Exploring variations in upper ocean structure for the last 2 Ma of the Nansha area by means of calcareous nannofossils

A great number of calcareous nannofossils have been found in the deep-sea sediments of 2.32 Ma at ODP Site 1143 located in the Nansha area, the southern South China Sea. The number of coccoliths varies from about 0.5×106 up to almost 53×106 coccoliths/g sediment, with an average of 16×106 coccoliths/g sediment. The accumulation rate of total coccoliths varies from 1×106 to 278×106 coccoliths/cm2 ka. The nannofossil assemblages are usually dominated by a lower-photic species-Florisphaera profunda, of which the average percentage is about 70% in all samples. The absolute abundance and the accumulation rate of nannofossils as well as the percentage ofF. profunda display significant oscillations on two different time scales. One is the fluctuation coincident with the glacial-interglacial cycle, and the other is the long-term changes on a time scale longer than 100 ka. Six evolutionary stages of calcareous nannofossils could be divided for the last 2.32 Ma, from which we can reconstruct the changes in the depth of nutricline of the Nansha area. In this paper, the possible mechanism resulting in these variations is also discussed.

Paleoproductivity records for the past 30 ka in the southern Nansha area, the South China Sea

This note presents productivity variations for the past 30 ka in the southern Nansha area, the South China Sea, from the gravity core 17962 (7°11 ′N, 112°5′E, core length: 8 m, water depth: 1 968 m). Estimated surface productivity demonstrates that at the last glacial maximum the productivity was about 1.6 times as much as that in the Holocene, and the change may be ascribed to an increase of terrestrial nutrients as sea level lowered in the glacial time.

Dynamics of picoplankton in the Nansha Islands area of the South China Sea

Dynamics of major picoplankton groups, Synechococcus (Syn), Prochlorococcus (Pro), picoeukaryotes (Euk) and heterotrophic bacteria (Bact) was investigated by flow cytometry for the first time in the Nansha Islands area in the South China Sea. Averaged over the whole investigation area, depth-weighted integrated cell abundance (DWA) of Syn, Pro, Euk and Bact was 1.6 (0.4-5.7)×103, 5.4 (0.1-7.3)×104, 0.7 (0.2-2.2)×103, and 2.3 (1.4-3.2)×105 cells/mL respectively. Picoautotrophic cell abundance was low in the northwest part of the Nansha Islands where surface water temperature was low and the upper mixed layer was shallow. Concurrently, a surface maximum vertical distribution pattern was observed in this area. While in the southeast and east zones where temperatures were relatively higher and nitraclines were deeper, picoplankton is abundant and a subsurface maximum around 50-75 m is observed. Coupling of horizontal and vertical distribution patterns of picoplankton abundance and hydrological status was found, suggesting a strong influence of currents and water column structure on picoplankton distribution in the investigation area. Contrary to that in the shelf water in the East China Sea, the relationship between Pro and Bact in the Nansha Islands area in the South China Sea was not significantly negative but weakly positive. Moreover, a similar distribution pattern of Syn and Pro was observed. Possible reasons for these differences in the two marine regimes were discussed.

ANALYSIS AND DISTRIBUTION FEATURES OF BENZOTHIOPHENE IN SEDIMENTS OF NANSHA ISLANDS SEA AREA

This work yielded an improved method for extracting and analysing benzothiophene in marine sediment.The detation limit was 0.05 ng S of benzothiophene, with precision of 8%. Benzothiophene was found in Nansha Islands sea area sediments and ranged from 1.1 -6.8 ng per gram dry sediment. Its concentration was closely correlated to hte organic carbon content in the sediment.Several source processes of benzohtiophene are discussed in this paper.

Reconstruction of surface ocean water pCO_(2(aq)) in Nansha area,the South China Sea during the last 30 ka

The reconstruction of pCO2 in the tropic ocean is one of the most important issues to understand global cli-matic changes. In this study, the high-resolution strati-graphic analysis of core 17962 was conducted, which is lo-cated in the southern South China Sea (SCS). The contents of sedimentary organic matter, the stable carbon isotopic composition of sedimentary organic matter, and the d 13C values of black carbon and terrigenous n-alkanes were de-termined. And the d 13Cwc value of carbon derived from aquatic was calculated. On the basis of d 13Corg-pCO2 equa-tion proposed by Popp et al. (1989), we estimated the pCO2 in the Nansha area, SCS, since the last glaciation using d 13Cwc instead of d 13Corg. The results show that the average pCO2 was estimated at 240 ppmV during the last glaciation, and at 320 ppmV in the Holocene. A comparison of surface sea pCO2 with the atmosphere CO2 recorded in the Vostok ice core, indicates that CO2 in surface water of the southern SCS could emit into atmosphere during the last 30 ka.

