A 13C NMR investigation of CO2 absorption and desorption in aqueous 2,2′-iminodiethanol and N-methyl-2,2′-iminodiethanol

The carbon dioxide capture and release from aqueous 2,2′-iminodiethanol (DEA) and N-methyl-2,2′-iminodiethanol (MDEA) have been investigated by means of ¹³C NMR spectroscopy. We have designed two experimental procedures using a gas mixture containing 12% (v/v) CO₂ in N₂ or air and 0.667 M aqueous solutions of DEA and MDEA. To understand the CO₂–amine reaction equilibria, separate experiments of CO₂ absorption (at 293, 313 and 333 K) and desorption (at boiling temperature, room pressure) were carried out. The ¹³C NMR analysis has allowed us to establish: (1) the percentage of CO₂ stored in solution as HCO₃^?, CO₃^2? and DEA carbamate; (2) the formation of DEA carbamate as a function of absorption temperature and time; (3) the slower decomposition of DEA carbamate than that of bicarbonate. In the experiments planned to test the reuse of the regenerated amines, the absorbent solution was continuously circulated in a closed cycle while it was absorbing CO₂ in the absorber (set at 293 K) and simultaneously regenerating amine in the desorber (set at 388 K). After the equilibrium has been reached (13 h), the CO₂ absorption efficiency is comprised between 84.0% (DEA) and 82.6% (MDEA) and the average amine regeneration efficiency ranges between 69.6% (DEA) and 78.2% (MDEA). Additionally, MDEA is more stable towards thermal degradation than DEA.     

Polychlorinated biphenyls in two salt marsh sediments of the Venice Lagoon

Polychlorinated biphenyls (PCBs) were measured in two dated salt marsh cores of the Venice Lagoon to assess their input chronology and to evaluate the importance of atmospheric deposition as a source. Sampling sites were chosen in order to evidence the differences between areas located leeward and windward with respect to inputs originating in both the city of Venice and the industrial area. Concentrations of PCB indicators (0.13-15.6 ng g?1) increased gradually from the 1930s, reached maxima from the 1950s to the late 1970s, and then decreased. PCB loadings to marshes are driven by both the atmospheric deposition and the resuspension of subtidal sediments, this latter being more important for heavier congeners. The downwind marsh recorded higher fluxes (0.06-9.72 ng cm?2 year?1) than the upwind one (0.01-0.53 ng cm?2 year?1). Recent fluxes are rather consistent with bulk deposition measurements. A higher contribution of CB-101 and CB-118 was detected in the intermediate layers of the downwind site, suggesting a different PCB source for the corresponding time interval. In the other marsh, PCBs showed a rather constant composition at all levels (mostly CB-153, CB-138 and CB-180), accounting for a regional influence. Deep layers showed an enrichment of higher chlorinated congeners at both sites, whereas recent samples conserve the patterns typical of surficial and subsurficial subtidal sediments. The scientific approach adopted in this research can be considered as a sort of methodological procedure for the determination of fluxes and pathways of PCBs through the study of marsh cores.     

Effects of nanoparticles in species of aquaculture interest

Recently, it was observed that there is an increasing application of nanoparticles (NPs) in aquaculture. Manufacturers are trying to use nano-based tools to remove the barriers about waterborne food, growth, reproduction, and culturing of species, their health, and water treatment in order to increase aquaculture production rates, being the safe-by-design approach still unapplied. We reviewed the applications of NPs in aquaculture evidencing that the way NPs are applied can be very different: some are direclty added to feed, other to water media or in aquaculture facilities. Traditional toxicity data cannot be easily used to infer on aquaculture mainly considering short-term exposure scenarios, underestimating the potential exposure of aquacultured species. The main outputs are (i) biological models are not recurrent, and in the case, testing protocols are frequently different; (ii) most data derived from toxicity studies are not specifically designed on aquaculture needs, thus contact time, exposure concentrations, and other ancillary conditions do not meet the required standard for aquaculture; (iii) short-term exposure periods are investigated mainly on species of indirect aquaculture interest, while shrimp and fish as final consumers in aquaculture plants are underinvestigated (scarce or unknown data on trophic chain transfer of NPs): little information is available about the amount of NPs accumulated within marketed organisms; (iv) how NPs present in the packaging of aquacultured products can affect their quality remained substantially unexplored. NPs in aquaculture are a challenging topic that must be developed in the near future to assure human health and environmental safety.

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Trace element contamination in the mine-affected stream sediments of Oued Rarai in north-western Tunisia: a river basin scale assessment

Environmental Geochemistry and Health - High-quality and accurate environmental investigations are essential for the evaluation of contamination and subsequent decision-making processes. A...     

