Degradation of toluene,xylene, and trimethylbenzene vapors by biofiltration: a comparison

This paper presents a comparative study of the biodegradation of three aromatic volatile compounds in a compost-based biofilter: toluene, xylene, and 1,2,4-trimethylbenzene, used in the course of this work for the first time in the field of biofiltration. Hence, three identical biofiltration units have been operated at the laboratory scale. During the experiments, nitrogen (as urea) was supplied at various concentrations to each reactor, via irrigated nutrient solutions. A comparative analysis of the results showed that the biodegradability scale followed the degree of substitution around the aromatic ring: toluene > xylene > trimethylbenzene, with 95, 80, and 70% maximum conversions, respectively. In addition, and despite the different removal levels achieved in the three bioreactors, it was established that from a reaction viewpoint, the degradation of the three compounds seemed to follow similar metabolic pathways involving methylcatechol isomers. Finally, by varying the nitrogen input concentrations in the three reactors, three degradation regimes have been highlighted: an N-limitation regime and an N-optimum regime, common to the three solvents, and an N-excess regime, favorable to the colonization of the filter beds by nitrifying species, which particularly affected the xylene and trimethylbenzene biodegradation.     

H2O2 formation from photocatalytic processes at the ZnO/water interface

The paper focuses on the production of H2O2 by photocatalysis over ZnO in an aerated aqueous phase. The presence of different reductants that increase the H2O2 production in the aqueous phase is analysed; particular attention is paid to nitrite, which has been shown to be the reductant that produces the most significant increments in the H2O2 production. The photocatalytic anodic decomposition of ZnO in the presence of the different reductants is also investigated. From the results obtained, the relevance of the ZnO photocatalysis in the formation of environmental hydrogen peroxide is estimated.     

Occupational exposure

Concentrations of polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN), polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), hexachlorobenzene and methylsulphonyl metabolites of PCB were determined in blood plasma from potentially exposed workers and controls. Three of the potentially exposed subjects had worked with cable incineration and two were electricians. Extraction of the organochlorine compounds and lipids were performed using the lipophilic gel Lipidex. Different adsorbents and gel permeation chromatography were applied for further purification of the samples and separation of analytes. Determinations of the chlorinated compounds were made by using gas chromatography with electron-capture detection and gas chromatography-mass spectrometry. Only small differences in the concentrations of organochlorine compounds were found in the plasma from the three subject groups. Thus, specific exposure of the workers could not be confirmed.     

Bioavailability and biodegradation of prosulfocarb in soil

Active microbial degraders of the herbicide prosulfocarb (PSC) were isolated to evaluate their performance in soil with a view to their use for bioremediation. The isolated cultures (a microbial consortium and a Pseudomonas sp. strain) were active when tested in mineral medium with PSC as the only carbon source, but had an adverse effect on the soil indigenous microflora. Biodegradation in the inoculated soils was thus lower than in the uninoculated soil when only the indigenous microflora was present. Further tests showed that the strong affinity of PSC for soil organic matter affected its bioavailability and hence its biodegradation by the inocula. Bioremediation of PSC contaminated soils could thus be undertaken by biostimulation of indigenous microflora.     

Effects of the phenylurea herbicide isoproturon on periphytic diatom communities in freshwater indoor microcosms

The toxic effects of the phenylurea herbicide Isoproturon -IPU: (3-(4-isopropylphenyl)-1, 1-dimethylurea)-were studied on the colonization of periphytic diatom communities, within indoor microcosms consisting of a mixed biotope (water column and natural sediment) and two biological species-rooted macrophyte cuttings (Elodea densa) and benthic bivalve molluscs (Corbicula fluminea). The periphyton, essentially composed of diatoms, was collected on artificial substrata (glass slides) in the upper layers of the water column, after two periods of exposure (34 and 71 days). IPU was initially added in the water or in the sediment compartment, at two nominal concentrations (L1 and L2 levels) for each contamination source-5 and 20 microg litre(-1) and 100 and 400 microg kg(-1) in sediment (w/w) respectively. The effects of IPU on the density and community structure of periphytic diatoms are described. A marked reduction in the diatom density was observed after 34 days exposure to the lower concentration of IPU in the water (5 microg litre(-1)). For the L2 levels, the very small number of live cells present did not permit quantification of the diatom density. After 71 days, recovery in community parameters occurred for the two contamination levels of the sediment and water column sources. Samples collected in the experimental units contaminated with the L2 levels were dominated by heterotrophic and smaller diatom species, such as Sellaphora seminulum. Data treatment based on factorial discriminant analysis enabled us to distinguish the different contamination conditions, with only 11 species from the 130 taxa identified.     

