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1.
The waters offshore the Shandong Peninsula separate the North Yellow Sea from the South Yellow Sea,and receive a large amount of terrestrial material from Chinese and Korean rivers,making it an ideal area for studying land-sea interactions.However,little attention has been given to measuring sediment transportation in most previous studies.Based on an analysis in composition of major and trace elements and particle size characteristics from 62 surface sediment samples from the northeastern region off Shandong Peninsula,the type,element composition,and controlling factors of the surface sediments were inve stigated.In addition,the transportation of sediments from source to sink was described from measured thermohaline data.The results show two types of surface sediments:sandy silt and silt.The sediments were mainly terrestrial;and marine carbonate had little effect on sediment composition.Shown on a binary diagram of Rb/Sc to Co/Sc,the Huanghe(Yellow) and Changjiang(Yangtze) rivers are the main sources of surface sediments in the study area.The component mixing model showed that the relative contribution of sediment from the Huanghe River was up to 92%,followed by the Changjiang River(8%).The Yellow Sea Warm Current and the North Shandong Peninsula Coastal Current met at ～3 7.7°N in the study area,and were the main forces carrying sediment from the two main river sources.However,there was a deficit of transported material into the study area in summer.The secondary distribution of sediment from the two river sources was controlled by tidal currents and waves.  相似文献   

2.
Clay minerals of 34 sediments collected from the northwestern continental shelf of the East China Sea have been determined by X-ray diffraction analysis. The clay mineral distribution is mainly controlled by the sediment source and the dominant circulation pattern. The predominant clay mineral in our study area is illite comprising more than 67% of the whole clay fraction. The highest concentration of illite (>68%) is found in the southeastern offshore parts beyond the reach of terrigenous input from the Jeju Island. It means that these illites are largely transported by the Kuroshio Current from the South China Sea (SCS). Smectite is highly concentrated in the northwest middle part and in the outer-shelf mud patch. It seems to be due to the high supply of smectite transported from China where fine-grained sediments are discharged from modern and ancient Huanghe (Yellow) River. The relatively high abundant kaolinite is likely derived from the Changjiang (Yangtze) River via the Taiwan Warm Current. In contrast, large amounts of chlorite and high chlorite/kaolinite ratios occur in the northwestern area, reflecting the transportation by the Yellow Sea Coastal Current from the southern Yellow Sea. The discrimination diagrams clearly show that the sediments in the northwestern East China Sea are ultimately sourced from Chinese rivers, especially from the Huanghe River, whereas the sediment in the northeast part might come from the Jeju Island. The muddy sediments of the Changjiang River’s submerged delta have much lower 87Sr/86Sr ratios (0.716 2–0.718 0) than those of the Shandong Peninsular mud wedge (0.721 6–0.724 9), which are supposed to be originated from the Huanghe River, suggesting the distribution pattern of 87Sr/86Sr ratios as a new tracer to discriminate the provenance of shelf sediments in the study area. The 87Sr/86Sr ratios of the outer-shelf muddy sediments ranged from 0.7169 to 0.7216 in a wide range and was between those of the Huanghe River and Changjiang River sediments, suggesting multiple sources of the sediment in the area.  相似文献   

3.
Li  Chao  Yang  Shouye  Lian  Ergang  Bi  Lei  Zhang  Zhaofeng 《中国海洋大学学报(英文版)》2015,14(3):399-406
The East China Sea(ECS) is a river-dominated epicontinental sea, linking the Asian continent to the northwestern Pacific via the large rivers originating from Tibetan Plateau. The relevant huge influx of riverine detritus has developed unique sedimentary systems in the ECS during the Quaternary, offering ideal terrestrial archives for reconstructing Quaternary paleoenvironmental changes and studying land-sea interactions. Overall, two characteristic river systems dominate the sedimentary systems and sediment source to sink transport patterns in the ECS, represented by the Changjiang(Yangtze River) and Huanghe(Yellow River) for the large river system and Taiwan rivers for the small river system. Given this, the sediments derived from both river systems bear distinct features in terms of parent rock lithology, provenance weathering and sediment transport. Previous studies mostly focus on either the ‘source' discrimination or the ‘sink' records of the sedimentary system in the ECS, while the source to sink process linking the land and sea, in particular its time scale, has been poorly understood. Here we introduce a newly-developed dating technique, the ‘comminution age' method, which offers a quantitative constraint on the time scale of sediment transfer from its ultimate source to the final depositional sink. This novel method is of great significance for improving our understanding on the earth surface processes including tectonic-climate driven weathering, and sediment recycling in relation to landscape evolution and marine environmental changes. The application of comminution age method in the ECS will provide important constraints on sediment source-to-sink process and more evidences for the construction of late Quaternary paleoenvironmental changes under these unique sedimentary systems.  相似文献   

