Germination, root elongation, and photosynthetic performance of plants exposed to sodium lauryl ether sulfate (SLES). An emerging contaminant

The anionic surfactant SLES (sodium lauryl ether sulfate) is an emerging contaminant, being the main component of foaming agents that are increasingly used by the tunnel construction industry. To fill the gap of knowledge about the potential SLES toxicity on plants, acute and chronic effects were assessed under controlled conditions. The acute ecotoxicological test was performed on Lepidum sativum L. (cress) and Zea mays L. (maize). Germination of both species was not affected by SLES in soil, even at concentrations (1200 mg kg−1) more than twice higher than the maximum realistic values found in contaminated debris, thus confirming the low acute SLES toxicity on terrestrial plants. The root elongation of the more sensitive species (cress) was instead reduced at the highest SLES concentration. In the chronic phytotoxicity experiment, photosynthesis of maize was downregulated, and the photosynthetic performance (PITOT) significantly reduced already under realistic exposures (360 mg kg−1), owing to the SLES ability to interfere with water and/or nutrients uptake by roots. However, such reduction was transient, likely due to the rapid biodegradation of the surfactant by the soil microbial community. Indeed, SLES amount decreased in soil more than 90% of the initial concentration in only 11 days. A significant reduction of the maximum photosynthetic capacity (Pnmax) was still evident at the end of the experiment, suggesting the persistence of negative SLES effects on plant growth and productivity. Overall results, although confirming the low phytotoxicity and high biodegradability of SLES in natural soils, highlight the importance of considering both acute and nonlethal stress effects to evaluate the environmental compatibility of soil containing SLES residues

Celle a combustibile microbiche terrestri: uno strumento efficace nel recupero di suoli contaminati e nella produzione di energia.

Una cella a combustibile microbica (MFC) è un sistema bio-elettrochimico che utilizza un microrganismo attivo come biocatalizzatore per la produzione di elettricità. Essa è costituita da due comparti, uno anodico ed uno catodico, separati da una membrana di scambio protonico. L’energia chimica di legame, disponibile grazie alla presenza di un substrato biodegradabile, viene trasformata direttamente in energia elettrica per azione microbica, che catalizza la rimozione degli elettroni dal substrato. I batteri presenti nella camera anodica, o comunque nel mezzo in cui è immerso l’anodo, sono in grado di convertire un’enorme varietà di substrati organici (acetato, glucosio, cellulosa, reflui di varia origine, contaminanti organici) in CO2, acqua ed energia. Tra le MFC, le Celle a Combustibile Microbiche Terrestri (Terrestrial Microbial Fuel Cells - TMFC), hanno come elettrolita il suolo. Esso è una matrice molto più complessa rispetto all’acqua, variando nella composizione granulometrica, nella capacita di ritenzione idrica, nella capacità di scambio cationico, nonché nella distribuzione dei contaminanti; pertanto le TMFC sono dei dispositivi di cui è ancora necessario esplorare tutte le potenzialità di applicazione per il recupero di suoli contaminati

Pesticide risk assessment and management in a globally changing world—report from a European interdisciplinary workshop

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA [Axe_IRSTEA]DTAM-QT2-ADAPTATION [TR2_IRSTEA]ARCEAU [TR2_IRSTEA]DTAMGlobal climate change will affect worldwide agriculture in many ways. The anticipated or already occurring changes raise concerns about the sustainability of production and the ability of agriculture to feed human populations. This appeals to sustainable agriculture providing ecosystem services more efficiently than today, and accordingly to substantial evolutions of pesticide risk assessment (RA) and risk management (RM). The RA/RM issues were discussed by two European research networks in a 2011 workshop. The RA-RM-monitoring conceptual cycle tends to be virtual, with poor connections between certain steps. The design of more comprehensive emissions scenarios could improve the accuracy of predicted runoff transport, while the microcosm/mesocosm approach could help establish causal relationships between fate / exposure and populations / communities. Combined with ecological modelling, effects can be extrapolated to higher spatial and temporal scales. Risk management of diffuse sources should be designed simultaneously at the watershed and individual plot scales. Monitoring is key to assessing the effectiveness of risk reduction measures reduce and evaluate the overall quality of the aquatic compartment. More flexible monitoring strategies clearly linked to RM decisions are therefore needed. Although some technical questions remain, it is time to apply passive samplers more routinely. A set of research and development needs covering the whole RA/RM cycle is listed in conclusion

