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1.
Wissem Frikha Habib Zargayouna Samia Boussetta Mounir Bouassida 《Geotechnical and Geological Engineering》2017,35(3):931-947
Tunis soft clay belongs to the category of problematic soils because of its weak strength characteristics, high compressibility and high content of organic matter (22%). Deep mixing column (DM) presents a well-developed technique to improve the properties of Tunis soft soils by increasing its bearing capacity and reducing settlements. This paper describes a laboratory experimental program performed to assess the effectiveness in improving the shear strength of Tunis soft clay. The two mains objectives of this research are to evaluate the effect of reinforcement by DM on the behaviour of the Tunis soft clay and to investigate parameters of influence on its strength characteristics. Five parameters are studied from the performed tests: (1) curing time: CT = 7, 14, 21 and 28 days; (2) injection pressure: IP = 50, 100 and 150 kPa; (3) water–cement ratio w/C = 0.7, 1 and 1.2; (4) rotation rate V = 15, 30 and 40 rpm and (5) consolidation pressure: б3 = 100, 150 and 200 kPa. 相似文献
2.
Nitrogen and phosphorus mineralization in sediments of Taihu Lake after the removal of light fraction organic matter 总被引:1,自引:1,他引:0
Chunxia Yang Shengrui Wang Xiangcan Jin Fengchang Wu 《Environmental Earth Sciences》2010,59(7):1437-1446
Mineralization of organic matter (OM) in sediment is crucial for biogeochemical cycle of nitrogen (N) and phosphorus (P) in
lake ecosystem. Light fraction OM (LFOM) is a reactive pool in sediment and is considered as labile fraction contributing
to N and P cycling. In our study, the effect of LFOM on the process and characteristics of N and P mineralization in sediments
of Taihu Lake were investigated with 77-day waterlogged incubation plus intermittent leaching at 27°C. Sediments from Yuantouzhu
(Y) and Gonghu (G) were used, which were removed the LF. Results indicated that the organic nitrogen mineralized ranged from
14.3 to 19.5% of total nitrogen (193.49–378.93 mg kg−1 sediment) and the organic phosphorus mineralized ranged from 5.7 to 7.9% of total phosphorus (19.86–60.65 mg kg−1 sediment). The heavily polluted sediment had a higher mineralization rate and net mineral-N and mineral-P than slightly polluted
sediment. LF stimulated the initial amounts of inorganic N and P and also can be the potential source for mineralization.
After the LFOM removal, the net mineral-N of Y and G decreased 116.47 mg kg−1 sediment and 48.03 mg kg−1sediment, respectively, and the net mineral-P decreased 2.67 mg kg−1sediment for Y and 4.82 mg kg−1sediment for G. Two models were used to fit the observed mineral-N data vs. incubation days using a non-linear regression
procedure: one is the effective cumulated temperature model, a thermodynamic model which assumes that N mineralization is
affected by temperature; the other is the single first-order exponential model, which is a dynamic model. Based on root mean
square error values for the two models, the effective cumulated temperature model made a better prediction of N mineralization
than the other model for all the four treatments. The single first-order exponential model underestimated N mineralization
during the first 14 days and the last 21 days, and overestimated it in the other days during the 77-day incubation. This indicated
that temperature was the primary factor influencing N mineralization and the amount of mineral-N were correlated significantly
with the effective cumulated temperature (T ≥ 15°C) and incubation time when waterlogged incubation plus intermittent leaching was used. 相似文献
3.
