Improvement of saponification extraction method for fatty acids separation from geological samples     

Jiang Chang  Yanqing Xia  Suping Ma  Xuan Fang  Minzhuo Sun 《中国地球化学学报》2016,35(2):148-155

The conventional saponification method could result in lower recoveries and artificial changes of long-chain fatty acids. The main reason is the error judgment of the intermediate layer suspended between the aqueous and organic layer during the liquid–liquid extraction process. This study shows that the intermediate layer consists of lots of medium- to long-chain carboxylic salts for their special physical and chemical properties. An improved saponification extraction method is also developed and the results show that the carboxylic salts distributed in the intermediate layer could be obtained completely, which greatly enhances the authenticity and accuracy of fatty acid analysis. Additionally, the possible reasons of formation of the intermediate layer are also discussed.  相似文献   

An optimized sequential extraction scheme for molybdenum association in environmental samples     

Liang Liang  Jian-Ming Zhu 《中国地球化学学报》2016,35(2):111-119

By comparing three sequential extraction procedures, a new optimized extraction scheme for the molybdenum association in environmental samples was proposed. Five operational steps were described as exchangeable (KH₂PO₄ + K₂HPO₄: including water-soluble), associated with organic matter (NaOH), Fe–Mn oxides and/or carbonates (HCl), sulfides (H₂O₂) and residue (HNO₃ + HF + H₂O₂). An optimized extraction scheme was compared with Tessier’s procedure and the Commission of European Communities Bureau of Reference (BCR) was applied to black shales. Results showed Tessier’s procedure gave the lowest concentration values for exchangeable molybdenum and the highest values for the residual molybdenum, which could not present the efficiency of the extraction reagents. BCR’s procedure showed the highest values in oxidizable molybdenum and presented four fractions of molybdenum, which did not demonstrate the fractions of molybdenum in the black shales in detail. The optimized extraction scheme demonstrated a certain improvement on extraction efficiency over Tessier’s procedure for the lowest residual molybdenum, and revealed more featured fraction information of molybdenum in black shales than BCR’s. Therefore, after a comparison with other two extraction procedures, the optimized extraction scheme proved suitable for the molybdenum in black shales and it also showed an accurate determination of the molybdenum in the fractions and source of bioavailable Mo.  相似文献   

Ra’s Abdah of the north Eastern Desert of Egypt: the role of granitic dykes in the formation of radioactive mineralization,evidenced by zircon morphology and chemistry     

Ali A. Omran  Osama K. Dessouky 《中国地球化学学报》2016,35(4):368-380

Syenogranitic dykes in the north of Egypt’s Eastern Desert are of geological and economic interest because of the presence of magmatic and supergene enrichment of radioactive mineralization. Zircon crystal morphology within the syenogranitic dykes allows precise definition of sub-alkaline series granites and crystallized at mean temperature of about 637 °C. The growth pattern of the zircons suggest magmatic and hydrothermal origins of radioactive mineralization. Hydrothermal processes are responsible for the formation of significant zircon overgrowth; high U-zircon margins might have occurred contemporaneously with the emplacement of syenogranitic dykes which show anomalous uranium (eU) and thorium (eTh) contents of up to 1386 and 7330 ppm, respectively. Zircon chemistry revealed a relative increase of Hf consistent with decreasing Zr content, suggesting the replacement of Zr by Hf during hydrothermal activity. Visible uranium mineralization is present and recognized by the presence of uranophane and autunite.  相似文献   

Geochemistry of sedimentary rocks from Permian–Triassic boundary sections of Tethys Himalaya: implications for paleo-weathering,provenance, and tectonic setting     

Akhtar R. Mir  V. Balaram  Javid A. Ganai  Shamim A. Dar  A. Keshav Krishna 《中国地球化学学报》2016,35(4):428-436

The geochemical characteristics of two sections—the Permian–Triassic boundary (PTB) Guryul Ravine section, Kashmir Valley, Jammu and Kashmir, India; and the Attargoo section, Spiti Valley, Himachal Pradesh, India—have been studied in the context of provenance, paleo-weathering, and plate tectonic setting. These sections represent the siliciclastic sedimentary sequence from the Tethys Himalaya. The PTB siliciclastic sedimentary sequence in these regions primarily consists of sandstones and shales with variable thickness. Present studied sandstones and shales of both sections had chemical index of alteration values between 65 and 74; such values reveal low-to-moderate degree of chemical weathering. The chemical index of weathering in studied samples ranged from 71 to 94, suggesting a minor K-metasomatism effect on these samples. Plagioclase index of alteration in studied sections ranged from 68 to 92, indicating a moderate degree of weathering of plagioclase feldspars. The provenance discriminant function diagram suggests that the detritus involved in the formation of present studied siliciclastic sedimentary rocks fall in quartzose sedimentary and felsic igneous provenances. These sediments were deposited in a passive continental margin plate tectonic setting according to their location on a Si₂O versus K₂O/Na₂O tectonic setting diagram.  相似文献   