Screening of benzodiazepines in thirty European rivers

Pharmaceuticals as environmental contaminants have received a lot of interest over the past decade but, for several pharmaceuticals, relatively little is known about their occurrence in European surface waters. Benzodiazepines, a class of pharmaceuticals with anxiolytic properties, have received interest due to their behavioral modifying effect on exposed biota. In this study, our results show the presence of one or more benzodiazepine(s) in 86% of the analyzed surface water samples (n = 138) from 30 rivers, representing seven larger European catchments. Of the 13 benzodiazepines included in the study, we detected 9, which together showed median and mean concentrations (of the results above limit of quantification) of 5.4 and 9.6 ng L−1, respectively. Four benzodiazepines (oxazepam, temazepam, clobazam, and bromazepam) were the most commonly detected. In particular, oxazepam had the highest frequency of detection (85%) and a maximum concentration of 61 ng L−1. Temazepam and clobazam were found in 26% (maximum concentration of 39 ng L−1) and 14% (maximum concentration of 11 ng L−1) of the samples analyzed, respectively. Finally, bromazepam was found only in Germany and in 16 out of total 138 samples (12%), with a maximum concentration of 320 ng L−1. This study clearly shows that benzodiazepines are common micro-contaminants of the largest European river systems at ng L−1 levels. Although these concentrations are more than a magnitude lower than those reported to have effective effects on exposed biota, environmental effects cannot be excluded considering the possibility of additive and sub-lethal effects

Rhizosphere Microbial Communities and Heavy Metals

The rhizosphere is a microhabitat where there is an intense chemical dialogue between plants and microorganisms. The two coexist and develop synergistic actions, which can promote plants’ functions and productivity, but also their capacity to respond to stress conditions, including heavy metal (HM) contamination. If HMs are present in soils used for agriculture, there is a risk of metal uptake by edible plants with subsequent bioaccumulation in humans and animals and detrimental consequences for their health. Plant productivity can also be negatively affected. Many bacteria have defensive mechanisms for resisting heavy metals and, through various complex processes, can improve plant response to HM stress. Bacteria-plant synergic interactions in the rhizosphere, as a homeostatic ecosystem response to HM disturbance, are common in soil. However, this is hard to achieve in agroecosystems managed with traditional practices, because concentrating on maximizing crop yield does not make it possible to establish rhizosphere interactions. Improving knowledge of the complex interactions mediated by plant exudates and secondary metabolites can lead to nature-based solutions for plant health in HM contaminated soils. This paper reports the main ecotoxicological effects of HMs and the various compounds (including several secondary metabolites) produced by plant-microorganism holobionts for removing, immobilizing and containing toxic elements

Overview of Direct and Indirect Effects of Antibiotics on Terrestrial Organisms

Antibiotics (ABs) have made it possible to treat bacterial infections, which were in the past untreatable and consequently fatal. Regrettably, their use and abuse among humans and livestock led to antibiotic resistance, which has made them ineffective in many cases. The spread of antibiotic resistance genes (ARGs) and bacteria is not limited to nosocomial environments, but also involves water and soil ecosystems. The environmental presence of ABs and ARGs is a hot topic, and their direct and indirect effects, are still not well known or clarified. A particular concern is the presence of antibiotics in agroecosystems due to the application of agro-zootechnical waste (e.g., manure and biosolids), which can introduce antibiotic residues and ARGs to soils. This review provides an insight of recent findings of AB direct and indirect effects on terrestrial organisms, focusing on plant and invertebrates. Possible changing in viability and organism growth, AB bioaccumulation, and shifts in associated microbiome composition are reported. Oxidative stress responses of plants (such as reactive oxygen species production) to antibiotics are also described

Effects of Wood Amendments on the Degradation of Terbuthylazine and on Soil Microbial Community Activity in a Clay Loam Soil