4.
The East China Sea continental shelf is a unique area for the study of land-sea interactions and paleoenvironmental change because it receives a large amount of terrestrial material inputs. In recent decades, human activities and global climate change have greatly aff ected river discharges into the sea. However, changes in the deposition process caused by these factors in the East China Sea continental shelf are unclear. We collected eight short sediment cores from the East China Sea inner shelf(ECSIS) using a box core sampler in 2012 and 2015. The grainsize, 2 10 Pb, and 1 37 Cs of these cores were analyzed in order to reconstruct the deposition history since the 1950 s, and to reveal human activity and climate change influences on sediment deposition in the ECSIS. Results indicated that sediment grain size became finer after 1969, turned coarser after 1987, and then further coarser since 2003, corresponding well to the three steps of sediment load drop in the Changjiang(Yangtze) River, which are mainly caused by human activities(particularly the closure of the Three Gorges Dam). Simultaneously, the East Asian Monsoon influenced the deposition process in the ECSIS by changing the intensity of coastal currents. Mean grain size variations in the fine-grained population(divided by grain size vs. standard deviation method) coincided with that of the East Asian Winter Monsoon strength and reflected its weakness in 1987. Abrupt changes in sediment grain size over a short time scale in these sediment cores were generally caused by floods and typhoons. Spectral analyses of the sediment cores showed periodicities of 10–11 and 20–22 years, corresponding to the periodicity of solar activity(Schwabe cycle and Hale cycle). Mean grain size time series also displayed a 3–8 year periodicity corresponding to El Ni?o Southern Oscillation periodic change.  相似文献   

5.
Investigations and studies for years all demonstrated that there is a patch of fine-grained mud in the central area of the South Yellow Sea. However, scientists have different opinions on its material source, genesis, and sedimentation intensity. Some believe that the materials come from the Huanghe River, some think that the mud area represents the depocentre of the South Yellow Sea, and some consider it as "relict mud ". The authors ' geochemical study reveals that the mud is multi-sourced, yet the material supply is not ample, and that a little amount of fine-grained suspended materials deposited slowly under the dynamic action of a cyclonic gyre formed the modern muddy sediment, which is named "multi-source modern mud ".  相似文献   

6.
The implementation of the water sediment regulation scheme (WSRS) is a typical example of artificially controlling land-source input.During WSRS,the water discharge of the Yellow River will increase significantly,and so will the input of terrigenous materials.In this study,we used a natural geochemical tracer 222Rn to quantify terrestrial inputs under the influence of the2014 WSRS in the Yellow River Estuary.The results indicated that during WSRS the concentration of 222Rn ...  相似文献   

7.
Based on high-resolution analysis to a 280-cm long sediment core obtained from the muddy area in the central Yellow Sea, we examined the provenance of muddy sediments and discussed the changing marine sedimentary environment since the middle Holocene. The results indicated that fine-grained sediments in the muddy area were mainly derived from the Huanghe(Yellow River) and Changjiang(Yangtze River) with considerable stepwise variations during the past 6.6 kyr. The Yellow Sea Warm Current was initiated at 6 kyr when the sea level was high together with the enhanced East Asian Winter Monsoon. These in combination established the framework of shelf circulation in the Yellow Sea that began to trap the river-derived fine-grained sediments. From 4.9 kyr to 2.8 kyr, both the Kushiro Current and East Asian Monsoon were significantly weakened, reducing the delivery of Changjiang sediments to the muddy area. As a result, the sediments were mainly originated from the Huanghe. From 2.8 kyr to 1.5 kyr the continuously weakened East Asian Winter Monsoon and enhanced Yellow Sea Warm Current entrapped more fine-grain sediments. Whereas the enhanced East Asian Winter Monsoon and the human caused increase in sediment load of the Huanghe since 1.5 kyr, and direct delivery of Huanghe sediments to the Yellow Sea during 1128–1855 AD might dominated the sedimentation in the study area. The stepwise variations of the sediment provenance and composition of the Central Yellow Sea muddy sediments are of importance to understanding the formation of muddy deposit in the central Yellow Sea and the associated variations of marine environment since the middle Holocene.  相似文献   

