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The cumulation of chromium(III) and (VI) has been studied in batch cultures of planktonic algae Microcystis incerta, Scedenesmus obliquus, Chlorella kessleri and Chlamydomonas geitleri at different chromium and algal cells concentrations. It has been found that chromium(VI) is practically not cumulated in algae, whereas chromium(III) is very rapidly cumulated in all types of algae investigated. The cumulation factor increases with the decrease of the radius of algae cells and it reaches the value of 106 for Microcystis incerta even after a few hours of contact. The kinetics, the cumulation factors and the capacity of algae to cumulate chromium(III) is practically the same for living as well as for dead cells and therefore it can be concluded that the cumulation of chromium(III) is due predominantly to the chemical sorption on the surface of algal cells. 相似文献
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利用~(210)Pb、~(137)Cs和~(241)Am计年法测算云南抚仙湖现代沉积速率 总被引：2，自引：0，他引：2
通过对云南抚仙湖沉积物柱芯样品的~(210)Pb、~(137)Cs和~(241)Am测试表明,柱芯剖面上有明显的1963年和1986年~(137)Cs蓄积峰,验证了1975年次级蓄积峰存在的可能性,这些峰形完好的蓄积峰对抚仙湖的现代沉积环境有明显的时标意义。利用~(137)Cs计年法得到抚仙湖沉积物自1963年、1975年及1986年以来到2007年的平均沉积速率分别为0.063g/(cm~2·a)、0.052g/(cm~2·a)和0.039g/(cm~2·a),说明了过去近五十年抚仙湖沉积速率整体上经历了一个由快到慢的过程。借助于~(241)Am的1963年蓄积峰可以提高~(137)Cs计年的准确性。根据~(210)Pb CRS计年模式,计算出每个样品深度所对应的年代,与~(137)Cs计年法比较存在一定的偏差,分析了两种计年方法存在差异性的原因。通过质量深度和年代分析,抚仙湖的沉积速率变化幅度比较大,表明抚仙湖近129年来的沉积环境不稳定,可能与相应历史时期的人类活动有密切的关系。 相似文献
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Kwokal Z Francisković-Bilinski S Bilinski H Branica M 《Marine pollution bulletin》2002,44(10):1152-1157
Anthropogenic mercury pollution was studied in Kastela Bay (Croatia), 10 years after chloralkaline plant (PVC) stopped production. The concentration of total mercury determined in sediments which are composed mainly of calcite and quartz, are in the range 14,280-30,400 ng/g. The values are higher than reported in the literature for Elbe and Seine estuaries and also above 25,000 ng/g used for criterion in remediation project in Minamata Bay. The concentration of methylmercury 6.05-36.74 ng/g are typical for slightly to highly contaminated estuarine sediments. The low ratio of methylmercury to total mercury found in sediments of Kastela Bay is in the range 0.04-0.18%. It can be explained that in this region predominate conditions which do not promote in-situ methylation. Sediments were found to be highly anoxic. Concentrations of total mercury in unfiltered surface waters are in the range 69-145 ng/l and in unfiltered bottom waters in the range 230-1,418 ngl(-1). High concentrations found in bottom waters suggest that either resuspension or partial dissolution of sediments takes place. An experiment performed on filtered and unfiltered waters showed that about 85% of total mercury in surface water and almost 100% in bottom water was retained on 45 microm filters. To demonstrate contrasts, two pristine estuaries from norths and south Europe were studied. Silicious sediments of Ore estuary (Sweden) and calcareous sediments of Krka estuary (Croatia) have total mercury concentrations close to accepted background level. The ratio of methylmercury to total mercury is < or = 1% in all samples with one exception. The highest observed ratio (2.70%) was in the surface sediment from E2 station in Krka estuary measured in March 2000. This location is suitable for studying methylmercury formation in pristine environment. 相似文献
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Amplitude regularities, intermittence statistics, and conditions of generation of magnetic (mag- netic impulse event, MIE) and geomagnetic storm sudden commencement (SSC) impulses were compara- tively analyzed. Common and different properties of MIE and SSC impulses observed in a high-latitude mag- netosphere were detected. It was shown that MIE impulses are observed against a background of relatively stable interplanetary medium parameters and mostly when the IMF sector structure is negative. SSC impulses are observed against a background of sharply increasing solar wind and IMF parameters and when the IMF sector structure is positive. The amplitude dynamics, depending on the geomagnetic latitude of MIE and SSC impulses relative to the noon meridian, as well as in the daytime and nighttime MLT sectors, is sim- ilar. The dynamics of the intermittence indices (α), depending on the geomagnetic latitude of MIE and SSC impulses in the same MLT sectors, is antiphase. Independently of the IMF sector structure, the amplitudes of MIE and SSC impulses increase with increasing geomagnetic latitude, and the intermittence indices change in antiphase. It is assumed that the degree of plasma turbulence at the front boundary of magneto- sphere at moderate geomagnetic activity is relatively high and sufficient for the generation of MIE impulsive regimes. At the same time, SSC impulses originate at a lower turbulence level in the subsolar magnetospheric region but under the external action of solar wind inhomogeneities on the magnetosphere. 相似文献
