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1.
Sea mullet (Mugil cephalus) were exposed to aqueous suspensions of tech-DDT in seawater, salinity 29.5±0.5‰. The 48 h LC50 calculated from these static bioassays ranged from 0.042 to 0.056 mg l.?1 DDT. Median survival times were then estimated at 15, 20, 25 and 30°C using the upper level of the 48 h LC50 range of concentrations, i.e. 0.056 mg l.?1. Results indicated that an increase in temperature produced a decrease in toxicity. However, 25°C was the only temperature at which the increase in survival time was statistically significant. Size differences within experimental fish did not contribute to MST.  相似文献   

2.
Competition and predation are the two major biotic interactions in zooplankton community. Various rotifer species exhibit polymorphism in lorica and spine morphology in the presence of predators and competitors, which effectively increases their defence competition capacity. This study compared life-history parameters between long-spined morph (LSM) and short-spined morph (SSM) of Keratella tropica at three temperatures. The results showed that both morphs showed significantly higher intrinsic rate of population increase at 25 °C than those at 20 °C and 30 °C. The intrinsic rate of population increase was significantly lower in LSM than SSM at 25 °C and 30 °C, and the net reproductive rate was significantly lower in LSM than SSM at 30 °C. These results suggested that K. tropica had cost on development of long spines, which, however, was dependent on temperature. Moreover, the competition outcome of LSM and SSM with Moina macrocopa were investigated at three densities of Scenedesmus obliquus (0.5 × 106, 1.0 × 106 and 2.0 × 106 cells/mL) and three initial densities of M. macrocopa (0.1, 0.3 and 0.9 ind./mL), revealing that both LSM and SSM populations decreased significantly at all tested algal densities and Moina levels. LSM showed higher population growth rate than SSM at lower algal density (0.5 × 106 cells/mL) and higher Moina densities (0.3 and 0.9 ind./mL), which suggested that LSM could be more effective to defend M. macrocopa. Three-way analysis of variance showed no significant effects of algal density on population growth rate of K. tropica, but interaction between algal density and M. macrocopa density significantly affected its population growth rate.  相似文献   

3.
《Marine pollution bulletin》2012,64(5-12):572-577
Samples of two seawater farmed fish (crimson snapper (Lutjanus erythopterus) and snubnose pompano (Trachinotus blochii)), water, air, sediment, fish feed, macroalgae and phytoplankton were collected from two estuarine bays (Daya Bay and Hailing Bay) in South China. The concentrations of persistent halogenated compounds (PHCs) including polybrominated diphenyl ethers (PBDEs), organochlorine pesticides and polychlorinated biphenyls (PCBs) varied widely with the different sample matrices under investigation. The compositional patterns in fish, fish feed, macroalgae and phytoplankton, as well as the good correlations between the abundances of p,p′-DDT and BDE-209 and their metabolites (i.e., p,p′-DDD and p,p′-DDE for p,p′-DDT and BDE-47 for BDE-209) in fish indicated the occurrence of DDT and PBDE biotransformation in fish body. Finally, the marine aquaculture environment in South China is somewhat biologically impaired by DDT-contaminated water, sediment and fish feed, and there may be some cancer risk associated with fish consumption for humans, especially for urban residents.  相似文献   

4.
Sweden     
Four invertebrate and one fish species (Cerastoderma edule, Mya arenaria, Arenicola marina, Crangon crangon, Solea solea) from a single area of the German Wadden sea were investigated for concentrations of ten organochlorine pollutants in 1976. PCB concentrations (wet tissue basis) were predominating with 10–200 ng g?1, while p,p′-DDD, dieldrin, α-HCH, γ-HCH and p,p′-DDE generally ranged between 1 and 10 ng g?1. Values of α-endosulfan were even lower; p,p′-DDT, endrin and heptachlor epoxide could not be detected. Residue levels in shrimps were close to the lower range of values which have been found in this species from other areas of the North Sea since 1974. The patterns of residue concentrations in the five aquatic species were remarkably different indicating species- and compound-specific bioaccumulation. Trophic level and lipid content were shown to be responsible for PCB concentrations increasing from bivalves to fish.  相似文献   

