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1.
Flow cytometry was used to examine immune responses in haemocytes of the green-lipped mussel Perna viridis under six combinations of oxygen level (1.5 mg O2 l(-1), 6.0 mg O2 l(-1)) and temperature (20 °C, 25 °C and 30 °C) at 24 h, 48 h, 96 h and 168 h. The mussels were then transferred to normoxic condition (6.0 mg O2 l(-1)) at 20 °C for further 24 h to study their recovery from the combined hypoxic and temperature stress. Esterase (Est), reactive oxygen species (ROS), lysosome content (Lyso) and phagocytosis (Pha) were reduced at high temperatures, whereas hypoxia resulted in higher haemocyte mortality (HM) and reduced phagocytosis. For HM and Pha, changes were observed after being exposed to the stresses for 96 h, whereas only a 24 h period was required for ROS and Lyso, and a 48 h one for Est. Recovery from the stresses was observed for HM and Pha but not other immune responses.  相似文献   

2.
《Marine pollution bulletin》2009,58(6-12):280-286
The effects of prolonged exposure to reduced oxygen levels (3.0 and 1.5 mg O2 l−1) on marine scavenging gastropods Nassarius festivus were studied for 8 weeks. The percentages of individuals engaged in feeding and amount of food consumed were reduced as oxygen level decreased; absorption efficiency, however, did not vary significantly with oxygen level. Oxygen consumption rates and specific oxygen consumption rates were lower at reduced oxygen levels. Reproduction occurred at all oxygen levels with less egg capsules being produced at lower oxygen levels. Egg size and number of eggs per capsule, however, were not significantly affected by oxygen level. The increase in shell length was 12%, 6% and 5% at 6.0 mg O2 l−1 (normoxia), 3.0 mg O2 l−1 and 1.5 mg O2 l−1, respectively. At the end of the experiment, the amount of energy allocated to growth and reproduction decreased at reduced oxygen levels with values obtained at 3.0 mg O2 l−1 and 1.5 mg O2 l−1 being 48% and 70% lower than those at 6.0 mg O2 l−1. At all oxygen levels, most of the accumulated energy was allocated to shell growth and reproduction, and the amount allocated to somatic growth was relatively insignificant. The reduction in energy allocated to reproduction was greater than that to shell growth as the oxygen level was reduced, indicating a strategic energy allocation of marine scavengers under stressful conditions to enhance survival.  相似文献   

3.
《Marine pollution bulletin》2012,64(5-12):230-236
The effects of hypoxia on the larvae of two sub-tidal nassariid gastropods, Nassarius siquijorensis and N. conoidalis were compared so as to understand how the species-specific tolerance to hypoxia might have resulted in changes in the abundance and distribution of these two species in the hypoxic Tolo Harbour, Hong Kong, since the 1980s. Respiration rates of N. siquijorensis and N. conoidalis larvae were reduced at 4.5 mg O2 l−1, or below, as compared with the normoxic control. Significant reduction in swimming velocity was also observed for 10-day old larvae which were exposed to <2.0 mg O2 l−1 for N. siquijorensis and <1.0 mg O2 l−1 for N. conoidalis. The 48 h LC50 values of N. siquijorensis and N. conoidalis larvae were 0.7 and 1.7 mg O2 l−1, respectively. The results suggested that N. siquijorensis are more tolerant to hypoxia than N. conoidalis.  相似文献   

