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1.
Ohne Zusammenfassung  相似文献   

2.
This study was designed to survey the reservoir sediment properties, assess the phosphorus (P) sorption isotherm, and analyze the relationship between sediment properties and sorption parameters. Physicochemical analysis indicated that sediment from the FUSHI reservoir in Zhejiang Province, China, has similar physical and chemical properties and has been contaminated by P. Sorption isotherm experiments showed that the sorption process could be described by Langmuir and Freundlich models. The parameters of Q max (Phosphorus sorption maximum) and K (Freundlich adsorption isotherm constant) ranged from 618.98 to 825.70?mg?kg?1 and 114.18 to 170.74?l?kg?1, respectively. EPC0 (zero P equilibrium concentration) ranged from 0.14 to 0.24?mg?l?1, more than the total P concentration in the water of the reservoir. Thus, the reservoir sediment releases P into the water and acts as a ??P resource??. The clay, Feo, Alt, and Fet?+?Alt content were the main active components in P sorption. Q max had a highly significant positive relationship with some properties and could be estimated by a combination of these.  相似文献   

3.
Zusammenfassung Sedimentäre Eisenerze können durch Ausflocken von Fe+++haltigen Solen und durch Ausfällen von Fe++haltigen Lösungen gebildet werden. Aus Solen gebildete Erze werden als Begleitelemente Kieselsäure und Aluminium anreichern, während aus Lösungen gebildete Erze manganreicher sind und Kieselsäure und Aluminium zurücktreten.  相似文献   

4.
Ohne Zusammenfassung  相似文献   

5.
《Quaternary Science Reviews》2004,23(11-13):1435-1454
Numerous short sediment cores have been retrieved from the central Arctic Ocean, many of which have been assigned sedimentation rates on the order of mm/ka implying that the Arctic Basin was starved of sediments during Plio–Pleistocene times. A review of both shorter-term sedimentation rates, through analysis of available sediment core data, and longer-term sedimentation rates, through estimates of total sediment thickness and bedrock age, suggests that cm/ka-scale rates are pervasive in the central Arctic Ocean. This is not surprising considering the physiographic setting of the Arctic Ocean, being a small land-locked basin since its initial opening during Early Cretaceous times. We thus conclude that the central Arctic Ocean has not been a sediment starved basin, either during Plio–Pleistocene times or during pre-Pliocene times. Rigorous chronstratigraphic analysis permits correlation of sediment cores over a distance of ∼2600 km, from the northwestern Amerasia Basin to the northwestern Eurasia Basin via the Lomonosov Ridge, using paleomagnetic, biostratigraphic, and cyclostratigraphic data.  相似文献   

6.
Heavy metal contamination in the sediment of the Second Songhua River   总被引：1，自引：0，他引：1  
The Second Songhua River was subjected to a large amount of untreated effluent from petrochemical industries in Jilin City in the 1960s to the 1970s. The objectives of this study were to investigate the mercury and other heavy metal contamination in the sediment of the river. The river bottom sediment was sampled from the river segment between Jilin City to Haerbin City in 2005. Total concentrations of Hg, Cd, Cu, Cr, Pb, Zn, Ni, As, Sc, and major cations （A1, Fe, Mg, Ca, K, Na） in the sediment were measured by atomic fluorescence spectrometer, ICP-MS, and ICP-OES, respectively, following digestion with various acids. We found the concentrations of most elements in the uncontaminated sediment were significantly correlated to those of Sc.  相似文献   

