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1.
长江口及其邻近海域表层沉积物中氧化还原敏感性微量元素的环境指示意义 总被引:5,自引:2,他引:3
对长江口及其邻近海域表层沉积物和底层悬浮体中氧化还原敏感元素分布规律和富集特征进行了分析与研究。结果表明氧化还原敏感元素在研究区具有明显的“离岸富集”特征,去除粒度效应、陆源碎屑来源组分和有机质的吸附作用等因素的影响之后,氧化还原敏感元素仍显示出在缺氧区的富集。通过同一站位底层悬浮体和沉积物中氧化还原敏感元素含量的分析比较,发现底层水缺氧是导致氧化还原敏感元素Mo、Cd、V等在沉积物中富集的主要原因。Mo、Cd、V等元素的不同富集程度可用来反映缺氧区的缺氧程度。因此,Mo, Cd, V等RSE在长江口外缺氧区及其邻近海域具有氧化还原环境指示意义,可以指示长江口外缺氧区的存在与大体范围,并可在一定程度上用来衡量缺氧区的缺氧程度。U理论上虽然也对环境的氧化还原条件敏感,但由于受陆源碎屑来源组分的影响较大,在长江口外缺氧区的富集并不明显,因此U在研究区不具有氧化还原环境指示意义。 相似文献
2.
In northern Jiangsu coastal zone area, Guanhe River is the biggest river and has the best navigation conditions among rivers
which flow into the Yellow Sea. The grain sizes show gradual increase from the high intertidal zone to lower intertidal zone.
The heavy metal values have slight changes along both sides of the river mouth, but show an evident change perpendicular to
the tidal flat. In the latter case, they show a good correlation with grain size fluctuation, that is, the heavy metal values
gradually decline when the grain size increases from the high intertidal zone to the lower intra-tidal zone. Analyses of the
heavy metal elements show that on the Guanhe estuary surface sediment, the content of the elements Hg, As and Cu is above
background values; Pb and Zn contents are rather close to the background values; and Cd content is less than the background
values. The element Hg comes out to be harmful in a medium level to ecological environment, while the elements of Cr, As,
Cu, Pb, Zn and Cd fall in a safe range of MPL. On the whole, Guanhe estuary tidal flat is not very harmful to the ecology
in terms of the heavy metals.
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Translated from Marine Geology & Quaternary Geology, 2007, 27(5): 23–32 [译自: 海洋地质与第四纪地质] 相似文献
3.
Hualing Wei Nianqiao Fang Xuan Ding Lanshi Nie Xiuming Liu 《Frontiers of Earth Science》2008,2(2):162-169
This paper presents pelagic records of planktic foraminifera, as well as data of stable isotope stratigraphy and carbonate
stratigraphy since 3.5 Ma B.P. from site ODP758 in the Ninetyeast Ridge of the Indian Ocean. Based on these data, manifestations
and related mechanisms of major tectonic and environmental events such as the rapid uplift of the Himalaya Mountains, “middle
Pleistocene climatic transition” and “mid-Brunhes dissolution event” in the region are discussed. According to the analysis
and comparison of various indices and changes in terms of foraminifera assemblage, paleotemperature, paleosalinity and themocline
from site ODP758, the authors deduce that the paleoclimatic changes might correlate with the mid-Pleistocene transition at
1.4–1.7 Ma B.P. The changes of CaCO3, mass accumulation rates (MAR) of CaCO3 and non- CaCO3 MAR indicate that the loaded terrigenous sediments increased at 1.7 Ma, which is in agreement with the uplift history of
the Qinghai-Tibet plateau as shown by the available data. The last two changes coincide with the uplift of the Qinghai-Tibet
plateau, hence they are called “Qinghai-Tibet movement” (1.7 Ma), and the “Kunlun-Yellow River movement” (1.2–0.6 Ma). The
changes of the CaCO3 content, coarse fraction (> 150 μm) content and planktonic foraminifera biostratigraphy show that strong dissolution of abyssal
CaCO3 occurred in the study region during 0.5–0.4 Ma. The event was consistent with the “mid-Brunhes dissolution event” in the
sedimentary records of the Atlantic Ocean, Pacific Ocean, Indian Ocean and Nansha sea area of the South China Sea.
