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1.
The spatial distribution of methane in the water and bottom sediments of the mouth area of the Severnaya Dvina River shows quite a similar character during the ice-cover and summer periods. It is characterized by the increase of the gas content from the head of the mouth area towards the delta with maximum values at the sites subjected to permanent anthropogenous impact. The difference consists in the higher level of the methane content in the bottom sediments during the winter period. At the same time, the excess of the winter to summer concentrations in the water was registered only at the stations within the impact area of the sources of anthropogenous contamination. As in the summer, the bottom sediments have a prevailing role in the formation of the level of the methane content in the water of the mouth area. The linear dependence between the concentrations of the total hydrogen sulfide and methane in the surface layer of the riverine sediments is probably caused by the parallel and nonconcurrent proceeding of the generation of these gases, which are controlled by the bacterial communities being not inhibitory to each other.  相似文献   

2.
In three sections in the Kara Sea, the contents of the dissolved and particulate organic carbon (the DOC and POC, respectively), as well as of the organic carbon of the bottom sediments (Corg) were determined. The contents of varied from 6.3 to 2400 μg/l for the DOC and from 0.84 to 12.2 mg of C/l for the POC. The average concentrations for all the samples tested amounted to 200 μg/l for the DOC (n = 78, σ = 368) and 2.7 mg/l for the POC (n = 92, σ = 2.7). The concentrations of Corg in the samples of the upper layer of the bottom sediments of the area treated varied from 0.13 to 2.10% of the dry substance at an average value of 0.9% (n = 21, σ= 0.49%). It is shown that the distribution of the different forms of organic matter (OM) is an indicator of the supply and spreading of the particulate matter in the Kara Sea and that the DOC and POC of the Kara Sea are formed under the impact of the runoff of the Ob and Yenisei river waters. It is found that the distribution of the OM of the bottom sediments in the surveyed area of the Kara Sea is closely related to their grain-size composition and to the structure of the currents in the area studied. The variations in the Corg content in the bottom sediment cores from the zone of riverine and marine water mixing represent the variability of the OM burial.  相似文献   

3.
The results of microbiological, biogeochemical, and isotope geochemical studies in the Kara Sea are described. The samples for these studies were obtained during the 54th voyage of the research vessel Akademik Mstislav Keldysh in September 2007. The studied area covered the northern, central, and southwestern parts of the Kara Sea and the Gulf of Ob. The quantitative characteristics of the total bacterial population and the activity of the microbial processes in the water column and bottom sediments were obtained. The total population of the bacterioplankton (BP) varied from 250000 cells/ml in the northern water area to 3000000 cells/ml in the Gulf of Ob. The BP population depended on the content of the water suspension. The net BP production was minimal in the central water area, amounting to 0.15–0.2 μg C/(l day), and maximal (0.5–0.75 μg C/(l day)) in the Gulf of Ob. The organic material at the majority of the stations in the Ob transect predominantly contained light carbon isotopes (−28.0 to −30.18‰) of terrigenous origin. The methane content in the surface water layer varied from 0.18 to 2.0 μl CH4/l, and the methane oxidation rate changed in the range of 0.1–100 nl CH4/(l day). The methane concentration in the upper sediment layer varied from 30 to 300 μl CH4/dm3; the rate of the methanogenesis was 44 to 500 nl CH4/(dm3 day) and that of the methane oxidation, 30 to 2000 nl CH4/(dm3 day). The rate of the sulfate reduction varied from 4 to 184 μg S/(dm3 day).  相似文献   

4.
Data are presented on the content of aliphatic and polycyclic aromatic hydrocarbons (AHC and PAH, respectively) in the interstitial waters and bottom sediments of the Kara Sea compared to the distribution of the particulate matter and organic carbon. It was found that the AHC concentrations within the water mass (16 μg/l on average) are mainly formed by natural processes. The AHC distribution represents the variability of the hydrological and sedimentation processes in different regions of the sea. The widest ranges of the concentrations were registered in the Ob Bay-Kara Sea section: in the water (10–310 μg/l for the AHC and 0.4–7.2 ng/l for the PAH) and in the surface layer of the bottom sediments (8–42 μg/l for the AHC and 9–94 ng/g for the PAH). The differentiation of the hydrocarbons (HC) in the different media follows the marginal filter’s regularities; therefore, no oil and pyrogenic compounds are supplied to the open parts of the sea. In the sediment mass, the HC content is determined by the variations in the oxidative conditions in the sediment and its material’s composition.  相似文献   