Distribution of Dissolved Inorganic Phosphate in Nansha Islands Sea Area, Southern South China Sea

Based on the survey data from the program Multidisciplinary Expedition to Nansha Islands Sea Area, the distribution of dissolved inorganic phosphate ( PO43--P ) in the sea water of Nansha Islands Sea Area is comprehensively analyzed in this paper. The results show that PO43--P concentration in the sea water of southeastern Nansha Islands Sea Area is commonly higher than that in the other sea areas; the vertical distribution of PO43--P concentration varies inconspicuously in different seasons; the concentration of PO43--P increases with water depth and changes most greatly in the layer of 50 ～ 100 m. The diurnal variation of PO43--P concentration differs in different seasons and at different observation stations. The distribution and variation of PO43--P concentration result from the physical and biological processes together.

Distribution of Organic Matter,Iron,Mangenese in Surface Sediments in the Nansha Islands Sea Area,South China Sea

Concentrations of organic matter, iron and manganese in the deep sea surface sediments in the Nansha Islands sea area, South China Sea are measured. Horizontal and vertical distributions of iron and manganese are discussed. The vertical distribution of iron and manganese in the sediments results from reduction, diffusion, and redeposition of manganese (or iron) oxide and hydroxide in the sediment. There are the maxima of iron and manganese in solid phase in the top of the sediment, which is caused by the penetration of O2 and the upward flux of Mn2+ ( or Fe2+ ). Manganese bacteria play a very important role in the cycle of solid-phase iron and manganese in the ocean environment. Manganese bacteria oxidize Mn2+ ( or Fe2+ ) in dissolved state to Mn4+ ( or Fe3+ ) in oxidized state under the aerobic condition, whereas they reduce iron and manganese in anaerobic conditions.

未来海上城市设计构想

基于粤港澳大湾区的发展战略和未来城市发展空间模式,将“未来”“海洋”与“城市”三者紧密结合进行研究设计,为未来城市向海洋拓展提供灵感与导向是未雨绸缪之举。2023“未来海上城市”研究生国际联合工作坊以广州南沙龙穴岛海域设计构想为题具有重要价值和意义。重庆大学设计小组方案融入海洋科创、海上人居、海上田园、海洋能源、海洋交通、海洋生态等要素,聚合科学与技术手段,从不同视角梳理总结未来海上城市发展模式和建设路径的可能性,是对未来海上城市建设模式和发展远景的探索与尝试。

城镇密集区公路桥群绿色建造创新探索

为提升城镇密集区公路绿色建造水平,结合南(沙)—中(山)高速的项目特点及工程需求,将绿色发展理念贯彻到公路设计、施工、运营、养护和管理的全寿命周期,重点研发了公路桥群工业化智能建造、公路资源综合利用、滨海湿地区公路环境保护与粤港澳大湾区交旅融合设计等四类十项创新技术。其中,预制梁环形生产线、非标准八车道等为项目特色首创技术,初步构建了典型城市群绿色桥群公路技术体系,并对未来重点发展方向进行了展望,以期丰富和完善粤港澳大湾区绿色公路技术体系,为其他高度城镇化区域可持续发展提供参考。

广州港南沙港区深厚层软土原位测试方法

广州南沙港区作为广州市重点发展的深水港,其港区内广泛分布深厚软土层,局部软土深度超过30 m。港区内软土层特征主要受两次大规模海侵、海退及珠江水系的影响。上层软土主要由淤泥组成,厚度约10~20 m,夹粉细砂薄层或条带状砂层;下层软土主要由淤泥质土组成,含有机质及腐木碎,厚度约4~8 m。软土参数是影响南沙港区工程建设的重要指标,采用原位测试不易受到影响,可准确呈现软土的力学性质。通过对比分析各种常用的原位测试方法,提出适用于南沙港区深厚软土层的原位测试方法。在工程实践中分别采用不同的原位测试方法获取工程参数,尤其采用不同规格的十字板板头进行十字板剪切试验,旨在为区域内同类软土勘察、设计及施工提供参考。