8.
Sedimentary sequence and sediment provenance are important factors when it comes to the studies on marine sedimentation. This paper studies grain size distribution, lithological characteristics, major and rare earth elemental compositions, micropaleontological features and ~(14)C ages in order to examine sedimentary sequence and sediment provenance of the core BH6 drilled at the mouth of the Yellow River in Bohai Sea. According to the grain size and the micropaleontological compositions, 4 sedimentary units have been identified. Unit 1(0–8.08 mbsf) is of the delta sedimentary facies, Unit 2(8.08–12.08 mbsf) is of the neritic shelf facies, Unit 3(12.08–23.85 mbsf) is of near-estuary beach-tidal facies, and Unit 4(23.85 mbsf–) is of the continental lake facies. The deposits from Unit 1 to Unit 3 have been found to be marine strata formed after the Holocene transgression at about 10 ka BP, while Unit 4 is continental lacustrine deposit formed before 10 ka BP. The provenances of core BH6 sediments show properties of the continental crust and vary in different sedimentary periods. For Unit 4 sediments, the source regions are dispersed while the main provenance is not clear, although the parent rock characteristics of a few samples are similar to the Luanhe River sediments. For Unit 3, sediments at 21.1–23.85 mbsf have been mainly transported from the Liaohe River, while sediments above 21.1 mbsf are mainly from the Yellow River and partially from the Liaohe River. For Unit 2, the sediments have been mainly transported from the Yellow River, with a small amount from other rivers. For Unit 1, the provenance is mainly the Yellow River catchment. These results help in better understanding the evolution of the Yellow River Delta.  相似文献   

9.
Both China and Vietnam confront the challenges of natural geohazards and environmental changes in their deltas and coastal zones due to rapid urbanization, economic development, and the impacts of global climate change. China and Vietnam initiated a comparative study of the Holocene sedimentary evolution of the Yangtze River Delta(YRD) and Red River Delta(RRD) for the period 2015–2018 in order to improve the understanding of the two delta evolution histories in the Holocene. Previous investigative data of the two rivers, onshore delta plains, and offshore subaqueous deltas have been explored and reinterpreted. New data gleaned from boreholes, piston cores, shallow seismic and hydrodynamic sources have been collected from the offshore YRD and the East China Sea inner shelf, and surface sediments and short cores have been collected from the RRD near-shore areas. Six focal areas of the joint project have been defined for comparative studies of the two deltas, including morphological development, sequential stratigraphy, coastline shifting, sedimentary characteristics, sedimentary dynamics, and correlation with anthropogenic global climate change. The results of these study areas are presented herein. The joint project also includes cooperative capacity building; exchanges of young scientists have been organized during the project period, and hands-on training in laboratory geochemical analysis, numerical modeling, and seismic data processing and interpretation have been provided by China and its Vietnamese geoscientist partners. Joint field excursions were organized to the upstream of the Yangtze and Red Rivers in Yunan Province, China, all the way downstream along the Vietnamese portion of the Red River. These joint studies have, over the past three years, improved understanding of the evolutionary history of these two major rivers and their mechanisms of source to sink. Joint project results of these two major deltas are not limited to the geosciences; the cooperative mechanical and operational experiences have been helpful for future cooperation in the field of marine geoscience between China and Vietnam, as well for cooperative activities with other ASEAN member countries.  相似文献   

10.
The Huanghe (Yellow) River, with annual sediment discharge about 11 ×108tons, contributes about 17% of the fluvial sediment discharge of world's 21 major rivers to the ocean because its middle reaches flow across the great Loess Plateau of China. Sediment discharge of the Huanghe River has a widespread and profound effect on sedimentation of the sea. The remarkable shift of its outlet in 1128-1855 A.D. to the South Yellow Sea formed a large subaqueous delta and provided the substrate for an extensive submarine ridge field.The shift of its outlet in the modern delta every 10 years is the main reason why with an extremely heavy sediment input and a micro- tidal environment, the Huanghe River has not succeeded in building a birdfoot delta like the Mississippi. The Huanghe River has consistently brought heavy sediment input to sea at least since 0.7 myr.B.P. Paleochannels, paleosols, cheniers and fossils on the sea bottom indicate that the Yellow Sea was exposed during the late Quaternary glacial low-sea l  相似文献   