5.
Data on the contents and compositions of the hydrocarbons (HCs)—aliphatic (AHCs) and polycyclic aromatic (PAHs)—are provided in comparison with the contents of the total organic carbon (Corg), the lipids in the particulates, and the Corg in bottom sediments. Particular attention has been paid to the distribution of the HCs in the water area of the Kravtsov oil field. It has been established that the concentrations of AHCs in the water are governed by the content of particulates, and the elevated AHC concentrations are confined to the coastal areas. In the water area of platform D-6, the sandy bottom sediments were notable for the great variability of the HC concentrations, both laterally and from year to year. In the summer of 2010, the content of AHCs averaged 40 μg/g (19% in the Corg), and that of PAHs, 23 ng/g. Natural seepage from the sediment mass is considered to be a source of HCs along with oil contamination.  相似文献   

6.
We report some main results of multidisciplinary investigations carried out within the framework of the Indian National Gas Hydrate Program in 2002–2003 in the Krishna–Godavari Basin offshore sector, east coast of India, to explore indicators of likely gas hydrate occurrence suggested by preliminary multi-channel seismic reflection data and estimates of gas hydrate stability zone thickness. Swath bathymetry data reveal new evidence of three distinct geomorphic units representing (1) a delta front incised by several narrow valleys and mass flows, (2) a deep fan in the east and (3) a WNW–ESE-trending sedimentary ridge in the south. Deep-tow digital side-scan sonar, multi-frequency chirp sonar, and sub-bottom profiler records indicate several surface and subsurface gas-escape features with a highly resolved stratification within the upper 50 m sedimentary strata. Multi-channel seismic reflection data show the presence of bottom simulating reflections of continuous to discrete character. Textural analyses of 76 gravity cores indicate that the sediments are mostly silty clay. Geochemical analyses reveal decreasing downcore pore water sulphate (SO4 2−) concentrations (28.7 to <4 mM), increasing downcore methane (CH4) concentrations (0–20 nM) and relatively high total organic carbon contents (1–2.5%), and microbial analyses a high abundance of microbes in top core sediments and a low abundance of sulphate-reducing bacteria in bottom core sediments. Methane-derived authigenic carbonates were identified in some cores. Combined with evidence of gas-escape features in association with bottom simulating reflections, the findings strongly suggest that the physicochemical conditions prevailing in the study area are highly conducive to methane generation and gas hydrate occurrence. Deep drilling from aboard the JOIDES Resolution during 2006 has indeed confirmed the presence of gas hydrate in the Krishna–Godavari Basin offshore.  相似文献   

7.
黄河三角洲潮滩剖面特征   总被引：4，自引：0，他引：4  
利用验潮、潮滩水准测量、沉积物分析和遥感资料,分析了黄河三角洲不同岸段潮滩的特征。水准测量表明,侵蚀潮滩剖面形态为下凹,而淤积潮滩则上凸,由高潮线至低潮线,潮滩沉积物均变粗,这种变粗趋势在北部侵蚀岸段和河口侧缘明显,在河口南侧稳定海岸则不明显。潮滩沉积物含水量为12.2%~32.2%,平均为21%,海滩表层沉积物不排水剪切强度在0.1~0.35 kg/cm2之间。受局限岸滩的平面形态和剖面形态受到周围大坝地形影响,具有和砂质海滩类似的形态,显示波浪对该潮滩的作用强烈,根据剖面测量结果与遥感图像,发现河口北侧有一个小的冲积扇。  相似文献   

8.
黄河三角州沿岸及相邻渤海海域碳酸盐研究(英文)   总被引：2，自引：0，他引：2  
对黄河三角州陆地上河道,河口、潮间带及毗邻渤海海域沉积物中的碳酸盐含量作了分析,在此基础上划分出含量不同的沉积区和亚区。沉积区的划分和其物源有十分良好的对应关系,同一沉积区内的亚区则主要和粒度有关,从而间接反映了水动力环境与生物作用的控制性影响。黄河口沉积物中碳酸盐含量与粒度成反比,其他物源的沉积物则各不相同。黄河口及邻近渤海海域中粘土粒级和碳酸盐含量等值线反映出黄河细粒级沉积物扩散的方向、强度和范围。海洋生源沉积是影响渤海东部和中部沉积物中碳酸盐含量分布的主要因素。  相似文献   

