This article reports high dechlorination of toxic polychlorinated biphenyls (PCBs) under mild conditions. PCBs are priority
pollutants acting as endocrine disruptors, human carcinogens and environmental estrogens. Previous remediation methods involving
high temperature and pressure have drawbacks such as high cost, de novo dioxins synthesis and difficult recovery of vaporized
PCBs. On the other hand, dechlorination methods using mild conditions show the problem of catalyst deactivation. Here, activated
carbon was used for the first time as catalyst to dechlorinate 2,4,5 trichlorobiphenyl. High dechlorination, of 87%, was achieved
under mild conditions. 2,4,5 trichlorobiphenyl was treated at 40–150°C with calcium hydroxide, sodium hydroxide and sulfur
in mixed water and organic solvents. Dechlorination products were biphenyl, orthohydroxy biphenyls, 2,4 dihydroxy biphenyls
and biphenyl-2-thiol. Dichlorobiphenyl and orthochlorobiphenyls were found in trace quantities. We found that carbon particles
catalysed dechlorination by substitution reactions and suppressed further chlorination. Dechlorination at biphenyl ortho position
was preceded by substitution reaction by hydroxyl and thiol ions. Moreover, in the absence of carbon, dechlorination was lower
and substituted products were not observed. These findings may be applied at industrial scale to remediate PCB-contaminated
waste. 相似文献
Objective: Streetcars/tram systems are growing worldwide, and many are given priority to increase speed and reliability performance in mixed traffic conditions. Research related to the road safety impact of tram priority is limited. This study explores the road safety impacts of tram priority measures including lane and intersection/signal priority measures.
Method: A before–after crash study was conducted using the empirical Bayes (EB) method to provide more accurate crash impact estimates by accounting for wider crash trends and regression to the mean effects. Before–after crash data for 29 intersections with tram signal priority and 23 arterials with tram lane priority in Melbourne, Australia, were analyzed to evaluate the road safety impact of tram priority.
Results: The EB before–after analysis results indicated a statistically significant adjusted crash reduction rate of 16.4% after implementation of tram priority measures. Signal priority measures were found to reduce crashes by 13.9% and lane priority by 19.4%. A disaggregate level simple before–after analysis indicated reductions in total and serious crashes as well as vehicle-, pedestrian-, and motorcycle-involved crashes. In addition, reductions in on-path crashes, pedestrian-involved crashes, and collisions among vehicles moving in the same and opposite directions and all other specific crash types were found after tram priority implementation.
Conclusions: Results suggest that streetcar/tram priority measures result in safety benefits for all road users, including vehicles, pedestrians, and cyclists. Policy implications and areas for future research are discussed. 相似文献
Shellac (SL) films were prepared by casting and were grafted with various acrylic monomers of different functionalities using
gamma radiation. Different formulations of shellac with varying concentrations (3, 5 and 7%) of these acrylic monomers such
as 2-hydroxyethyl methacrylate (HEMA), 2-ethylhexyl acrylate (EHA) and 1,4-butanediol diacrylate (BDDA) in methanol were prepared.
The pure shellac and other treated films were then irradiated under gamma radiation (Co-60) at different doses (0.5–5 kGy)
at a dose rate of 3.5 kGy/h where 1 Gy = 1 J/kg = 100 rads. The mechanical properties like tensile strength (TS) and elongation
at break (Eb) of the prepared films were studied. The mechanical properties of the irradiated shellac films demonstrated superior
values. Among the formulations, shellac grafted with BDDA (SL-g-BDDA) showed the highest TS and Eb values which were 543 and
168% higher than those of raw shellac films, respectively. The water uptake behavior of raw and treated films was also studied.
The raw film showed 11% water uptake but HEMA containing film showed 67%. In the soil burial test, HEMA containing shellac
film was rapidly degraded than other raw, EHA and BDDA grafted films. Thermal properties indicated that grafting of acrylic
monomers decreased the melting temperature of the pure shellac films. 相似文献
The genotoxicity of industrial wastewaters from Jajmau (Kanpur), was carried out by Ames Salmonella/microsome test, DNA repair-defective mutants, and Allium cepa anaphase–telophase test. Test samples showed maximum response with TA98 strain with and without metabolic activation. Amberlite resins concentrated wastewater samples were found to be more mutagenic as compared to those of liquid–liquid extracts (hexane and dichloromethane extracts). The damage in the DNA repair defective mutants in the presence of Amberlite resins concentrated water samples were found to be higher to that of liquid–liquid-extracted water samples at the dose level of 20 μl/ml culture. Among all the mutants, polA exhibited maximum decline with test samples. Mitotic index (MI) of root tip meristematic cells of A. cepa treated with 5, 10, 25, 50, and 100 % (v/v) wastewaters were significantly lower than the control. Complementary to the lower levels of MI, the wastewaters showed higher chromosomal aberration levels in all cases investigated. 相似文献
Environmental Science and Pollution Research - Real-time particulate matters (PM1, PM2.5, PM4, PM7, PM10, and TSP) with AEROCET 531S (USA), gaseous pollutants (NO2 and TVOC) with Aeroquel 500 gas... 相似文献
Thin films of gelatin were prepared by casting. Then the films were photocured and the mechanical properties were studied.