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Translated from Geological Bulletin of China, 2007, 26(12): 1627–1632 [译自: 地质通报] 相似文献
4.
To decipher the origin of oxygen-deficient shelfal deposits is significant for tracing the distribution of marine source rocks
and interpreting the evolution of depositional environment. The origin of the Middle Permian Chihsia Formation in South China
remains a puzzle for long with its evident oxygen-deficient features but diverse benthos. This paper shows a typical Chihsian
depositional rhythm composed of the massive and the laminated limestones with ecological and geochemical features. Massive
bioclastic limestone from the rhythm was aerobic in paleoxygenation condition indicated by both the ecological and geochemical
features. However, a contradictory oxygenation was inferred for the “laminated” counterpart from the rhythm, with the ecological
signal being aerobic and the geochemical one being anoxic. The difference in ecological and geochemical indications was interpreted
as the instability of paleoxygenation condition in shelf environments, caused by an enhanced paleoproductivity. Rhythmic occurrence
of the oxygen-deficient condition might have been stemmed from paleo-Tethyan paleocurrents flowing across South China.
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Translated from Earth Science—Journal of China University of Geosciences, 2007, 32(6): 789–796 [译自: 地球科学—中国地质大学学报] 相似文献
5.
Based on the high-resolution sporopollen and algae research of the sediments from core B106 in the northern South China Sea,
three sporopollen assemblage zones have been distinguished in ascending order: Zone 1 (294–194 cm): Pinus-Quercus (evergreen)-Gramineae-Polypodiaceae- Pterdium-Dicranopteris. Zone 2 (194–94 cm): Pinus-Quercus (evergreen)-Polypodiaceae-Pteridium- Dicranopteris. Zone 3 (94–4 cm): Pinus-Polypodiaceae-Pteridium-Quercus (evergreen)-Dicranopteris. The three sporopollen zones correspond to three stages of vegetation, climate and paleoenvironment evolution of the northern
part of the South China Sea since 11 000 years ago. Combined with AMS 14C dating, the sporopollen and algae data can be a scientific basis for stratigraphic division and reconstruction of paleoclimate
and paleoenvironment in the South China Sea.
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Translated from Marine Geology & Quaternary Geology, 2007, 27(5): 9–14 [译自: 海洋地质与第四纪地质] 相似文献
6.
Rock magnetic record of Cenozoic lake sediments from the Linxia basin and aridification of the Asian inland 总被引:1,自引:0,他引:1
High resolution research of rock magnetic records and quartz sands from the Maogou Section in the Linxia basin reveals that
after a relatively stable environment between 13.07 Ma and 8.6 Ma, the basin was gradually influxed by eolian dusts at about
8.6 Ma, with two rapid increases at about 6.4 Ma and 5.3 Ma, respectively. The study suggests that drying of northwest China
began at 8.6 Ma and strengthened rapidly at about 6.4 Ma and 5.3 Ma.
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Translated from Marine geology & Quaternary geology, 2007, 27(4): 103–110 [译自: 海洋地质与第四纪地质] 相似文献
7.
Two hundred and eighty-one samples, collected from drilling core NS93-5 located in the Nansha area of the South China Sea,
were used to study the magnetic characteristics of the sediments in the sea. Detailed rock magnetic results show that the
magnetic minerals of the sediments were dominated by ferrimagnetic minerals such as magnetite, and a small contribution of
hematite and maghematite also existed. The sediments recorded three negative values of remanence magnetic inclination at the
depth: 191–206 cm, 232–248 cm, and 292–308 cm. The corresponding ages of these negative values were 65.87–68.7 ka B.P., 73.4–80.8
ka B.P. and 108.4–113.6 ka B.P., respectively, according to stratigraphy of oxygen isotope, 14C, and the age of a volcanic ash layer. The negative value during 108.4–113.6 ka B.P. may be the record of a Blake event in
the sediments of the Nansha area.