9.
Rapid changes in the near-bottom water temperature are important environmental factors that can significantly affect the growth and development of species in the bottom culture. The object of this research is to investigate the mechanism causing these rapid changes within a bottom culture area near the Zhangzi Island. The hydrographic transects observations in the North Yellow Sea(NYS) suggest that our mooring station is very close to the tidal mixing front. The horizontal advection of the tidal front has induced the observed tidal change of bottom temperature at the mooring station. Analysis of the mooring near-bottom temperature and current measurements show that the angle between the tidal current horizontal advection and the swing of the tidal front is crucial in determining the variation trend of temperature. When the angle equals 90°, the horizontal tidal current advects along the isotherms so the temperature remains the same. When the angle is between 0° and 90°, the seawater moves from deep water to the warmer coastal zone and the temperature decreases. In contrast, the horizontal tidal advection moves the coastal warm water to the mooring station and the water temperature increases when the angle is between 90° and 180°. The amplitude of the temperature change is proportional to the magnitude of the horizontal temperature gradient and the tidal excursion in the direction of the temperature gradient. This study may facilitate the choice of culture area in order to have a good aquaculture production.  相似文献   

10.
基于遥感反演的莱州湾悬沙分布及其沉积动力分析   总被引：5，自引：3，他引：2  
选用1986-2004年不同时期的LandsatTM/ETM+影像,利用2004年黄河口附近实测数据推导的表层悬浮泥沙浓度反演模型,结合水文气象资料、多年水深数据和极端天气数模结果,研究了莱州湾西南近岸海域表层悬浮泥沙分布特征,结果表明,受黄河丰枯水期的影响,莱州湾西南部海域悬浮泥沙高浓度区主要分布于黄河口附近海域和西南沿岸,其枯水期的覆盖范围一般大于丰水期的。受潮流高流速场控制,黄河口外悬沙浓度高值区与海底泥沙堆积区对应较好,泥沙主要来源于陆源输沙和泥沙再悬浮;在西南近岸浅海区悬沙浓度高值区主要形成于泥沙的再悬浮,在近岸出现轻微冲刷。风等其他海洋动力因素,一般情况下对悬浮泥沙扩散的程度和范围具有一定的影响作用,但悬沙受潮流场影响而形成的总体扩散趋势未发生改变;极端条件下,风暴潮流使莱州湾西南部近岸浅海区的悬浮泥沙浓度显著增加。  相似文献   

11.
The transport pathways of fine sediments (fraction <2 μm) along the Brazilian continental shelf from Ceará to the Amazon River mouth were studied by means of clay mineral analyses. On the continental shelf southeast of the Amazon mouth, fluctuations in clay mineral compositions reflect simple mixing between the suspended load of the North Brazil Current and sediment from several smaller rivers. Previously, clay mineral variations west of the Amazon mouth have been explained by variable settling velocities of different grain-size classes within the <2 μm fraction or by selective coagulation of individual clay mineral groups. By contrast, our experiments with river bank samples show that selective coagulation does not occur in Amazon River sediments. A more appropriate explanation for observed variations in clay mineral composition off the Amazon mouth seems to be, similarly to that for the shelf between Ceará and the Amazon mouth, a mixing of Amazon sediments with suspended material of the North Brazil Current. This interpretation is supported by data on clay mineral composition east and south of the Amazon mouth, showing more affinity to sediments of the North Brazil Current than to the suspended load of the Amazon River. Additionally, relatively low sedimentation rates and low concentrations of fine-grained sediments on the shelf suggest that high riverine input by the Amazon River does not overprint the sediments of the North Brazil Current in this region. The strong North Brazil Current shunts the Amazon suspended load in a north-westerly direction along the north-eastern coast of South America. Hence, stronger sedimentation of Amazon sediments would occur only west of the river mouth.  相似文献   

12.
黄河三角洲孤东海域沉积物及水动力   总被引：7，自引：0，他引：7  
根据黄河三角洲孤东近岸海域表层沉积物取样、水文泥沙观测和风浪资料推算,分析沉积物特征和运移趋势,并通过水动力条件(潮流和波浪)探讨沉积物起动和输移特征。结果表明,孤东海域沉积物多为粉砂类物质,由内向外逐渐变细,分选变差,丁坝的修建对周围粒径分布影响明显;沉积物运移趋势受风成余流、岸线轮廓和丁坝工程修建的影响,不同区域表现为不同的输移方向;研究区水动力表现为波浪掀沙、潮流输沙的特征,由于潮流较小,不足以引起泥沙的起动,泥沙起动主要由波浪引起。  相似文献   