7.
Fourteen ferromanganese nodule–sediment pairs from different sedimentary environments such as siliceous ooze (11), calcareous ooze (two) and red clay (one) from Central Indian Ocean Basin (CIOB) were analysed for major, trace and rare earth elements (REE) to understand the possible elemental relationship between them. Nodules from siliceous and calcareous ooze are diagenetic to early diagenetic whereas, nodule from red clay is of hydrogenetic origin. Si, Al and Ba are enriched in the sediments compared to associated nodules; K and Na are almost in the similar range in nodule–sediment pairs and Mn, Fe, Ti, Mg, P, Ni, Cu, Mo, Zn, Co, Pb, Sr, V, Y, Li and REEs are all enriched in nodules compared to associated sediments (siliceous and calcareous). Major portion of Si, Al and K in both nodules and sediments appear to be of terrigenous nature. The elements which are highly enriched in the nodules compared to associated sediments from both siliceous and calcareous ooze are Mo – (307, 273), Ni – (71, 125), Mn – (64, 87), Cu – (43, 80), Co – (23, 75), Pb – (15, 24), Zn – (9, 11) and V – (8, 19) respectively. These high enrichment ratios of elements could be due to effective diagenetic supply of metals from the underlying sediment to the nodule. Enrichment ratios of transition metals and REEs in the nodule to sediment are higher in CIOB compared to Pacific and Atlantic Ocean. Nodule from red clay, exhibit very small enrichment ratio of four with Mn and Ce while, Al, Fe, Ti, Ca, Na, K, Mg, P, Zn, Co, V, Y and REE are all enriched in red clay compared to associated nodule. This is probably due to presence of abundant smectite, fish teeth, micronodules and phillipsite in the red clay. The strong positive correlation (r ? 0.8) of Mn with Ni, Cu, Zn and Mo and a convex pattern of shale-normalized REE pattern with positive Ce-anomaly of siliceous ooze could be due to presence of abundant manganese micronodules. None of the major trace and REE exhibits any type of inter-elemental relationship between nodule and sediment pairs. Therefore, it may not be appropriate to correlate elemental behaviour between these pairs.  相似文献   

8.
《中国地球化学学报》2006,25(B08):85-85
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9.
Arsenate adsorption was studied in three clastic sediments, as a function of solution pH (4.0–9.0) and arsenate concentration. Using known mineral values, protolytic constants obtained from the literature and K ads values (obtained by fitting experimental adsorption data with empirical adsorption model), the constant capacitance surface complexation model was used to explain the adsorption behavior. The experimental and modelling approaches indicate that arsenate adsorption increases with increased pH, exhibiting a maximum adsorption value before decreasing at higher pH. Per unit mass, sample S3 (smectite–quartz/muscovite–illite sample) adsorbs more arsenate in the pH range 5–8.5, with 98% of sites occupied at pH 6. S1 and S2 have less adsorption capacity with maxima adsorption in the pH ranges of 6–8.5 and 4–6, respectively. The calculation of saturation indices by PHREEQC at different pH reveals that the solution was undersaturated with respect to aluminum arsenate (AlAsO42H2O), scorodite (FeAsO42H2O), brucite and silica, and supersaturated with respect to gibbsite, kaolinite, illite and montmorillonite (for S3 sample). Increased arsenate concentration (in isotherm experiments) may not produce new solid phases, such as AlAsO42H2O and/or FeAsO42H2O.  相似文献   

10.
Measurements of 18 closely spaced beach profiles spanning Warilla Beach, N.S.W., over a 5‐year period have been examined for alongshore exchanges in beachface configuration. Horizontal slices of beach corresponding with berm, upper swash, upper and lower intertidal zones were examined by empirical orthogonal function (EOF) analysis. The first four EOF's for each of the four slices contain over 90% of the total variance for each slice. In each instance the first eigen‐function mode represents the onshore‐offshore component of beach response, and accounts for 50 to 60% of the variance. Subsequent modes describe alongshore exchange of sediment associated with large, standing, cellular water circulations of the embayment. Sediment shunts along each horizontal slice are determined by identification of nodal points in the eigen‐functions. These represent pivotal points through which sediment is transferred. The patterns of exchange vary considerably from slice to slice, reflecting change in the dominant beach processes from swash processes in the top of the beach to wave, tidal and current processes on the lower beach slope. Despite their disparity, similar periodicities are determined for the sediment exchanges in each slice. The amplitude spectra of the time series associated with each eigen‐function indicate that the exchanges take place at 24, 12 and 6 monthly periods.  相似文献   

