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1.
沉积物中元素碳的提取、鉴定及其古气候环境意义 总被引:1,自引:0,他引:1
通过化学氧化方法提取沉积物中元素碳物质,采用拉曼光谱对其进行分析鉴定,实验结果表明:元素碳是介于单晶石墨碳和无定形碳之间的一系列物质,是一种操作上的定义;化学氧化法提取沉积物中元素碳是可靠的,控制好氧化条件和时间,则能有效去除有机碳,保留元素碳成份。鉴于目前不同工作者由于不同的实验条件和方法下得到了不同结果,我们认为确定标准样及其浓度,统一实验方法是亟待解决的问题,进而统一这种碳微粒的名称,明确其定义,以利于相关研究的横向对比和深入。而在纵向研究方面,我们利用该实验流程提取灵台黄土剖面长时间序列黄土—古土壤样的元素碳,并进行元素碳含量的测定,结果表明元素碳记录能有效揭示古气候环境变化。在不同时间尺度上,元素碳记录有不同的气候指示意义,并且与其他气候环境指标能进行较好的对比,元素碳记录为古气候环境变化提供一新的指标。 相似文献
2.
Late Holocene high precipitation events recorded in lake sediments and catchment geomorphology,Lake Vuoksjávrátje,NW Sweden 下载免费PDF全文
Annika Berntsson Krister N. Jansson Malin E. Kylander Francois De Vleeschouwer Sebastien Bertrand 《Boreas: An International Journal of Quaternary Research》2015,44(4):676-692
In this paper, we show the potential of combining multi‐proxy analysis of lake sediments with catchment geomorphology to better understand palaeoenvironmental changes. Previous studies have suggested that alpine lakes in N Sweden may be highly sensitive to variations in catchment erosion and precipitation, and that this sensitivity may influence ecologically based reconstructions of past temperature changes. We analysed lake sediments covering the last 5100 years from the alpine Lake Vuoksjávrátje in NW Sweden in order to identify different erosional regimes in the lake catchment, sediment sources and lake sedimentary processes, which ultimately affect the palaeoecological record. The measured proxies include elemental geochemistry from XRF core scanning, grain size, sediment accumulation rates, fraction of terrestrial organic carbon and geomorphological mapping, supported by previously published chironomid and total organic carbon data. From the integrated results we identified time intervals when increased intensity of precipitation altered sedimentation and lake catchment erosional processes. The most prominent event occurred c. 2900 cal. a BP and is interpreted to be the result of excessive precipitation, possibly related to the climatic shift towards cooler and wetter conditions referred to as the 2.8 ka event. 相似文献
3.
Sediment particle size distribution and its environmental significance in Lake Erhai, Yunnan Province 总被引:1,自引:0,他引:1
A closed or semi-closed plateau lake, whose sediment records can provide us with plenty of fine and high resolution information,
is a sensitive indicator of climatic and environmental changes. During the reconstruction of various short-time-scale climatic
and environmental changes, the geochemical records in plateau-lake sediments are superior to other natural files. Based on
fine dissection of the vertical profile of sediment particle sizes, this paper reveals the quasi-periodical changes of sediment
particle sizes, which indicates the quasi-periodical fluctuations of the regional climate. A synthetic analysis of multiple
indexes shows that sediment particle size is a more sensitive and more effective index of climatic and environmental changes
than other geochemical indexes. High content of >20μm sediment particles and low content of 2–10μm sediment particles indicate a warm-dry climate and conversely a cold-humid climate, and their ratio can be used as an effective
index of climatic changes. The basic climate succession in the region of Lake Erhai is characterized as being alternatively
warm-dry and cold-humid and it has been developing into a warm-dry climate as a whole. There exist at least 2 time-scale quasi-periodical
fluctuations of the regional climate in Lake Erhai. At present, the region of Lake Erhai is at the end of the warm-dry period
and at the beginning of a cold-humid period, so the temperature will go down and the water level will rise.