5.
The State of São Paulo is the most developed area in Brazil and was impacted by persistent organic pollutants for several decades. This study investigated organochlorines in five species of small cetaceans (Pontoporia blainvillei, Stenella frontalis, Sotalia guianensis, Tursiops truncatus and Steno bredanensis) found dead along the coast of São Paulo between 1997 and 2003. DDTs (15.9 μg g−1 lipid; mean for all pooled individuals) and PCBs (8.08 μg g−1) exhibited the highest concentrations in the animals, reflecting large amounts formerly used in Brazil. Lower levels of mirex (0.149 μg g−1), HCB (0.051 μg g−1), CHLs (0.008 μg g−1) and HCHs (0.007 μg g−1) were detected in all species. Residual pattern of DDTs in dolphins suggests that o,p′-DDT is more recalcitrant than p,p′-DDT in the body of the animals and/or the environment. In contrast to p,p′-DDT, residues of o,p′-DDT seem to be preferentially converted into o,p′-DDD rather than o,p′-DDE.  相似文献   

6.
An apparatus designed to determine the complex shear modulus of rock samples by forced torsion oscillations at high temperature and in the seismic frequency band 0.003–30 Hz is briefly described. Measurements were performed on natural dunite from Åheim (Norway) up to 1400°C and on polycrystalline forsterite up to 1500°C at 1 atm pressure. The two materials were chosen to study, by comparison, the effect of melt on the elasticity and anelasticity of mantle rocks.Between 1000 and 1200°C the absolute values of the shear modulus G are almost equal for both materials. Above 1200°C G for natural dunite decreases progressively with temperature and at 1400°C and 1 Hz reaches ～13 of its value at 1100°C. In contrast, G of pure forsterite depends little on temperature. For petrological reasons, supported by simultaneous measurements of the electric resistivity, there is strong evidence that the decrease of G in dunite above 1200°C is due to melt from the lower melting components of the dunite. Based on different models estimates of the melt fraction are made.At high temperature, in both materials Q?1 is characterized by a monotonic decrease with frequency according to ω?α, with α ≈ 0.25. An apparent activation energy of 38±5 kcal mol?1 for forsterite and 48±8 kcal mol?1 for dunite was found with no significant change in the regime of partial melting. From this it is concluded that Q?1, even at partial melting, is dominated by solid state high temperature background absorption. There is no indication from these experiments for a constant-Q-band at low seismic frequencies or an increase of Q proportional to frequency as suggested by some seismologists. The present results are in good qualitative agreement with those for Young's modulus obtained previously by strain retardation experiments.  相似文献   

7.
The levels of phthalate ester plasticizers, DDT, DDE and polychlorinated biphenyls (PCBs) were determined in the tissues of 18 species of marine organisms from the northwestern Gulf of Mexico. Low levels of the most widely used phthalate, di-(2-ethylhexyl) phthalate, were found in the majority of the samples; no other phthalates were detected. DDT, DDE and PCBs were found in all samples, but at somewhat lower levels than those found in our 1971 survey. A decrease in p,p′-DDT/p,p′-DDE ratios relative to 1971 was also noted.  相似文献   

8.
To be used as proxies of seawater surface temperature(SST), the δ 18Oc values and Sr/Ca and Mg/Ca ratios of scleractinian coral skeletons must be verified by coral culture experiments in the laboratory. This paper describes a coral culture experiment that was conducted at several seawater temperatures T(21–28°C) using a tandem aquarium system and the new method for depositing coral skeletons grown under controlled conditions. The δ 18Oc values and the Sr/Ca and Mg/Ca ratios of the cultured coral were measured. We concluded that the δ 18Oc values and Sr/Ca and Mg/Ca ratios of the cultured coral are clearly correlated with T. The linear regression curve is δ18Oc(‰)=δ0.1427δT(°C)δ0.1495(n=18, r=0.955, p0.0001), and the slope of δ0.1427‰/°C is at the low end of the range of published values(δ0.13–δ0.29‰/°C). The Sr/Ca ratio decreases with increasing T, whereas the Mg/Ca ratio increases with increasing T, indicating a negative correlation between Sr/Ca and Mg/Ca. Their linear regression curves are Sr/Ca(mmol/mol)=δ0.04156δT+10.59(n=15, r=0.789, p0.005) and Mg/Ca(mmol/mol)= 0.04974δT+2.339(n=17, r=0.457, p0.05), respectively, which demonstrate that when Mg/Ca and Sr/Ca are increased by one unit, T increases by 5.19°C and decreases by 15.62°C, respectively. These variations are significantly lower than published values.  相似文献   