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Abstract The breakdown and separation or reattachment of boundary layers adjoining a mainstream are studied in the three related situations (i)-(iii) of the title. For (i) the classical steady boundary layer generally admits a logarithmic singularity in the displacement when breakdown occurs on a downstream-moving surface whereas the corresponding singularity for an upstream-moving surface can be logarithmic or of minus-one-sixth form. Conversely, the breakdown can be delayed to the onset of zero mainstream flow, in which case the displacement singularity is again logarithmic. In certain flows these singularities prove to be removable locally, yielding a breakaway separation or reattachment and including the first known successes of a classical strategy in describing large-scale separation. Other flows, by contrast, require an interactive strategy. Again, even on a fixed surface a breakdown different from Goldstein's can be produced if there is a moving section of surface further upstream. The application to (ii), semi-similar unsteady boundary layers, e.g. near an impulsively started wedge-like trailing edge, then follows readily and predicts analogous forms of singularity. The corresponding singularity in displacement predicted for fully unsteady classical boundary layers, (iii), occurs within a finite time and, like (i) (usually) and (ii), a three-tiered breakdown is involved at first. Subsequently interaction comes into play. Comparisons with numerical and/or earlier work are noted. In all three situations (i)-(iii), although the dynamics involved near breakdown, separation or reattachment are predominantly inviscid, the presence of small viscosity is of significance in enforcing smoothness of the local velocity profiles. 相似文献
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Instrumental neutron activation analysis was used for the determination of more than 20 trace and minor elements in water and silt samples (suspended load) of the river Aare. The samples were collected at four different locations along the river between its source and the lake of Bienne. The principal results are: 1. The concentrations of all elements investigated are much lower than WHO-limits for drinking water. 2. Human activities are responsible for an increase of some elements along the river. 3. The concentrations of dissolved trace elements are generally anticorrelated with the water flow rate. 4. The concentrations of the trace elements in particulates (in μg/l) are correlated with the flow rate of water. Except for Ca?Sr there are no significant interelement correlations for all four sampling stations. 相似文献
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《Acta Geochimica》2017,(3)
We analyzed the ~(87)Sr/~(86)Sr ratios of basaltic rocks and basin water in Xuyi,China,and found a big difference,which may challenge conventional wisdom on the contribution of basalt weathering in end-member analysis.Results of an in-house weathering experiment suggest that rainwater and dust are not responsible for the difference.By isolating the major minerals in basalt,we found that plagioclase has much higher ~(87)Sr/~(86)Sr ratios than bulk basalt and basin water,which might explain the difference in ~(87)Sr/~(86)Sr ratios of basalt and basin water.We inferthatlow-temperaturehydrothermalalteration increased the ~(87)Sr/~(86)Sr ratios of plagioclase.Future analyses of end-member contribution in a mixed-rock basin should take into account that basin water and plagioclase have higher ~(87)Sr/~(86)Sr ratios than basaltic rocks. 相似文献
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Zare MR Mostajaboddavati M Kamali M Abdi MR Mortazavi MS 《Marine pollution bulletin》2012,64(9):1956-1961
The natural radioactivity levels in sediment samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz canyon to Goatr seaport, as the first time has been determined. The results of measurements will serve as background reference level for Oman Sea coastlines. Sediments from 36 coastal and near shore locations were collected for analysis. Analysis on the collected samples were carried out to determine (235)U, (238)U, (232)Th, (40)K and (137)Cs using two high purity germanium detectors with 38.5% and 55% relative efficiencies. The concentration of (235)U, (238)U, (232)Th, (40)K and (137)Cs in sediment samples ranged between 1.01 and 2.87Bq/kg, 11.83 and 22.68Bq/kg, 10.7 and 25.02Bq/kg, 222.89 and 535.07Bq/kg and 0.14 and 2.8Bq/kg, respectively. The radium equivalent activity was well below the defined limit of 370Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. 相似文献
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Pampanin DM Camus L Gomiero A Marangon I Volpato E Nasci C 《Marine pollution bulletin》2005,50(12):512-1557
The aim of this study was to evaluate the susceptibility to pollutant mediated oxidative stress of the Mediterranean mussel Mytilus galloprovincialis in the Venice lagoon (Italy).
In June 2003, mussels from a farm were transplanted to eight sites in the lagoon for five weeks. Oxidative stress responses were measured by: (i) total oxyradical scavenging capacity (TOSC) assay, for an overall evaluation of the oxidative stress response capability; (ii) catalase (CAT), as a key enzyme involved in the antioxidant defence system; (iii) malondialdehyde (MDA), as an indicator of lipid peroxidation, to evaluate an oxidative damage; (iv) metallothioneins (MTs), as they play a role in the antioxidant defence.
