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991.
Directional traps, both horizontal and vertical, were used to assess the behavioural impact of phenanthrene application on soil springtail communities. Avoidance was not detected. Rather, a vertical attraction of the dominant species, Folsomia manolachei, was demonstrated, as well as a decrease in horizontal movements of Lepidocyrtus lanuginosus, another important species mainly captured at the soil surface. Ecological consequences of the results are discussed. 相似文献
992.
Martins AF Henriques DM Wilde ML Vasconcelos TG 《Journal of environmental science and health. Part. B》2006,41(3):245-252
The treatment of an effluent from the production of trifluraline was studied using a 1-L, semi-batch, tank-stirred glass reactor for performing three different advanced oxidation processes (photoperoxidation, Fenton, photo-Fenton). A commercial, medium-pressure mercury lamp was used for sample irradiation. The degradation was monitored by measurements of absorptiometric color reduction, UV-visible absorption spectra, and chemical oxygen demand (COD). The obtained results showed that the photo-Fenton process was the most effective treatment for the trifluraline effluent. 相似文献
993.
Tauhata L Vianna ME de Oliveira AE Ferreira AC Bragança MJ Clain AF de Faria RQ 《Journal of environmental radioactivity》2006,86(3):384-390
The Instituto de Radioprote??o e Dosimetria has been coordinating the National Intercomparison Program (PNI) for 15 years, from 1991 to 2005. The objective is to evaluate the analytical performance of the laboratories in low-level activity concentration radionuclide assays in environmental samples. This work presents an evaluation of PNI data from 42 intercomparison runs, which distributed to 22 Brazilian laboratories 2511 samples evaluating 5768 radionuclide assays involving 32 radionuclides in the period from 1991 to 2004. The laboratory performance was evaluated using the Normalized Standard Deviation used by the U.S. EPA. For comparison aims, the Normalized Deviation, used by BIPM was also applied. Laboratory performance were grouped and evaluated in three periods of 5 years each. The first period shows, an average value of good performance of 71.2%, the second shows an average of 78.6% and the last an average of 82.3%. Performance for each kind of radionuclide is also presented. 相似文献
994.
Roussel-Debet S Gontier G Siclet F Fournier M 《Journal of environmental radioactivity》2006,87(3):246-259
For 10 years, (14)C measurements have been performed around French nuclear power plant sites, both in zones influenced and zones not influenced by gaseous releases. Examining the results from these measurements in the terrestrial environment shows that the discharges have a very slight impact on the radiocarbon level (with a relative increase in the specific activity of the order of 3 Bqkg(-1)C in the influenced areas). In correlation, there is a near-negligible increase in dose, on average less than 0.1 microSvyr(-1), with reference to a dose from background radiation, which is of the order of 10 microSvyr(-1). The deltaC13 values are very similar between the influenced zone and the non-influenced zone, with a mean of -27 per thousand. The mean DeltaC14 varies from 101 per thousand in the non-influenced zone to 123 per thousand in the influenced zone. Moreover, a general reduction in (14)C concentration was found, with a time constant of the order of 95 years. The current level of (14)C specific activity in terrestrial environment is estimated to be 242+/-6 Bqkg(-1)C. 相似文献
995.
The Effects of Long-Term Grazing Exclosures on Range Plants in the Central Anatolian Region of Turkey 总被引:1,自引:0,他引:1
Over the last fifty years, almost half of the steppe rangeland in the Central Anatolian Region of Turkey (CAR) has been converted
to cropland without an equivalent reduction in grazing animals. This shift has led to heavy grazing pressure on rangeland
vegetation. A study was initiated in June 2003 using 6 multiscale Modified-Whittaker plots to determine differences in plant
composition between areas that have not been grazed in 27 years with neighboring grazed plant communities. A total of 113
plant species were identified in the study area with the ungrazed plots containing 32 plants more than the grazed plots. The
major species were Astragalus acicularis, Bromus tomentellus, Festuca valesiaca, Genista albida, Globularia orientalis, Poa bulbosa, and Thymus spyleus ssp rosulans. Grazing impacts on forbs were more pronounced than for grasses and shrubs. Based on Jaccard’s index, there was only a 37%
similarity of plant species between the two treatments. Our study led to four generalizations about the current grazing regime
and long-term exclosures in the steppe rangeland around the study area: (1) exclosures will increase species richness, (2)
heavy grazing may have removed some plant species, (3) complete protection from grazing for a prolonged period of time after
a long history of grazing disturbance may not lead to an increase in desirable plant species with a concomitant improvement
in range condition, and (4) research needs to be conducted to determine how these rangelands can be improved. 相似文献
996.