4.
Landfill leachates that contain persistent organic pollutants (POPs) are a big threat to groundwater systems and are projected to have hazardous effects in the long term if proper management strategies of the landfills are not put in place by those responsible. Monitoring the levels of POPs in landfill leachates is very crucial. This work presents an amperometric biosensor for determination of selected POPs in landfill leachates. The biosensor is based on kinetic inhibition of horseradish peroxidase (HRP). The enzyme was immobilised by electrostatic attachment on a polyaniline-modified Pt electrode surface. Selected POPs inhibited HRP enzyme activity and the decrease in the enzyme activity was used to determine these environmental pollutants. Selected polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs) and polychlorinated biphenyls (PCBs) were the analytes of choice because they are commonly found in South Africa water systems. Limits of detection for the amperometric biosensor were established as 0.014, 0.018, 0.022, 0.016 and 0.019 μg l−1 for BDE-100, PBB-1, PCB-1, PCB-28 and PCB-101, respectively. The HRP biosensor system gave different linear ranges for; BDE-100 (0.424–25.8 μg l−1), PBB-1 (0.862–13.4 μg l−1), PCB-1 (0.930–18.1 μg l−1), PCB-28 (0.730–15.7 μg l−1) and PCB-101 (0.930–27.1 μg l−1). Inhibition studies on HRP biosensor response toward the reduction of H2O2 in the absence and presence of the selected POPs were carried out to investigate the inhibition kinetics and its mechanism. The results obtained indicated that the inhibition mechanism was competitive for PBDEs and non-competitive for biphenyls (PCBs and PBBs). The application of the biosensor was tested on wastewater samples obtained from landfill leachate for determination of selected POPs. The leachate samples were found to contain PCB-28 (0.28 ± 0.03 μg l−1) and PCB-101 (0.31 ± 0.02 μg l−1). The samples were also analysed by GC–MS as a cross-check method and the two sets of results were in close agreement.  相似文献   

5.
《Marine pollution bulletin》2012,64(5-12):255-261
Mussels were maintained for 4 weeks under different combinations of dissolved oxygen concentration (1.5, 3.0 and 6.0 mg O2 l−1) and salinity (15, 20, 25 and 30) in a 3 × 4 factorial design experiment. Clearance rate (CR), absorption efficiency (AE), respiration rate (RR) and scope for growth (SFG) decreased with decreasing salinity and dissolved oxygen concentration (DO), while excretion rate (ER) increased with decreasing salinity and increasing DO. The O:N ratio was <10 at salinities of 15 and 20, irrespective of DO levels. SFG was negative in most of the treatments, except for those under 6.0 mg O2 l−1 or at a salinity of 30 when DO was lower. The results may help explain the distribution pattern of Perna viridis in Hong Kong waters and provide guidelines for mussel culture site selection.  相似文献   

6.
Aluminum incorporation into the high pressure polymorph of TiO2 with the structure of α-PbO2 has been studied from 10 to 20 GPa and 1300 °C by XRD, high-resolution 27Al MAS-NMR and TEM. Al-doped α-PbO2 type TiO2 can be recovered at atmospheric pressure. Al2O3 solubility in α-PbO2 type TiO2 increases with increasing the synthesis pressure. The α-PbO2 type TiO2 polymorph is able to incorporate up to 35 wt.% Al2O3 at 13.6 GPa and 1300 °C, being the substitution of Ti4+ by Al3+ on normal octahedral sites the mechanism of solubility. The transition to the higher pressure TiO2 polymorph with the ZrO2 baddeleyite structure, Akaogiite, has not been observed in the quenched samples at room pressure. The microstructure of the recovered sample synthesized at 16 GPa and 1300 °C points to the existence of a non-quenchable aluminum titanium oxide phase at these conditions.  相似文献   

7.
Water-pollution problems worldwide have led to an acute shortage of clean and pure water for both domestic and human consumption. Various technologies and techniques are available for water treatment which includes the use of activated carbon. In this study activated carbons used for the removal of lead (II) ions from water samples were prepared from maize tassels (an agricultural waste residue) which were modified using physical and chemical activation. In the physical activation CO2 was used as the activating agent, while in chemical activation H3PO4 with an impregnation ratio ranging from 1 to 4 was employed. The maize tassel was pyrolysed at different temperatures ranging from 300 °C to 700 °C in an inert atmosphere for a period of 60 min and activated at 700 °C for 30 min. The effects of activation temperature, impregnation ratio and duration were examined. The resultant modified tassels were characterised by measuring their particle-size distribution, porosities, pore volume, and pore-size distribution using scanning electron microscopy (SEM). The activated carbon produced by chemical activation had the highest BET surface area ranging from 623 m2 g−1 to 1 262 m2 g−1. The surface chemistry characteristics of the modified tassels were determined by FT–IR spectroscopy and Boehm’s titration method. The experimental data proved that properties of activated carbon depend on final temperature of the process, impregnation ratio and duration of the treatment at final temperature. The adsorption studies showed that chemically prepared activated carbon performed better than physically prepared activated carbon.  相似文献   