11.
The speciation of heavy metals is very important to evaluate their environmental impact. This issue has become an interested topic many decades ago and many significative studies were carried out such as direct detecting, calculation with mathematical model represented in recent years as well as Tessier＇s work in 1979, BCR＇s work in 1993, etc. In all of them, the methods recommended by Tessier and BCR are most often used in practical study today. But it should be seen that experimental schedule and agents define these methods including BCR＇s method, which improved on Tessier＇s method, only. In many cases, there always are deviations between analytical results and real content of the speciation. Otherwise, steps of the extraction experiment are always strict and excessive in the experimental process. The method, which is fitting to extract the speciation of bioavailability and easy to assess the effect of metals in the environment, is very anticipant. In this paper, the sequential three steps schedule of speciation analysis of copper in soil and water sediment is discussed as an example based on the comparative results of experimental analysis with the schedules of BCR＇s （mended by Rauret et al. in 1999） and TDPA （diethylenetriamine pentacetic acid） extraction, respectively. The results from sequential three steps method and other methods recommended by prevenient work suggest that the analytical schedule of sequential three steps of separating speciation （the speciation of easy effect to life-form, the speciation available to life-form, and the speciation of no effect to life-form） is valuable for copper speciation analysis in soil and sediment. Because of easy process and saving time to evaluate its availability for life form,  相似文献   

12.
Background: With development of intensive agriculture in the agricultural regions of the Northern provinces (Caspian Sea coasts), which involves frequent pesticide use in highly mechanized cash-crop cultures. To investigate and provide information on pest…  相似文献   

13.
Geochemical characteristics of marine sediment from the southern Drake Passage were analyzed to reconstruct variations in sediment provenance and transport paths during the late Quaternary. The 5.95 m gravity core used in this study records paleoenvironmental changes during the last approximately 600 ka. Down-core variations in trace element, rare earth element, and Nd and Sr isotopic compositions reveal that sediment provenance varied according to glacial cycles. During glacial periods, detrital sediments in the southern Drake Passage were mostly derived from the nearby South Shetland Islands and shelf sediments. In contrast, interglacial sediments are composed of mixed sediments, derived from both West Antarctica and East Antarctica. The East Antarctic provenance of the interglacial sediments was inferred to be the Weddell Sea region. Sediment input from the Weddell Sea was reduced during glacial periods by extensive ice sheets and weakened current from the Weddell Sea. Sediment supply from the Weddell Sea increased during interglacial periods, especially those with higher warmth such as MIS 5, 9, and 11. This suggests that the influence of deep water from the Weddell Sea increases during interglacial periods and decreases during glacial periods, with the degree of influence increasing as interglacial intensity increases.  相似文献   

14.
Adsorption and desorption are critical processes controlling the fate and transport of organic contaminants in natural environment. Numerous studies have shown that only a fraction of contaminants in soil or sediment can readily be desorbed to the aqueous phase, while desorption of the remaining fraction is very difficult and does not follow the conventional desorption models-a phenomenon typically referred to as ＂resistant desorption＂ or ＂sequestration＂ and is argued by many as the cause of reduced availability of contaminants in soil and sediment. While this reduced availability often reduces the effectiveness of soil and sediment remediation, the same effect can also greatly reduce risk of contaminated soil and sediment. The authors have conducted extensive lab and field studies to characterize the unique properties of sequestration of organic contaminants and to understand the mechanism（s） controlling sequestration. Thus far, over 50 different contaminant-soil/sediment combinations have been evaluated, using contaminants of varied physical-chemical properties （e.g., chlorinated benzenes, PAHs, PCBs, DDT, atrazine, hexachlorocyclohexane isomers, etc.）. Several unique characteristics of sequestration have been observed, and the most striking one is that despite the significant differences in chemical and soil properties, desorption of sequestered contaminants for all the contaminant-soil/sediment combinations exhibited very similar KOC （organic-carbon normalized partition coefficient） and very similar desorption kinetics.  相似文献   

15.
The development of a thin peat layer over metamorphic rock during the last cold stage in the Louisa and Melaleuca Plains and at Birch's Inlet, Tasmania, has recently been reported. This paper presents results of a numerical model on permafrost growth and decay, which explores the possibility of the development of a thin layer of permafrost for this particular depositional setting at the end of the last cold stage in Tasmania. The increase in thermal conductivity of peat sediments under frozen conditions results in a preferred penetration of the cold winter wave (in comparison to the summer wave) into the subsurface. The results of the model calculations suggest the development of a several metres‐thick permafrost layer, even under slightly positive mean annual temperatures in the region.  相似文献   