This project was supported by the National Natural Science Foundation of China (Nos. 49894170, 49773207). 相似文献
4.
Application of allochthonous organic carbon and phosphorus forms in the interpretation of past environmental conditions 总被引:2,自引:0,他引:2
Changwei Lü Jiang He Huimin Sun Hongxi Xue Ying Liang Saruli Bai Ying Sun Lili Shen Qingyun Fan 《Environmental Geology》2008,55(6):1279-1289
Organic matter in sediments, for instance, carbon, nitrogen and phosphorus, can be used to reconstruct the paleoecological
and pollution history of lakes and their catchment basins. In this paper, the contents of allochthonous organic carbon (allochthonous
OC) and autochthonous organic carbon (autochthonous OC) in sediment cores taken from Wuliangsuhai Lake and Daihai Lake in
northern China are quantified by using a binary model, and phosphorus forms in the sediment cores from the two lakes are extracted
by sequential extraction techniques. The results indicate that the palaeoenvironment and paleoclimate of Daihai Lake and
its catchment basin in the recent 250 years can be well reconstructed based on the content of allochthonous OC. The climate
was relatively humid and warm in the period of 1865–2005, while relatively dry and cold in the period of 1765–1865. The sedimentary
information of allochthonous OC in the 22–42-cm portion of the sediment cores in Daihai Lake corresponds to the final cold
fluctuation of the Little Ice Age that occurred since the Middle Holocene. The difference of phosphorus forms in the sediment
cores between the two lakes indicates that phosphorus input to the lakes and the correlation between phosphorus forms and
distribution and the changes of environment are influenced by the eutrophication mechanisms and environmental conditions of
the two lakes. 相似文献
5.
A. H. M. Selim Reza Jiin-Shuh Jean Ming-Kuo Lee Shang-De Luo Jochen Bundschuh Hong-Chun Li Huai-Jen Yang Chia-Chuan Liu 《Environmental Earth Sciences》2011,63(5):955-967
Two boreholes and ten piezometers in the Ganges flood plain were drilled and installed for collecting As-rich sediments and
groundwater. Groundwater samples from the Ganges flood plain were collected for the analysis of cations (Ca2+, Mg2+, K+, Na+), anions (Cl−, NO3
−, SO4
2−), total organic carbon (TOC), and trace elements (As, Mn, Fe, Sr, Se, Ni, Co, Cu, Mo, Sb, Pb). X-ray powder diffraction was
performed to characterize the major mineral contents of aquifer sediments and X-ray fluorescence (XRF) to analyze the major
chemical composition of alluvial sediments. Results of XRF analysis clearly show that fine-grained sediments contain higher
amounts of trace element because of their high surface area for adsorption. Relative fluorescence index (15–38 QSU) of humic
substance in groundwater was measured using spectrofluorometer, the results revealed that groundwater in the Ganges flood
plain contains less organic matter (OM). Arsenic concentration in water ranges from 2.8 to 170 μg/L (mean 50 μg/L) in the
Ganges flood plain. Arsenic content in sediments ranges from 2.1 to 14 mg/kg (mean 4.58 mg/kg) in the flood plains. TOC ranges
from 0.49 to 3.53 g/kg (mean 1.64 g/kg) in the Ganges flood plain. Arsenic is positively correlated with TOC (R
2 = 0.55) in sediments of this plain. Humic substances were extracted from the sediments from the Ganges flood plain. Fourier
transform infrared analysis of the sediments revealed that the plain contains less humic substances. The source of organic
carbon was assigned from δ13C values obtained using elemental analysis-isotope ratio mass spectrometry (EA-IRMS); the values (−10 to −29.44‰) strongly
support the hypothesis that the OM of the Ganges flood plain is of terrestrial origin. 相似文献
6.