9.
— We have evaluated how the parameters prescribing the slip-dependent constitutive law are affected by temperature and effective normal stress, by conducting the triaxial fracture experiments on Tsukuba-granite samples in seismogenic environments, which correspond to a depth range to 15 km. The normalized critical slip displacement D c almost remains constant below 300oC (insensitive to both temperature and effective normal stress σ n eff); D c increases with increasing temperature above 300 °C, and the rate of D c increase with temperature tends to be largest at higher σ n eff. The breakdown stress drop Δτ b for the granite at constant σ n eff is roughly 80 MPa below 300 °C, and does not depend on σ n eff. Above 300 °C, Δτ b decreases gradually with increasing temperature, and the rate of Δτ b reduction with temperature increases at higher σ n eff. The peak shear strength τ p increases nearly linearly with increasing σ n eff below 300 °C. However, τ p becomes lower above 300 °C, deviating from the linear relation extrapolated from below 300 °C. This is consistent with the onset of crystal plastic deformation mechanisms of Tsukuba granite.  相似文献   

10.
Activated carbons prepared from sunflower seed hull have been used as adsorbents for the removal of acid blue 15 (AB‐15) from aqueous solution. Batch adsorption techniques were performed to evaluate the influences of various experimental parameters, e. g., temperature, adsorbent dosage, pH, initial dye concentration and contact time on the adsorption process. The optimum conditions for AB‐15 removal were found to be pH = 3, adsorbent dosage = 3 g/L and equilibrium time = 4 h at 30°C. The adsorption of AB‐15 onto the adsorbent was found to increase with increasing dosage. It was found from experimental results that the Langmuir isotherm fits the data better than the Freundlich and Temkin isotherms. The maximum adsorption capacity, Qm (at 30°C) was calculated for SF1, SF2, and SF3 as 75, 125 and 110 mg g–1 of adsorbent, respectively. It was found that the adsorption follows pseudo‐second order kinetics. The thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were also evaluated. The activated carbons prepared were characterized by FT‐IR, SEM and BET analysis.  相似文献   