Translated from Marine Geology & Quaternary Geology, 2006, 26(1): 59–66 [译自: 海洋地质与第四纪地质] 相似文献
8.
Lei Shao Xiong Pang Changmin Chen Hesheng Shi Qianyu Li Peijun Qiao 《Frontiers of Earth Science》2008,2(2):138-146
A significant change in composition was recorded in late Oligocene sediments from the northern South China Sea. This abrupt
event coincided with the seafloor spreading axis jump across the Oligocene/Miocene boundary, leading to sedimentation breaks
and slumps as well as obvious changes in sediment geochemical composition, and representing the greatest tectonic activity
in the South China Sea region since the Oligocene. Through this tectonic event, the sedimentary environment in the Baiyun
sag area transformed from a continental shelf in the late Oligocene to a continental slope since the early Miocene, the provenance
of the sediments changed from neighboring areas to the hinterland of the South China block, and the sea level rose since the
early Miocene in the area. Therefore, this abrupt change event has a profound influence on the evolution of petroleum offshore
in the northern South China Sea.
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Translated from Geology in China, 2007, 34(6): 1022–1031 [译自: 中国地质] 相似文献
9.
This paper examines the surface sediments collected from Dongping Lake in China for speciation and distribution of toxic heavy metals (Cu, Pb, Ni, Cd) in different grain size fractions, and for the factors that need to be considered in potential hazard of metals to the environment. Four grain size fractions (<63, 63–78, 78–163 and 163–280 μm), divided in wet condition, and bulk samples less than 280 μm in diameter were analyzed for their distribution, density and appearance. A three-stage extraction procedure following the BCR protocol was used to chemically fractionate metals into “acid soluble”, “reducible”, “oxidizable” and “residual” fractions. Correlation analysis was used to analyze the datasets. The results showed that <63 μm grain size part constitutes the major proportion of the sediments, but its density is the smallest among the four grain size fractions. In general, the metal content curve against grain size presents “S” distribution, and the highest concentrations do not exist in <63 μm grain size. Appearance observation indicates that the adsorbed substance increases gradually along with the decreasing grain size. The dominant speciation of elements and the extent of pollution are responsible for the metal distribution in different grain size sediments. While studying bioavailability and mobilization of metals, it is advisable to take metal speciation, grain size distribution and density into consideration. 相似文献
10.
Chemodynamics of trace metal fractions in surface sediments of the Pandoh Lake,Lesser Himalaya,India
Anshumali A. L. Ramanathan Gurdeep Singh Gurmeet Singh Rajesh Ranjan Parijat Tripathi 《Environmental Geology》2009,57(8):1865-1879
The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface
sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary
organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme
(Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter,
respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and
summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites
due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability,
while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically
bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and
Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal
enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season. 相似文献
11.
The Late Permian Dalong Formation in Hubei, Hunan, Guizhou and Guangxi in South China could be subdivided into several sedimentary
types according to the lithology, indicative of the great spatial variations of both the lithology and sedimentary facies.
The Dalong Formation deposited during the highest transgression of Late Permian, in particular under the anaerobic and suboxic
conditions, which shows a strong linkage with the hydrocarbon source rocks. The Dalong Formation has some favorable properties
such as hydrocarbon source rocks, including the sediments deposited in highest transgression sea level, the deep slope sedimentary
environments and the low sedimentary rate, which raises the importance of the investigations on the sedimentary features,
the geochemical properties and their relationship with the oil potential.
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Translated from Earth Science—Journal of China University of Geosciences, 2007, 32(6): 774–780 [译自: 地球科学—中国地质大学学报] 相似文献
12.