Nuclear field shift effects on stable isotope fractionation: a review     

Sha Yang  Yun Liu 《中国地球化学学报》2016,35(3):227-239

An anomalous isotope effect exists in many heavy element isotope systems (e.g., Sr, Gd, Zn, U). This effect used to be called the “odd–even isotope effect” because the odd mass number isotopes behave differently from the even mass number isotopes. This mass-independent isotope fractionation driving force, which originates from the difference in the ground-state electronic energies caused by differences in nuclear size and shape, is currently denoted as the nuclear field shift effect (NFSE). It is found that the NFSE can drive isotope fractionation of some heavy elements (e.g., Hg, Tl, U) to an astonishing degree, far more than the magnitude caused by the conventional mass-dependent effect (MDE). For light elements, the MDE is the dominant factor in isotope fractionation, while the NFSE is neglectable. Furthermore, the MDE and the NFSE both decrease as temperatures increase, though at different rates. The MDE decreases rapidly with a factor of 1/T², while the NFSE decreases slowly with a factor of 1/T. As a result, even at high temperatures, the NFSE is still significant for many heavy element isotope systems. In this review paper, we begin with an introduction of the basic concept of the NSFE, including its history and recent progress, and follow with the potential implications of the inclusion of the NFSE into the kinetic isotope fractionation effect (KIE) and heavy isotope geochronology.  相似文献   

The effects of soil sand contents on characteristics of humic acids along soil profiles     

Xinyue Di  Hui Dong  Xianjin An  Haiming Tang  Baohua Xiao 《中国地球化学学报》2016,35(3):251-261

It is generally accepted that the compositions and properties of soil organic matter (SOM) are influenced by many factors. In order to reveal the effects of soil texture on characteristics and dynamics of SOM and its sub-fraction, humic acid (HA), along two soil profiles, a yellow soil profile and a purplish soil profile, under the same climate and vegetation conditions were determined. Results indicate that the decomposition and humification degrees of SOM and HA of the purplish soils are higher than those of the corresponding yellow soils indicated by A/O–A ratios of HAs, TOCs and HA yields of bulk soil samples, nevertheless, the development degree of the purplish soil is lower than that of the yellow soil. The variations of E₄/E₆ ratios of HAs along the soil profiles indicate the overall molecular sizes of HAs decreased downward along the soil profiles. A/O–A ratios of HAs decreased downward along both the soil profiles indicate that humification processes decrease downward along both the soil profiles. Leaching of SOM shows significant effects on the distribution and characteristics of HAs in the yellow soil profile but the purplish soil profile, which is consistent with the higher hydrophobicity of HAs in purplish soils, shows that the distribution characteristics of SOM along the soil profiles are a complex result of the combination of soil texture and characteristics of SOM itself. The remarkably different sand contents are concluded tentatively as one of reasons to the different distributions and dynamics of HAs along the soil profiles, however, to profoundly understand the evolution and transport of SOM along soil profiles needs more researches.  相似文献   

Fractionation characteristics of rare earth elements (REEs) linked with secondary Fe,Mn, and Al minerals in soils     

Chunying Chang  Fangbai Li  Chengshuai Liu  Jianfeng Gao  Hui Tong  Manjia Chen 《中国地球化学学报》2016,35(4):329-339

Soil secondary minerals are important scavengers of rare earth elements (REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs (La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs (LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs (HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs. The substantial fractions of REEs in soils extracted by oxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile (10 %–30 %), which were similar to the mass fraction of Fe (10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.  相似文献   

Fifteen Years of Ocean Observations with China Argo     

Liu Zenghong  Wu Xiaofen  Xu Jianping  Li Hong  Lu Shaolei  Sun Chaohui  Cao Minjie 《地球科学进展》2016,31(5):445-460