The TOSC analysis revealed a reduced capability to eliminate: (i) peroxyl radical in mussels transplanted at Palude della Rosa, Valle Millecampi and Chioggia; (ii) hydroxyl radical at Campalto and Valle Millecampi; (iii) peroxynitrite at Valle Millecampi.
Inhibition in CAT activity, observed in all the monitored sites, confirms the presence of an oxidative pressure in transplanted mussels.
In addition, Pearson correlation analysis was performed in order to observe possible links between the various parameters. The PCA was a powerful tool to discriminate impacted sites, suggesting that the mussels transplanted throughout the Venice lagoon were subjected to different levels of oxidative pressure. Furthermore, it provided an easy and useful tool to summarize the obtained results. 相似文献
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Figueroa FL Korbee N Abdala R Jerez CG López-de la Torre M Güenaga L Larrubia MA Gómez-Pinchetti JL 《Marine pollution bulletin》2012,64(2):310-318
The biofiltration capacity, biomass-yield and accumulation of N- and C-compounds of Hydropuntia cornea were analyzed. Algae were grown in different conditions for 28 d: outdoor and indoor, with or without fishpond effluents. N-uptake efficiency of these effluents was higher than 95% after 7 d both outdoors and indoors. N-enriched conditions reduced the extent of photoinhibition and increased the maximal quantum yield in H. cornea. The biomass-yield was higher in outdoor grown-algae after 7 d and decreased independently of the treatment after 28 d. N, acid polysaccharide (AP) and mycosporine-like amino acid (MAA)-yields decreased throughout the experiment in all conditions. The highest MAA-yield was observed in fishpond effluent outdoor-grown algae, indicating a positive effect of increased radiation on MAA accumulation. However, APs were higher under N-depleted conditions. The use of MAAs as UV-screening and antioxidants, and the use of AP as immunostimulants are discussed. 相似文献
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I. A. Ansari 《洁净——土壤、空气、水》1987,15(2):175-178
This paper deals with the toxicity of sodium nitrite to freshwater fishes, Channa punctatus (BL.) and Mystus (M). vittatus (Bl.) as to determine the acute toxicity. The LC 50 values were obtained by using a static bioassay method for a period of 24, 48, 72 and 96 hour intervals. The LC 50 values of sodium nitrite for C. punctatus were 375, 325, 250 and 200 ppm and for M. (M). vittatus 164, 140, 90 and 64 ppm, respectively. A profuse mucus secretion was evident at higher concentrations as compared to lower ones. The probable causes of mortality of the fishes are also discussed. 相似文献
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Carrick M. Eggleston 《Aquatic Sciences - Research Across Boundaries》1993,55(4):240-249
Scanning tunneling microscopy (STM) is used to observe, at the atomic scale, Cr(III) adsorbed to hematite (001) surfaces from aqueous solution. The Cr(III) adsorbates are relatively immobile, but estimated activation energies for surface self-diffusion are lower than those for water or hydroxyl substitution in aqueous Cr(III). Possible causes are effects of STM imaging (artifacts), high ligand-substitution rates for adsorbed species, or participation of substrate Fe (III) ligand exchange. STM imaging of suitable aqueous surface complexes is shown to be feasible, and constitutes a new way to study the relationships between microscopic and macroscopic chemical behavior of adsorbed species in aqueous systems. 相似文献
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F. Bella P. F. Biagi M. Caputo G. Della Monica A. Ermini P. V. Manjgaladze V. Sgrigna D. O. Zilpimiani 《Pure and Applied Geophysics》1995,144(2):277-300
Daily averaged tilt component data from two sites of the Central Apennines (Italy) and of the Southern Caucasus (Georgia), respectively, revealed intermediate-term tilts as possible precursors to earthquakes (M=3.0÷4.7) which occurred in the above-mentioned seismic areas within a distance of 50 km from the sites. A good temporal correlation as well as a fair spatial correspondence between these residual tilts (with amplitude and duration of some microradians and months, respectively) and main shocks were pointed out, by removing both secular trends and seasonal thermoelastic effects from the raw tilts. An attempt was made to justify the above-mentioned results, based on the assumption that the observed intermediate-term preseismic tilts are the manifestation of aseismic creep episodes of comparable duration in the fault materials of thrust faults close to the tilt sites. The mechanism refers to a strain field slowly propagating from the preparation focal area to the tilt site, through crustal blocks separated by weak transition zones. This propagation is thought to be the cause of the local aseismic fault slip recorded by the tiltmeters. Previously, both discrete structures and strain propagation effects were revealed in the Central Apennines and are thought also to exist in the Southern Caucasus. As in the past, the rheological properties of fault materials are revealed as viscoelastic ones. In fact, creep equations obtained by applying several viscoelastic models on our data, proved to fit quite well some of the observed tilt precursors, producing viscosity and rigidity values very similar to those reported in literature.Professor Petr Viktorovich Manjgaladze died during the writing of this paper 相似文献