Based on sampling depths, the research environment of the soil in a study area is divided into two parts: the I environment
(I-E) and the II environment (II-E). The results of the statistical analysis of arsenic (As) in the soil of the I-E indicates
that the statistical characteristic value obey a normal distribution. The mean value of As is close to the world mean value,
China and Tianjin City. Also, the contrast between the spatial change characteristics of As of the I-E and the II-E soils
showed that the I-E resembles the II-E in the content variety of As. On the other hand, geochemistry methods were applied
in the estimation of contaminated extent. The results indicated that the contamination extent of the north of Tianjin City
has not been serious.
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Translated from Geological Bulletin of China, 2007, 26(11): 1486–1493 [译自: 地质通报] 相似文献
13.
The paper presents the molybdenum isotope data, along with the trace element content, to investigate the geochemical behavior
of authigenic Mo during long-term burial in sediments in continental margin settings of the Yangtze block, as well as their
indication to the burial of original organic carbon. The burial rate of original organic carbon was estimated on the basis
of the amount of sedimentary sulfur (TS content), whilst the carbon loss by aerobic degradation was estimated according to
calculated Mn contents. On these points, the original organic carbon flux was calculated, exhibiting a large range of variation
(0.17–0.67 mmol/m2/day). The strong correlation between sedimentary Mo isotope values and organic carbon burial rates previously proposed on
the basis of the investigations on modern ocean sediments, was also used here to estimate the organic carbon burial rate.
The data gained through this model showed that organic carbon burial rates have large variations, ranging from 0.43–2.87 mmol/m2/day. Although the two sets of data gained through different geochemical records in the Yangtze block show a deviation of
one order of magnitude, they do display a strong correlation. It is thus tempting to speculate that the Mo isotope signature
of sediments may serve as a tracer for the accumulation rate of original organic carbon in the continental margin sediments.
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Translated from Earth Science—Journal of China University of Geosciences, 2007, 32(6) [译自: 地球科学—中国地质大学学报] 相似文献
14.
Bed sediment-associated trace metals in an urban stream, Oahu, Hawaii 总被引:78,自引:0,他引:78
R. A. Sutherland 《Environmental Geology》2000,39(6):611-627
Of the 117 stream and lake systems sampled nationwide, fish from Manoa Stream on Oahu, Hawaii, have consistently shown the
highest Pb concentrations. Therefore a detailed study was conducted to examine total metal contents in bed sediments from
a 5.8-km stretch of Manoa Stream. A total of 123 samples (<63 μm) were examined for 18 elements and 14 samples for 21 elements.
Selected samples were also examined using different leach solutions to examine metal phase associations. All trace metal data,
computations of enrichment ratios and the modified index of geoaccumulation point to mineralogical control for Cr and Ni;
minor anthropogenic contamination for Ba, Cd, Cu, Hg and Zn; and a very strong contamination signal for Pb. Maximum Pb contents
(up to 1080 mg kg−1) were associated with anthropogenic material dumping in minor tributaries, storm sewer sediments and sediments in the “lower”
section of the basin. Proportionally Pb had the highest non-residual component of elements examined; dominantly in the reducible
phase associated with Mn and amorphous Fe oxyhydroxides. The contamination signal was typically lowest in the “undisturbed”
headwater reach of the basin (above 5.1 km) with significant increases throughout the “residential” and “commercial-institutional”
zones of the mid-basin. The spatial pattern of bed sediment contamination and evidence from storm sewer-outlet sediments strongly
indicates that Pb, and to a lesser degree some other metals, is still being transported to the stream and the primary agent
is soil erosion and transport of metals sorbed to sediments. The primary source of sediment-associated metals is considered
to be the automobile, though other minor sources can not be ruled out.
Received: 3 November 1998 · Accepted: 26 January 1999 相似文献
15.
The calci-mircobialite is a special carbonate buildup, which is formed due to the activities of different kinds of microbes.