Variations of immune parameters in terrestrial isopods: a matter of gender, aging and Wolbachia

Ecological factors modulate animal immunocompetence and potentially shape the evolution of their immune systems. Not only environmental parameters impact on immunocompetence: Aging is one major cause of variability of immunocompetence between individuals, and sex-specific levels of immunocompetence have also been frequently described. Moreover, a growing core of data put in light that vertically transmitted symbionts can dramatically modulate the immunocompetence of their hosts. In this study, we addressed the influence of gender, age and the feminising endosymbiont Wolbachia (wVulC) on variations in haemocyte density, total PO activity and bacterial load in the haemolymph of the terrestrial isopod Armadillidium vulgare. This host–symbiont system is of particular interest to address this question since: (1) wVulC was previously shown as immunosuppressive in middle-aged females and (2) wVulC influences sex determination. We show that age, gender and Wolbachia modulate together immune parameters in A. vulgare. However, wVulC, which interacts with aging, appears to be the prominent factor interfering with both PO activity and haemocyte density. This interference with immune parameters is not the only aspect of wVulC virulence on its host, as reproduction and survival are also altered.     

How does economic complexity influence environmental degradation? New insights from African countries

This paper seeks to investigate the effect of economic complexity on environmental degradation in 20 selected African countries over the period 1991–2014. The Feasible Generalized Least Square (FGLS), and Driscoll-Kraay estimators (DK) are used to capture the objectives of the study. The results suggest that economic complexity and economic growth enhance environmental degradation. Also, natural resources rents and globalization improve environmental quality. Furthermore, the findings reject the U-shaped relationship between economic complexity and environmental degradation. In addition, the Dumitrescu-Hurlin panel causality test shows a bidirectional causal relation between economic complexity and environmental degradation. Taking into account the ecological deficit or ecological reserve status of country, it is shown that while the natural resource rents reduce environmental degradation in ecological reserve countries, they increase environmental degradation in ecological deficit countries. The results are robust when an alternative measure of economic complexity is used. Based on these findings, the paper suggests that the governments of African countries should take into account economic complexity when designing their environmental protection policies.     

Temporal changes in the trophic ecology of the asymbiotic gorgonian Leptogorgia virgulata

Gorgonians are widespread sub-littoral benthic suspension feeders in the world oceans. However, data on their trophic ecology and role in benthic–pelagic coupling and biogeochemical cycles remain limited. This study assesses the trophic ecology of Leptogorgia virgulata in the Skidaway River estuary, USA (31.9896N, 81.0242W) by analysing carbon and nitrogen isotopic signatures of its soft tissue and different-sized fractions of particulate organic matter (POM) in its environment. Samples were taken in 5 April, 2 August, and 15 October 2012 and 11 January 2013. Results support a distinct temporal shift in the diet of L. virgulata from the POM fraction <10 µm (i.e. pico- and nanoplankton) to the 10–63-µm fraction (i.e. microplankton). This trophic regime is likely associated with the natural abundance of prey items within these size classes, thus suggesting that L. virgulata may be an opportunistic feeder, and seasonal shifts in food availability in the water column affect its diet. As such small prey items affect the bioenergetics of L. virgulata, it is important to understand the implications of changes in food availability associated with environmental drivers on the physiology and population dynamics of this dominant species in the western Atlantic Ocean.