11.
The heavy mineral compositions of the sediments in core D04 with a length of 20.2 m from the muddy area outside the Oujiang Estuary along the coast of Zhejiang-Fujian Provinces have been analyzed. Core D04 can be divided into three units: DU1(0–7.4 m), DU2(7.4–11.4 m) and DU3(11.4–20.2 m). The results showed that the heavy minerals are authigenic pyrite(65.6%)– hornblende(16.0%) – epidote(4.6%) assemblages. The core sediments are mainly composed of clayey silt, which belongs to the clinoform deposit formed since 5.8 kyr, indicating a weak hydrodynamic environment. The deposition rates changed in the trend of high-low-high upward. Quantitative analysis shows that the core sediments were mainly from the suspended sediments of the Changjiang(Yangtze) River, accounting for 79.2%, with only 10.0% from Oujiang, and 10.8% from other provenance. The Oujiang-derived sediments were gradually increased from the bottom unit DU3(3.1%) to the top unit DU1(17.8%), but the Changjiang-derived sediments were gradually decreased. The source changes are closely related to the development of Yangtze River Delta and Wenzhou Bay, climate changes and human activities. During the period of 2.1–3.7 kyr, the sediment supply was greatly reduced due to the poor reclamation capacity of the river basins, resulting in a low deposition rate. Since 2 kyr, the enhancement of human activities in the Yangtze River Basin and the Oujiang River Basin led to more soils to be eroded and transported to the study area. Due to the short distance of the site of core D04 from the Oujiang River mouth, the study area received more Oujiang-derived sediments when upper unit(DU1) deposited than the lower units(DU2 and DU3).  相似文献   

12.
The three-river source region(TRSR), located in the Qinghai-Tibet Plateau in China, suffers from serious freeze-thaw(FT) erosion in China. Considering the unique eco-environment and the driving factors of the FT process in the TRSR, we introduce the driving force factors of FT erosion(rainfall erosivity and wind field intensity during FT period) and precipitation during the FT period(indicating the phase-changed water content). The objective was to establish an improved evaluation method of FT erosion in the TRSR. The method has good applicability in the study region with an overall precision of 92%. The spatial and temporal changes of FT erosion from 2000 to 2015 are analyzed. Results show that FT erosion is widely distributed in the TRSR, with slight and mild erosion being the most widely distributed, followed by moderate erosion. Among the three sub-regions, the source region of the Yellow River has the slightest erosion intensity, whereas the erosion intensity of the source region of Yangtze River is the most severe. A slight improvement can be observed in the condition of FTerosion over the whole study region from 2000 to 2015. Vegetation coverage is the dominant factor affecting the intensity of FT erosion in the zones with sparse vegetation or bare land, whereas the climate factors play an important role in high vegetation coverage area. Slopes28° also have a significant effect on the intensity of FT erosion in the zones. The results can provide a scientific basis for the prevention and management of the soil FT erosion in the TRSR.  相似文献   

13.
The páramo of the Northern Andes provide critically important ecosystem services to the Northern Andean region in the form of water provisioning and carbon sequestration, both of which are a result of the páramo?s organic-rich soils. Little is known, however, about the hydro-geomorphic characteristics of the rivers that drain these ecosystems. With impending plans for widespread hydro-development and increasing implementation of carbon-sequestering compensation for ecosystem services programs in the region it is imperative that we develop a thorough understanding of the hydrogeomorphic role that rivers play in this unique ecosystem. The objective of this study was to quantify bank erosion along an Amazonian headwater stream draining a small, relatively undisturbed páramo catchment to gain a better understanding of the natural erosion regime and the resulting sediment contributions from this unique ecosystem. This study implemented a combination of field, laboratory, and Geographic Information Systems techniques to quantify bank erosion rates and determine a bank erosion sediment yield from the Ningar River, a small páramo catchment(22.7 km~2) located in the eastern Andean cordillera of Ecuador. Results show that bank erosion rates range from 3.0 to ≥ 390.0 mm/yr, are highly episodic, and yield at least 487 tons of sediment annually to the Ningar River. These results imply that 1) páramo ecosystems substantially contribute to the sediment load of the Amazon River basin; 2) bank erosion is a potentially significant flux component of basin-scale carbon cycles in páramo ecosystems; and 3) hydrologic alteration campaigns(dam building) will likely critically alter these contributions and concomitantly disconnect a critical source of sediment and nutrients to downstream ecosystems.  相似文献   