Abundant microfossils preserved in the microbialite show the high-level productivity during deposition, while characteristic
sedimentary minerals and geochemical compositions suggest an anoxic marine environment for organic burial. The high-level
productivity and anoxic sedimentary environment favor the efficient preservation of organic matter and thus the formation
of source rocks. On these points, microbialites could be one of the potential hydrocarbon source rocks, awaiting further geobiological
investigation and exploration. Precambrian and some of the great transitional stages in Phanerozoic are critical periods when
microbialites were well developed. Widespread microbialites have been found in North and South China. Bitumen observed in
many outcrops of Precambrian and late Devonian microbialites further raises the possibility of the calci-microbialite as a
potential hydrocarbon source rock.
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Translated from Earth Science-Journal of China University of Geosciences, 2007, 32(6): 797-802 [译自: 地球科学-中国地质大学学报] 相似文献
16.
Tang Feng Song Xueliang Yin Chongyu Liu Pengju S. M. Awramik Wang Ziqiang Gao Linzhi 《Frontiers of Earth Science》2007,1(2):142-149
A morphologically more diverse assemblage of Longfengshaniaceae has been found in the uppermost Ediacaran (Sinian) Jiucheng
Member, Yuhucun Formation at Jinning and Jiangchuan, eastern Yunnan, South China. A majority of them are different from the
Longfengshania found in the Neoproterozoic Changlongshan Formation, Yanshan Mountain area, North China and the Little Dal Group, North America.
They are mainly characterized by a more varied, often thallus-like appearance with no branches, such as oval, pyriform, spindle,
shovel, heart, ribbon and balloon shapes, and more sturdy stalk-like projection (stipe) with a smooth connection on the basal
part of the thallus. In addition, they appear to have a remarkable attaching organ of lanceolate, shuttle-like or short stem-like
structure at the base of the stipe. Six distinct morphological taxa are recognized, including one new genus, two new species
and three conformis species. The characteristics of the family and the genus Longfengshania are further discussed in this paper. The new discoveries of these carbonaceous macrofossils identified as Longfengshaniaceae
algae on the basis of the diagnostic forms and anastomosis patterns of their thalli and stipes demonstrate that an important
evolutionary radiation of metaphytes took place in the last Ediacaran stage. The flourishing of the benthonic thallophytes
attached to the substrate from eastern Yunnan and considered to be photosynthetic alga probably provided continuous nutritional
habitats for the explosion and diversification of the Early Cambrian “Chengjiang biota”.
Translated from Acta Geologica Sinica, 2006, 80(11): 1643–1649 [译自: 地质学报] 相似文献
17.
Jianyu Chen Delu Pan Mingliang Liu Zhihua Mao Qiankun Zhu Ninghua Chen Xiaoyu Zhang Bangyi Tao 《Estuaries and Coasts》2017,40(4):1055-1065
The Changjiang Estuary is one of the largest estuaries in the world, where hypoxia frequently occurs during the summer season. Recent routine surveys in the observed area found that the low dissolved oxygen (DO) in the summer bottom water was not rapidly expanding with increasing nutrient loads in Changjiang diluted waters. Based on the remote sensing data and in situ data, we examined the historic seasonal hypoxia observations for the bottom waters of the Changjiang Estuary and investigated the short- and long-term effects that runoff had on variations in DO and chlorophyll-a (Chl-a). Our analysis indicated that the recent areal variation in hypoxia was due to the changing Chl-a distribution and stratification conditions. The correspondence between hypoxia and surface Chl-a concentration showed that remotely sensed Chl-a larger than 3.0 mg L?1 was an essential condition for the formation of hypoxia off the Changjiang Estuary. The trend of Chl-a concentration was significantly impacted by the Three Gorges Dam (TGD), and the inter-annual variation of Chl-a was weakly affected by global-scale climate variability. After the TGD impoundment, the sediment loading in the Changjiang runoff and suspended sediments in Changjiang Estuary in August decreased, and the high Chl-a concentration moved landward. These shifted the hypoxia from its optimal forming conditions. 相似文献
18.
