北冰洋西部沉积物有机碳、氮同位素特征及其环境指示意义

通过对楚科奇海及邻近的北冰洋深水区表层沉积物中有机碳同位素含量(δ13C)、氮同位素含量(δ15N)及生物成因SiO₂(BSiO₂)含量分析,结果表明海源和陆源有机质的分布受海区环流结构和营养盐结构所制约.楚科奇海中西部和楚科奇海台受太平洋富营养盐海水的影响,海洋生产力高,沉积物中海源有机质和BSiO₂含量高;靠阿拉斯加一侧海域海水的营养盐含量和生产力都偏低,沉积物中陆源有机质比重增加;在研究区北部和东北部的楚科奇高地和加拿大海盆,冰封时间较长,营养盐供应少,海洋生产力低,但来自马更些河和阿拉斯加北部的陆源有机质增多,沉积物中BSiO₂含量小于5%,海源有机质百分含量小于40%.由于亚北极太平洋水通过楚科奇海向北冰洋海盆输送,研究区营养盐池表现为开放系统,营养盐的利用率与它的供应成反比,与海洋生产力成反比.     

渤海湾西岸全新世以来沉积物地球化学与黏土矿物特征及其对环境和气候的响应

通过对渤海湾西岸BXZK11孔沉积物黏土矿物、地球化学元素组分、粒度分析以及AMS14C年代测定并与研究区周边6个具有较好年龄控制的钻孔剖面对比,结合黏土矿物蒙脱石/(伊利石+绿泥石)比值以及元素Al/Si和Al/Na比值对气候变化的响应,探讨了渤海湾西岸地区全新世以来沉积环境以及气候变化过程.结果表明,末次盛冰期到8...     

Geochemical signature as paleoenvironmental markers in Holocene sediments of the Tinto River estuary (Southwestern Spain)

High absolute concentrations of metals associated to sulfide deposits located at the river source (Fe, Cu, Zn, Pb, Cd, and As) have been determined from the study of major and trace element concentrations in sediment samples obtained in two vibracores in the Tinto River estuary. In most cases, the enrichment factor (EF) for these metals is over 2. Cu, Zn and As have much higher EF, over 10 in surficial samples. Fe oxy-hydroxide precipitation in high-chlorinity zones and its scavenging effect on metals is the main control process on the chemical composition of sediment. Vertical evolution of the sedimentary and geochemical characteristics of the cores show that the estuary has undergone a process of progressive shallowness and a relative increase in acidic river water volume with respect to seawater. This effect has originated a downstream displacement of acid mixing processes affecting the estuary, which is reflected in higher metal concentrations in sediments of the outer zones of the system.     

南海北部海域沉积物中生物钡、碳氮同位素的组成特征及其与表层水体初级生产之间的关系

通过对采集自南海北部的D06和S0612两个短柱状沉积物样品中的不同赋存形态钡、有机碳和生物硅的含量以及有机质碳氮同位素组成的分析,结果表明沉积物中的钡主要以碎屑钡和自生的生物钡形式存在。沉积物中生物钡的含量在10.3~385.2 μg/g之间,平均值为177.0 μg/g,据此计算的新生产力在12.3~146.7 mg/（d·m2）（以碳计）之间,平均为78.9 mg/（d·m2）;D06站计算的结果和附近站位的实测值相当。沉积物中有机碳的含量在0.64%~1.34%之间,平均值为0.89%,C/N比值为4.96~5.93,平均值为5.54。有机碳的δ13C值在-22.98‰~-20.73‰之间,平均值为-21.46‰,依据端元组份同位素组成计算的陆源有机质比率显示,D06站位的有机质主要来自海洋生物,而S0612站位则受陆源有机质的影响较大。沉积物中有机质的δ15N值在3.96‰~6.29‰之间,平均值为5.26‰,反映的是该海区氮源的同位素组成,而不受硝酸盐利用率的影响。     