The concentrations of six heavy metals (Fe, Mn, Ni, Cu, Pb and Zn) were studied in 11 hard and 4 soft common coral species
collected from Hurghada, Wadi Al-Gemal and Gola’an along the Red Sea coast to assess the differential abilities of corals
to concentrate and assimilate the heavy metals inside soft coral tissues and hard coral skeletons. These results reveal the
order of Fe > Zn > Ni > Pb ≥ Mn > Cu. Fe recorded significant high concentrations in mushroom (funnel) forms of the soft corals
at the different sites; 125.19, 101.71 and 90.44 ppm at Gola’an, Hurghada and Wadi Al-Gemal, respectively. The soft coral
species recorded the highest average concentration of Mn, Ni, Cu and Zn than the hard corals, which were 13.22, 16.05, 13.08
and 148.17 ppm, respectively. Generally, soft corals show higher metal concentrations than the hard ones; moreover, Hurghada
recorded a higher trend of metal concentrations in soft and hard corals than the other sites. The study concluded that many
biological and local environmental factors influenced the metal occurrences and uptakes in both coral forms such as, the exposed
surface area for metal uptake, turbidity, overlying mucus thickness and the ability of metals to substitute inside the crystal
lattice of the hard corals. 相似文献
4.
Mohammed Hail Hakimi Wan Hasiah Abdullah Mohamed Ragab Shalaby 《Arabian Journal of Geosciences》2012,5(4):817-831
The upper part of Madbi Formation organic-rich shale is considered an important regional source rock in the Masila Basin,
Yemen. Ten cutting samples from this Upper Jurassic organic-rich shale were collected from wells drilled in the Kharir Oilfield,
Masila Basin in order to geochemically assess the type of organic matter, thermal maturity and depositional environment conditions.
Results reveal that Upper Jurassic organic-rich shale samples contain high organic matter more than 2.0 wt.% TOC and have
very good to excellent hydrocarbon potential. Marine algae organic matter is the main source input for the Upper Jurassic
shale sequence studied. This has been identified from organic petrographic characteristics and from the n-alkane distributions, which dominated by n-C14-n-C20 alkanes. This is supported by the high value of the biomarker sterane/hopane ratio that approaches unity, as well as the
relatively high C27 sterane concentrations. A mainly suboxic depositional environment is inferred from pr/ph ratios (1.75–2.38). This is further
supported by relatively high homohopane value, which is dominated by low carbon numbers and decrease towards the C35 homohopane. The concentrations of C35 homohopane are very low. The depositional environment conditions are confirmed by some petrographic characteristics (e.g.
palynofacies). Detailed palynofacies analysis of Madbi shales shows that the Madbi shale formation is characterised by a mix
of amorphous organic matter, dinoflagellates cysts and phytoclasts, representing a suboxic, open marine setting. The Upper
Jurassic marine shale sequence in the Masila Basin is thermally mature for hydrocarbon generation as indicated by biomarker
thermal maturity parameters. The 22 S/22 S + 22R C32 homohopane has reached equilibrium, with values range from 0.58 to 0.62 which suggest that the Upper Jurassic shales are
thermally mature and that the oil window has been reached. 20 S/(20 S + 20R) and ββ/(ββ + αα) C29 sterane ratios suggest a similar interpretation, as do the moretane/hopane ratio. This is supported by vitrinite reflectance
data ranging from 0.74% to 0.90%Ro and thermal alteration of pollen and spore. The thermal alteration index value is around 2.6–3.0, corresponding to a palaeotemperature
range of 60–120°C. These are the optimum oil-generating strata. On the basis of this study, the Madbi source rock was deposited
under suboxic conditions in an open marine environment and this source rock is still within the oil window maturity range. 相似文献
5.