11.
Zusammenfassung In der vorliegenden Arbeit wird die Fermentation der organischen Stoffe des Kl?rschlammes vom kinetischen Standpunkt untersucht. Für die Faulgasproduktion ist die T?tigkeit der Methanbakterien entscheidend. Bei der ?batch?-Fermentation des Kl?rschlammes mit Trockensubstanzgehalt von 5% wurde die maximale Wachstumsrate der Methanbakterien für die folgenden Inkubationstemperaturen bestimmt: für 20°C 0,02 Tage−1, für 30°C 0,09 Tage−1, für 50°C 0,17 Tage−. Im semikontinuierlichen Prozess wurde der spezifische Wirkungsgrad als Quotient der aus 1 Liter Faulraum produzierten Faulgasmenge (im ml) zum Inhalt der organischen Stoffe im Rohschlamm (in g/l) ausgedrückt. Die Abh?ngigkeit des spezifischen Wirkungsgrades von der Raumbelastung für Temperaturen von 20°C, 30°C und 50°C wurde graphisch dargestellt. Die Verdünnungsrate, bei der die maximalen Werte des spezifischen Wirkungsgrades erreicht wurden, sind für 20°C 0,12 Tage−1, für 30°C 0,21 Tage−1 und für 50°C 0,28 Tage−1. Entsprechende Werte des spezifischen Wirkungsgrades waren der Reihe nach: 20 ml/g pro Tag, 63 ml/g pro Tag und 100 ml/g pro Tag. Die minimale Generatinsdauer der Methanbakterin betr?gt für 20°C 3,1 Tage, für 30°C und 50°C weniger als 2,5 Tage. Aus dem Vergleich des ein- und zwistufigem Betriebs geht hervor, dass bei einer l?nger als 10 Tage w?hrenden Aufenthaltsdauer der spezifische Wirkungsgrad der beiden Systeme identisch ist, bei kürzerer Aufenthaltsdauer leistet jedoch der einstufige Betrieb mehr.
Summary The purpose of this study is to estimate the fermentation of the organic matter in sewage sludge from the point of view of kinetics. The activity of methane bacteria seems to be essential for the sludge gas production. In the batch fermentation of sludge containing about 5% of dry solids, the maximal growth rate for methane bacteria at given incubation temperatures was found to be: at 20°C 0,02 days−1, at 30°C 0,09 days−1, and at 50 °C 0,17 days−1. For the semi-continous process, the specific efficiency of the fermentation system was expressed as the relation between the quantity (in ml) of sludge gas produced daily in a one liter digestion area and the volatile solids content in raw sludge (in g/l). The dependence of the specific efficiency upon the volume load at temperatures of 20°C, 30°C, and 50°C was determined graphically. The dilution rate for maximal values of the unit efficiency attained was at 20°C 0,12 days−1, at 30°C 0,21 days−1, and at 50°C 0,28 days−1, corresponding maximal values of specific efficiency were 20 ml/g per day, 63 ml/g per day and 100 ml/g per day. Minimal generation time of methane bacteria is at 20°C 3,1 days, at 30°C and at 50°C less than 2,5 days. Comparison betwen single stage and two-stage operations, with detention periods of more than 10 days, shows that the specific efficiency is very much the same in both systems. However, at shorter detention periods and with the same digestion capacity, the single stage operation is more efficient.
  相似文献   

12.
We present the main seismological results of our study of the Campania-Lucania earthquake of 23 November 1980. A complete set of far field and local data has been analysed. From long-period body waves data we determine the fault plane solution (φ1 = 140°,δ1 = 60°,φ2 = 75°,δ2 = 54°), a depth of 15 km and calculate a seismic moment of 6 × 1025 dyne cm and a source duration of 6 s. From data of a local network deployed immediately after the event we determine aftershock locations: they are aligned in a direction NW-SE that fit extremely well with the focal solution determined above. We can choose as fault plane the plane striking 140° and dipping at 60° and the event is a normal event with a large component of left-lateral strike slip. The source area evaluated from this aftershock distribution 14 km × 40 km is quite suitable for an earthquake of a seismic moment of 6 × 1025 dyne cm.  相似文献   

13.
Respiration rates (mg O2 g?1 AFDW h?1) of Leuctra hippopus, Sericostoma personatum, Helodes minuta, Gammarus pulex and Asellus aquaticus were studied across an oxygen gradient at 2.8 and 6.3 °C, corresponding to an expected 3.5 °C increase in Danish winter stream temperature. Species were selected from the Danish Stream Fauna Index (DSFI), representing an expected hierarchy of tolerance towards water quality degradation. We expected that low-ranking, tolerant species (i.e. indicators of bad water quality) would have the capacity to regulate their oxygen uptake relatively independently of oxygen availability (oxy-regulators) and high-ranking, sensitive species (i.e. indicators of good water quality) would be less able to do so (oxy-conformers). For all species respiration rate was higher (although non-significantly) at 6.3 °C. The species’ oxy-regulatory capacity did not consistently reflect their DSFI ranking. As expected, and in accordance with its DSFI ranking, A. aquaticus had the highest oxy-regulatory capacity with the ability to regulate O2 uptake until an oxygen saturation of only 20%, which did not change with increasing temperature, emphasizing the robustness of A. aquaticus towards changes in the environment. S. personatum, H. minuta and G. pulex revealed no oxy-regulatory capacity. In contrast, the plecopteran L. hippopus did display an unexpected oxy-regulatory capacity. Though an increase in temperature changed L. hippopus’ capacity to oxy-regulate (the critical limit increased from 32.5 to 43.5% oxygen), respiration rates did not change significantly in spite of the temperature increase. This result contradicts the general belief that stoneflies, because of their affinity to well oxygenated habitats, are conformers. Our findings call for further studies on the respiratory conformer–regulator concept and its role as an eco-physiological trait for bio-assessment.  相似文献   