8.
At the appropriate times, silica diffusion in clay is possibly the rate determining process for the dissolution of vitrified waste disposed of in a clay layer. For testing this hypothesis, combined glass dissolution/silica diffusion experiment are performed. SON68 glass coupons doped with the radioactive tracer 32Si are sandwiched between two cores of humid Boom Clay, heated to 30 °C. Due to glass dissolution, 32Si is released and diffuses into the clay. At the end of an experiment, the mass loss of the glass coupon is measured and the clay core is sliced to determine the diffusion profile of the 32Si released from the glass in the clay.Both mass loss and the 32Si diffusion profile in the clay are described well by a model combining glass dissolution according to a linear rate law with silica diffusion in the clay. Fitting the experiments to this model leads to an apparent silica diffusion coefficient in the clay between 7 × 10−13 m2/s and 1.2 × 10−12 m2/s. Previously determined values from diffusion experiments at 25 °C are around 6 × 10−13 m2/s (In-Diffusion experiments) and 2 × 10−13 m2/s (percolation experiments). The maximal glass dissolution rate for glass next to clay is around 1.6 × 10−7 g glass/m2 s (i.e. 0.014 g glass/m2 day). In undisturbed clay, the measured silica concentration is around 5 mg/L. Combining these values with the previously measured (In-Diffusion experiments) product of accessible porosity and retardation factor, leads in two ways to a silica glass saturation concentration in clay between 8 and 10 mg Si/L.Another candidate for the rate determining process of the dissolution of vitrified waste disposed in a clay layer is silica precipitation. Although silica precipitation due to glass dissolution has been shown experimentally at 90 °C, extending the model with silica precipitation does not lead to much better fits, nor could meaningful values of a possible precipitation rate be obtained.  相似文献   

9.
Adsorption of Pb2+ from aqueous solution onto a sugarcane bagasse/multi-walled carbon nanotube (MWCNT) composite was investigated by using a series of batch adsorption experiments and compared with the metal uptake ability of sugarcane bagasse. The efficiency of the adsorption processes was studied experimentally at various pH values, contact times, adsorbent masses, temperatures and initial Pb2+ concentrations. A pH of 4.5 was found to be the optimum pH to obtain a maximum adsorption percentage in 120 min of equilibration time. The composite showed a much enhanced adsorption capacity for Pb2+ of 56.6 mg g−1 compared with 23.8 mg g−1 for bagasse at 28 °C. The Langmuir adsorption isotherm provided the best fit to the equilibrium adsorption data. The pseudo first-order, pseudo second-order, intraparticle diffusion and Elovich kinetics models were used to analyse the rate of lead adsorption and the results show that the Elovich model is more suitable. The thermodynamic parameters of adsorption, namely ΔG°, ΔH° and ΔS°, were determined over the temperature range of 20–45 °C. The adsorption of Pb2+ onto both bagasse and the sugarcane bagasse/MWCNT composite was found to be spontaneous but for the former adsorbent it was enthalpy-driven whereas for the latter it was entropy-driven. Desorption of the lead-loaded adsorbents was fairly efficient with 0.1 mol dm−3 HCl. Overall this composite has the potential to be a good adsorbent for the removal of Pb2+ from wastewaters.  相似文献   