贵州荔波董哥洞3号石笋的同位素年龄及古气候信息 总被引:12,自引:2,他引:12
石笋是岩溶记录中最全面、最系统的古气候环境信息库,研究表明,洞穴内、外环境变化,都不同程度地显示在石笋的组成、结构构造、沉积 (生长 )纹层及其层面构造、沉积速率和古气候环境变化等方面。利用洞穴石笋保存的信息重建古环境,是近 2 0年来的热门课题之一。当前全球气候变化预测研究中,洞穴石笋的高分辨率定年和碳、氧同位素组成的变化规律,为这个领域的突破和填补空白作出了重大贡献。本文通过对荔波董哥洞 3号石笋进行热电离质谱 (TIMS)U-系测年及碳氧同位素分析,获得了距今 16.33万年至 9.13万年的古气候信息。石笋在大于 16.33万年前开始生长,9.13万年后停止生长,平均沉积速率为 2.87mm/ 100a(未扣出间断时间 ),属中更新世的产物。其年龄与δ18O的变化可与深海岩芯V2 8~ 2 38同位素记录所揭示的第五和第六阶段以及与北方离石黄土层 (L2 )和下马兰黄土第一古土壤层 (S1)进行对比。它反映此阶段区内经历了寒冷和温暖 (间夹冷期 )等气候变化,与全球古气候变化波动基本一致,同时也存在地区性的气候变化。 相似文献
7.
Two vibrocores from the inner shelf off Hong Kong are investigated to compare the contents of organic and inorganic carbon
in postglacial sediments. The compositions of organic elements and carbonate are highly variable in the core sediments, but
overall drop within the compositional ranges of modern seabed sediments in the Zhujiang estuarine and its shelf area. The
Holocene sediments in the inner shelf have never been subject to subaerial exposure and the organic matter and carbonate can
be preserved well. The burial of carbon in river-dominated shelf environments is highly dependent on the river flux with time.
Nevertheless, it is difficult to establish a simple relationship between carbon burial in sediments in relation to climatic
changes of basin-wide scale due to complex controls of production, transport and deposition of organic matter and carbonate.
Our study suggests that the organic carbon to nitrogen ratio can not reliably identify the sources of depositional organic
matters because of selective decomposition of organic matter components during humification and sedimentation. Caution is
therefore needed in using organic elemental compositions as indicators of organic matter sources and paleoenvironmental changes
in the East Asian continental shelves where intense river-sea interaction and variable carbon flux in geologic record occur. 相似文献
8.
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.
__________
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
9.
Kristensen E 《Geochemical transactions》2001,2(1):92
Known effects of bioturbation by common polychaetes (Nereis spp. and Arenicola marina) in Northern European coastal waters on sediment carbon diagenesis is summarized and assessed. The physical impact of irrigation and reworking activity of the involved polychaete species is evaluated and related to their basic biology. Based on past and present experimental work, it is concluded that effects of bioturbation on carbon diagenesis from manipulated laboratory experiments cannot be directly extrapolated to in situ conditions. The 45–260% flux (e.g., CO2 release) enhancement found in the laboratory is much higher than usually observed in the field (10–25%). Thus, the faunal induced enhancement of microbial carbon oxidation in natural sediments instead causes a reduction of the organic matter inventory rather than an increased release of CO2 across the sediment/water interface. The relative decrease in organic inventory (G b /G u) is inversely related to the relative increase in microbial capacity for organic matter decay (k b /k u). The equilibrium is controlled by the balance between organic input (deposition of organic matter at the sediment surface) and the intensity of bioturbation. Introduction of oxygen to subsurface sediment and removal of metabolites are considered the two most important underlying mechanisms for the stimulation of carbon oxidation by burrowing fauna. Introduction of oxygen to deep sediment layers of low microbial activity, either by downward irrigation transport of overlying oxic water or by upward reworking transport of sediment to the oxic water column will increase carbon oxidation of anaerobically refractory organic matter. It appears that the irrigation effect is larger than and to a higher degree dependent on animal density than the reworking effect. Enhancement of anaerobic carbon oxidation by removal of metabolites (reduced diffusion scale) may cause a significant increase in total sediment metabolism. This is caused by three possible mechanisms: (i) combined mineralization and biological uptake; (ii) combined mineralization and abiogenic precipitation; and (iii) alleviation of metabolite inhibition. Finally, some suggestions for future work on bioturbation effects are presented, including: (i) experimental verification of metabolite inhibition in bioturbated sediments; (ii) mapping and quantification of the role of metals as electron acceptors in bioturbated sediments; and (iii) identification of microbial community composition by the use of new molecular biological techniques. These three topics are not intended to cover all unresolved aspects of bioturbation, but should rather be considered a list of obvious gaps in our knowledge and present new and appealing approaches. 相似文献
10.