14.
The apparent equilibrium constant, K 1 ′ , for the first acidity constant of carbonic acid has been determined in a lake water of 1.6 mM ionic strength in the temperature interval 4–18°C. The experimental method used comprises pH measurements in situ (NBS scale) with a probe and an IR-method for the selective determination of [H2CO3] and [HCO 3 ? ] in water samples. In the temperature interval studied the results can be described by the equation logK 1 ′ =126.39?6320.81/T?19.5682 ln T and are in agreement with the values of K 1 ′ obtained by the empirical equation presented by Millero [15]. This experimental agreement justifies thermodynamic calculations in the carbonate system based on field data. Also the experimental method described can be used to evaluate the acid-base balance of organic rich natural waters.  相似文献   

15.
Reviewing 92 measurements of lunar sample dielectric constant versus density at frequencies above 100 kHz, gives the relationK′ = (1.93 ± 0.17)p by regression analysis, where K′ is the dielectric constant of a soil or solid at a density ofpg/cm3. This formula is the geometric mean between the dielectric constant of vacuum (1) and the zero porosity dielectric constant of lunar material. Similarly, the loss tangent (D) can be described byD = [(0.00053 ± 0.00056) + (0.00025 ± 0.00009)C]p whereD is the loss tangent at densitypg/cm3 withC percent of total FeO + TiO2 (approximately proportional to ilmenite content). Using the density versus depth relations derived from lunar surface core tubes, and from laboratory studies of lunar soil compression gives a model of the dielectric properties as a function of depth in the lunar regolith. The dielectric constant increases smoothly with depth, as a function of the soil compaction only. The loss tangent, however, is more sensitive to the ilmenite content than it is to density. Neither dielectric constant nor loss tangent varies significantly with the temperature observed in a lunar day.  相似文献   

16.
Hydrothermal experiments in the temperature range 750–1020°C have defined the saturation behavior of zircon in crustal anatectic melts as a function of both temperature and composition. The results provide a model of zircon solubility given by: In DZrzircon/melt= ?3.80?[0.85(M?1)]+12900/T where DZrzircon/melt is the concentration ratio of Zr in the stoichiometric zircon to that in the melt, T is the absolute temperature, and M is the cation ratio (Na + K + 2Ca)/(Al · Si). This solubility model is based principally upon experiments at 860°, 930°, and 1020°C, but has also been confirmed at temperatures up to 1500°C for M = 1.3. The lowest temperature experiments (750° and 800°C) yielded relatively imprecise, low solubilities, but the measured values (with assigned errors) are nevertheless in agreement with the predictions of the model.For M = 1.3 (a normal peraluminous granite), these results predict zircon solubilities ranging from ～ 100 ppm dissolved Zr at 750°C to 1330 ppm at 1020°C. Thus, in view of the substantial range of bulk Zr concentrations observed in crustal granitoids (～ 50–350 ppm), it is clear that anatectic magmas can show contrasting behavior toward zircon in the source rock. Those melts containing insufficient Zr for saturation in zircon during melting can have achieved that condition only by consuming all zircon in the source. On the other hand, melts with higher Zr contents (appropriate to saturation in zircon) must be regarded as incapable of dissolving additional zircon, whether it be located in the residual rocks or as crystals entrained in the departing melt fraction. This latter possibility is particularly interesting, inasmuch as the inability of a melt to consume zircon means that critical geochemical “indicators” contained in the undissolved zircon (e.g. heavy rare earths, Hf, U, Th, and radiogenic Pb) can equilibrate with the contacting melt only by solid-state diffusion, which may be slow relative to the time scale of the melting event.  相似文献   

