Nitrogen sources in the South China Sea, as discerned from stable nitrogen isotopic ratios in rivers, sinking particles, and sediments

Stable nitrogen isotopic ratios were measured in sinking particles and surface sediments from the South China Sea (SCS) in order to study recent nitrogen sources and degradation. Average δ¹⁵N values of 16 sediment traps deployed at seven locations in the northern, central and southern SCS were uniformly low, ranging between 2.7 and 4.5‰ with a winter minimum in the northern and central SCS. Enhanced nitrogen contents and δ¹⁵N values were noted in samples affected by swimmers, comprising between 5 and 20% of total nitrogen fluxes. Nitrate sources were subsurface waters from the western Pacific, which were isotopically depleted due to the remineralization of nitrogen from nitrogen fixation in surface waters. Nitrogen fixation in the SCS contributed up to 20% to the settling particles. In the southern SCS, resuspended matter close to the shelf added to the sinking particulates. The long-term trap record from the central SCS revealed decreasing δ¹⁵N values during the 1990s, which correspond with findings from the North Pacific Subtropical Gyre and may be attributable to increased nitrogen fixation due to global warming-related stratification. This trend may be restricted to the 1990s but could also persist due to the projection of more frequent occurrence of El Niño conditions.The δ¹⁵N increase from swimmer-free trap averages of 2.7–3.6‰ to values of 5–6‰ in underlying deep-sea sediments was in the same range as in other deep ocean areas. Similar to results from the northern Indian Ocean, this increase could be related to isotopic enrichment during amino acid degradation. The lowest sedimentary δ¹⁵N values characterize the Pinatubo ash layer deposited off Luzon in an event of mass sedimentation in 1991. The fast deposition of organic matter drawn from the surface waters with the ash in the form of vertical density currents evidently preserved the planktonic δ¹⁵N signal.     

由东海、黄海沉积物中有机碳含量及稳定同位素组成重建200a以来初级生产力历史记录

从20世纪80年代以来古生产力的重建研究一直是国内外海洋生态学研究的热点,但已有的大多数研究是在深海区;而陆架区的特点是来自陆源物质的影响往往比较明显,因此,研究难度远较深海区大。利用现代沉积物中的有机碳稳定同位素组成来估算海源碳的含量,在此基础上,结合调查区域表层沉积物中的几个初级生产力的代表性指标(浮游植物总量、叶绿素a浓度以及硅藻含量)的调查资料,寻求岩心中海源碳与古生产力指标的相关关系,再由南黄海冷涡沉积区3个典型柱状沉积物中海源碳重建了200a以来高分辨率的古生产力记录,这对陆架海生态环境演变规律的研究有重要意义。对重建所得到的南黄海近代初级生产演化因素的初步探讨表明,近200a来初级生产力波动升高与海水表层温度的升高趋势是一致的,但其最主要的控制因素还是营养盐的供应,其中陆源营养物质和污染物质的影响起到了重要的作用。     

南黄海表层沉积物粒度特征季节变化及其影响因素

通过对南黄海春季和秋季27个相同站位表层沉积物的粒度分析,并结合水文观测资料,研究了南黄海表层沉积物粒度的季节变化,参考文献资料初步讨论了粒度变化的影响因素。研究结果显示,按照Folk分类,南黄海表层沉积物可以分为粉砂质砂、砂质粉砂、粉砂和泥四种类型。秋季与春季相比,总体上砂和粉砂的含量增加,黏土含量降低,相应地平均粒径相对变粗,分选系数和峰态的变化较小,而偏态表现为更加正偏。季节性变化还表现出明显的区域差异,主要是受环流系统、河流来沙及波浪的季节性变化的影响。     

黄东海沉积物中的还原无机硫

Cold diffusion methods are used to separate and quantify the three reduced inorganic sulfur species into acid volatile sulfide(AVS), pyrite–S and element sulfur(ES) in the sediments of the Yellow and East China Seas. The results show that up to 25.02 μmol/g of AVS, 113.1 μmol/g of pyrite–S and 44.4 μmol/g of ES are observed in the sediments of the Yellow Sea and East China Sea. Pyrite–S is the predominant sulfide mineral in the sediments, while the concentration of AVS is quite low at most stations in the study area. The amounts and reactivity of organic matter are the primary limited factor for the sulfide formation, while an iron limitation and a sulfate limitation are not observed in the sediments of the Yellow Sea and East China Sea. The irregular profiles of the three reduced inorganic sulfur species also reflected the comprehensive influence of sediment composition and sedimentation rates.     