Marina A. Morlock Hendrik Vogel James M. Russell Flavio S. Anselmetti Satria Bijaksana 《第四纪科学杂志》2021,36(6):1040-1051
Continental and marine sediments are composed of a mixture from different sources and are influenced by a variety of environmental factors and transport processes prior to deposition. For analysis and interpretation, these sources and processes are often challenging to disentangle. We show that end-member modelling of X-ray fluorescence (XRF) core-scanning data helps to overcome these challenges by unmixing different environmental signals from high-resolution sediment geochemical records. We apply this approach to a 100 m long lacustrine succession from Lake Towuti, Indonesia, to separate the regional climate and tectonic history from local ecological and diagenetic processes. The resulting six end-members (EMs) are interpreted to represent changes in ecological (EM1), climatic (EMs 2–4), tectonic (EM 5) and geomorphic (EM6) processes determining changes in sediment composition. Because end-member analysis allows for the tracking of transient and overlapping processes, climatic changes can be followed throughout the 100 m-long succession, suggesting alternating wet and dry periods in Central Sulawesi over long (several 100 000 years) time scales. We show that end-member analysis on elemental data sets offers a detailed and objective means to disentangle depositional processes in sedimentary successions resulting from varying tectonic and environmental factors involved in sediment formation and deposition. 相似文献
11.
Authigenic carbonates in methane seeps from the Norwegian sea: Mineralogy, geochemistry, and genesis
A. Yu. Lein A. I. Gorshkov N. V. Pimenov Yu. A. Bogdanov P. Vogt O. Yu. Bogdanova V. M. Kuptsov N. V. Ul’yanova A. M. Sagalevich M. V. Ivanov 《Lithology and Mineral Resources》2000,35(4):295-310
Authigenic carbonates in the caldera of an Arctic (72°N) submarine mud volcano with active CH4bearing fluid discharge are formed at the bottom surface during anaerobic microbial methane oxidation. The microbial community
consists of specific methane-producing bacteria, which act as methanetrophic ones in conditions of excess methane, and sulfate
reducers developing on hydrogen, which is an intermediate product of microbial CH4 oxidation. Isotopically light carbon (δ13Cav =−28.9%0) of carbon dioxide produced during CH4 oxidation is the main carbonate carbon source. Heavy oxygen isotope ratio (δ18Oav = 5%0) in carbonates is inherited from seawater sulfate. A rapid sulfate reduction (up to 12 mg S dm−3 day−1) results in total exhausting of sulfate ion in the upper sediment layer (10 cm). Because of this, carbonates can only be
formed in surface sediments near the water-bottom interface. Authigenic carbonates occurring within sediments occur do notin situ. Salinity, as well as CO
3
2−
/Ca and Mg/Ca ratios, correspond to the field of nonmagnesian calcium carbonate precipitation. Calcite is the dominant carbonate
mineral in the methane seep caldera, where it occurs in the paragenetic association with barite. The radiocarbon age of carbonates
is about 10000 yr. 相似文献
12.