10.
《Marine pollution bulletin》2009,58(6-12):867-872
Sediment sampled from Taichung Harbor was mixed with local reservoir sediment at different weight ratios to prepare lightweight aggregate at 1050, 1100, and 1150 °C. A pressure of 3000 or 5000 psi was used to shape the powder mixtures into pellets before the heating processes. The results indicate that the leaching levels of trace metals from the lightweight aggregate samples are considerably reduced to levels less than Taiwan Environmental Protection Administration regulatory limits. Increasing final process temperature tends to reduce the bulk density and crushing intensity of lightweight aggregate with a concomitant increase in water sorption capability. Lightweight aggregate with the lowest bulk density, 0.49 g cm−3 for the 5000 psi sample, was obtained with the heating process to 1150 °C. Based on the X-ray absorption near edge structure results, FeSO4 decomposition with a concomitant release of SOx (x = 2, 3) is suggested to play an important role for the bloating process in present study.  相似文献   

11.
Soda lakes and pans represent saline ecosystems with unique chemical composition, occurring on all continents. The purpose of this study was to identify and characterise the main environmental gradients and trophic state that prevail in the soda pans (n = 84) of the Carpathian Basin in Central Europe. Underwater light conditions, dissolved organic matter, phosphorus and chlorophyll a were investigated in 84 pans during 2009–2010. Besides, water temperature was measured hourly with an automatic sensor throughout one year in a selected pan. The pans were very shallow (median depth: 15 cm), and their extremely high turbidity (Secchi depth median: 3 cm, min: 0.5 cm) was caused by high concentrations of inorganic suspended solids (median: 0.4 g L−1, max: 16 g L−1), which was the dominant (>50%) contributing factor to the vertical attenuation coefficient in 67 pans (80%). All pans were polyhumic (median DOC: 47 mg L−1), and total phosphorus concentration was also extremely high (median: 2 mg L−1, max: 32 mg L−1). The daily water temperature maximum (44 °C) and fluctuation maximum (28 °C) were extremely high during summertime. The combination of environmental boundaries: shallowness, daily water temperature fluctuation, intermittent hydroperiod, high turbidity, polyhumic organic carbon concentration, high alkalinity and hypertrophy represent a unique extreme aquatic ecosystem.  相似文献   

12.
《Geofísica Internacional》2014,53(4):411-423
An investigation of the effect of some human activities on the magnetic susceptibility and frequency dependent susceptibility was conducted on top soil samples from, a commercial area, a motor park and a school environment in Jalingo, Taraba State, N-E Nigeria. The purpose was to assess the variation of magnetic susceptibility with different land use, detect pollution hotspots using magnetic proxy parameters and evaluate the contribution of superparamagnetic (SP) grain size contribution to the magnetic susceptibility from calculation of the frequency dependence of magnetic susceptibility (MS). The results of the mass specific low frequency magnetic susceptibility measurements showed significant enhancement with values ranging from 67.8 − 495.3 × 10−8 m3kg−1 with a mean value of 191.61 × 10−8 × m3kg−1 for the Jalingo College of Education (JCOE) data; 520.1 − 1612.8 × 10−8 m3kg−1 with a mean value of 901.34 × 10−8 m3kg−1 for the Jalingo main Market (JMM) and 188.5 − 1203.6 × 10−8m3kg−1 with an average value of 574 92 × 10−6 m3kg−1 for the Jalingo Motor Park (JMP). The significant magnetic enhancement indicates high concentration of ferrimagnetic minerals in the soil and hence increased pollution. The magnetic susceptibility of the different land use studied decreased in the order commercial area (market) > motor park > school premises. The results of the percentage frequency dependence susceptibility showed that most of the samples had a mixture of SP and coarse multi domain grains or SP grains < 0.05 µm. The value of χfd% range from 2.68 to 13.80% with an average value of 8.67% in the JCOE samples, 0.49 to 10.04% with an a-verage of 5.05% in the JMM samples and 0.56 to 13.04% with an average value of 5.86% in the JMP samples.  相似文献   