The tensile strength of UV cured gelatin films showed about 10% enhancement than that of raw gelatin films. Minor amount of
urea (1–5%) was used as additive in aqueous gelatin solution and films were prepared using same technique. Four formulations
were prepared in methanol with 2-ethylhexyl acrylate in the presence of photoinitiator (darocur-1664). The films were soaked
in the prepared formulations and then cured under UV radiation at different intensities (5–25 passes). Percentage of urea,
monomer concentration, soaking time and radiation intensities were optimized with the extent of polymer loading, TS and elongation
at break of the photocured film. The films containing 2% urea, cured with 3% EHA for 3 min at 15th UV pass showed the highest
mechanical properties. A significant improvement of TS (31%) occurred when EHA (3%) was incorporated. 相似文献
Forests represent more than just a livelihood to many people in developing countries. In Bangladesh, for example, overwhelming poverty and socio-economic pressures have resulted in an unstable situation where intensive pressure on forest resources is having increasingly negative consequences for the population. Some studies have evaluated the benefits of people-oriented forestry activities from an investment, as well as a participant, point of view. In the study area located in the Tangail Forest Division, a total of 11,854 ha of woodlot, 2704 ha of agroforestry and 945 km of strip plantations have been raised in a benefit-sharing program that is inclusive of land encroachers and other economically disadvantaged people. Since 2000-2001, a total of 3716 ha of woodlot, 890 ha of agroforestry and 163 km of strip plantations have been harvested to the benefit of 6326 individuals. Investment analysis indicates that woodlot plantation is not financially viable but agroforestry is the most profitable. These results were somewhat unexpected since initial analysis suggested that the woodlot plantation profit would be greater than, or at least equal to, that of the agroforestry plantation if the number of planted seedlings per unit area was taken into account. The per unit area net present value (NPV) was highest in the agroforestry plantation ($1662) and negative in the woodlot plantation (-$397). The benefit cost ratio (BCR) was also highest in the agroforestry plantation (1.64) and lowest in the woodlot plantation (0.86). This study also showed that some individuals who were formally classified as encroachers have now become vital stakeholders. On average, participants received $800, $1866 and $1327 over the course of 13 years from strip, agroforestry and woodlot plantations, respectively. Average annual return per participant was $62, $144 and $102, respectively, which was in addition to each individual's yearly income. This added income is a significant contribution to monetary resources and improves socio-economic conditions at a grass roots level. Overall then this program can be considered a financial success as a plantation raising strategy. However, despite this financial progress, the program cannot be considered a true form of participatory people-oriented forestry because it shows serious deviations from the original concept or model for participatory people-oriented forestry that is outlined in the project document. These discrepancies are especially notable with regard to (i) beneficiary selection, (ii) gender equity, (iii) professional attitude and corruption, (iv) funding and (v) program approach. However, other countries faced with similar challenges of forest overuse and degradation may adopt this practice for achieving self-reliance and environmental stability. 相似文献
Lumber used to construct raised garden beds is often treated with chromated copper arsenate (CCA). This project aimed to determine (i) how far As, Cu, and Cr had diffused away from CCA-treated wood surfaces in raised garden beds under realistic conditions, (ii) the uptake of these elements by crops, and (iii) the effect of CCA solution on soil bacteria. This study showed that As, Cu, and Cr diffuse into soil from CCA-treated wood used to construct raised garden beds. To determine crop uptake of these elements, contaminated soil 0 to 2 cm from the treated wood was obtained from two different beds (40-50 mg kg(-1) As); control soil was collected 1.5 m away from the treated wood (<3-10 mg kg(-1) As). Four replicates of carrot (Daucus carota var. sativus Hoffm. cv. Thumbelina), spinach (Spinacia oleracea L. cv. Indian Summer), bush bean (Phaseolus vulgaris L. cv. Provider), and buckwheat (Fagopyrum esculentum Moench cv. Common) were grown in pots containing these soils in a greenhouse. After harvest, plant materials were dried, ground, digested, and analyzed for As by inductively coupled plasma-hydride generation (ICP-HG). Concentrations of As in all crops grown in contaminated soils were higher than those from control soils. The levels of As in the crops remained well below the recommended limit for As set by the United States Public Health Service (2.6 mg kg(-1) fresh wt.). To determine if bacteria in soils 0 to 2 cm from the treated wood had higher resistance to Type C chromated copper arsenate (CCA-C) solution than those from reference soils, dilution plates were set up using quarter-strength tryptic soy agar (TSA) media and 0 to 22.94 g L(-1) (0-1.25% v/v) CCA-C working solution. The microorganisms from soils adjacent to treated wood had greater growth on the CCA-amended media than those from reference soils outside the bed. 相似文献
Environmental Science and Pollution Research - Argemone mexicana(Pepaveraceae) is an important medicinal plant commonly known as ‘maxican prickly poppy’ and is traditionally used to... 相似文献
Environmental Chemistry Letters - Nanomaterials are now widely used in various industries such as automotive, biomedical, cosmetics, defense, energy, and electronics, due to their unique... 相似文献