17.
Relaxation experiments on vitreous SiO2, densified at 900°C, 20 kbar to a permanent density of 2.36 g cm?3 yield an activation energy of69 ± 5kcal mol?1 in the temperature range 700–800°C. The data can be used to estimate minimum cooling rates, maximum depositional temperatures or maximum thicknesses of shock-metamorphosed rocks containing diaplectic glasses, if relaxation of a glass densified under dynamic conditions is assumed to be similar to that of statically densified glass.  相似文献   

18.
Radiogenic Ar diffusion from phlogopite mica has been measured at 900° and 1080°C at 15 kbars pressure, using a Griggs-type hot creep tester operated at hydrostatic pressure, and followed by standard mass spectrometric analysis. The diffusion coefficients fall within the uncertainty of the diffusion results reported by Giletti (1974) at 1 kbar at 900° and on extrapolation of that Arrhenius plot to 1080°C. That linear plot is given by D0 = 0.75 and Q = 57.9kcal/g-atom Ar. In the observed temperature range, the effect of pressure up to 15 kbars is not significant. A second Ar diffusion, which employed Ca(OH)2-CaO as a water buffer, was run at 1 atm H2O pressure and 550°C for 781 days. The resulting diffusion coefficient agrees, within the uncertainty, with the extrapolation of the earlier curve. This result, and both earlier ones at 600°, are similar in that they fall below the curve. Consequently, despite the agreement within the uncertainty, it is possible that diffusion of Ar from phlogopite below 650°C is somewhat slower than given by the above equation parameters.  相似文献   

19.
A dielectric model for thawed and frozen Arctic organic-rich soil (50% organic matter) has been developed. The model is based on soil dielectric measurements that were collected over ranges of gravimetric moisture from 0.03 to 0.55 g/g, dry soil density from 0.72 to 0.87 g/cm3, and temperature from 25 to −30 °C (cooling run) in the frequency range of 0.05–15 GHz. The refractive mixing dielectric model was applied with the Debye multi-relaxation equations to fit the measurements of the soil’s complex dielectric constant as a function of soil moisture and wave frequency. The spectroscopic parameters of the dielectric relaxations for the bound, transient bound, and unbound soil water components were derived and were complimented by the thermodynamic parameters to obtain a complete set of parameters for the proposed temperature-dependent multi-relaxation spectroscopic dielectric model for moist soils. To calculate the complex dielectric constant of the soil, the following input variables must be assigned: (1) density of dry soil, (2) gravimetric moisture, (3) wave frequency, and (4) temperature. The error of the dielectric model was evaluated and yielded RMSEε′ values of 0.348 and 0.188 for the soil dielectric constant and the loss factor, respectively. These values are on the order of the dielectric measurement error itself. The proposed dielectric model can be applied in active and passive microwave remote sensing techniques to develop algorithms for retrieving the soil moisture and the freeze/thaw state of organic-rich topsoil in the Arctic regions.  相似文献   

20.
Ultrasonic compressional wave velocity Vp and quality factor Qp have been measured in alkali basalt, olivine basalt and basic andesite melts in the frequency range of 3.4–22 MHz and in the temperature range of 1100–1400°C. Velocity and attenuation of the melts depend on frequency and temperature, showing that there are relaxation mechanisms in the melts. Complex moduli are calculated from the ultrasonic data. The results fit well a complex modulus of Arrhenius temperature dependence with log-normal Gaussian distribution in relaxation times of attenuation. The analysis yields average relaxation time, its activation energy, relaxed modulus, unrelaxed modulus and width of Gaussian distribution in relaxation times. Relaxed modulus is smaller (17.5 GPa) for basic andesite melt of high silica and high alumina contents than for the other two basalt melts (18.1–18.4 GPa). The most probable relaxation times decrease from ～ 3 × 10?10 s for basic andesite to ～ 10?11 s for alkali basalt at 1400°C. Activation energies of attenuation, ranging from 270 to 340 kJ mol?1 in the three melts, are highest in basic andesite. Longitudinal viscosity values and their temperature dependences are also calculated from Vp and Qp data. The volume viscosity values are estimated from the data using the shear viscosity values. Longitudinal, volume and shear viscosities and their activation energies are highest in the basic andesite melt of the most polymerized structure.  相似文献   

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