Organic aerosol molecular composition and gas–particle partitioning coefficients at a Mediterranean site (Corsica)

Molecular speciation of atmospheric organic matter was investigated during a short summer field campaign performed in a citrus fruit field in northern Corsica(June 2011). Aimedat assessing the performance on the field of newly developed analytical protocols, this work focuses on the molecular composition of both gas and particulate phases and provides an insight into partitioning behavior of the semi-volatile oxygenated fraction. Limonene ozonolysis tracers were specifically searched for, according to gas chromatography–mass spectrometry(GC–MS) data previously recorded for smog chamber experiments. A screening of other oxygenated species present in the field atmosphere was also performed. About sixty polar molecules were positively or tentatively identified in gas and/or particle phases. These molecules comprise a wide range of branched and linear, mono and di-carbonyls(C_3–C7),mono and di-carboxylic acids(C_3–C_18), and compounds bearing up to three functionalities.Among these compounds, some can be specifically attributed to limonene oxidation and others can be related to α- or β-pinene oxidation. This provides an original snapshot of the organic matter composition at a Mediterranean site in summer. Furthermore, for compounds identified and quantified in both gaseous and particulate phases, an experimental gas/particle partitioning coefficient was determined. Several volatile products, which are not expected in the particulate phase assuming thermodynamic equilibrium, were nonetheless present in significant concentrations. Hypotheses are proposed to explain these observations, such as the possible aerosol viscosity that could hinder the theoretical equilibrium to be rapidly reached.     

The importance of glutathione and phytochelatins on the selenite and arsenate detoxification in Arabidopsis thaliana

We investigated the role of glutathione(GSH) and phytochelatins(PCs) on the detoxification of selenite using Arabidopsis thaliana. The wild-type(WT) of Arabidopsis thaliana and its mutants(glutathione deficient Cad 2–1 and phytochelatins deficient Cad 1–3) were separately exposed to varying concentrations of selenite and arsenate and jointly to both toxicants to determine their sensitivities. The results of the study revealed that, the mutants were about 20-fold more sensitive to arsenate than the WT, an indication that the GSH and PCs affect arsenate detoxification. On the contrary, the WT and both mutants showed a similar level of sensitivity to selenite, an indication that the GSH and PCs do not significantly affect selenite detoxification. However, the WT is about 8 times more sensitive to selenite than to arsenate, and the mutants were more resistant to selenite than arsenate by a factor of 2. This could not be explained by the accumulation of both elements in roots and shoots in exposure experiments. The co-exposure of the WT indicates a synergistic effect with regards to toxicity since selenite did not induce PCs but arsenic and selenium compete in their PC binding as revealed by speciation analysis of the root extracts using HPLC–ICP–MS/ESI–MS. In the absence of PCs an antagonistic effect has been detected which might suggest indirectly that the formation of Se glutathione complex prevent the formation of detrimental selenopeptides. This study, therefore, revealed that PC and GSH have only a subordinate role in the detoxification of selenite.     

Identification of trail pheromone compounds from the labial glands of the stingless bee Geotrigona mombuca

Foragers of several species of stingless bees deposit pheromone spots in the vegetation to guide recruited nestmates to a rich food source. Recent studies have shown that Trigona and Scaptotrigona workers secrete these pheromones from their labial glands. An earlier report stated that species within the genus Geotrigona use citral from their mandibular glands for scent marking. Since convincing experimental proof for this conjecture is lacking, we studied the glandular origin of the trail pheromone of Geotrigona mombuca. In field bioassays, newly recruited bees were diverted by artificial scent trails that branched off from the natural scent trail deposited by their nestmates only when they were baited with extracts from the foragers’ labial glands. Compounds extracted from the mandibular glands, however, did not release trail following behavior. This demonstrates that the trail pheromone of G. mombuca is produced in the labial glands, as in Trigona and Scaptotrigona. Furthermore, in chemical analyses citral was identified exclusively in the foragers’ mandibular glands, which disproves its supposed role as a trail pheromone. The labial glands contained a series of terpene- and wax type esters, with farnesyl butanoate as major constituent. We, therefore, postulate that the trail pheromone of G. mombuca is composed of a blend of esters.     

A sonographic approach to the prenatal diagnosis of skeletal dysplasias

Skeletal dysplasias are a heterogeneous group of conditions, many of which present unexpectedly in the prenatal period with a variety of ultrasound findings. Accurate prenatal diagnosis can now be facilitated using exome sequencing approaches, but in order to interpret results, accurate and detailed phenotyping is required. Here, we describe the sonographic approach to the prenatal diagnosis of skeletal abnormalities and illustrate how taking a systematic approach can facilitate diagnosis.     

Influence of earthworm bioturbation on metals phytoavailability and human gastric bioaccessibility

Environmental Science and Pollution Research - At the global scale, urban agriculture is increasingly developing in cities due to demographic growth and sustainable food concerns. But, urban soils...     

Comparison of inorganic and composite ferric oxide sorbents for arsenic removal

Three different sorbents based on hydrated ferric oxide (GEH, ArsenX^np and Lewatit FO 36) were compared from the viewpoints of their column operation. Particle size distribution, pressure drop across the column and ferric oxide content were measured. Sorption capacities under the presence of accompanying ions were measured in batch wise and column experiments.