13.
《Marine pollution bulletin》2012,64(5-12):445-451
All four Chlorella species, including one commercially available species, Chlorella vulgaris and three local isolates, Chlorella sp. (1uoai), Chlorella sp. (2f5aia) and Chlorella miniata (WW1), had a rapid and high ability to remove nonylphenol (NP). Among these species, C. vulgaris had the highest NP removal (nearly all NP was removed from the medium) and degradation abilities (more than 80% of NP was degraded) after 168 h, followed by WW1 and 1uoai; 2f5aia had the lowest NP degradation ability. The NP removal by C. vulgaris was less affected by growth conditions, but its biodegradation efficiency was significantly increased by temperature and light intensity, suggesting that the biodegradation ability was positively related to photosynthetic and metabolic activities. These results indicated that C. vulgaris was the most suitable species for effective removal and biodegradation of NP, especially under 25 °C with light illumination and initial biomass between 0.5 and 1.0 mg chlorophyll l−1.  相似文献   

14.
We report observations of seasonal and local time variation of the averaged electron and iron concentrations, as well as simultaneous measurements of the two species, above the Arecibo Observatory (18.35°N, 66.75°N), Puerto Rico. The average Fe profile between 21:00 and 24:00 LT has a single peak at about 85 km with the exception of the summer when an additional peak exists at about 95 km. The higher Fe peak in the summer is correlated with higher electron concentrations in this season. The three nights of simultaneous measurements of electron and iron concentrations show that narrow layers of Fe and electrons are well correlated. Comparison of the climatological and simultaneous Fe and electron data suggests that recombination of Fe+ plays an important role in determining the Fe profile in the upper part of the Fe layer. Above 93 km, the Fe concentration appears to increase after sunset if the electron concentration exceeds about 4000 electrons cm−3. The average rate of Fe production is about 0.1 atom cm−3 s−1 for all seasons at 100 km in the early evening hours. A chemical model reveals that the concentration of Fe+ must be 50–80% of the total ionization over Arecibo for typical equinox conditions to explain the observed rate of Fe production. These high relative Fe+ concentrations are consistent with in situ observations that Fe+ is usually the dominant ion in sporadic E layers in the nighttime lower E region. This suggests that the source of Fe+ is provided by sporadic E layers descending over Arecibo after sunset. The Fe density between 80 and 85 km decreases during the night, for all seasons. This is attributed to the formation of stable molecular Fe species, such as FeOH, due to the increase in O3 and decrease in atomic O and H during the night at these altitudes.  相似文献   

15.
《Marine pollution bulletin》2013,76(1-2):133-139
Effective control of outbreaks of Acanthaster planci represents the most immediate and practical intervention to reverse sustained declines in coral cover on reefs in the Indo-Pacific. This study explored the minimum doses of oxbile, oxgall, and thiosulfate-citrate-bile-sucrose agar (TCBS) that result in reliable and comprehensive mortality when injected into adult A. planci. The minimum doses required to induce 100% mortality among starfish (n = 10) were 4 g l−1 of oxbile, 8 g l−1 of oxgall and 22 g l−1 of TCBS. Moreover, there was no evidence of unintended side effects for other coral reef organisms (e.g., scleractinian corals, echinoderms and fishes) when using oxbile, oxgall, or TCBS at minimum doses. The effectiveness of peptones in killing crown-of-thorns starfish was also tested, but inconsistency in the results revealed that these proteins are unreliable.  相似文献   