14.
Wetlands are sensitive to climate change, in the same time, wetlands can influence climate. This study analyzed the spatio-temporal characteristics of wetland change in the semi-arid zone of Northeast China from 1985 to 2010, and investigated the impact of large area of wetland change on local climate. Results showed that the total area of wetlands was on a rise in the study area. Although natural wetlands(marshes, riparians and lakes) decreased, constructed wetlands(rice fields) increased significantly, and the highest increase rate in many places exceeded 30%. Anthropogenic activities are major driving factors for wetland change. Wetland change produced an impact on local climate, mainly on maximum temperature and precipitation during the period of May–September. The increase(or decrease) of wetland area could reduce(or increase) the increment of maximum temperature and the decrement of precipitation. The changes in both maximum temperature and precipitation corresponded with wetland change in spatial distribution. Wetland change played a more important role in moderating local climate compared to the contribution of woodland and grassland changes in the study area. Cold-humid effect of wetlands was main way to moderating local climate as well as alleviating climatic warming and drying in the study area, and heterogeneity of underlying surface broadened the cold-humid effect of wetlands.  相似文献   

15.
Mineralogical analysis was performed on bulk sediments of 79 surface samples using X-ray diffraction. The analytical results, combined with data on ocean currents and the regional geological background, were used to investigate the mineral sources. Mineral assemblages in sediments and their distribution in the study area indicate that the material sources are complex. （1） Feldspar is abundant in the sediments of the middle Chukchi Sea near the Bering Strait, originating from sediments in the Anadyr River carried by the Anadyr Current. Sediments deposited on the western side of the Chukchi Sea are rich in feldspar. Compared with other areas, sediments in this region are rich in hornblende transported from volcanic and sedimentary rocks in Siberia by the Anadyr Stream and the Siberian Coastal Current. Sediments in the eastern Chukchi Sea are rich in quartz sourced from sediments of the Yukon and Kuskokwim rivers carried by the Alaska Coastal Current. Sediments in the northern Chukchi Sea are rich in quartz and carbonates from the Mackenzie River sediments. （2） Sediments of the southern and central Canada Basin contain little calcite and dolomite, mainly due to the small impact of the Beaufort Gyre carrying carbonates from the Canadian Arctic Islands. Compared with other areas, the mica content in the region is high, implying that the Laptev Sea is the main sediment source for the southern and central Canada Basin. In the other deep sea areas, calcite and dolomite levels are high caused by the input of large amounts of sediment carried by the Beaufort Gyre from the Canadian Arctic Islands （Banks and Victoria）. The Siberian Laptev Sea also provides small amounts of sediment for this region. Furthermore, the Atlantic mid-water contributes some fine-grained material to the entire deep western Arctic Ocean.  相似文献   

16.
Virtual Huanghe River System： Framework and Technology   总被引：2，自引：0，他引：2  
1 Introduction Huanghe (Yellow) River basin is located in 32°–42°N, 96°–119°E. The area of the catchment is more than 752,000km2. The river is 5464km long with a drop in elevation of 4830m. Among the whole area, the moun- tainous and stone area accounts for 29%, loess and hills area 46%, sandy area 11% and plain area 14%, respec- tively. Different natural landscapes exist in this area. The Huanghe River flows through the Loess Plateau, where the soil is eroded seriously (Wang, 2002;…  相似文献   

17.
We use the particle size of sediments in core YS01 A to study the sedimentary environment of the mud deposit in the central South Yellow Sea of China during late Marine Isotope Stages 3(MIS3;40.5 kyr–31.3 kyr).In addition,the East Asian Monsoon and its relationship with the North Atlantic Ocean climate change are discussed based on the sensitive grain-size calculation and the spectrum analysis.The results show that during late MIS3,the muddy area in the central South Yellow Sea experienced the evolution of coastal facies,shallow marine facies,coastal facies,and continental facies,with weak hydrodynamic conditions.Compared with other climate indicators,we found that there were many century to millennium-scale climate signals documented in the muddy area sediments in the central South Yellow Sea.According to our particle size results,three strong winter monsoon events occurred at 37.6 kyr,35.6 kyr and 32.2 kyr.The East Asian Winter Monsoon records in core YS01 A are consistent with the Greenland ice core and the Hulu cave stalagmite δ~(18)O.The millennial and centennial scale cycles,which are 55 yr,72 yr,115 yr,262 yr respectively,correspond to solar activity cycles,while the 1049 yr and 2941 yr cycles correspond to the Dansgaard-Oeschger cycles.These cycles indicate that the paleoclimate evolution of the area was controlled by the solar activities,with the high-latitude driving thermohaline circulation as the main energy conveyor belt,followed by the sea-air-land amplification of the winter monsoon variation in the central Yellow Sea in the late MIS3.  相似文献   