Tracing the origin of Pb using stable Pb isotopes in surface sediments along the Korean Yellow Sea coast

To investigate the factors controlling lead (Pb) concentration and identify the sources of Pb in Yellow Sea sediments along the Korean coast, the concentration of Pb and Pb isotopes in 87 surface and 6 core sediment samples were analyzed. The 1 M HCl leached Pb concentrations had a similar geographic distribution to those of fine-grained sediments, while the distribution of residual Pb concentrations resembled that of coarse-grained sediments. Leached Pb was presumed to be associated with manganese (Mn) oxide and iron (Fe) oxy/hydroxide, while residual Pb was associated with potassium (K)-feldspar, based on good linear relationships between the leached Pb and the Fe/Mn concentrations, and the residual Pb and K concentrations. Based on a ratio–ratio plot with three isotopes (²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb) and the geographic location of each sediment, sediments were categorized into two groups of samples as group1 and group2. Group 1 sediments, which were distributed in Gyeonggi Bay and offshore (north of 36.5°N), were determined to be a mixture of anthropogenic and natural Pb originating from the Han River, based on a ²⁰⁸Pb/²⁰⁶Pb against a Cs/Pb_leached mixing plot of core and surface sediments. Group 2 sediments, which were distributed in the south of 36.5°N, also showed a two endmembers mixing relationship between materials from the Geum River and offshore materials, which had very different Pb concentrations and isotope ratios. Based on the isotopes and their concentrations in core and surface sediments, this mixing relationship was interpreted as materials from two geographically different origins being mixed, rather than anthropogenic or natural mixing of materials with the same origin. Therefore, the relative percentage of materials supplied from the Geum River was calculated using a two endmembers mixing model and estimated to be as much as about 50% at 35°N. The spatial distribution of materials derived from the Geum River represented that of fine-grained sediments originating from the Geum River. It was concluded that Pb isotopes in sediments could be used as a tracer in studies of the origin of fine-grained sediments along the Korean Yellow Sea coast.     

黄、渤海沉积物中陆源脂类有机质的组成分布与转化特征

本文对黄、渤海表层沉积物中脂类化合物的组成进行了分析研究。结果表明,黄、渤海表层沉积物有机碳的含量为0.03%~1.02%,以黄河口含量最低,黄河口外和双台子河口外,以及北黄海和南黄海中部含量较高。有机质碳稳定同位素δ13C的分布为-21.55‰~-24.28‰,表征其陆海双重来源特征,并且海源特征由河口向海、由近岸向离岸逐渐增强。陆源脂类化合物以河口处略高,河道处略低,由河口向渤海中部和靠近渤海海峡方向迅速降低,表现出显著的河流输入特征;其形态组成由河道的游离态接近100%的绝对优势,迅速转变为渤海中部的以皂化结合态为主（大于50%）,仅在渤海中部和渤海海峡附近存在小于5%的矿物结合态,转化程度较低。北黄海中部和南黄海中部泥质区的有机碳和陆源脂类化合物显著富集,但其对总有机碳的相对贡献较小;其中皂化结合态超过50%,矿物结合态小于10%,说明其具有中等偏高的转化程度。     

南黄海中西部全新世地层沉积特征

南黄海是典型的物源供给丰富的宽广陆架海,全新世沉积记录十分丰富,具有分辨率高、空间分布不连续和沉积记录片段性等特征。根据近年来在南黄海采集的大量高分辨率浅地层剖面资料,结合多个钻孔的岩性特征和AMS14C测年数据,较为系统精细地揭示了南黄海全新世沉积的时空分布特征。根据沉积体空间分布范围、成因机制和物质来源,南黄海全新世沉积可划分为4个独立的沉积体,呈现出不同的声学反射特征,主要为加积进积反射、平行或透明弱反射、中高角度进积反射和中高角度倾斜-斜交反射。根据估算,河流物质输入约占到南黄海全新世沉积总量的78%,其他物质来源主要为海侵过程中较强的海洋动力侵蚀、改造和再分配的底床物质。本文的研究可为厘清南黄海全新世沉积体精细演化过程的动力学机制研究提供更多可靠的证据。     