巴丹吉林沙漠南缘高台盐湖记录的中晚全新世气候变化

位于季风边缘区和受西风环流显著影响的巴丹吉林沙漠南缘的高台盐湖提供了中晚全新世亚洲干旱区气候变化的可靠记录。在OSL测年的基础上,通过对高台盐湖剖面CaCO3含量、色度（L*、a*、b*）、粒度端元组分（EM）等环境代用指标的综合分析,重建了我国西北地区中晚全新世的气候变化。结果表明,中晚全新世高台盐湖地区气候变化经历了4个阶段：约7.1～5.3 ka,代表河流作用的EM2占主导,为浅湖/滨湖相沉积环境,气候相对干旱;5.3～1.2 ka期间,代表悬移作用的EM1占主导,指示深湖相沉积环境,CaCO3含量和a*和b*指示流域降水增多,地表侵蚀加强,近源物质输入较多,为中晚全新世以来的最湿润期;1.2～0.2 ka期间,EM2指示沉积环境转为滨湖/浅湖相沉积,气候变干;0.2 ka以来,气候进一步变干,湖泊消亡,演变为现代沙丘堆积。区域古气候替代记录的对比表明,高台地区中晚全新世以来演化过程与中亚干旱区湖泊记录具有一致性,气候变化主要受西风环流与高纬度北大西洋共同影响。     

Organic carbon and nitrogen isotopes in surface sediments from the western Arctic Ocean and their implications for sedimentary environments

1 IntroductionFor several reasons, the Arctic Ocean and itsmarginal seas are key areas for understanding ocean-ic circulation and global climate system ( Clark,1982; Hansen et al., 1983; Walsh et al., 1996;Overpeck et al., 1997). First, the Arctic Ocean i…     

早全新世白令海北部陆坡沉积环境快速变化

理解增暖背景下海洋环境的演化过程是海洋学和气候学一项重要的研究内容。在地质时期,地球经历了多次增暖时段（包括早全新世）,这为认识海洋环境演化过程提供了重要参考。早全新世全球气候经历了快速增暖,并伴随着冰原融化和海平面快速上升,对包括白令海在内的高纬边缘海的沉积过程和海洋环境产生显著影响。白令海发育宽阔的大陆架,毗邻北美大陆,接受来自育空河、阿纳德尔河和库斯科维姆河物质的供给。目前我们对白令海如何响应早全新世气候的认识还存在明显不足。本研究对位于白令海北部陆坡LV63-19-3岩心沉积物中陆源碎屑组份进行了高分辨率调查,结合沉积年龄模型,研究了早中全新世（距今11.7～5.5 ka）白令海北部陆坡陆源沉积演化过程。研究结果显示,在距今11.5～11 ka,白令海北部陆坡沉积速率高达392.9 cm/ka,在距今约9.7 ka以后降至17.2 cm/ka。在距今11～10.7 ka,发现一层厚约40 cm的暗色纹层状沉积层。在高沉积速率时段,沉积物平均粒径较细,距今9 ka以来平均粒径逐渐增大。主微量元素分析结果表明,陆源碎屑沉积物母岩性质以长英质沉积物为主,并存在少量火山碎屑源贡献。白令海北部陆坡高沉积速率事件对应于冰原融水脉冲（MWP）-1B事件（距今11.4～11.1 ka）,并导致白令海陆坡硅质生产力勃发。在距今11～10.7 ka研究区春夏季海冰覆盖增加抑制表层水体氧供给,夏、秋季持续冰川融水和高表层生产力进一步加剧了水体层化和海洋内部消耗,共同促进了纹层状沉积层的形成。距今9 ka以来白令海季节性海冰活动增强,但是陆源碎屑物质质量累积速率则逐渐减小,表明随着海平面上升,供给到研究区的陆源物质减少。我们认为早全新世白令海北部陆坡沉积环境快速变化是海平面、冰融水脉冲事件和季节性海冰活动共同作用的结果,实际上受高纬日射量、北美大陆冰原融化和全球气候变化控制。     