16.
1IntroductionGlobal change studies on the decennial and cen-tennial timescales,which can help put together the in-formation from long timescale study and meteorologicalstudy,is crucial for predicting future global changes(Hegerl,1998;Wang Pinxian and Jian Zhimin,1999;Wang Sumin et al.,1998).Lacustrine sedi-ments characterized by their continuity,major sedi-mentation rate,and high resolution can provide usefulinformation for reconstructing the past global changes(Steven,1996;Wang Sumin and …  相似文献   

17.
Zusammenfassung Die eisenoolithischen Lias--Erze der Lagerstätten Echte, Markoldendorf und Holtensen wurden chemisch, spektralanalytisch, röntgenographisch und optisch untersucht.Wie schonC. W. Correns undW. v. Engelhardt zeigten, gestattet die röntgenographische Methode eindeutige Aussagen über den Mineralbestand der feinkörnigen sedimentären Eisenerze.Petrographisch unterscheiden wir drei Erzsorten: Grüne Chamositerze, rote Hämatiterze und braune Nadeleisenerze. Die Minerale der Chamositerze sind: Chamosit, Siderit und Kalkspat neben geringen Mengen von Quarz und Pyrit. Hämatiterze bestehen aus Hämatit und Calcit neben geringen Mengen Chamosit und Siderit.  相似文献   

18.
The causal links between physical erosion and chemical weathering remain poorly constrained, despite their importance for understanding landscape evolution, nutrient supply for ecosystem development, and the quantitative impact of tectonic uplift on the long-term carbon cycle and Earth＇s climate. This is partly because weathering processes are particularly complicated at high erosion rates, where there are a variety of controlling parameters. The Himalayas provide an ideal natural laboratory for studying weathering processes across an environmental gradient undergoing rapid erosion. We have previously used solute budgets to determine weathering rates in small catchments in the High Himalayas and Middle Hills of central Nepal. In-situ weathering rates are highest in the warmer Middle Hills, while the total riverine budgets suggest that much of the weathering of High Himalayan material must occur after erosion, during transport through the Ganges Plain （West et al., 2002）. Here, we will present new data on the geochemistry of the solid phase （soils and sediments） from these small Himalayan catchments, including time constraints from U-series analysis. This will provide information about the residence time of material in the weathering environment, and its relation to weathering rates.  相似文献   

19.
《中国地球化学学报》2006,25(B08):134-135
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20.
In the history, the Yellow River nurtured Chinese civilization. It is respected as the ＂ancestor of the four large rivers in China＂ and praised as ＂the mother river of China＂. At the same time, the Yellow River is regarded as ＂the misery of China＂ and considered as the most complex river hard to control in the world. Today, the Yellow River is also one large river greatly influenced by human activities in the world. The safety of the Yellow River, particularly flood control, is always the most important issue for governing and developing the country. Great achievements have been made after many years of efforts for controlling the Yellow River. However, since the nineties of 20 century, some new problems occurred, such as sharp reduction of flux to sea, dry rivercourse, worsen environment, etc. Rapidly shrinking riverbed and two-level perched stream are disadvantageous to flood safety especially. The new concepts and new practices are urgently needed to control the river. Therefore, the Yellow River Conservancy Committee of Ministry of Water Resources had continuously carded out flow and sediment diversion each year from 2002 to 2005. To timely probe into the new issues produced after flow and sediment diversion, and in order to deepen the understanding of rules for the Yellow River＇s water and sediment and provide reference and experience to the researchers for other large rivers, five hydrologic and hydraulic characteristics of the Yellow River, such as lack of water, much of sediment, different resources of water and sediment, inconsistency between water and sediment and frequency of sink switching and route changing, are described. Flow and sediment diversion of the Yellow River is also reviewed. Under flow and sediment diversion,  相似文献   

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