This study was designed to investigate seasonal changes on food available for benthic consumers in relation to tidal levels
and sediment depth in an estuarine beach. The relationships between the biochemical characteristics of sedimentary organic
matter and benthic macrofauna were analyzed quarterly over 2 years (from January 1997 to January 1999), in an estuarine soft
intertidal zone from the NW coast of Spain (42°64′04″N, 8°88′36″W). Sediment samples were collected to provide a two-dimensional
view of macroinfauna distribution in the intertidal zone and its relationship with the quantity and quality of the organic
matter. The nutritional value of organic matter (i.e., lipid, protein, and carbohydrate) and the content of chlorophyll a of the sediment were measured. Macrofaunal assemblages and food availability in the sediment were studied at three tidal
levels on the shore: two intertidal and one supratidal. Macroinfauna and biochemical compounds showed a clear vertical stratification
with the highest macrofaunal abundance at the superficial layer of the sediment, where redox potential discontinuity was also
observed. Crustaceans were found mainly inhabiting the supratidal level of the estuarine beach, while polychaetes and mollusks
occupied the intertidal level. Food availability, measured as biopolymeric carbon, and also chlorophyll a from the sediment were better related to macroinfauna abundance, biomass, and abundance of main taxonomic groups. Macrofauna
assemblages showed particular distribution in both vertical and horizontal ranges suggesting specific preferences to several
abiotic factors. No clear seasonal pattern was found in macrofauna and sedimentary organic characteristics suggesting that
macrofaunal assemblages are controlled by complex and unpredictable factors, including small-scale changes in substrate and
hydrological characteristics. 相似文献
6.
Zhemin Shen Jianda Zhang Liya Qu Zeqin Dong Shenshen Zheng Wenhua Wang 《Environmental Geology》2009,57(6):1399-1407
Wanshan mercury mine is the largest cinnabar deposit in Guizhou, China. Few effective methods had been achieved to remedy
Hg heavily contaminated field soils. In this paper, a modified EK method with approaching cathodes (AC-EK) and an I−/I2 lixiviant was described to remedy mercury-contaminated field soils near Wanshan mercury mine. Paddy Soil I and Paddy Soil
II were sampled and contained 576.73 ± 45.50 and 491.35 ± 4.73 mg/kg Hg, respectively. Although they contained 6.9 and 9.4%
organic matter respectively, more than 92 and 89% Hg were removed by AC-EK within 5 days. Removal ratio increased by 0.21
and 0.68 times using EK process with ACs over that with one single cathode (SC-EK). AC-EK method saved nearly 26.4–28.1% electric
power as compared to SC-EK method. As an I−/I2 lixiviant solution was used to solubilize HgS(HgO) during EK process, the bonding of Hg to organic functional S groups should
be less important than the binding to inner sites of organic matter in soil. The relationship between EK remediation effect
and soil organic matter content was fitted to a linear model. It turned out that when soil OM increased by 1.0%, EK removal
ratio (%) of Hg would decrease by 2.63%. 相似文献
7.
Bicyclic sesquiterpenoids are mostly used to illustrate the origins of organic matter and genetic types of crude oil presently.In this paper,the relationship between distributions and compositions of C16 homodrimane in immature to mature source rocks and evolution of organic matter was studied,and the correlation between C16 homodrimane at immature to low mature stages and thermal evolution of organic matter was analyzed.The results show that in terrestrial facies depositional system,the ratio of 8α(H)-homodrimane to 8β(H)-homodrimane has a high sensitivity about the maturity’s minor changes at immature to low mature stages.It is found that when the vitrinite reflectance R0<0.7%,the ratio significantly decreases with increasing burial depth or maturity.This kind of phenomenon reveals that these parameters may be the useful maturity indicators for determining the relative maturation of organic matter at immature to low mature stages,and have certain practical value in biogeochemical and en- vironmental geochemical research on low mature oil and gas. 相似文献
8.
Deep-seated gas is defined in this paper as natural gas generated under the combined action of high temperature, high pressure,
and environment media. As to organic matter vertical evolution, deep-seated gas is natural gas, which is generated and deposited
under the position of an oil generation window. Deep-seated gas exploration is an important potential field for oil-gas exploration.
Also, it is an inexorable trend to the further development of oil and gas provinces. In this paper, the authors will examine
and distinguish the concept of deep-seated gas, and discuss the distribution and gas source of deep-seated gas. It is pointed
out that kerogen, assemble dissoluble organic matter and disperse dissoluble organic matter all have contributed to deep-seated
gas generation, especially disperse dissoluble organic matter in composite and superimposed sedimentary basin. In the end,
according to the structural evolution and hydrocarbon source rock depositional distribution, the distribution of deep-seated
gas in China is predicted.