997.
Ormeño E Mévy JP Vila B Bousquet-Mélou A Greff S Bonin G Fernandez C 《Chemosphere》2007,67(2):276-284
The effects of water deficit stress and plant water potential (psi) on monoterpene and sesquiterpene leaf emissions from Rosmarinus officinalis, Pinus halepensis, Cistus albidus and Quercus coccifera were studied over 11 days of water withholding (from t(1) to t(11)), after substrates had achieved their field capacity (control pots: t(0)). Volatile compounds were sampled from the same twig per plant all throughout the study, using a dynamic bag enclosure system. Volatiles, collected in Tenax TA, were studied by means of GC-FID and GC-MS. Monoterpene emissions of water stressed plants (t(1)-t(11)) were either similar to those of control seedlings (R. officinalis and Q. coccifera) or higher (P. halepensis and C. albidus). By contrast, sesquiterpene emissions were strongly reduced or inhibited after four days of water withholding, particularly for R. officinalis, thus altering terpene emission composition. Despite the positive effect of water stress on leaf monoterpene emissions of P. halepensis and C. albidus, the significant correlation between these emissions and psi showed a slow decrease of these emissions over long term water deficit periods. This contrasted with the rapid decline of sesquiterpene emissions of R. officinalis according to lower values of psi. These results provide an overall picture of the different responses of monoterpene and sesquiterpene emissions to progressive water loss. They also reveal the utility of using psi for estimating some emission rates of some species according to drought conditions. 相似文献
998.
The effects of charge reversal about the measured point of zero charge (pH(0) approximately 5.2) of untreated and treated Sete Lagoas lateritic soil of Brazil on aqueous polymer sorption was investigated. The polymers are anionic sodium carboxymethyl cellulose (CMCA), nonionic polyethylene oxide (PEO), and cationic polyacrylamide (PAM). They were prepared at aqueous concentrations and pH ranges of 0.1-2.0 g l(-1) and 2-9, respectively. Soil treatment involved the removal of iron oxides by treatment with dithionate-bicarbonate-citrate. Batch sorption test results show that the presence of iron oxides in lateritic soil tends to suppress sorption of CMCA (especially at pH=pH(0)) and PEO (for the whole pH range) but has uncertain effects on cationic PAM sorption. CMCA sorption on the untreated soil improves on either side of pH(0), in direct proportionality to solution concentration, except at pH<4.0, where disassociation of the polymer molecules may decrease sorption energy. Increase in the sorption of non-cationic polymers (CMCA and PEO) at pH>pH(0) is attributable to dispersion of clay, cation bridging and polymer molecular reconfiguration. For cationic PAM, electrostatic bonding to negatively charged soil particle surfaces accounts for the sorption increase. For treated soil samples, polymer sorption pattern is similar to those expected for the montmorillonitic clayey soils of temperate zones. These results indicate that the pH(0) of lateritic soils, within the regime that exists in the field, should be considered in assessing the potential effectiveness of polymer dust suppressants for tropical lateritic soils. 相似文献
999.
1000.
Flávia Gonçalves Domingues Ferreira Maria Alice Gomes de Andrade Lima Yêda Medeiros Bastos de Almeida Glória Maria Vinhas 《Journal of Polymers and the Environment》2010,18(3):196-201
Blends of LDPE/modified starch were prepared, sterilized by gamma radiation and investigated with respect to their microbial
degradation by a mixture of fungal strains in liquid medium after 90 days, was analyzed by carbon dioxide (CO2) production (Sturm test). Biodegradation of blends was evaluated by Fourier transform infrared spectroscopy (FTIR) and X-ray
diffraction; mechanical testing, scanning electron microscopy (SEM). The biodegradation of LDPE/modified starch blends was
attributed to microbiological attack, with alterations in the chemical structure of the blend with an increase in the carbonyl
and vinyl indices and the appearance of new crystalline symmetry generating a crystalline domain not existing before in the
blend and decrease in the mechanical properties. 相似文献