Investigation of biogeochemistry and amino acids on a 30-m-long core from Mansar Lake has thrown light on palaeoclimate variability
during the Holocene period. The C/N ratio between 6 and 10 with some deviations and δ13C mostly between −20 and −22‰ in the
shallow core, as well as a C/N ratio greater than 13 reaching from 19 to 20 and correspondingly lower δ13C of –28‰ in the
deeper core suggest an aquatic source of carbon in the former and a cellulose-rich land plant source in the latter. This is
supported by the abrupt increase in organic carbon content in the deeper core compared to the shallow core, which indicates
a hot and wet climatic regime during the early Holocene and dry and cold during the late Holocene period. The amino acid data
AA-C/C% and AA-N/N% are higher in shallow sediments compared to deeper sediments, indicating an aquatic plant source in the
shallow core and greater supply of land plant sources in the deeper core. The lower percentage of the non-protein amino acids
β-alanine (ALA) and γ-amino-butyric acid in the shallow core compared to the deeper core indicates different sources of organic
matter in the lake basin. The higher amino acid ratio Asp/β-Ala (16.99 av.) and Glu/γ-Aba (18.18 av.) in the shallow core
and lower ratios (10.32 and 12.41 av.) in the deeper core, and Asp/Glu (1.52 av.) and β-Ala/γ-Aba (1.61 av.) ratios in the
former, which are potential indicators of the nature of the organic matter, are higher in the shallow core relative to the
deeper core (1.33 and 1.23 av.), indicating relative biodegradation of organic matter in deeper sediments. It has been observed
that the organic matter associated with the dry season is relatively less biodegraded, as evidenced from their higher ratios,
and is more biodegraded in the wet season as their ratios are lower in the river sediments. In the absence of a bacterial
contribution of organic matter from the soil source in this lake, since Mansar Lake is a non-drainage type, it is envisaged
that the climatic variation may be responsible for biodegradation in the deeper core sediments. Therefore, the C/N ratio and
δ13C values supported by amino acid data, the latter being significant in revealing primary productivity and a terrestrial
source of organic matter, suggest a hot and wet climatic regime during the early Holocene (ca. 7580 bp) and a dry and cold in the late Holocene period (ca. 4050 bp). 相似文献
13.
Metabolic effects on stable carbon isotopic composition of freshwater bivalve shell Corbicula fluminea 总被引:1,自引:0,他引:1
The stable isotopic composition of the bivalve shell has been widely used to reconstruct the pa-laeo-climate and palaeo-environment. The climatic and environmental significance of carbon isotopic composition of the bivalve shell is still in dispute, and incorporation of metabolic carbon can obscure carbon isotope records of dis-solved inorganic carbon. This study deals with freshwater bivalve, Corbicula fluminea aragonite shell. The results indicated that the δ13C values of bivalve shells deposited out of equilibrium with the host water and showed an onto-genic decrease, indicating that there are metabolic effects and more metabolic carbon is incorporated into larger shells. The proportion of metabolic carbon of shells varies between 19.8% and 26.8%. However, δ13CS can still be used as qualitative indicators of δ13CDIC and environmental processes that occurred during shell growth. 相似文献
14.
We conducted rock magnetic and paleomagnetic research on two deep-sea sediment cores from the west Philippine Sea, located
to the east of Benham Rise with the length of 4 m and water depth of over 5000 m. At the bottom of core 146 occurs a reversal
of inclination and deflection of relative declination, which is recognized as Brunhes-Matuyama Polarity Boundary (MBPB). No
reversal occurs in core 89, which implies a younger bottom age than that of core 146. Rock magnetic results reveal magnetic
uniformities in mineralogy, concentration and grain size along the two cores, thus relative paleointensity variations are
acquired. The three normalizers-anhysteresis remanent magnetization (ARM), magnetic susceptibility (k) and saturation isothermal remanent magnetization (SIRM) are used for normalization to obtain relative paleointensities.
