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Trace metals are known to stimulate the activity of anaerobic methanogenic bacteria involved in the degradation of organic matter. The objective of this research was to investigate the effect of three trace metals, iron, nickel and cobalt on the activity of halophilic methanogens, digester sludge and a mixed culture of halophilic bacteria and digester sludge, at various salt concentrations. Iron slightly stimulated both initial and maximum specific methanogenic activity (SMA) of halophilic methanogens at all salt concentrations. Iron addition was also able to increase both initial and maximum SMA of the mixed culture. Iron could not stimulate either initial or maximum SMA of digester sludge at salt concentrations of more than 10 g/L. Adding cobalt showed no benefit on the initial and maximum SMA of halophilic methanogens. A slight increase in the initial SMA was observed in mixed culture when cobalt was injected to the system containing sodium concentrations of 10–30 g/L. At salt concentrations above 40 g/L, cobalt could stimulate the maximum SMA of mixed culture. No benefits were found when cobalt was added to the digester sludge at sodium concentrations higher than 20 g/L. Nickel was observed to increase the initial SMA of digester sludge at all salt concentrations, and the maximum SMA of mixed culture at salt concentrations of 30–50 g/L.  相似文献   
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Wastewater containing high concentrations of salt, are difficult to treat using biological treatment processes, especially anaerobic processes. Limited information is available on methanogenic activity in saline environments. The objective of this research was to investigate the activity of halophilic methanogens, digester sludge and a mixed culture of halophilic and methanogenic bacteria, at various levels of salinity, in terms of lag period and specific methanogenic activity (SMA) at two temperatures. For the halophilic bacteria at 35 °C, the initial SMA ranged from 0.46 to 0.90 g acetate/g VSSd, but decreased at higher salt concentrations. The maximum SMA varied from 1.2 to 2.08 g acetate/g VSSd. High sodium chloride concentrations had a significant adverse effect on digester sludge. At 25 °C, at salt concentrations of 30 g/l and above, the digester sludge could not acclimate even in 50 days. Little difference was observed in the maximum SMA of mixed culture and halophilic bacteria at high salt concentrations of40–50 g/l.  相似文献   
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A fast and economical routine sample preparation system is described for direct counting of14C for hydrological purposes. The method employs commercially available CO2 absorbers, such as Carbosorb, and liquid scintillation counters. The maximum error involved individual analyses is about ±4pmc (1 δ) on the Beckman counter and about ±2 pmc on the Quantulus counter with a resulting detection limit of 21,000–29,000 a for the Beckman LS7500 and 1220 Quantulus, respectively for a counting time of 1000 min. To avoid physical weighing procedures, an indirect method is presented to determine the grams of C absorbed in the counting solution by using the H-# quench monitor technique available in the Beckman liquid scintillation counters. On one sample preparation system at least five samples can be prepared per normal working day. The applicability of the CO2-absorption method is discussed with reference to two field sites and with reference to comparisons with data obtained on the same samples measured with conventional techniques.  相似文献   
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Surface soil and sediment samples were collected from the surroundings of the Ittehad Chemical Industries Kalashah Kaku industrial zone to assess residual level of 19 organochlorine pesticides (OCPs) and identify their sources. DDTs and HCHs were most prevalent OCPs and general pattern of contamination followed the order: ∑DDT > ∑HCH > dicofol > endrin > heptachlor > dieldrin > endosulfan II. Total measured concentrations of HCHs (6.38–121.71 ng/g) and DDTs (759.65–1811.98 ng/g) were greater in the soil samples collected from fodder/rice fields irrigated with the factory effluents and in the surrounding of waste disposal site. Ratios of β to γ-HCH highlighted an old mixed source of technical HCH and lindane in surface soils. Predominance of p,p′-DDT and p,p′-DDE among isomers and metabolites showed that large quantity of technical grade DDT is still present in the surrounding surface soils. Six soil samples were categorized as heavy polluted soils (class III category of DDT > 1,000 ng/g), two soil samples into less polluted soil between class I and II (50–500 ng/g) and 28 soil samples as non-polluted (<50 ng/g) according to environmental quality standards for surface soils. Six soil samples were categorized as less polluted between class I and II of HCHs (50–500 ng/g). Greater concentration of DDTs and HCHs above quality guideline poses potential exposure risk to biological organisms, safety of agricultural products and human health in the surrounding of the Ittehad Chemical Industries.  相似文献   
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The results obtained from an investigation of suspended particulate matter in the metropolitan city of Lahore (Pakistan) are reported and analysed in this paper. X-ray diffraction studies of the airborne matter collected from va-rious urban and suburban sites show that non-clay minerals such as quartz, calcite and albite are contained in most of the samples in almost comparable amounts. Chemical analysis of some samples was carried out for complementing the x-ray diffraction data. The amount of quartz in the samples of dusty areas was found to be an order of magnitude more than in the samples of relatively cleaner areas. As the dust particles of these compounds are poor substrate for promoting nucleation of ice in the atmospheric clouds, they are liable to stay steadily in the atmosphere as pollutants.A comparison of the results of the airborne particulates and the soil samples collected from various sites show that the sources of quartz, calcite and albite in the airborne matter are both local and remote.  相似文献   
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A fossil-bearing locality near Padhri village, Dhok Pathan, 55 km away from the tehsil Dina, Jhelum District, in the Potwar Plateau, Middle Siwaliks, Punjab, northern Pakistan, is significantly rich in mammalian fossils. This site has provided an abundant mammalian fossil fauna of Late Miocene age from the Dhok Pathan Formation (Fm.). The recovered material belongs to four families: Equidae (horses), Rhinocerotidae (rhinos), Bovidae (cows), and Suidae (pigs). We discovered a new skull of hipparionine Hipparion theobaldi from this locality along with 22 specimens from the associated assemblage of fossil mammals. The recovered material includes seven other species: the aceratheriine Chilotherium intermedium, boselaphines Tragoportax punjabicus, Selenoportax vexillarius, Pachyportax latidens, the antelope Gazella lydekkeri and suinine Propotamochoerus hysudricus. The specimens are isolated teeth, fragments of maxilla, mandibles and horn cores. The Dhok Pathan Fm. is generally composed of claystone, siltstone and sandstone beds and, based on the mammalian fauna, the Padhri fossil locality is dated as Late Miocene. Thi99s formation was deposited in a subtropical paleoenvironment and the predominance of fossil bovids indicates extremely moist conditions with small but frequent standing water bodies.  相似文献   
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