黄海表层沉积物的矿物组成特征及其物源分析

以黄海66个表层沉积物为研究对象,通过粒度、黏土矿物和碎屑矿物分析,研究了黄海表层沉积物的粒度分布与矿物组成特征,探讨了研究区沉积物的矿物组成特征对其物源、沉积环境的指示意义。黄海表层沉积物平均粒径为5.2Φ,分选较差;黏土矿物组合类型为伊利石-高岭石-蒙脱石-绿泥石,其中伊利石的含量最高,蒙脱石的含量最低;碎屑矿物（粒径为0.063～0.125 mm）平均含量为8.07%,标准偏差为4.03,分布趋势与平均粒径分布基本一致,轻矿物以石英和长石为主;重矿物以角闪石和绿帘石为主,其次是不透明矿物和片状矿物,重矿物主要集中分布于黄海南部。物源识别结果表明：黄海的东北部海域接受鸭绿江沉积物的供应;黄海北部主要为黄河源沉积物;南黄海西部沉积物主要为黄海沿岸流南下带来的现代黄河物质和再悬浮的老黄河沉积物;南黄海中部沉积物来源复杂以黄河沉积物为主,长江沉积物的供应较少。     

黄东海表层沉积物中磷的赋存形态和分布特征及其对生态系统的潜在影响

For better understanding the phosphorus(P) cycle and its impacts on one of the most important fishing grounds and pressures on the marine ecosystem in the Yellow Sea(YS) and East China Sea(ECS), it is essential to distinguish the contents of different P speciation in sediments and have the knowledge of its distribution and bioavailability. In this study, the modified SEDEX procedure was employed to quantify the different forms of P in sediments. The contents of phosphorus fractions in surface sediments were 0.20–0.89 μmol/g for exchangeable-P(Exch-P), 0.37–2.86 μmol/g for Fe-bound P(Fe-P), 0.61–3.07 μmol/g for authigenic Ca-P(ACa-P), 6.39–13.73μmol/g for detrital-P(DAP) and 0.54–10.06 μmol/g for organic P(OP). The distribution of Exch-P, Fe-P and OP seemed to be similar. The concentrations of Exch-P, Fe-P and OP were slightly higher in the Yellow Sea than that in the East China Sea, and low concentrations could be observed in the middle part of the ECS and southwest off Cheju Island. The distribution of ACa-P was different from those of Exch-P, Fe-P and OP. DAP was the major fraction of sedimentary P in the research region. The sum of Exch-P, Fe-P and OP may be thought to be potentially bioavailable P in the research region. The percentage of bioavailable P in TP ranged from 13% to 61%. Bioavailable P burial flux that appeared regional differences was affected by sedimentation rates, porosity and bioavailable P content, and the distribution of bioavailable P burial flux were almost the same as that of TP burial flux.     

黄海区水母类的生态研究

本文根据１９８２年４月２１日～５月１２日，７月２３日～８月５日，１０月１２～３０日在３４°３０′Ｎ以北．１２４°Ｅ以西黄海水域污染现状综合调查中获得的样品和资料，分析了本海区水母类的种类组成，数量分布以及季节变化。调查海区共鉴定有３４种水母，其中优势种有盘形美螅水母Ｃｌｙｔｉａｄｉｓｃｏｉｄａ，四枝管水母Ｐｒｏｂｏｓｃｉｄａｃｔｙｌａｆｌａｖｉｃｉｒｒａｔａ，五角水母Ｍｕｇｇｉａｅａａｔｔａｎｔｉｃａ。秋季（１０月）为水母类总个体数的高峰期（８．６７个／ｍ３）。水母类的分布与水温、盐度密切相关，海流或水团也起重要作用．水母类分布的变更可以反映出沿岸水和外海水相互推移和消长状况。     

夏季南黄海颗粒氮同位素分布特征及影响因素研究

黄海是人类活动影响显著的半封闭陆架边缘海,在夏季存在特征鲜明的冷水团结构。为研究南黄海颗粒态氮的循环转化过程,本文通过分析2016年夏季南黄海水体颗粒物和表层沉积物的碳、氮含量及同位素,探讨南黄海近岸海域和冷水团海域颗粒物和表层沉积物氮含量、同位素的分布差异和影响因素。近岸海域颗粒氮(Particulate Nitrogen,PN)呈现出含量较高、氮同位素值(δ15N_PN)垂向差异较小、沉积物总氮(Total Nitrogen,TN)含量较低且氮同位素值(δ15N_TN)偏负的分布特征;冷水团海域PN呈现出含量低、δ15N_PN垂向差异显著、沉积物TN含量高且δ15N_TN偏正的分布特征。通过海底边界剪切应力模拟、环境因子分析并结合颗粒物与沉积物δ15N示踪分析,发现南黄海海域颗粒态氮及同位素分布主要受到水体/底边界动力过程影响,陆源输入和矿化过程亦共同参与调控。     