The three normalization results are averaged to indicate the paleoitensity of the cores and are further stacked together to
get a synthetic curve for west Philippine Sea (named asWPS800 in this paper). Based on the magnetic correlation between cores
and paleointensity to Sint800, we transfer the changes of rock magnetic parameters from depth to time. Furthermore, the astronomically
tuned oxygen isotope from ODP site 1143 in the south China Sea is used for the glacial and interglacial indicator. Three concentration
proxies (ARM, k and SIRM) and grain size indicators (k
ARM/SIRM, k
ARM/k) are examined according to the paleointensity-assisted chronology. The grain size changes in the two cores display a consistent
pattern with the climatic changes embodied by oxygen isotope. The magnetic sizes are usually coarser in glacial periods and
finer in interglacial times, which may reflect the influence of chemical erosion rather than fining from sea level rising
on the source sediment. Furthermore, the sub-peaks and sub-troughs in interglaciations almost correspond with that of oxygen
isotope records, which means sedimentation can reflect the subtle changes in interglaciations. This kind of revelation of
climatic fluctuation by magnetic size is also found in the South China Sea, which shows a common pattern of magnetic signals
to climate at least within East Asia. The concentration of ARM (representing more about fine grain) also shows similar response
to glacial and interglacial cycles, that is, high in interglacial cycle and low in glacial cycle; but k and SIRM (reflecting more about coarse grain) lack the response to the climatic cycles. At the same time, S-ratio lacks the
correlation with aeolian dust record and rhythmic changes, indicating the dominant source of main magnetic carrier (low coercivity
magnetite) is the suspended matter instead of dust. The decreasing trend of sedimentation rate from west to east also reveals
that the sediments are mainly from west Luzon and adjacent land. Grain sizes first became coarse and then stable around 400
ka B.P., and at the same time all the magnetic contents lowered and amplitude of magnetic mineral changes increased. The magnetic
transition around 400 ka B.P. is simultaneous with the decreases of carbonate content, reflecting a global carbonate dissolution
event, i.e. mid Brunhes event. The synchronization of magnetic content and grain size with climatic cycles of glacials and
interglacials imply the validity of paleointesnityassisted chronology. Also, the response of rock magnetic signals to stable
oxygen isotope changes and carbonate variation reveals that rock magnetismmethod can be an effective tool for paleoclimatic
and paleoceanographic research.
__________
Translated from Quaternary Sciences, 2007, 27(6): 1040–1052 [译自 : 第四纪研究] 相似文献
15.
The stage height, dissolved oxygen, and redox potential of the surface water and sediments of an intertidal Texas wetland
were evaluated using continuous monitoring techniques. Surface water oxygenation was most drastically affected by photosynthesis,
which served to elevate daytime oxygen concentrations compared to those measured at night. Colder temperatures affected dissolved
oxygen concentrations by increasing solubility and decreasing heterotrophic consumption. Waters of the San Jacinto River were
generally more oxygenated than those in the wetland, and incoming tides typically elevated dissolved oxygen levels unless
the tide was in direct conflict with the daily photosynthetic cycle. The redox potentials in the sediments could not be correlated
with a daily cycle as was found in the surface waters. Redox potentials in the intertidal zone fluctuated between −150 mV
and 300 mV throughout normal cycles of periodic inundation and exhibited decreasing potentials with depth. Sediments further
from the waterline had denser vegetation and exhibited higher redox potentials under similar hydrodynamic loading. During
extremely dry periods, redox potentials varied from 300 mV to 600 mV, and deeper sediments were often more oxygenated than
sediments closer to the sediment-air interface, due to the higher rates of metabolism in the upper stratum. Rates of oxidation
and reduction in the sediments were lognormal and evenly distributed about the steady state, with maximum rates of 300 mV
min−1 during intermittent periods of inundation. The results show that biological carbon oxidation in sediments can entirely deplete
oxygen from surface waters overlying the mud flats, that vegetation serves to oxygenate the rhizosphere, and although redox
potential changes can be large in the dynamic intertidal zone, large changes are infrequent. 相似文献
16.
