Recent Advances in Marine Geodesy of China

The ocean accounts for approximately 71%of the total area of the Earth.Whether it is studying the shape of the Earth itself through geodesy or the future development of earth system science,strengthening the construction of ocean geodesy disciplines and innovating ocean geodetic observation technologies have evident theoretical and practical significance.In recent years,the discipline of ocean geodesy in China has been continuously developing and growing,and notable breakthroughs have been made in ocean satellite geodesy and seafloor geodetic observation technology.Research on ocean geodetic observation models and algorithms has also made great progress.

Seafloor geodetic network establishment and key technologies

Seafloor geodetic network construction involves the development of geodetic station shelter, network configuration design, location selection and layout, surveying strategy, observation model establishment and optimization, data processing strategy and so on. This paper tries to present main technological problems involved in the seafloor geodetic network construction, and seek the technically feasible solutions. Basic conceptions of developing seafloor geodetic station shelters for shallow sea and deep-sea are described respectively. The overall criteria of seafloor geodetic network construction for submarine navigation and those of network design for crustal motion monitoring are both proposed. In order to enhance application performances of the seafloor geodetic network, the seafloor network configuration should prefer a symmetrical network structure. The sea surface tracking line measurements for determining the seafloor geodetic station position should also adopt an approximately symmetrical configuration, and we recommend circle tracking line observations combined with cross-shaped line(or double cross-shape line) observations for the seafloor positioning mode. As to the offset correction between the Global Navigation Satellite System antenna phase center and the acoustic transducer, it is recommended to combine the calibration through external measurements and model parameter estimation. Besides, it is suggested to correct the sound speed error with a combination of observation value correction and parameterized model correction, and to mainly use the model correction to reduce the influence of acoustic ray error on the seafloor positioning. Following the proposed basic designs, experiments are performed in shallow sea area and deep-sea area respectively. Based on the developed seafloor geodetic shelter and sufficient verification in the shallow sea experiment, a long-term seafloor geodetic station in the deep-sea area of 3000 m depth was established for the first time, and the preliminary positioning result shows that the internal precision of this station is better than 5 cm.

Trace detection of Ce^(3+) by adsorption strip voltammetry at a carbon paste electrode modified with ion imprinted polymers

To develop a convenient method for sensitive and selective determination of Ce3＋ in aqueous phase with complicated matrices, a carbon paste electrode（CPE） modified with ion imprinted polymers（IIPs） were fabricated. The polymers were prepared by precipitation polymerization using Ce3＋ as template, allyl phenoxyacetate（APA） as monomer, ethylene glycol dimethacrylate（EGDMA） as crosslinker and azobisisobutyronitrile（AIBN） as initiator under the molar ratio of Ce3＋, APA and EGDMA as 1：4：40, respectively. Ce3＋ was detected directly by differential pulse adsorptive stripping voltammetry（DPASV） and its oxidation peak appears at about 0.93 V. All parameters affecting the sensor＇s response are optimized and a calibration curve is plotted at a linear range of 1.0 × 10^（-6）-1.0 x 10^（-5） mol/L and 1.0×10^（-5）-2.0 × 10^（-4）mol/L with the detection limit of 1.5 × 10^（-7） mol/L. All other rare earth ions have no interference with the determination of Ce^（3＋） even at a concentration 500 times higher than that of Ce^（3＋）.This sensor was successfully applied to determination of Ce^（3＋） in two catalyst sample solutions with RSD≤3.3%（n = 5）and recoveries in the range of 99.2%-106.5% at our optimal conditions.

Mid-Holocene seawater preserved in the deepest oceanic blue hole

南海三沙永乐蓝洞是目前已探知的最深海洋蓝洞,洞内70~100 m深的区域存在明显的温度、盐度及溶解氧等跃层结构.海水碳14测年显示该跃层之下的海水年龄约为6000~6600年,这是迄今为止在全球海洋中发现的年龄最古老的海水,对应的跃层也是最古老的.由于蓝洞独特的垂向几何形态,洞内的混合过程接近于分子混合,因此这些海水被很好地封存了数千年.古老海水的形成时间与中全新世发生在雷州半岛的极端冷事件时间大致相同,表明在全新世中期南海北部确实存在极端冷过程.该发现对研究全新世的海洋与气候演变具有重要科学意义.