12 páginas, 5 figuras.-- The original publication is available at www.springerlink.comThe herbicide terbuthylazine is widely used within the EU; however, its frequent detection in surface and groundwater, together with its intrinsic toxicological properties, may pose a risk both for human and environmental health. Organic amendments have recently been proposed as a possible herbicide sorbent in soil, in order to limit herbicide movement from soil to water. The environmental fate of terbuthylazine depends not only in its mobility but also in its persistence. The latter is directly dependent on microbial degradation. For this reason, the effects of pine and oak residues on terbuthylazine soil microbial community functioning and on the potential of this community for terbuthylazine degradation were studied. For this purpose, degradation kinetics, soil dehydrogenase activity and the number of live bacteria were assessed in a clay loam soil treated with terbuthylazine and either amended with pine or oak wood or unamended (sterilised and non-sterilised). At day 65, 85%of the herbicide applied still persisted in the sterile soil, 73 % in the pine-amended one and 63 % in the oak-amended and unamended ones. Pine residues increased the sorption of terbuthylazine to soil and hampered microbial degradation owing to its high terbuthylazine sorption capacity and a decrease in the bioavailability of the herbicide. On the contrary, in the presence of oak residues, the herbicide sorption did not increase significantly. The overall results confirm the active role of the soil microbial community in terbuthylazine degradation in amended and unamended soils and in a liquid enrichment culture performed using an aliquot of the same soil as the inoculum. In this clay loamsoil, in the absence of amendments, the herbicide was found to be quite persistent (t1/2>95 days), while in the enrichment culture, the same natural soil bacterial community was able to halve terbuthylazine in 24 days. The high terbuthylazine persistence in this soil was presumably ascribable to its texture and in particular to the mineralogy of the clay fraction.This work was funded by the CSIC/CNR Bilateral Agreement ‘Adsorption and degradation of pesticides in soils modified with low cost biomaterials: Study of the microbial communities responsible for the biodegradation’ (project reference 2006IT0022).Peer reviewe

Belowground microbiota and the health of tree crops

Trees are crucial for sustaining life on our planet. Forests and land devoted to tree crops do not only supply essential edible products to humans and animals, but also additional goods such as paper or wood. They also prevent soil erosion, support microbial, animal, and plant biodiversity, play key roles in nutrient and water cycling processes, and mitigate the effects of climate change acting as carbon dioxide sinks. Hence, the health of forests and tree cropping systems is of particular significance. In particular, soil/rhizosphere/root-associated microbial communities (known as microbiota) are decisive to sustain the fitness, development, and productivity of trees. These benefits rely on processes aiming to enhance nutrient assimilation efficiency (plant growth promotion) and/or to protect against a number of (a)biotic constraints. Moreover, specific members of the microbial communities associated with perennial tree crops interact with soil invertebrate food webs, underpinning many density regulation mechanisms. This review discusses belowground microbiota interactions influencing the growth of tree crops. The study of tree-(micro)organism interactions taking place at the belowground level is crucial to understand how they contribute to processes like carbon sequestration, regulation of ecosystem functioning, and nutrient cycling. A comprehensive understanding of the relationship between roots and their associate microbiota can also facilitate the design of novel sustainable approaches for the benefit of these relevant agro-ecosystems. Here, we summarize the methodological approaches to unravel the composition and function of belowground microbiota, the factors influencing their interaction with tree crops, their benefits and harms, with a focus on representative examples of Biological Control Agents (BCA) used against relevant biotic constraints of tree crops. Finally, we add some concluding remarks and suggest future perspectives concerning the microbiota-assisted management strategies to sustain tree crops

The Role of the Bacterial Community of an Agroecosystem in Simazine Degradation

The use of pesticides and fertilizers in agricultural practice is the main source of soil and groundwater contamination. S-Triazines are among the most used herbicides in the world for selective weed control in several types of crops. The homeostatic capability of an agroecosystem to remove a triazinic herbicide, simazine, was assessed in microcosms treated with the herbicide in presence/absence of urea fertilizer. The latter, as well as a fertilizer, is also one of the last by-products before simazine mineralization. The biodegradation, in terms of disappearance of 50% of the initial concentration (DT50), was compared to the degradation and metabolite formation occurring in sterilized soil. Moreover, the bacterial community response was assessed in terms of abundance and community structure by the epifluorescence direct count method and fluorescence in situ hybridization. The results show that the microbial community has a primary role in simazine degradation and that this process is due to the presence of a microbial pool working in succession and of which the metabolism may be modulated by exogenous sources of nitrogen, like urea. The latter influences the degradative pathway with a greater formation and accumulation of the desethyl-simazine metabolite, which is a hazardous contaminant of soil and groundwater ecosystems, as well as its parent compound