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Potassium isotopic signatures of modern offshore detrital sediments from different climatic regimes and the implications

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Science China Earth Sciences 2024年第2期67卷 405-419页

作者： Jun MU Tianyu CHEN Qian YU Shichao AN Jianfang CHEN Xuefa SHI Weiqiang LI state Key laboratory for Mineral Deposits Research School of Earth Sciences and EngineeringNanjing UniversityNanjing210023China Ministry of Education Key laboratory for coast and island development School of Geography and Ocean ScienceNanjing UniversityNanjing210023China state Key laboratory of Satellite Ocean Environment Dynamics Second Institute of OceanographyMinistry of Natural ResourcesHangzhou310012China Key laboratory of Marine Geology and Metallogeny First Institute of OceanographyMinistry of Natural ResourcesQingdao266061China

Potassium isotopes are a novel tracer for continental *** K isotope studies on chemical weathering generally targeted weathering profiles under a particular climate region,yet the effects of chemical weathering on K isotopes under different climatic backgrounds remain ***,little is known about the K isotope signatures of modern unconsolidated detrital ***,we report K isotopic data of surficial seafloor sediments from continental shelves along the east coast of China(ECC),as well as those around the tropical Hainan island in the northern South China *** ECC sediments have a relatively narrow distribution ofδ^(41)K(with reference to NIST3141a)values,which range from(-0.40±0.01)‰to(-0.57±0.04)‰,with an average of(-0.51±0.09)‰.By contrast,δ^(41)K values of Hainan offshore sediments display a larger variation,ranging from(-0.28±0.07)‰to(-0.67±0.02)‰.Theδ^(41)K values of Hainan offshore sediments exhibit negative correlations with the chemical index of alteration(CIA),Al/K,Ti/K,and total iron(FeT),which underlines the control of chemical weathering on K isotopic signatures of detritus inputs into *** also measured Mg isotope compositions for the same samples;interestingly,the variability inδ^(26)Mg of the samples is small(~0.24‰)for all ECC and Hainan offshore sediments,andδ^(26)Mg values do not show clear correlations with indexes of chemical *** study demonstrates the link between K isotopic variability of detrital sediments and climatic conditions including rainfall intensity,which indicates that K isotopes of the detrital component of marine sediments could be applied to study Earth’s climate in deep ***δ^(41)K values of the offshore detrital sediments are significantly less variable than those of pelagic marine sediments,highlighting the importance of distinguishing the effects of diagenesis and neoformation of clay minerals from continental weathering in attempts to study deep-time climate-weathering

关键词： Potassium isotopes Magnesium isotopes Chemical weathering Detrital sediments Climatic regimes Mean annual precipitation

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Discovery and features of vertical zonations of tidal salt-marsh foraminifera in Jianchuan, North Jiangsu Province, China

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Acta Oceanologica Sinica 2002年第1期21卷 87-94页

作者：尤坤元张兆干吴小根施炳文 state pilot laboratory of coast & island Exploitation Nanjing University Nanjing 210093 China

Through densified surface sampling of foraminifera and accurate elevation measurement a-long three transect lines in open-coast tidal salt-marsh of Jianchuan, particular salt-marsh foraminifera assemblages were found. The salt-marsh foraminifera assemblages are distributed in well-defined vertical zonations with respect to elevation and closely parallel marsh floral zonations. At the top of the vertical zonation all foraminifera disappear abruptly which are accurately located at the highest high water datum. This distribution pattern can be used to relocate former sea levels accurately (to an accuracy of within ±5 cm). A modern regional criterion of foraminifera for relocating the former sea levels in high resolution in our country is provided, and deficiencies of studying the vertical zonation only in sheltered coast salt-marsh abroad are filled up.