18.
River runoff is affected by many factors, including long-term effects such as climate change that alter rainfall-runoff relationships, and short-term effects related to human intervention(e.g., dam construction, land-use and land-cover change(LUCC)). Discharge from the Yellow River system has been modified in numerous ways over the past century, not only as a result of increased demands for water from agriculture and industry, but also due to hydrological disturbance from LUCC, climate change and the construction of dams. The combined effect of these disturbances may have led to water shortages. Considering that there has been little change in long-term precipitation, dramatic decreases in water discharge may be attributed mainly to human activities, such as water usage, water transportation and dam construction. LUCC may also affect water availability, but the relative contribution of LUCC to changing discharge is unclear. In this study, the impact of LUCC on natural discharge(not including anthropogenic usage) is quantified using an attribution approach based on satellite land cover and discharge data. A retention parameter is used to relate LUCC to changes in discharge. We find that LUCC is the primary factor, and more dominant than climate change, in driving the reduction in discharge during 1956–2012, especially from the mid-1980 s to the end-1990 s. The ratio of each land class to total basin area changed significantly over the study period. Forestland and cropland increased by about 0.58% and 1.41%, respectively, and unused land decreased by 1.16%. Together, these variations resulted in changes in the retention parameter, and runoff generation showed a significant decrease after the mid-1980 s. Our findings highlight the importance of LUCC to runoff generation at the basin scale, and improve our understanding of the influence of LUCC on basin-scale hydrology.  相似文献   

19.
As a major sediment area in the upper Yangtze River, Jialing River basin experienced substantial land-use changes, many water conservancy projects were constructed from the 1980 s onward to promote water and soil conservation. The water and sediment yield at the watershed outlet was strongly affected by these water conservation works, including ponds and reservoirs, which should be considered in the modelling. In this study, based on the observed data of the Weicheng River catchment, the relationships between precipitation, runoff, vegetation, topography and sediment yield were analyzed, a distributed runoff and sediment yield model(WSTD-SED) was developed, and the hydrological processes of different land-use scenarios were simulated by using the model. The main results are summarized as follows: 1) there is an alternating characteristic in river channels and reservoirs in the Jialing River hilly area, with scour occurring in wet years and deposit occurring in dry years. 2) Most of the sediment deposited in river channels and reservoirs is carried off by the largest flood in the year. 3) The model yielded plausible results for runoff and sediment yield dynamics without the need of calibration, and the WSTD-SED model could be usedto obtain qualitative estimates on the effects of land use change scenarios. 4) The modelling results suggest that a 10% increase in cropland(dry land) reforestation results in a 0.7% decrease in runoff and 1.5% decrease in sediment yield.  相似文献   

20.
Large amounts of sediments originating from the Changjiang(Yangtze) River are deposited in the subaqueous delta and in the adjacent muddy area off the mouth and on the inner shelf of the East China Sea. The terrestrial sediments deposited in these areas not only contain information about the composition and environment of the source area, but they also record changes in anthropogenic activities. A sediment piston core(CJ0702) was extracted from the Changjiang subaqueous depocenter(31.00°N, 122.67°E) in a water depth of 22.0 m. The core was subsampled at 1 – 2 cm intervals and analyzed for grain size, clay mineralogy, and major element geochemistry. Results indicate a relatively high sediment accumulation rate of approximately 3.11 cm yr~(-1). These parameters exhibited only minor cyclical fluctuations in the core, which resulted from many factors. During the past 120 years, the Changjiang River-derived sediment is the primary source of sediment in the offshore mud area without evidence for the Yellow River-derived sediment increasing. After the trunk stream shifted from the North Branch to South Branch, the variations of proxies are controlled by the periodic fluctuation possibly linked to El Ni?o-Southern Oscillation(ENSO) and the Pacific Decadal Oscillation(PDO). In addition, anthropogenic heavy metal concentrations can be divided into three stages, which coincide well with economic development and environmental protection policies.  相似文献   

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