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591.
Gonzalez-Mendoza D Ceja-Moreno V Gold-Bouchot G Escobedo-Graciamedrano RM Del-Rio M Valdés-Lozano D Zapata-Perez O 《Chemosphere》2007,67(2):330-334
Two groups of Avicennia germinans plants with differences in the radical architecture were exposed under hydroponic conditions to 95ppm of cadmium (Cd) for a period of 24h. Later, Cd concentration in roots, stems and leaves was determined by graphite furnace atomic absorption spectrophotometry. Our results showed that, for both groups of plants, the roots accumulated higher concentration of Cd as compared to stems and leaves, though, the plants of group B displayed enhanced radical architecture, better growth performance, and lower Cd concentration as compared to plants of group A. In contrast, low values of leaves/roots Cd transportation index, and bioaccumulation factor were found in plants of group B. These results suggest that the higher radical architecture developed in plants of group B might better adjust the uptake of Cd as a result of an integrated network of multiple response processes for instances, production of organic acids, antioxidative replay, cell-wall lignification and/or suberization. Further studies will be focused in understanding the role of the radical system in mangrove plants with the rhizosphere activation and root adsorption to soil Cd under natural conditions. 相似文献
592.
Aerobic degradation of di- and trichlorobenzenes by two bacteria isolated from polluted tropical soils 总被引:7,自引:0,他引:7
Two polychlorinated biphenyl (PCBs)-degrading bacteria were isolated by traditional enrichment technique from electrical transformer fluid (Askarel)-contaminated soils in Lagos, Nigeria. They were classified and identified as Enterobacter sp. SA-2 and Pseudomonas sp. SA-6 on the basis of 16S rRNA gene analysis, in addition to standard cultural and biochemical techniques. The strains were able to grow extensively on dichloro- and trichlorobenzenes. Although they failed to grow on tetrachlorobenzenes, monochloro- and dichlorobenzoic acids, they were able to utilize all monochlorobiphenyls, and some dichlorobiphenyls as sole sources of carbon and energy. The effect of incubation with axenic cultures on the degradation of 0.9 mM 1,4-dichlorobenzene, 0.44 mM 1,2,3- and 0.43 mM 1,3,5-trichlorobenzene in mineral salts medium was studied. Approximately, 80-90% of these xenobiotics were degraded in 200 h, concomitant with cell increase of up to three orders of magnitude, while generation times ranged significantly (P<0.05) from 17-32 h. Catechol 1,2-dioxygenase and catechol 2,3-dioxygenase activities were detected in crude cell-free extracts of cultures pre-grown with benzoate, with the latter enzyme exhibiting a slightly higher activity (0.15-0.17 micromolmin(-1) mg of protein(-1)) with catechol, suggesting that the meta-cleavage pathway is the most readily available catabolic route in the SA strains. The wider substrate specificity of these tropical isolates may help in assessing natural detoxification processes and in designing bioremediation and bioaugmentation methods. 相似文献
593.
Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol in supercritical water 总被引:1,自引:0,他引:1
Effects of potassium alkalis and sodium alkalis on the dechlorination of o-chlorophenol (o-CP) in supercritical water (SCW) were studied in this paper under the conditions of 450 degrees C and 25 MPa. Experimental results indicated that the dechlorination of o-CP can be accelerated significantly by all alkalis investigated. The dechlorination of o-CP proceeded mainly via two pathways: hydrodechlorination and hydrolysis. Both of the two pathways can be promoted by alkalis, and the dechlorination of o-CP can be accelerated by both the cations and hydroxide ion dissociated from alkalis. The overall dechlorination of o-CP can be accelerated by cations via promoting the hydrodechlorination pathway, while, hydroxide ion via promoting the hydrolysis pathway. In addition, the hydrodechlorination can be accelerated faster by sodium alkalis than that by potassium ones, while, the hydrolysis can be promoted faster by potassium alkalis. This difference may be caused by the different charge density between potassium ion and sodium ion, and the different solubility and dissociation constant between potassium alkalis and sodium alkalis in SCW. Dechlorination of o-CP with addition of alkalis prior to supercritical water oxidation (SCWO) process not only can avoid the reactor corrosion caused by the generated hydrochloric acid in direct SCWO of o-CP, but also can reduce the formation of toxic chlorinated byproducts compared with direct SCWO process or SCWO of o-CP with addition of alkali. 相似文献
594.