酸洗法测定海洋沉积物有机碳和无机碳含量的致命缺陷

Organic and inorganic carbon contents of marine sediments are important to reconstruct marine productivity,global carbon cycle, and climate change. A proper method to separate and determine organic and inorganic carbons is thus of great necessity. Although the best method is still disputable, the acid leaching method is widely used in many laboratories because of its ease-of-use and high accuracy. The results of the elemental analysis of sediment trap samples reveal that organic and inorganic carbon contents cannot be obtained using the acid leaching method, causing an infinitely amplified error when the carbon content of the decarbonated sample is 12%±1% according to a mathematical derivation. Acid fumigation and gasometric methods are used for comparison, which indicates that other methods can avoid this problem in organic carbon analysis. For the first time, this study uncovers the pitfalls of the acid leaching method, which limits the implication in practical laboratory measurement, and recommends alternative solutions of organic/inorganic carbon determination in marine sediments.     

楚科奇海表层沉积物的生源组分及其对碳埋藏的指示意义

工业革命以来大气中CO₂浓度由280 ppm剧增至375 ppm,是导致全球气候变暖的主要原因[1]。海洋作为大气CO₂的“汇”之一,每年可吸收人类释放CO₂气体总量的30%,对全球碳循环的收支平衡有重要作用[2]。两极地区是CO₂的主要汇区,也是全球变化的重要反馈窗口。因此,了解碳在北冰洋的生物地球化学循环过程是十分必要的[3-4]。海洋中的生源沉积物主要来自于海洋上层浮游生物碎屑的沉降,主要由蛋白石(以生物硅代替,BSi)、碳酸钙(CaCO₃)和有机质(通常用有机碳替代,TOC)组成[5]。     

长江古河谷早中全新世沉积物碳埋藏通量与来源解析

为了研究长江古河谷地区早中全新世沉积物的碳埋藏速率及来源,进行了ZK1孔沉积物总有机碳（TOC）、总氮（TN）及δ¹³C的测定,结合AMS¹⁴C（植物碎屑、贝壳）测年、有孔虫及粒度数据,分析了长江古河谷碳埋藏的时空分布特征与TOC来源。采用历史地理学、沉积地质学结合测年数据进行了年代地层划分,自下而上分别为U1潮汐河道、U2河口湾、U3潮流砂脊和U4前三角洲。沉积物受到水深、径流、河口余环流、潮流、波浪、风暴与再矿化等作用或因素影响,TOC平均值为0.41%,低于长江河口表层沉积物基准值0.46%。ZK1碳埋藏通量（TOC_BF）介于7.4～110.5 g/(m²·a)之间,差异较大。TOC_BF数值主要受控于沉积速率。δ¹³C与TOC/TN（C/N） 投影点结果表明,TOC来源表现为多源特征,且整体表现为偏陆源特征。C/N与δ¹³C线性拟合相关性高,适合采用C/N与δ¹³C进行TOC来源的定量分析。基于C/N与δ¹³C采用三端源模型进行了TOC来源分析。U2、U3沉积期处于全新世大暖期,其海源碳与陆源碳较U1、U2沉积单元高,这主要与海洋、陆地初级生产力的提高有关。ZK1海洋浮游植物对TOC的贡献量平均值为31%。河口浮游植物对TOC的贡献量平均值为31%。陆源有机碳对TOC的贡献量平均值为38%。整体来看,陆源有机碳的贡献量大于河口浮游植物与海洋浮游植物的贡献量,这与图解法的分析结果基本一致。     

杭州湾表层沉积物有机碳分布、来源及近20年来的变化

根据2002年、2008年、2012年、2017年和2022年夏季采样分析结果,对杭州湾表层沉积物中有机碳（TOC）时空分布变化进行了研究。结果表明研究区TOC平均值分别为0.55%(n=16)、0.50%(n=112)、0.44%(n=38)、0.53%(n=38)和0.51%(n=38),总体上呈现南北高东西低的“X”形平面分布特征,高值区出现在北岸金山至南汇咀海域和南侧镇海至慈溪海域,相关性分析表明TOC分布受到沉积物类型的控制,主要赋存于细颗粒沉积物内。沉积物的氧化还原环境也对TOC分布有显著影响。分区进行5个年份TOC统计分析显示,20年来北部海域先减后增,变化较为明显,南部和东部海域2017年增大之后减小,西部海域变化不大。TOC随时间的变化受到自然条件和人为活动造成的长江入海泥沙和有机物质通量下降、海洋源增加等因素的影响。C/N、δ13C特征表明,研究区沉积物中有机碳陆源贡献比例大都在30%～70%,站点差异较大,北岸近岸海域和东南侧海域陆源有机碳比例较高,湾中部和东部海域有机碳的海洋源比例较高。     