基于GMS的地面沉降模型的研究和实践应用

以南沙地面沉降区域为研究对象,运用GMS软件模拟分析压缩土层、建筑荷载、地下水位等要素对地面沉降的影响程度,采用试错法,建立有效的地面沉降模型,并结合现状及历史数据进行预测和推演,模拟多种工况下南沙区地下水水位变化和地面沉降的变化量,结果表明:南沙区地面沉降较为严重的区域主要集中在龙穴岛北部,其建筑荷载造成的沉降量最大可达到149 mm。该模型的构建及运用为南沙区在地面沉降管理决策方面起到良好的辅助作用,具有应用性和实践意义。

系统思维下规划体检评估的思考与实践——以广州市南沙新区为例

党的“十八大”以来,中国经济从高速增长转向高质量发展,城市规划建设管理更加注重以人为本和全面协调、可持续。利用体检评估手段,评价规划实施成果及识别城市发展中的阶段性问题,推动解决“城市病”,成为政府提高治理能力的重要手段之一。相比过去重指标的评估方法,新时期的规划体检评估不再是纯数据的理性评估,而是一种系统性的评估。本文提出从目标、时间、空间、要素四大维度出发,构建“四维”规划体检评估指标体系并探索评估方法。同时,结合广州市南沙新区的规划体检评估项目,阐释“四维”评估体系的实践应用,为新时期规划体检评估提供新的理论体系探索和实践参考。

南海南沙海区沉积有机质分布特征及其指示意义

对现在过程的研究可为了解过去沉积环境演变信息提供重要线索。对南海南沙广阔海域23个现代表层沉积物样品总有机碳(TOC)、总氮(TN)含量及同位素组成(δ13CTOC和δ15N)进行测试分析,以期通过沉积有机质的现代组成分布特征为反演其历史时空分布变化规律及其驱动机制提供参考。南沙海区表层沉积物TOC/TN(5.5~7.9,平均为6.5±0.6)和δ13CTOC(–21.9‰~–18.7‰,平均为–21.0‰±0.7‰)揭示了沉积有机质主要来自海源贡献;δ13CTOC与TOC和TOC/TN的相关性分析表明了TOC未受明显的早期成岩作用影响,因此表层沉积物TOC可用于反映现代上层海水生产力状况。南沙海区表层沉积物TOC(0.32%~0.97%,平均为0.67%±0.17%)呈现明显的西-东向分布差异,高值主要位于西部前缘地带,低值主要分布在东部海域。表层沉积物TOC的地理分布特征表明了西南夏季风对南沙海域表层海水生产力的主要调控作用—由夏季风产生的越南上升流和湄公河陆源输入带来的高通量营养盐促进了西部前缘海域浮游植物的勃发,而随着站位距离的增加其施肥效应越来越弱。表层沉积物TOC和TN的强相关性(R2=0.95)以及δ15N的空间分布特征暗示了南沙海域沉积物δ15N未受陆源河流影响,记录了上层海水δ15N信号,从而指示了相关的氮循环过程。

地理信息时空数据中台的构建与应用——以南沙新区为例

南沙新区作为粤港澳大湾区的几何中心,在“三区一中心”的发展格局下,城市快速发展建设累积了海量多源异构地理信息数据。综合大数据、云计算、物联网等技术,基于中台的架构理念,从数据模型、存储管理、空间索引、轻量化和制图引擎等方面构建了面向南沙新区的地理信息时空数据中台,并作为智慧南沙的地理信息数据底座,挖掘当前累积的多源异构地理数据的应用价值,实现“一处建设、多处应用”,为南沙新区建设提供持续全面的数据服务支撑。