Translated from Geology in China, 2006, 33(5): 937–943 [译自: 中国地质] 相似文献
9.
Talitha L. F. Costa Michelle P. Araújo Bastiaan A. Knoppers Renato S. Carreira 《Aquatic Geochemistry》2011,17(1):1-19
In the present work, we evaluated the origin of organic matter in the tropical estuarine-lagoon system of Mundaú–Manguaba,
NE Brazil, by considering the bulk (organic carbon and chlorophyll-a) and lipidic (n-alcohols and sterols) composition of suspended particles. Water samples were collected in August 2006 from
24 stations covering the salinity gradient from the rivers down to the sea outlet. Chlorophyll-a (Chl-a) varied from 22.7 to 134.1 μg L−1 in the lagoons, indicating eutrophic to hypertrophic conditions at the time of sampling. The high correlation between Chl-a and phytol together with the molar C:N ratio indicated the presence of fresh and recently produced autochthonous particulate
organic matter throughout the system, except for the river samples. The elevated concentrations of short-chain n-alcohols
and phytosterols, mainly 24-methylcholesta-5,24(28)-dien-3β-ol, also corroborated the predominance of autochthonous organic
matter in the lagoons but were generated by distinct sources: cianobacteria in the freshwater Manguaba lagoon and diatoms
in the brackish Mundaú lagoon compartments. Input of terrestrial organic matter was only detected in the rivers themselves
or at the upper river–lagoon interfaces. Coprostanol indicated contamination by sewage in Mundaú lagoon and in some rivers,
but at lower levels when compared to other Brazilian coastal lagoons and estuaries. 相似文献
10.
Zoophycos in deep‐sea sediments indicates high and seasonal primary productivity: Ichnology as a proxy in palaeoceanography during glacial–interglacial variations 下载免费PDF全文
Trace fossils provide valuable palaeoenvironmental information in hemipelagic settings. This is particularly true in the case of Zoophycos, an easily recognizable trace fossil in core. At IODP site U1385, Zoophycos was found throughout an interval representing 1.5 Ma, covering 45 glacial–interglacial cycles mediated by obliquity (41 ka) and short‐term eccentricity (100 ka). Zoophycos is most common in sediments deposited during glacial times and when the sedimentation rate was intermediate and primary production was high and seasonal. Occurrences of Zoophycos elsewhere support a similar relationship with seasonal organic‐matter deposition. This is particularly significant considering that seasonality of organic‐matter deposition is difficult to decipher from the sediment record. Zoophycos appears to represent a useful proxy to characterize high and seasonal organic‐matter deposition and primary productivity in Neogene hemipelagic deposits. 相似文献
11.
This study examined freshwater discharge of dissolved organic matter (DOM) to the shallow Lavaca–Matagorda (LM) Bay estuarine
system along the central Texas coast and investigated whether chromophoric DOM (CDOM) photochemical reactions have the potential
to stimulate microbial activity within LM estuarine waters. Dissolved organic carbon (DOC) concentrations ranged from 3 to
10 mg C l−1 and CDOM levels (reported as a
305) ranged from 8 to 77 m−1 during April and July, 2007, when the LM system was experiencing very high freshwater inputs. DOC and CDOM levels were well-correlated
with salinities > 3, but exhibited considerable variability at salinities < 3. CDOM photobleaching rates (i.e., decrease in
a
305 resulting from exposure to solar radiation) for estuarine samples ranged from 0.014 to 0.021 h−1, corresponding to photobleaching half-lives of 33–50 h. Our data indicate when Matagorda Bay waters photobleach; dissolved
organic carbon utilization is enhanced perhaps due to enhanced microbial respiration of biologically labile photoproducts
(BLPs). Net ecosystem metabolism calculations indicate that most of the LM system was net heterotrophic during our study.