大鹏澳养殖区柱状沉积物中氮、磷的分布特征及污染状况研究

为研究海水养殖对海湾沉积物的累积影响, 对大亚湾的大鹏澳养殖区沉积物柱状样中总氮、总磷和有机碳的含量及剖面分布特征进行了研究, 并探讨了海水养殖区沉积物中氮、磷的污染状况。结果表明, 网箱养殖区、贝类养殖区和对照区等3个区域柱状样中总氮的含量范围分别为638.2—3803.9mg.kg-1、740.9—2152.1mg.kg-1和343.2—471.9mg.kg-1, 总磷的含量范围分别为344.7—3233.9mg.kg-1、297.9—497.5mg.kg-1和650.2—1327.2 mg.kg-1, 有机碳的含量范围分别为0.96%—2.22%、0.87%—1.13%和0.69%—0.95%。该三个因子的含量均从底层至表层呈增加趋势, 但网箱养殖区上层增加幅度最为剧烈, 贝类区次之, 对照区变化幅度最小。所有柱状样中, 总氮含量均超标, 但网箱养殖区总氮污染最为严重, 贝类养殖区次之, 对照区最轻; 网箱养殖区的总磷在上层的不同深度超标, 而贝类养殖区及对照区柱状样的总磷含量均未超标。     

渤海表层沉积物中有机碳的分布和来源

大河影响下的陆架边缘海沉积有机碳的分布和来源是全球碳循环研究的重要内容。本研究于2012年5月采集了渤海海域的29个表层沉积物样品,分析了粒度组成、总有机碳(TOC)、总氮(TN)、木质素含量和稳定碳同位素丰度(δ13C)等参数,结合基于蒙特卡洛模拟的三端元混合模型,定量研究了沉积物中有机碳的分布和来源情况,并讨论了其影响因素。结果表明,研究区域表层沉积物中TOC含量为0.19%~0.81%,渤海中部泥质区站位(大于0.65%)明显高于其周围砂质区域站位(小于0.40%);TOC与黏土含量也有显著的正相关性,说明细颗粒沉积物容易富集有机碳。沉积有机碳的δ13C范围为-23.7‰~-21.8‰,显示沉积有机碳是海源和陆源有机碳的混合输入。木质素参数,如C/V、S/V和LPVI的数值范围显示研究区域表层沉积物中木质素主要来源于被子植物草本组织与木本组织的混合,同时有少量裸子植物的贡献。基于蒙特卡洛模拟的三端元混合模型显示研究区域沉积物中有机碳主要来源于海洋浮游植物,平均为64%,陆源有机碳中来自土壤的贡献最高(平均为27%),C₃维管植物的贡献较少(平均为9%)。海洋浮游植物有机碳主要分布在渤海中部泥质区及离岸较远的区域,而土壤有机碳和C₃维管植物有机碳则主要沉积在河口附近及近岸区,并可以离岸输运到较远的地方。     

黄河下游-河口-邻近海域表层沉积物中木质素的特征及其示踪意义

河流输入的陆源有机碳在河口和陆架区的生物地球化学过程是全球碳循环的重要环节,对陆源有机质的输入量的估算是研究陆架区的生物地球化学过程的基础。黄河输沙量极大,为探究其携带的陆源有机质对陆架边缘海有机碳库的影响,以黄河河口及邻近渤海海域为研究对象,分析了表层沉积物中的木质素,结合总有机碳含量、总氮含量和有机碳稳定同位素评估了表层沉积物中有机碳的组成、来源和分布。8种木质素酚单体中,紫丁香基酚类(S)与香草基酚类(V)的含量比值S/V(0.63±0.31)和肉桂基酚类(C)与香草基酚类含量比值C/V(0.25±0.15),反映出研究区陆源有机碳主要来自草本被子植物。V系列中木质素酸(Ad)与木质素醛(Al)的比值(Ad/Al)V较高(0.53±0.14),表明陆源有机质的降解程度较高。利用稳定碳同位素比值δ13C和木质素含量Λ8相结合的土壤有机质-陆生维管植物-水生有机质三端元模型对陆源有机物的贡献的分析结果显示,土壤有机质、陆源维管植物和水生有机质的平均贡献分别为59.9%±15.0%、7.3%±7.0%、32.8%±11.8%。土壤在陆源有机质中的贡献占有绝对优势,可能与该区域沉积物的主要源区——黄土高原植被覆盖率低、土壤侵蚀严重有关。     