Geochemical Characteristics of Amino Acids in Sediments of Lake Taihu, A Large, Shallow, Eutrophic Freshwater Lake of China 总被引:1,自引:0,他引:1
Xin Yao Guangwei Zhu Linlin Cai Mengyuan Zhu Linlin Zhao Guang Gao Boqiang Qin 《Aquatic Geochemistry》2012,18(3):263-280
To examine the biogeochemistry of amino acids (AAs) in the sediment of Lake Taihu, surface sediments (0–3 cm) and deeper sediments
(18–21 cm) were collected at 21 sites from different ecotype zones of the lake. AAs were extracted from the sediments, and
the total hydrolyzable amino acids (THAA) were determined by high-performance liquid chromatography instrument. The THAA contents
in Taihu sediment were much lower than that in marine sediments, ranging from 6.84 to 38.24 μmol g−1 in surface sediments and from 2.91 to 18.75 μmol g−1 in deeper sediments in Taihu, respectively. AAs were a major fraction of the organic matter (OM) and organic nitrogen in
Taihu sediments. The AAs on average contributed 8.2% of organic carbon (OC) and 25.0% of total nitrogen (TN) from surface
sediments, and 5.9% of OC and 20.5% of TN in deeper sediments, respectively. AA composition provided very useful information
about the degradation of OM. Glycine (Gly) and lysine (Lys) were the predominant forms of AAs in the sediments, irrespective
of lake regions, followed by alanine, glutamic acid, serine (Ser), and aspartic acid (Asp). The high concentrations of Gly,
Lys, and Ser suggested that these forms of AAs were relatively refractory during OM degradation in sediments. The relationship
between the Asp/Gly ratio and Ser + Thr [mol%] indicated that OM in surface sediment was relatively fresher than that in deeper
sediments. The AAs-based degradation index (DI) gave a similar conclusion. The composition and DI of AAs in surface sediments
are markedly different across different zones in Taihu. The percentages of AAs to organic carbon (AA-C%) and total nitrogen
(AA-N%) were higher in phytoplankton-dominated zones than those in macrophyte-dominated zones. These results suggest that
DI could provide useful information about the degradation of OM in shallow lakes such as Taihu. 相似文献
17.
以青藏高原西南部塔若错的34cm浅湖芯为研究对象,对其沉积物样品进行总有机碳、无机碳、总氮、微量元素、正构烷烃含量及碳氮比等多项指标的分析测定。采用过剩210Pb和137Cs计年法对该湖芯进行了定年和沉积速率研究,获得了近300年的连续湖泊沉积环境序列。在明确了各指标气候环境指示意义的前提下,综合对比分析湖芯中各项气候环境指标,并结合定年结果重建了塔若错湖区近300年来的气候环境变化。结果表明:塔若错湖区气候环境变化可分为3个明显阶段:早期为1705~1778年,该地区气候环境温暖湿润,湖区植被广泛发育;中期为1778~1860年,湖区处于小冰期末次阶段,气候环境寒冷而湿润,植被发育受阻;后期为1860年至今,为小冰期结束后偏暖干化时期。其中,后期又可分为3个亚阶段:1860~1924年,湖区气候环境稍暖且干旱,植被稍有发育;1924~1969年,湖区气候环境呈现偏冷干特点,植被发育暂缓;1969年至今,湖区气候回暖,环境干旱化有所缓解,植被开始逐渐发育。在气候冷暖变化上,该湖芯记录与古里雅冰芯记录和青海湖湖泊沉积记录都有较好的可对比性,只是在起讫年代上存在一些差异。 相似文献
18.