For 15 years since the beginning of China Argo project, China has deployed over 350 profiling floats in Pacific and Indian ocean, and constructed China Argo ocean observing network. Moreover, we have setup the Argo data receiving, processing and distributing system, and developed various Argo data products using Argo observations, which has promoted the progress of ocean data sharing in China. The abundant Argo data have become a main data source in oceanic and atmospheric basic researches and operational applications. A batch of important achievements in basic research and operational application have been brought, e.g. in aspects of tropical cyclone (typhoon), ocean circulation, meso-scale eddy, turbulence, heat/salt storage and transport and water mass, as well as in ocean, atmosphere/climate operational forecasting and predicting. With the extension of the international Argo program from “Core Argo” to “Global Argo”, we are faced with great challenges in the long-term maintaining and sustained developing of our Argo ocean observing network. It is suggested that we should take the opportunity to construct China regional Argo ocean observing network as soon as possible in adjacent northwestern Pacific and Indian ocean using Chinese BeiDou profiling floats, which will make us to take responsibility and obligation of a big country for addressing global climate changes and preventing natural disasters.  相似文献   

Active Characteristics and Paleoearthquakes in the West Kalpin Nappe Since the Holocene,SW Tianshan Mountain     

Li An  Ran Yongkang  Liu Huaguo  Xu Liangxin 《地球科学进展》2016,31(4):377-390

the Kalpin nappe is an important multiple thrust system. It is important to study the Cenozoic tectonic of the Tianshan Mountain. Holocene active characteristics and paleoearthquake of the Kalpin nappe can be used to evaluate the neotectonic of this area. In this paper, we accurately measured the fault scarp in the front of three thrust-fold faults and analyzed paleoearthquake events in the trenches of the Kalpin nappe. Using the ¹⁰Be exposure age, we obtained those geomorphic surface ages and paleoearthquake times. The result showed that the slip rates of the west Kalpintag fault, aozitag fault and the tuoketag fault were 1.45(+1.68/-0.44) mm/a, 0.81(+0.35/-0.19) mm/a and (0.3±0.05) mm/a, respectively since the Holocene. The slip rate indicated that the increased activity transferred from back-row fault to front-row fault and accorded with the piggy-back propagation model in the Tianshan Mountain. Displacements and recurrence intervals of paleoearthquakes was similar to the slip rate characteristics. It also showed paleoearthquakes in the front row fault were stronger than paleoearthquakes of the back row fault. The strong paleoearthquake which caused the highest surface rupture happened in the Kalpintag fault. The interval of paleoearthquakes was about 4 ka and the displacement of every paleoearthquake was about 3 m in the west Kalpintag fault; the interval of paleoearthquakes was about 2 ka and the displacement of every paleoearthquake was about 1m in the aozitag fault; the tuoketag fault ruptured only one paleoearthquake since 7 ka. The Piqiang tear fault was the tectonic result of different shortening rate between the west Kalpin system and the east Kalpin system. The shortening rate of west Kalpin system was obviously stronger than the east Kalpin system. The huge separation distance was near 20 km between the east and the west back-row fault. Because the slip rate of system transferred to the front-row fault in the piggy-back propagation model, the separation distance (~4 km) between the east and the west front-row fault was increasing.  相似文献   

Using Geomechanical Method to Predict Tectonic Fractures in Low-Permeability Sandstone Reservoirs     

Feng Jianwei  Ren Qiqiang  Xu Ke 《地球科学进展》2016,31(9):946-967

Understanding and interpreting the timing, location, orientation, and intensity of natural fractures within a geological structure are commonly important to both exploration and production planning activities of low-porosity and low-permeability carbonate reservoirs. In this study, we explore the application of comprehensive geomechanical methods to quantitatively characterize the fracture parameters based on Strain Energy Density Theory, such as linear fracture density and volume fracture density. This study approach is based on the idea that energy generated by tectonic stress on brittle sandstone,which can be distinguished fracture surface energy, friction energy dissipation and residual strain energy and natural fractures can be interpreted or inferred from geomechanical-model-derived strains. For this analysis, we model an extension and compression compound fault block developed in a mechanically stratified sandstone and shale sequence because mechanics experimental data and drilling data exist that can be directly compared with model results.However, the results show that the approach and our study conclusion are independent of the specified structural geometry, which can correlate fracture parameters in different stages with different tectonic activities, and finally build and visualize fracture networks in sandstone. The presence or absence of filling minerals in fractures is shown to strongly control the destruction and transformation of low-permeability sandstone, and this control possesses crucial implications for interpreting fracture aperture and reservoir flow simulation.  相似文献