16.
《Continental Shelf Research》2007,27(10-11):1584-1599
Historic data from the Russian-American Hydrochemical Atlas of Arctic Ocean together with data from the TRANSDRIFT II 1994 and TUNDRA 1994 cruises have been used to assess the spatial and inter-annual variability of carbon and nutrient fluxes, as well as air–sea CO2 exchange in the Laptev and western East Siberian Seas during the summer season. Budget computations using summer data of dissolved inorganic phosphate (DIP), dissolved inorganic nitrogen (DIN) and dissolved inorganic carbon (DIC) gives that the Laptev Sea shelf is a net sink of DIP and DIN of 2.5×106, 23.2×106 mol d−1, respectively, while it is a net source of DIC (excluding air–sea exchange) of 1249×106 mol d−1. In the East Siberian Seas the budget computations give 0.5×106, −11.4×106 and −173×106 mol d−1 (minus being a sink) for DIP, DIN, and DIC, respectively. In summers, the Laptev Sea Shelf is net autotrophic while the East-Siberian Sea Shelf is net heterotrophic, and both systems are weak net denitrifying. The Laptev Sea Shelf takes up 2.1 mmol CO2 m−2 d−1 from atmosphere, whereas the western part of the East-Siberian Sea Shelf loose 0.3 mmol CO2 m−2 d−1 to the atmosphere. The variability of DIP, DIN and DIC fluxes during summer in the different regions of the Laptev and East Siberian Seas depends on bottom topography, river runoff, exchange with surrounding seas and wind field.  相似文献   

17.
The objective of this study was to explore the slope position and land use change effects on the variability in magnetic susceptibility and 137Cs inventory as the soil redistribution indicators in a hilly semiarid calcareous area in Iran. The selected study area is located in a hilly region with pasture and cultivation land use of Fereydunshahr, Isfahan Province in west-central Iran. In the two mentioned dominant ecosystems, four slope positions including summit, shoulder, backslope and footslope were identified and in each land use and slope position, three cores were selected to collect 72 soil samples from three depths (0–10, 10–20, 20–30 cm) in an area of 15 × 15 cm. Additional 28 soil samples were collected from the reference site for soil loss and deposition calculations by using the Cs-137 measurement. The results of the study with the use of the Cs-137 technique showed that the average soil loss in the pasture land (46.4 t ha− 1 yr− 1) was significantly (p < 0.05) lower than the average soil loss in the cultivated land (80.4 t ha− 1 yr− 1). The highest soil loss in both land uses was obtained in the shoulder position, 60.1 and 84.4 t ha− 1 yr− 1, respectively, for the pasture and cultivated lands. Moreover, the highest rates of soil deposition was observed in a footslope position in both land uses and they were 34 and 32.4 t ha− 1 yr− 1 for the pasture and cultivated lands, respectively. Magnetic susceptibility was significantly (p < 0.05) greater in pasture (χlf = 41.51 × 10− 8 m3/kg) than in the cultivated land (χlf = 34.90 × 10− 8 m3/kg). The pasture land with a lower soil loss rate, indicated significantly higher magnetic susceptibility in all landform positions as compared to that in the cultivated land. The results of the correlation analysis showed that among the studied soil physico-chemical properties, χlf (r = 0.83, p < 0.01) in the pasture land had the highest correlation with the Cs-137 inventory. Throughout the non-linear regression analysis, χlf was introduced for relating soil parameters and the cesium inventory explained 68% and 79% of the total variability of 137Cs in the pasture and cultivated lands, respectively. The results implied that the variability in the magnetic susceptibility within the hillslope is consistent with the variation of the Cs-inventory; and the results thus demonstrate the slope and land use effects on soil redistribution.  相似文献   