We estimate that BLP formation could support up to 20% of the daily microbial respiratory C demand in LM surface waters and
combined with direct photochemical oxygen consumption could have an important influence on O2 cycles in the LM system. 相似文献
12.
Based on the tested data of pressure and vitrinite reflectance of some wells in sedimentary basins, abnormal high pressure
is regarded as not the only factor to retard the increase of vitrinite reflectance (R
o). Apart from the types of the organic matter, the physical environment (temperature and pressure) and chemical environment
(fluid composition and inorganic elements) will result in the abnormal vitrinite reflectance values in the sedimentary basins.
This paper tested trace elements and vitrinite reflectance data from the the abnormal high pressure and normal pressure strata
profiles, respectively, and found that the acidic and lower salinity starta are favorable for the increase of R
o. By discussing the corresponding relationship between the contents of some trace elements in the mudstone and the vitrinite
reflectance values, the typical trace elements were found to suppress and/or catalyze the vitrinite reflectance of organic
matter, while the elements of Ca, Mn, Sr, B, Ba and P may result in the retardation of R
o. However, elements of Fe, Co, Zn, Ni and Rb may catalyze the organic matter maturation. This study is conductive to the organic
maturation correction, oil and gas assessment and thermal history reconstruction by the paleothermometry.
Translated from Acta Geologica Sinica, 2006, 80(11): 1760–1769 [译自: 地质学报] 相似文献
13.
Copper contamination in soils and vegetables in the vicinity of an abandoned copper mine in China was investigated. The Cu
concentrations of 93 soil samples ranged from 30.4 to 3,191 mg kg−1 soil for a mean of 816.8 mg kg−1 soil. Among 15 samples from a 0 to 20-cm soil layer used for the toxicity characteristic leaching procedure (TCLP) test,
the highest value of Cu-TCLP was 133.8 mg kg−1 soil and the TCLP values were positively correlated with the total Cu content of the soils. The sequential extraction of
soils in the 0–20-, 20–40-, and 40–60-cm soil layers showed that Cu existed mainly in the Fe–Mn oxide fraction, sulfide/organic
fraction, and residual fraction. The copper contamination of 21 species of vegetables from in situ sampling was also examined.
Cu concentrations in the edible portions of Brassica chinensis and Solanum melongena were higher than the FAO/WHO standard (40 mg kg−1 DW). The health risk of copper for local inhabitants from consuming these vegetables was assessed on the basis of the target
hazard quotient. Enriched concentrations of copper were also found in situ in eight cultivars of B. chinensis planted in the fields, with two levels of Cu concentration. The results showed that there is severe copper contamination
in this mine area, and the pollutant in soils show a high risk of leaching into the groundwater and diffusing through the
food chain. 相似文献
14.
Sudip Jyoti Sahu Bibhash Nath Sharmi Roy Biswapati Mandal Debashis Chatterjee 《Environmental Earth Sciences》2012,65(3):813-821
Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long-term detrimental
effects to surface soils. Such contamination can also directly affect human health when irrigated crops, such as rice, vegetable
and fruits, are used for human consumption. Therefore, an understanding of the leaching behavior of As in surface soils is
of high importance, because such behavior may increase the bioavailability of As in the soil horizon. In this study, we have
investigated the role of phosphate ions in leaching and bioavailability of As in the soil horizon, where drinking groundwater
contains elevated levels of As (≥50 μg/L). Soil and groundwater samples were characterized in the laboratory and measured
for physical and chemical constituents. The soils are generally neutral to slightly alkaline in character (pH range 7.5–8.1)
with low to moderate levels of free Fe2O3, Al2O3, CaCO3, organic carbon, and clay content. The measured electrical conductivity (mean 599 μS/cm) of the soils demonstrates their
non-saline nature. The Eh values (range −37 to −151 mV) of the groundwater indicate anoxic condition with low to moderate
levels of bicarbonate (range 100–630 mg/L) and phosphate (range 0.002–4.0 mg/L). The arsenic content (range 50–690 μg/L; mean
321 μg/L) in groundwater has exceeded both WHO recommended guideline values (10 μg/L) and the National safe drinking water
limit (50 μg/L). Regression analyses demonstrate that the bioavailability of As in the soil horizon is mainly controlled by
the composition of free Fe2O3 and CaCO3 content of the soils. However, application of P could increase bioavailability of As in the soil horizon and become available
to plants for uptake. 相似文献
15.