Ramalina maciformis and Ramalina lacera were exposed to different solutions and UV-B to seek for alterations in the PSII photosynthetic quantum yield (F(v)/F(m)), in response to chemicals and radiation. For R. maciformis, significant alterations of the F(v)/F(m) ratio occurred only in response to different bisulphite solutions. The F(v)/F(m) ratio decreased most in R. maciformis and R. lacera following exposure to 5 and 1 mM bisulphite, respectively. Significant differences in F(v)/F(m) ratios were observed for R. lacera in response to different solutions and light at different wavelengths, this being synergistic. The PSII system was unaffected by simulated acid rain in both lichens. R. maciformis, in particular, may survive limited acid rain exposure owing to high Ca oxalate accumulation. The F(v)/F(m) ratio decreased most in R. lacera following short-term exposures to CuSO(4), suggesting that this species is more sensitive to Cu ions under acidic conditions. 相似文献
595.
The accumulation of lipofuscin, which is an indictor of physiological age, in the brain of juvenile European lobster (Homarus gammarus L.) was monitored for 22 mo in three experimental temperature regimes that simulated seasonal variation in temperature in
the geographic range of this species. Metabolic rate responses to changes in temperature were estimated by measuring the activity
of the electron transport system (ETS) in muscle tissue and in vivo rates of oxygen consumption. Lipofuscin accumulation oscillated
with simulated seasonal changes in temperature and was described by seasonalised von Bertalanffy growth functions. The incremental
accumulation in lipofuscin between sampling dates was linearly related to the number of degree days that accumulated between
dates, irrespective of the amplitude of temperature fluctuation that had occurred. ETS activity increased with acclimation
temperature and was modelled using a polynomial function. This indicated a lower temperature sensitivity in the temperature
mid-range (12 to 16 °C), although the Q10 for this mid-range was 2.1. ETS activity in lobsters acclimated to 8 and 18 °C and assayed at 13 °C was similar, indicating
no compensation for changes in environmental temperature. Oxygen consumption rate was significantly higher at 14 °C than at
10.5 °C and had a Q10 of 3.6, again suggesting no compensation to temperature change. The absence of metabolic compensation in response to temperature
change in H. gammarus is consistent with the predictability of changes in temperature and food availability in the sub-littoral environment of
this species. As lipofuscin accumulates according to metabolic rate, and metabolic rate in H. gammarus is directly correlated with temperature, geographic differences and long-term temporal trends in temperature will need to
be considered when converting physiological age indices, obtained from lipofuscin estimates, to a chronological scale.
Received: 27 April 2000 / Accepted: 21 July 2000 相似文献
596.
597.
Coral Bleaching and Global Climate Change: Scientific Findings and Policy Recommendations 总被引:3,自引:0,他引:3
Abstract: In 1998, tropical sea surface temperatures were the highest on record, topping off a 50-year trend for some tropical oceans. In the same year, coral reefs around the world suffered the most extensive and severe bleaching ( loss of symbiotic algae) and subsequent mortality on record. These events may not be attributable to local stressors or natural variability alone but were likely induced by an underlying global phenomenon. It is probable that anthropogenic global warming has contributed to the extensive coral bleaching that has occurred simultaneously throughout the reef regions of the world. The geographic extent, increasing frequency, and regional severity of mass bleaching events are an apparent result of a steadily rising baseline of marine temperatures, combined with regionally specific El Niño and La Niña events. The repercussions of the 1998 mass bleaching and mortality events will be far-reaching. Human populations dependent on reef services face losses of marine biodiversity, fisheries, and shoreline protection. Coral bleaching events may become more frequent and severe as the climate continues to warm, exposing coral reefs to an increasingly hostile environment. This global threat to corals compounds the effects of more localized anthropogenic factors that already place reefs at risk. Significant attention needs to be given to the monitoring of coral reef ecosystems, research on the projected and realized effects of global climate change, and measures to curtail greenhouse gas emissions. Even those reefs with well-enforced legal protection as marine sanctuaries, or those managed for sustainable use, are threatened by global climate change. 相似文献
598.
599.
本文从分析我国传统的经济增长方式入手,通过对资源近视症”的表现及后果的分析,提出西部西地区,特别是西部少数民族地区只有树立全面的资源观,立足优势,面向市场,抓住机遇,合理开发资源和利用资源,才能走出一条符合本民族,本地区实际的可持续发展之路。 相似文献
600.