Liu Gang Liu Puling Yang Mingyi Cai Chongfa Xu Wennian Zhang Qiong Yang Wei 《Environmental Earth Sciences》2013,70(7):2997-3004
The substitutive climatic proxies contain climate data, including temperature, rainfall, monsoon, and so on. However, the environmental significance and relationships among climatic proxies remain uncertain. In this research, soil samples from three soil profiles in the Holocene at the middle Chinese Loess Plateau were studied to analyze the change of seven substitutive climatic proxies. The rescaled range analysis method and Pearson correlation coefficient were employed to determine the significance and relationships among these proxies. The results indicated that the magnetic susceptibility of soil, total ferrum content, and pH can reflect changes in both temperature and rainfall during soil formation. In addition, calcium carbonate content and total organic carbon were mainly affected by the rainfall and temperature, respectively. Particle size composition (clay fraction <0.005 mm and coarse silt 0.01–0.05 mm) is an effective means by which to describe the effects of the East Asian winter monsoon. The results of this study provide theoretical basis and scientific reference for further paleoclimate evolution research. 相似文献
19.
Dubravka Relić Dragana Đorđević Aleksandar Popović 《Environmental Earth Sciences》2011,63(6):1303-1317
We used elemental carbon, nitrogen, hydrogen and sulfur as well as ratios of hydrogen and nitrogen with total organic carbon
for investigation of source and conditions of organic matter in alluvial Danube sediments. We also determined the pseudo total
concentrations of metals presented as a sum of extracted concentration after five sequential extraction steps. The pseudo
total metal concentrations were found to be (mg kg−1) for Mn, 666; Fe, 25,852; Mg, 16,193; K, 2,063; Ni, 32.4; Zn, 72.2; Pb, 15.0; Cu, 26.0 and for Cr, 15.9. Correlation analysis
and two multivariate analysis methods (principal component and cluster analysis) were helpful in determining the associations
between the pseudo total extracted fractions of metals and with elemental carbon, hydrogen, nitrogen, sulfur, total inorganic
and organic carbon. These correlations will help us to identify substrates of trace metals in different oxic/anoxic conditions.
The correlation results of the trace metals and Fe, K, Mg and Mn suggest their adsorption, mainly onto Fe and Mn (hydro)oxides
and K alumosilicates, whereas correlations of metals with sulfur indicate that they were precipitated as Fe-sulfides. 相似文献
20.
Chemical characteristics and pollution sources of petroleum hydrocarbons and PAHs in sediments from the Beiluohe River,Northern China 总被引:4,自引:0,他引:4
To determine the degree of hydrocarbon contamination and the contribution of local petroleum industries to contaminant loadings
in sediments from the Beiluohe River, China, 12 surface sediment samples were collected for geochemical analysis in 2005.
Sediment samples were extracted by organic solvents, separated by silica gel column chromatography and the profiles of n-alkanes, biomarkers and polycyclic aromatic hydrocarbons (PAHs) in sediments were analyzed by gas chromatography with flame
ionization detector and gas chromatography/mass spectroscopy. Concentrations of total hydrocarbons in the sediments varied
from 12.1 to 3,761.5 μg g−1 dry wt, indicating that most sediments in Beiluohe River was only slightly to moderately contaminated by hydrocarbons. Concentrations
of PAHs for six samples (sum of 16 isomers) varied from 17.7 to 407.7 ng g−1 dry wt and at present low levels of PAHs did not cause adverse biological effects in Beiluohe River sedimentary environment.
PAH compositions, n-alkanes and biomarker profiles all suggested that there were different sources of contaminations in studied areas. n-Alkanes reflect two distinct sources: a fossil n-alkane series from crude oil at sites S40, S43, S87 and plantwax n-alkanes at sites S39 and S45. Judged by their PAH ratios, the sediments at site S15 were pyrolytic, sediments at S17 and
S43 were petrogenic, and sediments at S39, S40 and S64 had a mixture source of pyrolytic and petrogenic. 相似文献