关键词： Jianchuan of North Jiangsu Province open-coast tidal salt-marsh vertical zonation of foraminifera high resolution criterion for former sea levels

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SAND DUNE coast—AN EFFECT OF LAND-SEA INTERACTION UNDER THE NEW GLACIAL ARCTIC CLIMATE

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Journal of Geographical Sciences 1992年第1期3卷 37-54页

作者： Wang Ying Zhu Dakui state pilot laboratory of coast & island Exploitation Nanjing University

A comparative study on sand dune coasts of Bohai Sea and Mauritania along Atlantic Ocean shows that the dune coast might be an effective example of land-sea interaction,and gives insight on the formative mechanism of this kind of *** dune coast develops when strong prevailing onland winds blow large amount of sand up from the sea shore;medium tidal range and gentle coastal slope are also the basic factor to improve the development of sand *** the cold phase of Holocene under the Arctic climate influence,it offers a better environment to satisfy all the factors for sand dune development.

关键词： Dune coast land-sea interaction cold phase of Holocene

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Diurnal variations of carbon dioxide,methane,and nitrous oxide fluxes from invasive Spartina alterniflora dominated coastal wetland in northern Jiangsu Province

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Acta Oceanologica Sinica 2017年第4期36卷 105-113页

作者： XU Xinwanghao FU Guanghe ZOU Xinqing GE Chendong ZHAO Yifei Ministry of Education Key laboratory for coast and island development Nanjing University Nanjing 210023 China

The invasions of the alien species such as Spartina alterniflora along the northern Jiangsu coastlines have posed a threat to biodiversity and the ecosystem ***,limited attention has been given to their potential influence on greenhouse gas（GHG） emissions,including the diurnal variations of GHG fluxes that are fundamental in estimating the carbon and nitrogen *** this study,we examined the diurnal variation in fluxes of carbon dioxide（CO_2）,methane（CH_4）,and nitrous oxide（N2O） from a *** intertidal flat in June,October,and December of 2013 and April of 2014 representing the summer,autumn,winter,and spring seasons,*** found that the average CH_4 fluxes on the diurnal scale were positive during the growing season while negative *** tidal flat of *** acted as a source of CH_4 in summer（June） and a combination of source and sink in other *** observed higher diurnal variations in the CO_2 and N_2O fluxes during the growing season（1 536.5 mg CO_2 m^（–2） h^（–1） and 25.6 μg N_2O m^（–2） h^（–1）） compared with those measured in the non-growing season（379.1 mg CO_2 m^（–2） h^（–1） and 16.5 μg N_2O m^（–2） h^（–1））.The mean fluxes of CH_4 were higher at night than that in the daytime during all the seasons but *** diurnal variation in the fluxes of CO_2 in June and N_2O in December fluctuated more than that in October and ***,two peak curves in October and April were observed for the diurnal changes in CO_2 and N_2O fluxes（prominent peaks were found in the morning of October and in the afternoon of April,respectively）.The highest diurnal variation in the N_2O fluxes took place at 15：00（86.4 μg N_2O m^（–2） h^（–1）） in June with an unimodal *** logging in October increased the emission of CO_2（especially at nighttime）,yet decreased N_2O and CH_4 emissions to a different degree on the daily scale because of the restrained diffusion rates of the *** seasonal and diurnal variations of

关键词： methane nitrous oxide carbon dioxide diurnal variation S.alterniflora

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Landscape and land use in southern Hainan island,China

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Chinese Science Bulletin 2001年第S1期46卷 102-104页

作者： ZHANG Yongzhan MARTINI I.Peter GE Chendong ZHU Dakui state pilot laboratory of coast&island development Nanjing UniversityNanjing 210093China Department of Land Resource Science University of GuelphGuelphONCanadaNIG 2W1

According to the landscape/land use relation of southern Hainan island, four main zones are considered: the mountain and high hill zone, the inner coastal zone, the shoreline zone and the marine zone. The economic boo... 详细信息

关键词： landscape land use southern Hainan island.