2005-2020年南沙新区建设用地时空演变及结构分析

南沙新区是国家级新区,承担着重要的经济发展任务,开展新区建设用地时空分布特征分析,对全面掌握新区建设用地信息、制定科学规划战略等有着重要作用。本文基于高分辨率遥感影像,结合POI等专题数据,获取2005—2020年连续年份的建设用地数据,利用建设用地扩展指数与空间分析方法,揭示了研究区建设用地的时空变化特征及新增建设用地亚类变化情况。结果显示:1)研究区建设用地规模呈上升趋势,受政策利好影响,部分年份增速加快,尤其2019年后,新增建设用地面积、扩展强度和扩展速度明显加快;2)重心轨迹为“‘东南—西北’”点向东南方向移动,空间分布呈“分散—聚拢—分散—聚拢”的波动发展趋势。3)扩展模式以外延式为主,填充式比重逐渐增加。4)新增建设用地的类型结构中,以交通设施用地和住宅用地为主,占总新增面积的59%,工矿用地在个别年份有突出增长,商业设施用地和公共设施用地在2020年明显快速新增。

基于GIS的南沙新区建成区时空演变特征分析

以广州南沙新区作为研究区域,利用卫星遥感和地理信息技术在快速、精准监测建成区变化和空间分析的技术优势,以2015—2017年为监测时点,在提取各监测时点广州南沙新区建成区现状范围的基础上,结合南沙新区的专项规划、统计年鉴、人口普查数据、经济统计数据等专题资料,以地理空间的视角研究南沙新区建成区时空演变特征和驱动力因子,为南沙新区规划建设提供有效数据参考。

广州南沙新区高快速路系统提升规划研究

基于粤港澳大湾区发展规划提出的背景,以广州南沙新区为例,探讨高快速路网体系提升的研究要点。通过梳理南沙新区现状高等级路网体系,提出优化高快速路系统、提升衔接道路功能、完善节点布局和形式等策略及方案,使高快速通道系统能充分发挥其对地方的服务功能,并减少过境交通对城市的影响,从而支撑南沙新区社会经济快速发展的需求。

粤港澳大湾区融合型社会建设的问题与对策——基于广州南沙的案例研究

社会融合不仅是港澳地区融入国家发展大局的关键表征,也是《粤港澳大湾区发展规划纲要》明确指出的重要内容。为了分析和讨论粤港澳三地在融合型社会建设领域的既有措施、现状问题以及提升对策,选取了广州南沙为研究案例,以中国式现代化的3个坐标--物质、制度与人的现代化为分析框架,阐释了软基建在粤港澳融合型社会建设方面的现代化内涵;在此基础上,通过分析南沙在社会融合方面的经验做法与现存不足,探索以粤港澳深度融合型社会建设为目标的大湾区社会建设方案。研究认为,广州南沙目前主要在就业、医疗、教育这三大“软基建”的核心领域发力,通过政策支持体系与合作平台建设这两方面的具体措施,来促进粤港澳三地在社会建设领域的融合式发展。研究表明,广州南沙需要通过“产城人”关系、公共服务供给体系以及民生资源共享生活圈等方面的对策与措施,加强粤港澳大湾区的融合型社会建设,在民生领域率先构建粤港澳三地的融合型社会发展建设格局。

春季南沙海域鸢乌贼种群结构特征的研究

种群问题是渔业生物学研究的基础。根据2011年春季罩网渔船调查数据,研究了南沙海域鸢乌贼（Sthenoteuthis oualaniensis）的种群组成、胴长分布、雌雄比例、性腺发育等种群结构特征。结果显示：1）南沙海域存在中型和微型2个鸢乌贼种群,分别占渔获总尾数的88.92%和11.08%,微型种群渔获量少但也遍布整个调查海域;2）中型和微型种群渔获胴长范围分别为69-231 mm和51-125 mm,2个种群雌性的平均胴长均大于雄性;3）中型和微型种群中雌性个体分别占48.48%和61.88%,2个种群不同胴长组性比随着胴长的增加变化规律相似,即由开始阶段雌雄基本接近,到雄性个体占优,再到雌性个体占优,直至全部为雌性;4）微型种群性腺发育早于中型种群,雄性个体性腺发育早于雌性个体,雌、雄初次性成熟胴长（ML50%）中型种群分别为179.7 mm和125.6 mm,微型种群分别为94.8 mm和81.1 mm。鸢乌贼雌雄比例的变化与雄性个体的生长发育密切相关。