18.
High-pressure phase relations in the system NaAl3Si3O11–CaAl4Si2O11 were examined at 13–23 GPa and 1600–1900 °C, using a multianvil apparatus. A Ca-aluminosilicate with CaAl4Si2O11 composition, designated CAS phase, is stable above about 13 GPa at 1600 °C. In the system NaAl3Si3O11–CaAl4Si2O11, the CAS phase dissolving NaAl3Si3O11 component coexists with jadeite, corundum and stishovite below 22 GPa, above which the CAS phase coexists with Na-rich calcium ferrite, corundum and stishovite. At 1600 °C, the solubility of NaAl3Si3O11 component in the CAS solid solution increases with increasing pressure up to about 50 mol% at about 22 GPa, above which the solubility decreases with pressure. The maximum solubility of NaAl3Si3O11 component in the CAS phase increases with temperature up to around 70 mol% at 1900 °C at 22 GPa. The dissociation of NaAlSi2O6 jadeite to NaAlSiO4 calcium ferrite plus stishovite occurs at about 22 GPa. Lattice parameters of the CAS phase with the hexagonal Ba-ferrite structure change with increase of the NaAl3Si3O11 component: a-axis decreases and c-axis slightly increases, resulting in decrease of molar volume. Enthalpies of the CAS solid solutions were measured by high-temperature drop-solution calorimetry techniques. The results show that enthalpy of hypothetical NaAl3Si3O11 CAS phase is much higher than the mixture of NaAlSi2O6 jadeite, corundum and stishovite and is close to that of the mixture of NaAlSiO4 calcium ferrite, corundum and stishovite. When we adopt the Na:Ca ratio of 75:25 of the natural Na-rich CAS phase in a shocked Martian meteorite, Zagami, the phase relations determined above suggest that the natural CAS phase crystallized from melt at pressure around 22 GPa and temperature close to or higher than 2000–2200 °C. The inferred P, T conditions are consistent with those estimated using other high-pressure minerals in the shocked meteorite.  相似文献   

19.
Diamond bearing kimberlite pipes are exposed across the north-central part of the Siberian platform. Three main time intervals are considered to be the age of emplacement: the Devonian–Early Carboniferous, Triassic, and Cretaceous. However, isotopic age data from of the pipes are scattered and provide a very broad age interval for the magmatic activity. New paleomagnetic poles from four kimberlite pipes (Eastern Udachnaya, Western Udachnaya, International and Obnazhennaya) are obtained to estimate their paleomagnetic age. The mean primary magnetization directions for the pipes are as follows: D = 4.3°, I = − 44.5° (k = 29.4, α95 = 7.4°, N = 14); D = 340.5°, I = − 65.6° (k = 12.9, α95 = 19.4°, N = 6); D = 291.1°, I = − 78.1° (k = 27.5, α95 = 14.9°, N = 5); and D = 306.7°, I = − 82.6° (k = 38.4, α95 = 5.8°, N = 17), respectively. On the basis of a comparison with the Siberian apparent polar wander path (APWP) we estimate the age of kimberlite magmatism, assuming primary magnetizations in these rocks. The paleomagnetic ages are as follows: 428 ± 13 Ma for Eastern Udachnaya; 251 ± 30 Ma for International pipe; and 168 ± 11 Ma for Obnazhennaya pipe. The Western Udachnaya pipe was remagnetized and no clear paleomagnetic age could be determined. The ages of magmatic activity span the Early Silurian to Middle Late Jurassic. Early Silurian magmatism could be associated with the formation of the Viluy rift. Middle to Late Jurassic magmatic activity is most likely related to subduction related to the accretion of surrounding terranes to Siberia.  相似文献   

20.
We present the new 14C extraction line at ETH Zürich. This system is designed to extract in situ-produced cosmogenic 14C from terrestrial quartz samples, and to obtain pure CO2 gas for analysis with a gas ion source Accelerator Mass Spectrometry (AMS) system. Samples are degassed at 1550–1600 °C without the use of a fluxing agent. Gas purification is achieved by a series of cryogenic traps and passage through hot Ag and Cu wool/mesh. Graphitization and, thus, sample dilution is not required. Tests to determine the CO2 recovery after gas extraction and cleaning yielded consistently good recovery rates of >99.8% (n = 7). The 14C blank contribution from the all-metal tubing system is negligible. Our preliminary procedural blank estimate – deriving mostly from the hot extraction furnace – is <5 × 105 14C atoms. Extraction tests on two quartz samples by stepped-heating show a quantitative separation of atmospheric 14C at ≤500 °C from the in situ component above 1200 °C. Based on these data, we estimate to achieve a complete 14C extraction from a quartz sample.  相似文献   

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