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Observations and analyses of floc size and floc settling velocity in coastal salt marsh of Luoyuan Bay, Fujian Province, China

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Acta Oceanologica Sinica 2010年第3期29卷 116-126页

作者： WANG Aijun YE Xiang CHEN Jian Open laboratory for coast and Ocean Environmental Geology Third Institute of Oceanography State Oceanic Administration Xiamen 361005 China Key laboratory of Ministry of Education for coast and island development Nanjing University Nanjing 210093 China

In coastal environments, fine-grain sediments often aggregate into large and porous flocs. ElectroMagnetic Current Meters （EMCM） and Laser In Situ Scattering and Transmissometry （LISST-ST） have been deployed within a Spartina alterniflora marsh of the Luoyuan Bay in Fujian Province, China, to measure the current velocity, the floc size and the settling velocity between 15 and 22 January 2008. During the observations, the near-bed water was collected in order to obtain the suspended sediment concentration （SSC） and constituent grain size. Data show that：（1） the nearbed current velocities vary from 0.1 to 5.6 cm/s in the central Spartina alterniflora marsh and 0.1–12.5 cm/s at the edge; （2） the SSCs vary from 47 to 188 mg/dm 3 . The mean grain size of constituent grains varies from 7.0 to 9.6 μm, and the mean floc sizes （MFS） vary from 30.4 to 69.4 μm. The relationship between the mean floc size and settling velocity can be described as： w s =ad b , in which w s is the floc settling velocity （mm/s）, a and b are coefficients. The floc settling velocity varies from 0.17 to 0.32 mm/s, with a mean value of 0.26 mm/s, and the floc settling velocity during the flood tide is higher than that during the ebb tide. The current velocity and the SSC are the main factors controlling the flocculation processes and the floc settling velocity.

关键词： Spartina alterniflora marsh current velocity suspended sediment concentration mean floc size floc settling velocity Luoyuan Bay

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Spatial Variations in Depth-distribution of Trace Metals in coastal Wetland Sediments from Quanzhou Bay,Fujian Province,China

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Chinese Geographical Science 2009年第1期19卷 62-68页

作者： WANG Aijun CHEN Jian Open laboratory of Ocean ＆ coast Environmental Geology Third Institute of Oceanography State Oceanic Administration Xiamen 361005 China Ministry of Education Key laboratory for coast and island development Nanjing University Nanjing 210093 China

Four short cores were obtained from the coastal wetland of the Quanzhou Bay,Fujian Province,China,and sediment samples were analyzed with a Mastersizer 2000 for grain size analysis and an Inductively Coupled Plasma Atomic Emission Spectrometer(ICP-AES) for trace metal analysis. The results of grain size analysis show that the wetland sediments are mainly composed of silt and clay,and the distribution of median grain size is affected by human activities obviously. The results of trace metal analysis show that the wetland sediments mainly originate from terrestrial materials in the Luoyangjiang River estuary and from contaminants discharged from adjacent rivers in Shuitou area. The heavy metal contamination in Luoyangjiang estuary decreased from 1984 to 2004 due to industry transformation,but has increased since 2004 because of the discharge of contaminants to the Jinjiang River and much living sewerage to the bay,and a large number of trace metals are trapped within Spartina alterniflora marsh.

关键词： coastal wetland trace metal grain size Spartina alterniflora marsh Quanzhou Bay

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Distribution characteristics of heavy metals in surface sediments and core sediments of the Shenzhen Bay in Guangdong Province,China

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Acta Oceanologica Sinica 2009年第6期28卷 53-60页

作者： ZUO Ping WANG Yaping MIN Fengyang CHENG Jun Key laboratory of coast and island development Ministry of Education Nanjing UniversityNanjing 210093 China

The concentration of zinc, chromium, cadmium, nickel, lead and copper was measured on both surface sediments and core sediments in the Shenzhen Bay. The average contents of all metals have exceeded the background values in the coastal zone of Guangdong Province. Cadmium is a heavy pollution matter which indicates a strong pollution level according to the ecological risk coefficient method. The ecological risk index of the whole area is 299 which belongs to middle and strong level. The area with strong pollution level is the near shore area closing to the inside of Shenzhen Bay, Shakou area is in the middle level while the weak pollution level occurs in Shenzhenhe Estuary according to ecological risk index. The four sediment cores can be divided into two parts based on lead-210 dating, sediments size analysis and economic development period in surrounding areas since 1950 with strong human intervention. The sediment size, deposition rate and human activities have positive relationship with the contents of heavy metals which directly impact the pollution level of heavy metals in sediments in Shenzhen Bay.