Vertical distribution patterns of organic geochemical constituents and the enzymes aminopeptidase and β-glucosidase provide
insights about the nature and reactivity of sediment organic matter in the sandy sediments of two shallow “South Texas” estuaries.
Sediment total organic carbon (TOC) δ13C values indicated that the organic matter (OM) was derived more from a mixture of seagrass and phytoplankton than from terrigenous
OM. Down-core amounts of TOC and total nitrogen (TN) were <0.2% of dry weight, respectively. Enzyme activities were highest
near surface and ranged from 25 to 1 μM/h for aminopeptidase as compared to 5 to 0.2 μM/h for glucosidase. In Aransas Bay,
aminopeptidase activity correlated with sediment TN content (r
s = 0.30) and β-glucosidase with TOC content (r
s = 0.27). In Copano Bay, aminopeptidase correlated with TOC, TN, and carbohydrate content (r
s = 0.89, 0.90, and 0.83, respectively). Variations of glucosidase activity also related positively to TOC, TN, and total carbohydrate
content (r
s = 0.68, 0.77, and 0.48, respectively). Overall, enzyme activities in these low OM, sandy sediments resembled those for other
benthic marine environments. 相似文献
16.
Katalin Báldi 《International Journal of Earth Sciences》2006,95(1):119-142
Benthic foraminifera and stable isotopes analyses revealed changes emerging in the paleoceanographic scenery in the Paratethys.
The percentage of inbenthic, oxyphylic taxa and diversity in the benthic foraminiferal assemblage showed increasing food supply
(organic matter), decreasing oxygen level and growing stress on the sea floor. Oxygen isotopes measured in planktonic and
benthic foraminifera pointed to strengthening stratification during the Badenian period. The carbon isotopes indicated intensified
accumulation of light marine organic matter. This increasing stratification trend is especially pronounced by Late Badenian
(13.5–13 Ma) when surface water oxygen isotope values are rather negative. A simple two-layer circulation model was worked
out for the Badenian Paratethys explaining these characteristic environmental changes. An antiestuarine (lagoonal) circulation is assumed for the Central Paratethys during the Early (16.4–15 Ma) and mid Badenian (15–13.5 Ma). The mid Badenian
period of time comprises the short episode of evaporite formation in the Carpathian Foredeep and the Transylvanian Basin.
Evidence presented here supported a reversal of circulation to estuarine type after the deposition of salts by Late Badenian (13.5–13 Ma). The Early Badenian antiestuarine circulation is suggested
to associate with the high temperatures of the Mid-Miocene Climatic Optimum, and the Late Badenian estuarine circulation with
the cooler period following it. 相似文献
17.