Temporal changes of a macrobenthic assemblage in harsh lagoon sediments

An opportunistic macrobenthic assemblage was studied from 2001 to 2003 in a central area of the Cabras lagoon (western Sardinia, Italy), known to be affected by environmental disturbances (i.e. organic over-enrichment of sediments, and episodic events of hypoxia/anoxia and sulphide development). We identified recurrent seasonal changes in this macrobenthic assemblage, with a general impoverishment in summer and a recovery in winter/spring. The nereids Neanthes succinea and Hediste diversicolor were found to replace the spionid Polydora ciliata as the most dominant species in the summer for 3 consecutive years. Occasional, unsynchronized appearances of small-sized deposit feeders, such as Tubificidae, Capitella cf. capitata, chironomid larvae and Hydrobia spp., were observed in winter/spring. We suggest that these changes are driven by the interplay of environmental conditions (worse in summer) with numerous biotic factors. This includes different tolerance levels of taxa to low oxygen concentrations and sulphides, variability in larval supply and post-larval transport, as well as competition for space and food between and within different functional groups, and facilitation through animal bioturbation and sediment reoxidation. A conceptual model is proposed to demonstrate how environmental conditions and biotic interactions may control the benthic assemblage in such a harsh lagoon environment.     

Biomarkers of Middle to Late Jurassic marine sediments from a canonical section: New records from the Yanshiping area,northern Tibet

The Yanshiping section, which includes the Quemo Co, Buqu, Xiali, Suowa and Xueshan Formations (Yanshiping Group) exposes organic-rich Middle to Late Jurassic deposits in the Qiangtang Basin of northern Tibet. The biostratigraphic data, from bivalves, brachiopods as well as dinoflagellate cysts, define a Bajocian to Tithonian age. This study focuses on the biomarkers present in these mudstones and limestones to determine the sources, thermal maturity and depositional environment of the organic matter. Most samples show a clear dominance of short-chain (C₁₅–C₂₀) n-alkanes with a maximum at C₁₉ or C₁₉ with a secondary maximum at C₂₃ except for the sample BP01(22)S1 where the predominant range is C₂₂ to C₂₆ with a maximum at C₂₄, significant CPI and odd-to-even predominance. The hopanoids and steroids suggest that the sources of organic matter were dominated by phytoplankton, especially algae, as the primary source. Furthermore, the Pr/Ph, Pr/nC₁₇ and Ph/nC₁₈, with relatively low values plus high abundance of 17α(H)-hopanes, support deposition in dysoxic to reducing, relatively shallow-water depositional settings, and the presence of gammacerane indicates normal marine salinity and/or water-column stratification. All samples are fairly mature with respect to petroleum generation, a conclusion supported by maturity parameters such as C₃₁ 22S/(22S + 22R) hopanes and C₂₉ ααα20S/(20S + 20R) steranes.     