Yu Zou Dongna Liu Hongwei Kuang Changgui Song Yuxiang Sun 《International Geology Review》2020,62(11):1433-1449
ABSTRACT Mesoproterozoic red beds near ancient coasts have not aroused extensive interest. A new geochemical study of the alternating red and grey dolostones from the Yangzhuang Formation provides a better understanding of the redox conditions of nearshore sedimentary environments. In this contribution, whole-rock samples are characterized by positive correlations of rare earth elements (REE) vs. Th and FeT vs. Th and flat-type REE distribution patterns, indicating massive terrigenous input, which is considered to be inherited from felsic rocks. Relatively high (Femag+Feox)/FeT and Fe3+/Fe2+ ratios in red beds indicate more oxidized conditions in supratidal environments compared with the lower oxygen contents in intertidal environments. Under these two distinct chemical sedimentary conditions, acetic acid-leached red and grey samples both have HREE-depleted distributions, suggesting significant freshwater invasion. Moreover, limited terrigenous redox-sensitive elements (RSEs) can reach the coast where the red beds are deposited, whereas relatively high RSE enrichment factors originating from shallow oceans are recorded in grey beds. In the Mesoproterozoic, limited oxidative weathering, shallow seawater desalination, and low organic production occurred near the coast. Meanwhile, a prolonged period of low Mo and U availability preserved in carbonate minerals confirmed that marine oxygen levels failed to satisfy the deposition of offshore red beds. During the regression, potentially exposed sediments connected to atmospheric oxygen guaranteed the oxidation of iron and the formation of red beds, and these events were coupled with negative δ13Ccarb shifts in the Yanliao rift zone. 相似文献
19.
The North Qilian orogenic belt is an elongate tectonic unit that lies between the North China plate to the north and the Middle
Qilian microplate to the south, and is formed by a collision of the two plates in the Caledonian. The Shihuigou Section from
Yongdeng County, Gansu Province, is in the eastern sector of the North Qilian Mountains, spanning the Ordovician island-arc
zones. The Zhongpu Group is distributed in the Shihuigou area and composed of medium-basic volcanic rocks and volcanic clastic
rocks interspersed with cherts, limestones, slates, and metamorphic sandstones. The geochemistry of chert from the Zhongpu
Group reveals that all cherts coexisting with island-arc volcanic rocks formed in a continental margin basin environment.
Research results of the rare earth elements reveal that these cherts formed in a relatively deep-water basin with no significant
terrestrial interference. Therefore, it is inferred that the North Qilian orogenic belt was previously an archipelagic ocean
in the Ordovician.
Translated from Geological Review, 2006, 52(2): 184–189 [译自: 地质论评] 相似文献
20.
Zheng Jianping Yu Chunmei Yuan Xiaoping Yin Li Jiao Shujuan Tang Huayun Zhang Zhihai Lu Fengxiang 《Frontiers of Earth Science》2007,1(1):37-43
A petrochemical analysis was undertaken of peridotitic xenoliths in volcanic rocks that erupted from the Paleozoic to the
Cenozoic within the eastern part of the North China craton, and the peridotites as tectonic intrusion in the Early Mesozoic
from the Sulu orogen. The results show that the cratonic mantle, which was refractory and existed when the kimberlites intruded
in the Paleozoic, had almost been replaced by the newly accreted fertile lithospheric mantle during the Mesozoic-Cenozoic.
The erosion, metasomatism, and intermingling caused by the accreted asthenospheric material acting on the craton mantle along
the weak zone and deep fault (such as the Tanlu fault) in the existing lithosphere resulted in the lithospheric thinning at
a larger scale 100 Ma ago (but later than 178 Ma). The largest thinning would be in the Eogene. The upwelling asthenospheric
material transformed into accreted lithospheric mantle due to the asthenospheric temperature falling in the Neogene (leading
to relatively slight lithospheric incrassation), and finally accomplished mantle replacement. The peridotitic body in the
Sulu orogen represents the products spreading from the modified cratonic lithospheric mantle.
Translated from Earth Science—Journal of China University of Geosciences, 2006, 31(1): 49–56 [译自: 地球科学—中国地质大学学报] 相似文献