Dimethyl disulfide and dimethyl trisulfide: so similar yet so different in evoking biological responses in saprophilous flies

Dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) are used by saprophilous insects to locate breeding sites (decaying organic matter), and by brood-site deceptive flowers to attract such insects. However, little is known about the relative importance of these two compounds in eliciting electrophysiological and behavioral responses in the insects. Here, we compared the relative attractiveness of DMDS and DMTS to saprophilous flies in field choice experiments and tested whether potential differences in field responses can be explained by differences in electrophysiological antennal responses to these compounds. Field experiments revealed that the attractiveness of a mixture of these compounds is due to DMTS alone. This result was confirmed by electroantennographic recordings in which flies of four tested species of Calliphoridae (Lucilia sericata, L. caesar, Calliphora vicina, Protocalliphora azurea) and one Muscidae (Musca domestica) respond clearly to DMTS, but not to DMDS. In house flies, however, DMTS elicited electrophysiological responses only, not reflected in behavioral assays. Despite the fact that DMTS and DMDS exhibit similar chemical structures, both the electroantennographic and field responses from saprophilous flies to these two compounds strongly differed. Our study suggests that oligosulfide-responsive saprophilous flies rely on DMTS and not DMDS for finding appropriate breeding sites and that DMTS and not DMDS could act as a key mediator for pollinator attraction in brood-site deceptive plants.     

Genetic diagnosis by chorionic villus sampling before 8 gestational weeks: Efficiency,reliability, and risks on 317 completed pregnancies

Transabdominal chorionic villus sampling (TA-CVS) was attempted in 328 high-risk pregnancies at 6–7 weeks of gestation. Sampling was feasible in 97.7 per cent of cases; chorionic tissue specimens of more than 10 mg were obtained in 94.4 per cent ofcases at the first needle insertion and in 100 per cent after a second attempt. Fetal karyotyping succeeded in 99.4 per cent of cases, while no diagnostic failures were reported in enzymatic and DNA analyses. Fetal loss rate in the first 4 weeks after CVS was significantly higher than in the later CVS series (7.2 vs. 2.5 per cent), but 50 per cent of losses were observed within 2 weeks in cases of inviable aneuploidies. A high incidence of severe limb abnormalities (1.6 per cent) was detected in pregnancies intended to continue, confirming the aetiological role of early CVS. Unclear visualization of the placental limits and poor control of the needle path are thought to be the main reasons for the vascular disruption of the chorionic plate, and thereby hypoxic embryo tissue damage. A better selection of cases, together with high-resolution vaginal ultrasound visualization, and analytical techniques requiring a minimal amount of tissue should avoid any teratogenic effect of early CVS.     

Phytotoxicity to and uptake of enrofloxacin in crop plants

Phytotoxicity of enrofloxacin on crop plants Cucumis sativus, Lactuca sativa, Phaseolus vulgaris and Raphanus sativus was determined in a laboratory model: the effect of 50, 100 and 5000 microgl(-1) were evaluated after 30 days exposure by measuring post-germinative growth of primary root, hypocotyl, cotyledons and leaves. Concentrations between 50 and 5000 microgl(-1) induced both toxic effect and hormesis in plants, by significantly modifying both length of primary root, hypocotyl, cotyledons and the number/length of leaves. A toxic effect is induced by high concentration (5000 microgl(-1)), while hormesis occurs at low concentrations (50 and 100 microgl(-1)). A continuum between toxic effect and hormesis is found in the four plant species. Both toxic effect and hormesis can be related to an efficient plant drug uptake, in the order of microgg(-1). Plants are able to metabolize enrofloxacin into ciprofloxacin, as also happens in animals; Cucumis, Lactuca and Phaseolus biologically convert about one quarter of stored enrofloxacin. The ecological implication of enrofloxacin contamination in terrestrial environments is discussed.     

Tire debris organic extract affects Xenopus development

Tire debris (TD) and its organic components were identified as a main source of PM10 atmospheric and water pollution. Because few data are available on the embryotoxic effects of TD organic components, the lethal and teratogenic potential of tire debris organic extract (TDOE) was evaluated using the frog embryo teratogenesis assay-Xenopus (FETAX), coupled with a histopathological screening of the survived larvae. From stage 8 to stage 47, Xenopus laevis embryos were exposed to TDOE at concentrations of 50, 80, 100, 120 and 140 mg/L. The results showed 50 mg/L TDOE to be the non-observable effect concentration (NOEC). TDOE mortality at 80 mg/L was significantly higher than the control, but did not increase further with higher concentrations. A good concentration-response was observed for percentages of malformed larva and from 80 mg/L on these percentages were significantly higher than the control. Therefore, probit analysis gave a 144.6 mg/L TC50. At 120 and 140 mg/L, many larvae were plurimalformed. The most frequent alterations observed were abnormal gut coiling, microphthalmia, monolateral anophthalmia, and narrowing eyes. The histological screening mainly revealed ocular malformations such as double retina, retina nervous cell layer coiling, and altered lens. Moreover severe vacuolisation and necrosis were scored in liver and axial musculature. These results strongly support the assumption that TDOE is a powerful teratogen for X. laevis.