13.
Authigenic carbonates from methane seeps of the Congo deep-sea fan   总被引：1，自引：2，他引：1  
Submersible investigations with the ROV Victor 6000 of some pockmark structures on the seafloor of the Congo deep-sea fan have shown that they are active venting sites of methane-rich fluids, associated with abundant fauna and carbonate crusts. Moreover, methane hydrates have been observed both outcropping and deep in the sediments in the centre of the “Regab” giant pockmark. Authigenic carbonates, mostly calcite sometimes mixed with aragonite, are cementing the sedimentary matrix components and fauna; diatoms are abundant but only as moulds, indicating that biogenic silica dissolution occurred in situ synchronous with carbonate precipitation. The occurrence of diagenetic barite and pyrite in some carbonate crusts demonstrates that they can be formed either within the sulphate/methane transition zone or deeper in sulphate-depleted sediments. The oxygen isotopic compositions of the diagenetic carbonates (3.17–6.01‰ V-PDB) indicate that precipitation occurred with bottom seawater mixed with a variable contribution of water from gas hydrate decomposition. The very low carbon isotopic compositions of the diagenetic carbonates (−57.1 to −27.75‰ V-PDB) demonstrate that carbon derives mostly from the microbial oxidation of methane.  相似文献   

14.
Seismic profiling with 3.5-kHz and GeoPulse in the Amazon submarine delta indicates that gas-charged sediments cover an area greater than 31,000 km2. Gas appears on seismic profiles as gas-brightening reflectors near the river mouth, where mud and sand are well stratified. In fine sediments of the distal portion of the system, gas turbidity zones predominate. Biogenic gas is generated during degradation of terrestrial and marine organic matter by bacteria. The depth of gas in sediment below the seabed depends in part on anaerobic methane oxidation and the base of the sulfate reduction zone and on stratigraphic traps.  相似文献   

15.
The material was collected in the Ob River estuary and over the adjacent shallow Kara Sea shelf between 71°14′0 and 75°33′0N at the end of September 2007. Latitudinal zoning in the phytoplankton distribution was demonstrated; this zoning was determined by the changes in the salinity and concentration of nutrients. Characteristic of the phytocenosis in the southern desalinated zone composed of freshwater species of diatom and green algae were the high population density (1.5 × 106 cells/l), biomass (210 μgC/l), chlorophyll concentration (4.5 μg/l), and uniform distribution in the water column. High primary production (∼40 μgC/l/day) was recorded in the upper 1.5-m layer. The estuarine frontal zone located to the north contained a halocline at a depth of 3–5 m. Freshwater species with low population density (2.5 × 105 cells/l), biomass (24 μgC/l), and chlorophyll concentration (1.5 μg/l) dominated above the halocline. Marine diatom algae, dinoflagellates, and autotrophic flagellates formed a considerable part of the phytocenosis below the halocline; the community characteristics were twofold lower as compared with the upper layer. The maximal values of the primary production (∼10 μgC/l per day) were recorded in the upper 1.5-m layer. The phytocenosis in the seaward zone was formed by marine alga species and was considerably poorer as compared with the frontal zone. The assimilation numbers at the end of the vegetation season in the overall studied area were low, amounting to 0.4–1.0 μgC/μgChl/h in the upper layer and 0.03–0.1 μgC/μgChl/h under the pycnocline.  相似文献   

16.
黄河水下三角洲沉积物输运及海底冲淤研究   总被引：2，自引：0，他引：2  
根据黄河水下三角洲的特点,建立了一个垂直平均二维沉积物输运数学模型,结合潮流和沉积物资料,模拟研究了沉积物输运机制和海底冲淤演变过程。模拟结果表明,垂直河口射流的潮流决定了本区沉积物净输运的总体格局,风应力对悬浮泥沙和推移质泥沙运动也起到重要作用。潮流底应力和活动层厚度分布表明,黄河口门和埕岛油田附近海域是潮流底应力和活动层厚度高值区,为沉积物活跃区,海底稳定性弱,易于侵蚀再搬运。冲淤计算表明,埕岛油田附近海域为冲刷中心区;现在河口水下三角洲在断流时为冲刷区,正常行河时则转为淤积区。  相似文献   