Lars Chresten Lund-Hansen Thorbjørn Joest Andersen Morten Holtegaard Nielsen Morten Pejrup 《Estuaries and Coasts》2010,33(6):1442-1451
Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM),
and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66°) in August 2007 along with
optical properties. These comprised diffuse attenuation coefficient of downwelling PAR (K
d(PAR)), upwelling PAR (K
u(PAR)), particle beam attenuation coefficient (c
p), and irradiance reflectance R(−0, PAR). PAR is white light between 400 and 700 nm. The estuary receives melt water from the Greenland Inland Ice and stations
covered a transect from the very high turbid melt water outlet to clear marine waters. Results showed a strong spatial variation
with high values as for suspended matter concentrations, CDOM, diffuse attenuation coefficient K
d(PAR), particle beam attenuation coefficients (c
p), and reflectance R(−0, PAR) at the melt water outlet. Values of optical constituents and properties decreased with distance from the melt water
outlet to a more or less constant level in central and outer part of the estuary. There was a strong correlation between inorganic
suspended matter (SPMI) and diffuse attenuation coefficient K
d(PAR) (r
2 = 0.92) and also for particle beam attenuation coefficient (c
p; r
2 = 0.93). The obtained SPMI specific attenuation—K
d*(PAR) = 0.13 m2 g−1 SPMI—and the SPMI specific particle beam attenuation—c
p* = 0.72 m2 g−1—coefficients were about two times higher than average literature values. Irradiance reflectance R(−0, PAR) was comparatively high (0.09−0.20) and showed a high (r
2 = 0.80) correlation with K
u(PAR). Scattering dominated relative to absorption—b(PAR)/a(PAR) = 12.3. Results strongly indicated that the high values in
the optical properties were related to the very fine particle sizes (mean = 2–6 μm) of the suspended sediment. Data and results
are discussed and compared to similar studies from both temperate and tropical estuaries. 相似文献
18.
The Plio-Quaternary conglomeratic sets within the marine environment of the Viranşehir coast (W Mersin, S Turkey) are responsible
for the evolution of sandy and gravely beaches due to their control on various factors such as sea floor irregularity, wave
energy, and organic activity. The conglomeratic sets close to the shoreline (50–150 cm) act as wave breakers, creating hard
substratum and high energy, well-oxygenated environment for organisms like Patella sp., Phoronida worms and Brachidontes pharaonis (Fischer P. 1870). The boring activities of these organisms have disintegrated the sandy matrix of these sets. Finer-grained
matrix sediments have been transported to the interset and open sea, while cobble–pebbles have been carried landwards and
have created imbricated gravely beach deposits without matrix. Sandy beach is evolving where the conglomeratic sets away from
the shoreline (5.0–10.0 m). In this example, sets form a bar; causing fivefold division as backshore, berm, surf zone, bar
and offshore from land to sea. Poorly sorted, cobbles-pebbles cobbles and pebbles are found associated with the high-energy
environments of bars, whilst well-sorted sands are observed in low energetic environments on shore. The sets and recent shell
fragments are the main sources of coastal sediments in Viranşehir. However, the amount of shell fragments decrease towards
the active river mouth. This is due to sediment and fresh water influx from the river causing deteriorated temperature, salinity
and light penetration of the marine environment resulting in less organic diversity.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
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
20.
Trace metals (Cd,Pb, Cu,Zn and Ni) in sediment of the submarine pit Dragon ear (Soline Bay,Rogoznica, Croatia) 总被引:1,自引:0,他引:1
Vertical profiles of trace metal (Cd, Pb, Zn, Cu, Ni) concentrations, organic matter content, carbonate content and granulometric
composition were determined in two sediment cores from the submarine pit Dragon Ear (Middle Adriatic). Concentrations of the
analyzed metals (Cd: 0.06–0.12 mg kg−1, Pb: 28.5–67.3 mg kg−1, Zn: 17.0-65.4 mg kg−1, Cu: 21.1–51.9 mg kg−1, Ni: 27.8–40.2 mg kg−1) were in usual range for Adriatic carbonate marine sediments. Nevertheless, concentrations of Cu, Zn, and especially Pb in
the upper layer of sediments (top 12 cm) were higher than in bottom layer, while Cd and Ni concentration profiles were uniform.
Regression analysis and principal component analysis were used to interpret distribution of trace metals, organic matter and
carbonate content in sediment cores. Results of both analysis showed that concentrations of all trace metals in the core below
the entrance to the pit were significantly positively correlated with organic matter and negatively correlated with carbonate,
while in the core more distant from the entrance only Pb showed significant positive correlation with organic matter. Obtained
results indicated that, except for lead which was enriched in surface sediment, in the time of sampling (before the building
of the nautical marina) investigated area belonged to unpolluted areas. 相似文献