桑沟湾及附近海域表层沉积物碳氮同位素分析及有机质来源

Naturally existing stable carbon and nitrogen isotopes are important in the study of sedimentary organic matter sources. To identify the sources of sedimentary organic matter in Sanggou Bay and its adjacent areas, which is characterized by high-density shellfish and seaweed aquaculture, the grain size, organic carbon(OC), total nitrogen(TN), carbon and nitrogen isotopic composition(δ13C and δ15N) of organic matter in the surface sediment were determined. The results showed that, in August, sedimentary OC and TN ranged from 0.17% to 0.76% and 0.04% to 0.14%, respectively. In November, OC and TN ranged from 0.23% to 0.87% and 0.05% to 0.14%, respectively. There was a significant positive correlation between OC and TN(R=0.98, P0.0001), indicating that OC and TN were homologous. In August, the δ13C and δ15N of organic matter varied from-23.06‰ to-21.59‰ and 5.10‰ to 6.31‰, respectively. In November, δ13C and δ15N ranged from-22.87‰ to-21.34‰ and 5.13‰ to 7.31‰, respectively. This study found that the major sources of sedimentary organic matter were marine shellfish biodeposition, seaweed farming, and soil organic matter. Using a three-end-member mixed model, we estimated that the dominant source of sedimentary organic matter was shellfish biodeposition, with an average contribution rate of 65.53% in August and 43.00% in November. Thus, shellfish farming had a significant influence on the coastal carbon cycle.     

Distribution and texture of the bottom sediments in a semi-enclosed coastal inlet, the Izmit Bay from the eastern sea of Marmara (Turkey)

Thirty-one surficial sediment samples were collected from the floor of Izmit Bay with a grab onboard the R/V Bilim in summer 1987 and analysed for their grain size, total carbonate, and organic carbon distribution.Low calcareous-terrigenous mud (2–45% CaCO₃) with a relatively high silt percentage was the principal sediment type found on the floor of Izmit Bay. Sediments rich in sand and gravel usually occur in the narrow and shoal areas of the bay, where biogenic and topography-related hydrodynamic conditions are dominant factors controlling the nature of bottom deposits. The carbonates are made up almost entirely of the remains of calcareous organisms. Organic carbon concentrations of the sediments (0·35-1·62%) are probably associated with the high primary production rates in this region. Thus, the rates of sedimentation in the Izmit Bay calculated from the organic carbon and primary productivity data are estimated to be up to 70 cm/1000 years.     

Varied pathways of river-borne clay minerals in a near-shore marine region: A case study of sediments from the Elbe- and Weser rivers,and the SE North Sea

The <2 μm fraction of 45 sediment samples from the Elbe and Weser rivers and from the southeastern North Sea (German Bight) was analyzed for its contents of clay minerals and selected chemical elements. This was done to provide new information to the controversial question about the origin and distribution of clays in this near-shore marine region. The proportions of smectite, chlorite, illite and kaolinite were determined from intensities of the (001) basal reflection of the XRD pattern using weighted integrated factors and IR-mineral spectra, which were fitted to the values of the chemical analyses. Illite – the major clay mineral – was characterized by its K/Rb ratios and K-Ar ages. Anthropogenic metal contamination was demonstrated by the Cu, Pb and Zn contents.     

Riverine dominance of a nearshore marine demersal food web: evidence from stable isotope and C/N ratio analysis

The Thukela Bank, KwaZulu-Natal, supports a diverse ecosystem and South Africa’s only prawn fishery. Oceanographic studies suggest riverine input is not important for the biology of this system, whereas biological studies suggest the contrary, with prawn catches increasing with increased fluvial run-off. The aim of this study was to determine (i) the importance of riverine and marine organic matter for the Thukela Bank food web; and (ii) whether there are seasonal changes in the Thukela River stable isotope values, and, if so, whether these are reflected in the isotope values of demersal organisms. Estuarine organic matter, sediments and demersal organisms were collected from several sites across the bank in the wet and dry seasons of 2008, 2009 and 2010. Marine particulate organic matter was also collected in 2010 and analysed for δ13C and δ15N, as well as C/N ratios. There were strong seasonal changes in isotopic values of organic matter and fauna, especially faunal δ13C. There was an apparent time-lag in organisms assimilating riverine organic matter isotopic values, with the isotopic signature of demersal organisms reflecting that of riverine organic matter from the previous season, which is likely the result of tissue turnover time. In 2010, Thukela Bank sediment organic matter was of riverine origin and this maintained the demersal food web. We conclude that Thukela River organic matter is an important input to the food web of the Thukela Bank, indicating that any future damming of the catchment area could have serious consequences for this ecosystem.