17.
在南黄海太阳沙西侧潮流脊槽海域进行了密集网格的高分辨率浅地震勘探,测线间距主要为120 m和200 m。沉积物穿透厚度最大约80~90 m,划分为2个地震层序(SQ1和SQ2),细分为5个亚层(U1~U5)。位于下部的层序1(U1)为晚更新世陆相沉积,上部的层序2(U2~U5)以全新世海相沉积为主。根据地震相特征研究了各亚层的沉积环境,从晚更新世晚期以来,研究区经历了三角洲辫状河流—河流刻蚀—古河道充填—河口滨海—三角洲滨浅海—现代潮流脊槽的沉积环境演变过程。在早全新世中期,研究区发育了一条窄河口型潮流沙脊,并随海平面的快速上升而被掩埋。现代潮流沙脊形成于末次高海面后,与古潮流沙脊没有继承关系,与晚更新世古地形也没有关系,受控于潮流系统。  相似文献   

18.
用吹扫-捕集法对东沙群岛西南和西沙海槽附近海域5个站位水柱中的甲烷浓度进行了测定,在其中的3个站位发现了甲烷高浓度异常。在东沙群岛西南海域的E105A和E106两站位近底层海水中甲烷浓度均出现异常增加,其值分别为4.25和10.64 nmol/dm3。在西沙海槽附近的E413站位甲烷异常出现在1 750,1 900和2 050 m深的近底层水中,浓度分别达5.17,8.48和8.70 nmol/dm3。在近底层海水中出现的甲烷高浓度异常是由于沉积物下部甲烷渗漏活动造成的,结合前人在这两个海域沉积物的地球物理和化学调查资料,认为可能是与冷泉渗漏或天然气水合物分解有关。2007年5月在探测到甲烷高浓度明显异常的东沙群岛西南神弧海域,获得了天然气水合物的实物样品,但是西沙海槽附近海域近底层水的甲烷高浓度异常是来源于天然气水合物还是来源于冷泉需要进一步加以确认。  相似文献   

19.
We report measurements of iron, nutrients, dissolved oxygen, humic-type fluorescence intensity and chlorophyll a concentrations in the coastal waters at the inflow (western) and outflow (eastern) ends of Tsugaru Strait (Japan) in June 2003 and 2004. Two different water masses (intensive eastward flow “subtropical Tsugaru Warm Current Water (TWCw)” and weak westward flow “subarctic Oyashio Water (OW)”) were observed at the eastern end of the strait. TWCw at the southern part of the eastern strait was vertically homogeneous with a uniform concentrations of iron (0.7–1.1 nM for labile dissolved Fe and 14–20 nM for total dissolvable Fe in 2003) as well as other chemical, biological and physical components throughout the water column of 200 m due to strong vertical mixing in the strait. The degree of mixing in the Tsugaru Warm Current (TWC) is predominantly affected by diurnal tidal current, which is strong during the period of tropical tides and weak during the period of equinoctial ones. The especially strong vertical water mixing in 2003 is caused by large dissipation energy input due to the bottom friction of passage-flow through the strait and tidal current. At the northern part of the eastern strait, the fresh surface layer overlying the OW and the deep-bottom waters in 2003 contained large concentrations of dissolved iron, resulting from iron supplied from river runoff and shelf sediments, respectively. These results suggest that the most important mechanism for transporting iron in the strait is the strong vertical water mixing due to the tidal current, and that the iron sources in the coastal waters are the organic-associated, iron-rich freshwater input into the surface water.  相似文献   

20.
分别于2012年3月和7月对长江口及其邻近海域水体中溶解态铝的分布及其影响因素进行了研究,并在2012年3月至2013年11月期间对长江徐六泾进行了连续观测。结果表明,徐六泾溶解态铝在夏季出现最高值,在冬季呈现最低值,平均值分别为(313±130)nmol/L和(140±43)nmol/L,表现出与径流量相似的季节变化规律。受陆源输入变化的影响,长江口溶解态铝的浓度由近岸向外海逐渐降低,且呈现出明显的季节性差异,即7月明显高于3月。3月表、底层海水中溶解态铝的浓度范围分别为21~129 nmol/L和27~146 nmol/L,平均值分别为(49±21)nmol/L和(59±27)nmol/L;7月表、底层溶解态铝的浓度范围分别为6~332 nmol/L和9~252 nmol/L,平均值分别为(66±69)nmol/L和(83±74)nmol/L。在7月,表、底层溶解态铝呈现显著性差异,底层沉积物的再悬浮可能是造成差异的主要原因。调查结果表明,溶解态铝在长江口呈现出清除型行为,清除主要发生在咸淡水混合初期,初步计算出7月份溶解态铝的清除率约为55%。  相似文献   

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