Organic carbon stable isotope ratios of continental margin sediments

Stable isotope ratios (δ¹³C) of total organic carbon were measured in surface sediments from the continental margins of the northern and western Gulf of Mexico, the north coast of Alaska and the Niger Delta. Gulf of Mexico outer-shelf isotope ratios were in the same range as has been reported for Atlantic coastal shelf sediments, ?21.5 to ?20‰. Off large rivers including the Mississippi, Niger and Atchafalaya (Louisiana), δ¹³C values increased from terrigenous-influenced (around ?24‰) to typically marine ($\text{～?20‰}$) within a few tens of kilometers from shore. This change was accompanied by a decrease in the amount of woody terrigenous plant remains in the sediment. Alaskan continental margin samples from the cold Beaufort Sea had isotopically more negative carbon (?25.5 to ?22.6‰) than did warmer-water sediments. The data indicate that the bulk of organic carbon in Recent sediments from nearshore to outer continental shelves is marine derived.     

南黄海沉积物中活性铁氧化物对有机碳的保存作用

土壤和沉积物中活性铁对有机质的吸附对有机质具有长期稳定和保存作用,从而在地质时间尺度上缓冲大气CO₂浓度。本文利用连二亚硫酸钠还原性溶解提取活性铁氧化物（FeR）及与之结合的有机碳（Fe-OC）,定量研究了南黄海沉积物中FeR与OC之间的结合方式以及FeR对OC的保存作用,讨论了深度增加对二者相互作用的影响。结果表明,南黄海沉积物中Fe-OC占沉积物总有机碳的份数（f_Fe-OC）为（13.2±7.47）%,即活性铁对OC的年吸附量为0.72 Mt,占全球边缘海沉积物TOC年埋藏通量的0.44%。Fe-OC的平均OC:Fe为4.50±2.61,表明共沉淀作用对有机质的保存起重要作用,且其比值随海源有机质含量增加而增加。Fe-OC稳定碳同位素（δ13C_Fe-OC）结果表明,FeR优先保存活性有机质,但这种选择性随OC:Fe增大而减弱。随深度增加,f_Fe-OC和δ13C_Fe-OC均未表现出显著变化,这与该海域沉积物中有机质活性较低、铁还原作用较弱有关。     

Sediment transport in the Yellow Sea and East China Sea

Eight survey cruises in different seasons have been conducted in the Yellow Sea (YS) and East China Sea (ECS) during the period from 2000 to 2008. Suspended sediment concentration (SSC) and hydrological data were collected during each cruise. Data analysis showed that total suspended sediment mass was approximately 0.18 × 10⁹ tons in the surveyed area during spring and autumn seasons. Highly turbid waters were found in the shallow waters between the Subei coast, the Changjiang estuary and the Zhejiang coast with seasonal variations.     

黄海冷水团附近沉积物中的趋磁细菌及磁小体的特性研究

对黄海冷水团附近海域的沉积物进行了富集、荧光显微镜观察、电镜观察,并对其中大小均匀、形状规则的高密度颗粒进行了能谱分析。结果显示,在黄海冷水团附近有趋磁细菌和磁小体的存在。     

山东半岛北部滨浅海区表层沉积物铝物源鉴别

Surface sediment samples in the near shore area of the north Shandong Peninsula are collected for grain size and element analyses. The results indicate that the surface sediments in the study area are primarily composed of the silt-sized components similar to the Huanghe River. The total concentration of aluminum varies from 5.57% to7.37%(average(6.33 ± 0.40)%), and its spatial distribution is mainly controlled by the grain size. Correlations between the ratio of aluminum to titanium concentration and aluminum concentration, titanium concentration and the mean grain size indicate that aluminum in the near shore surface sediments is affected majorly by the terrigenous source, and partially by the anthropogenic source. The ratios of aluminum to titanium concentrations are larger than the background value of loess matter at some stations due to the existence of excess aluminum associated with human activities. Thus, the sources of aluminum should be identified firstly when aluminum is used as an index of terrigenous matter even in the near shore area dominated by terrigenous deposits.     