关键词： surface sediments core sediments distribution characteristics pollution assessments Shenzhen Bay in Guangdong Province

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Invasive Spartina alterniflora-induced factors affecting epibenthos distribution in coastal salt marsh, China

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Acta Oceanologica Sinica 2013年第2期32卷 81-88页

作者： XIE Wenjing GAO Shu School of Geographic and Oceanographic Sciences Nanjing University Key laboratory of coast and island development of Ministry of Education Nanjing University

Artificially introduced cordgrass, Spartina alterniflora, rapidly colonized the intertidal flats of the Jiangsu coast, eastern China. The epibenthos on an intertidal flat invaded by S. alterniflorawere studied, to identify how local epibenthos species react to an altered environment. Epibenthic samples and surficial sediment samples were collected along a shore-normal profile in 50 quadrats at ten stations across the Spartina salt marsh; and five control quadrats for a station located on the barren sandy-mud flat. The grain size param- eters of the surficial sediments show that S. alterniflora altered the grain size gradient along the profile of the intertidal zone by trapping fine-grained sediments. Spartina alterniflora could inhabit lower elevation- s than indigenous salt marsh vegetation, thus creating larger areas of finer surficial sediments, which was suitable for not only native epibenthic species but also species which do not exist on the barren sandy-mud flat. Correlation analyses show that the epibenthos were sensitive to sediment grain size and type, on the invaded S. alterniflora salt marsh. Further, there was an interspecific relationship affecting the distribution of epibenthos. The results show that epibenthos preferred ecological niches, within the Spartina salt marsh, even in the same sampling station.

关键词： benthos ecology exotic plant species grain size tidal-flat sedimentation Jiangsu coast

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On the sediment age estimated by ^(210)Pb dating: probably misleading “prolonging” and multiple-factor-caused “loss”

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Acta Oceanologica Sinica 2018年第6期37卷 30-39页

作者： JIA Jianjun YANG Yang CAI Tinglu GAO Jianhua XIA Xiaoming LI Yan GAO Shu state Key laboratory of Estuarine and coastal Research East China Normal University Key laboratory of coast and island development of MOE Nanjing University state Research Centre for island Exploitation and Management Second Institute of Oceanography State Oceanic Administration College of the Environment and Ecology Xiamen University

The radionuclide ^（210） Pb is suitable for century-scale dating and has been used to calculate the sedimentation rate in a variety of environments. However, two common ways to apply 210 Pb dating techniques may give misleading results. One is ＂prolonging of age＂, i.e., using the calculated sedimentation rate to date back to 200 or 300 *** practice must be treated with caution because the 210 Pb dating techniques do not guarantee direct dating for ages much older than 100 years. Another is ＂loss of age＂, i.e., the calculated time span between the topmost layer and the 210 Pb background layer in cores is less than 100 years when an apparent sedimentation rate is used in the calculation. Here, we propose that based on the principle of 210 Pb dating, the upper limit of age suitable for direct210 Pb dating is between 110 and 155 years. The ＂prolonging＂ application is acceptable only if the sedimentary environment in the past several hundred years was stable and the sedimentation rate was generally constant, and verification with independent evidence（such as historical records or biomarker methodology） is ***, after analyzing many published and collected data, we found four possible reasons for the ＂loss of age＂. First, the compaction effect of sediment should be corrected in laboratory analysis or else the calculated age will be underestimated. Second, the accuracy and uncertainty of 210 Pb activity measurement affect the judgment of the background. To be cautious, researchers are apt to choose a background activity with a younger age. Third,use of a slightly smaller value of supported 210 Pb activity in a calculation will lead to considerable underestimation of the time span. Finally, later-stage erosion and migration are common for sedimentation, which lead to loss of sedimentary records and are often reflected as a ＂loss of age＂ in cores. We believe that proper use of 210 Pb dating data may provide helpful information on our understanding of sedi

关键词： ^210Pb dating sedimentation rate sediment flux

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