The aim of this study was to investigate the toxicity of copper on the aquatic lichen Dermatocarpon luridum focusing on the activities of some antioxidant enzymes. Investigations were conducted using increasing copper concentrations (0.00, 0.25, 0.50, 0.75 and 1.00 mM CuSO(4) x 5H(2)O) in synthetic freshwater that emulated the major ion compositions of its natural water biota; time course measurement was 0, 3, 6, 12, 24 and 48 h. The copper concentration in thalli increased with its increase in the medium and the duration of treatment. Copper induced lipid peroxidation, measured using the hydroperoxi-conjugated dienes (HPCD) concentration. The decrease in the protein concentrations was similar in thalli exposed to copper concentrations above 0.50 mM and the decrease was twice lower in thalli exposed to 0.25 mM copper. The activities of antioxidant enzymes measured were differently affected by copper excess. For 0.25 mM copper, the activities of SOD (superoxide dismutase) and APX (ascorbate peroxidase) were unchanged when compared with unstressed thalli whereas the CAT (catalase) activity increased and the GR (glutathione reductase) activity decreased. The activities of SOD and APX increased in thalli exposed to concentrations above 0.50mM copper. The CAT activity increased after the first 3h of experiments at these concentrations and then decreased with the duration of treatment at an activity lower than in the unstressed plant. Whereas the APX activity increased, the GR activity similarly decreased for the copper concentration tested whatever the duration of the experiment. 相似文献
An analytical methodology was developed to characterize the colloidal distribution of trace elements of interest in environmental waters sampled in a same site and enables the different colloidal distributions from waters to be compared. The purpose was to provide consistent information related to the origin and nature of colloids responsible for the transport of trace element(s). The work was motivated by the observed enhanced mobility of uranium in soil. The colloidal size continuum was investigated by a multi-technique approach involving asymmetric flow field-flow fractionation (AF4) coupled with ultraviolet spectroscopy (UV), multi angle light scattering (MALS), and atomic mass spectrometry (ICPMS). To take into consideration the size and shape variability specific to each sample, the size distributions were established from the gyration radii measured from MALS, also considering the size information from standard nanospheres fractionated by AF4. A new parameter called “shape index” was proposed. It expresses the difference in hydrodynamic behavior between analytes and spherical particles taken as reference. Under AF4 diffusion conditions, it can be considered as an evaluator of the deviation from the sphericity of the fractionated analytes. AF4-UV-MALS-ICPMS enabled the dimensional and chemical characteristics of the colloidal size continuum to be obtained. As a “proof of concept”, the developed methodology was applied at a field scale, in a reference study site. In order to have a “dynamic understanding”, the investigation was based on the joint characterization of colloids from surface waters and soil leachates from static and dynamic processes. In the water samples of the study site, the continuum of gyration radius ranged from a few nanometers up to 200 nm. Colloids containing iron, aluminum, and organic carbon were involved in the uranium transport in the soil column and surface waters. The colloidal uranium concentration in the surface water increased from the upstream location (approximately 13 ng (U) L?1) to the downstream location (approximately 60 ng (U) L?1).