Burial fluxes and sources of organic carbon in sediments of the central Yellow Sea mud area over the past 200 years

Long-term changes of composition,sources and burial fluxes of TOC(total organic carbon) in sediments of the central Yellow Sea mud area and their possible affecting factors are discussed in this paper.Firstly,similarity analysis is employed to confirm that the carbon burial features resulted from two collected cores are typical in the central Yellow Sea mud area where YSWC(Yellow Sea Warm Current) is prevalent.On this basis,the burial flux of TOC here was considered to be 235.5–488.4 μmol/(cm2?a) since the first industrial revolution,accounting for about 70%–90% among burial fluxes of TC(total carbon) in the sediments.Compared TOC/TC ratio in the two cores with that in other marine sediments worldwide,we suggest that the growth of calcareous/non-calcareous organisms and dissolution of IC(inorganic carbon) are important factors controlling the TOC/TC ratio in sediment.Results of two-end mixed model based on δ13C data indicate that marine-derived organic carbon(OCa)is the main part among total burial organic carbon which accounts for a ratio over 85%.Due to the high TOC/TC ratio in the two cores,TC in the sediments also mainly exists as OCa,and the proportion of OCa is about 60%–80%.Away from the shore and relatively high primary production in upper waters are the main reasons that OCa is predominant among all burial OC in sediments of the central Yellow Sea mud area.Burial of OC in this mud area is probably mainly influenced by the human activities.Although the economic development during the late 19 th century caused by the first industrial revolution in China did not obviously increase the TOC burial fluxes in the sediments,the rise of industry and agriculture after the founding of new China has clearly increased the TOC burial flux since 1950 s.Otherwise,we also realize that among TC burial fluxes,TIC account for about 10%–30% in sediments of the central Yellow Sea mud area,so its burial could not be simply ignored here.Distinct from TOC burial,long-term TIC burial fluxes variations relate with climate changes more closely:the East Asian summer monsoon may influence the strength of the Huanghe River(Yellow River) flood,which could further affect the transport of terrestrial IC from land to the central Yellow Sea as well as the burial of these IC in the sediments.     

冬、夏季渤黄海表层沉积物粒度特征差异及其成因分析

对渤海、黄海海域冬、夏两季表层沉积物取样,通过激光粒度仪得出粒度参数,进而分析讨论冬季强的沿岸流的作用、黄海暖流、夏季冷水团的影响以及地形、海底地貌特征、物源特征等对表层沉积物分布造成的影响。结果表明,冬、夏两季渤黄海表层沉积物粒度特征总体上相差不大,但部分海域如渤海中北部、渤海中南部、北黄海西北部近渤海海峡北部海域、山东半岛东北部海域、南黄海中部沉积物粒度特征存在明显季节性差异。表层沉积物粒度特征季节性差异与地形地貌、沿岸流、黄海暖流、黄海冷水团及物源密切相关。本研究对于探讨渤黄海不同季节表层沉积物沉积特征的影响机制、了解渤黄海区海洋动力过程的季节差异有积极意义。     

北黄海表层沉积物中甲藻孢囊的分布特征

2009年和2010年采集北黄海15个站位的表层沉积物样品进行甲藻孢囊分析,共鉴定出甲藻孢囊28种(隶属13个属)和2种未定种,优势种为膝沟藻(Gonyaulax spp.)、塔马/链状亚历山大藻(Alexandriumcatenella/tamarense)和微小/相似亚历山大藻(Alexandrium minutu...     

东、黄海沉积物-水界面营养盐交换速率的研究

2000年10月和2001年5月随“东方红2号”考察船在东、黄海进行考察,在A2、E2、E4、E5、E65个站位作了培养实验,研究沉积物-水界面在氧化和还原条件下的交换通量。在东海海域,NO3-、PO43-、总磷(TDP)由水向沉积物中扩散,NH4 、SiO32-由沉积物向水中扩散,NO3-、TDP、NH4 在还原条件下的交换通量大于氧化条件下的交换通量,PO43-、SiO32-在氧化还原条件下的交换通量基本一致。在黄海海域,两站位各溶解态营养盐的迁移方向有较大差异。在距离陆地较近的海域,各溶解态营养盐多由水中向沉积物中扩散,且距离陆地越近,交换通量越大。在东、黄海海域,沉积物释放的SiO32-对初级生产力的贡献分别为13%、10%~18%,与河流输送和大气沉降相比,沉积物对黄海、东海SiO32-的贡献分别占90%、86%,说明沉积物是SiO32-的源。而在整个东、黄海海域,对于溶解无机氮(DIN)和PO43-来说,它们的交换通量为负值,即沉积物从水体中吸附溶解无机氮和磷,说明沉积物是DIN和PO43-的汇。