Europe concerning the use of plants and their associated microorganisms whether or not combined with amendments for the revitalization or remediation of contaminated soils and undeep groundwater. Contaminations with trace elements (except radionuclides) and organics will be considered. Because remediation with transgenic organisms is largely untested in the field, this topic is not covered in this review. Brief attention will be paid to the economical aspects, use, and processing of the biomass.

Conclusions and perspectives

It is clear that in spite of a growing public and commercial interest and the success of several pilot studies and field scale applications more fundamental research still is needed to better exploit the metabolic diversity of the plants themselves, but also to better understand the complex interactions between contaminants, soil, plant roots, and microorganisms (bacteria and mycorrhiza) in the rhizosphere. Further, more data are still needed to quantify the underlying economics, as a support for public acceptance and last but not least to convince policy makers and stakeholders (who are not very familiar with such techniques).