Analytical models were developed that simulate stable isotope ratios of volatile organic compounds (VOCs) near a point source contamination in the unsaturated zone. The models describe diffusive transport of VOCs, biodegradation and source ageing. The mass transport is governed by Fick's law for diffusion. The equation for reactive transport of VOCs in the soil gas phase was solved for different source geometries and for different boundary conditions. Model results were compared to experimental data from a one-dimensional laboratory column and a radial-symmetric field experiment. The comparison yielded a satisfying agreement. The model results clearly illustrate the significant isotope fractionation by gas phase diffusion under transient state conditions. This leads to an initial depletion of heavy isotopes with increasing distance from the source. The isotope evolution of the source is governed by the combined effects of isotope fractionation due to vaporisation, diffusion and biodegradation. The net effect can lead to an enrichment or depletion of the heavy isotope in the remaining organic phase, depending on the compound and element considered. Finally, the isotope evolution of molecules migrating away from the source and undergoing degradation is governed by a combined degradation and diffusion isotope effect. This suggests that, in the unsaturated zone, the interpretation of biodegradation of VOC based on isotopic data must always be based on a model combining gas phase diffusion and degradation. 相似文献
Studies related to phytoremediation by conifers are still at their beginning. Thus, we investigated the ability of a hybrid larch (Larix x eurolepis) to accumulate cadmium (Cd). One-month-old clonal plantlets grown in vitro were exposed for 1 week to a high Cd concentration (1.5 mM). No significant effect was observed on root and shoot biomass, root length, and needle number as a result of Cd treatment. Leaf photosynthetic pigment content and total soluble protein concentration in roots and shoots remained unchanged compared to control plantlets. Taken together, these results suggested that hybrid larch tolerated Cd in our conditions. The high Cd concentration in shoots (200 μg Cd gram?1 dry weight) showed the good capacity of larch to translocate Cd and thus a potential use of this species for phytoremediation. Furthermore, under our conditions, phytochelatin biosynthesis pathway was slightly stimulated, suggesting that this pathway did not reach the threshold and/or another mechanism of Cd storage may be involved to explain larch tolerance to Cd. 相似文献
Boundary layer interactions with canopies control various environmental processes. In the case of dense and homogeneous canopies,
the so-called mixing layer analogy is most generally used. When the canopy becomes sparser, a transition occurs between the
mixing layer and the boundary layer perturbed by interactions between element wakes. This transition has still to be fully
understood and characterized. The experimental work presented here deals with the effect of the canopy density on the flow
turbulence and involves an artificial canopy placed in a fully developed turbulent boundary layer. One and two-component velocity
measurements are performed, both within and above the canopy. The influence of the spacing between canopy elements is studied.
Longitudinal velocity statistical moments and Reynolds stresses are calculated and compared to literature data. For spacings
greater than the canopy height, evidences of this transition are found in the evolution of the skewness factor, shear length
scale and mixing length. 相似文献
From May 2002 to October 2003, a fortnightly sampling programme was conducted in a restricted macrotidal ecosystem in the
English Channel, the Baie des Veys (France). Three sets of data were obtained: (1) physico-chemical parameters, (2) phytoplankton community structure illustrated
by species composition, biovolume and diversity, and (3) primary production and photosynthetic parameters via P versus E curves. The aim of this study was to investigate the temporal variations of primary production and photosynthetic parameters
in this bay and to highlight the potential links with phytoplankton community structure. The highest level of daily depth-integrated
primary production Pz (0.02–1.43 g C m−2 d−1) and the highest maximum photosynthetic rate PBmax (0.39–8.48 mg C mg chl a−1 h−1) and maximum light utilization coefficient αB [0.002–0.119 mg C mg chl a−1 h−1 (μmol photons m−2 s−1)] were measured from July to September. Species succession was determined based on biomass data obtained from cell density
and biovolume measurements. The bay was dominated by 11 diatoms throughout the year. However, a Phaeocystis globosa bloom (up to 25 mg chl a m−3, 2.5 × 106 cells l−1) was observed each year during the spring diatom bloom, but timing and intensity varied interannually. Annual variation of
primary production was due to nutrient limitation, light climate and water temperature. The seasonal pattern of microalgal
succession, with regular changes in composition, biovolume and diversity, influenced the physico-chemical and biological characteristics
of the environment (especially nutrient stocks in the bay) and thus primary production. Consequently, investigation of phytoplankton
community structure is important for developing the understanding of ecosystem functioning, as it plays a major role in the
dynamics of primary production. 相似文献
The objectives in this work were to investigate a conceptual layout for an inexpensive and simple system that would treat primary municipal wastewater to discharge standards. A commercial hydroponic system was adapted for this study and the wastewater was used to irrigate Datura innoxia plants. Influent and effluent samples were collected once a month for six months and analysed to determine the various parameters relating to the water quality. The legal discharge levels for total suspended, biochemical oxygen demand and chemical oxygen demand were reached with the plant system after 24 h of wastewater treatment. Total nitrogen and total phosphorus reduction were also obtained. NH4(+)-N was reduced by 93% with nitrification proving to be the predominant removal process. Significant nitrification occurred when the BOD5 level dropped 45 mg/l. Similar results were obtained for six months although the sewage composition varied widely. D. innoxia develops and uses the wastewater as the unique nutritive source. 相似文献