Occurrence and evolution of the Xiaotangshan hot spring in Beijing, China

Thermal groundwater occurs in bedrock aquifers consisting of the dolomite of the Wumishan Group of the Jixianin System and the Cambrian carbonate in the Xiaotangshan geothermal field near the northern margin of the North China Plain, China. The hot water in the geothermal field of basin-type discharges partly in the form of the Xiaotangshan hot spring under natural conditions. The hot water has TDS of less than 600 mg/L and is of Na·Ca-HCO₃ type. The geothermal water receives recharge from precipitation in the mountain area with elevation of about 500 m above sea level to the north of the spring. Thermal groundwater flows slowly south and southeast through a deep circulation with a residence time of 224 years estimated with the Ra–Rn method. The Xiaotangshan hot spring dried up in the middle of the 1980s owing to the increasing withdrawal of the hot water in the geothermal field in the past decades. The water level of the geothermal system still falls continually at an annual average rate of about 2 m, although water temperature changes very little, indicating that the recharge of such a geothermal system of basin-type is limited. Over-exploitation has a dramatic impact on the geothermal system, and reduction in exploitation and reinjection are required for the sustainable usage of the hot water.     

A nitrate and silicate budget in the equatorial Pacific Ocean: a coupled physical–biological model study

A coupled physical–biological model was developed to simulate the low-silicate, high-nitrate, and low-chlorophyll (LSHNLC) conditions in the equatorial Pacific Ocean and used to compute a detailed budget in the Wyrtki box (5°N–5°S, 180–90°W) for the major sources and cycling of nitrogen and silicon in the equatorial Pacific. With the incorporation of biogenic silicon dissolution, NH₄ regeneration from organic nitrogen and nitrification of ammonia in the model, we show that silicon recycling in the upper ocean is less efficient than nitrogen. As the major source of nutrients to the equatorial Pacific, the Equatorial Undercurrent provides slightly less Si(OH)₄ than NO₃ to the upwelling zone, which is defined as 2.5°N–2.5°S. As a result, the equatorial upwelling supplies less Si(OH)₄ than NO₃ into the euphotic zone in the Wyrtki box, having a Si/N supply ratio of about 0.85 (2.5 vs. 2.96 mmolm⁻² day⁻¹). More Si(OH)₄ than NO₃ is taken up with a Si/N ratio of 1.17 (2.72 vs. 2.33 mmolm⁻² day⁻¹) within the euphotic zone. The difference between upwelling supply and biological uptake is balanced by nutrient regeneration and horizontal advection. Excluding regeneration, the net silicate and nitrate uptakes are nearly equal (1.76 vs. 1.84 mmolm⁻² day⁻¹). However, biogenic silica export production is slightly higher than organic nitrogen (1.74 vs. 1.59 mmolm⁻² day⁻¹) following a 1.1 Si/N ratio. In the central equatorial Pacific, low silicate concentrations limit diatom growth; therefore non-diatom new production accounts for most of the new production. Higher silicate supply in the east maintains elevated diatom growth rates and new production associated with diatoms dominate upwelling zone. In contrast, the new production associated with small phytoplankton is nearly constant or decreases eastward along the equator. The total new production has a higher rate in the east than in the west, following the pattern of surface silicate. This suggests that silicate regulates the diatom production, total new production, and thereby carbon cycle in this area. The modeled mean primary production is 48.4 mmolCm⁻² day⁻¹, representing the lower end of direct field measurements, while new production is 15.0 mmolCm⁻² day⁻¹, which compares well with previous estimates.     

Research on the spectral analysis and test method of period signals in monthly mean sea level

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一类序同态的构造

作者定义了从L_1~X到L_2~Y的映射σ,证明了σ是满足σ(x_λ~0)=σ(λ)∧σ(x_(I_1)~0)的保并映射的充要条件是σ(A)=∨g(λ)∧f(Aλ),其中f为X到L_1~Y的映射,g为L_1到L_2~Y的保并映射,且有f(X)≤g(I_1);最后证明了一类序同态的分解定理,它们是前人相应结果的推广与补充。     

南沙群岛珊瑚礁地貌图像信息管理系统

运用面向对象的软件开发技术,结合珊瑚礁地貌学、计算机图像学和计算机信息管理技术,在Windows平台上研制开发出南沙群岛珊瑚礁地貌图像信息管理系统。该系统集文件管理、数据库管理和图形、图像管理于一体,具有信息检索输出、信息编辑和信息维护等功能,以图形用户介面交互,达到"所见即所得"的效果。     

Several significant hydrographic characteristics and their formation mechanism in the South China Sea during the spring and summer of 1998

INTRODUCTIONTheSCSisthelargestmarginseainthewestoftheNorthPacificOcean .Theprevailingwindinwinterisnortheast,whileinsummeritissouthwest .Itisstilluncertainthathowthecirculationandtemperature -salinityfieldassociatewiththemonsoonforcingandaccompanywithseveralkindsofvariationsbeforeorafterthesummermonsoonburst .DuringSECMEXin 1 998,twointensiveobservationperiods (IOP)havebeencarriedoutntheSCS (Fig 1 ) :IOP1 ,from 1 0Aprilto 5May ;IOP2 ,from 1 2JunetoJuly 6 ,inordertounderstandthe…     

头足类视觉特性的电生理研究 Ⅰ.无针乌贼视网膜电图的特性

乌贼是重要的海洋水产资源之一,对其视觉特性的研究在理论上和实践上显然都有一定的意义。视网膜电图(ERG)作为网膜的综合电活动是反映视觉特性的一个良好指标。乌贼的ERG的特性至今缺乏系统的研究。本文对其ERG的波形和适应特性作了较详细的描述。续文将报导对ERG的光谱敏感性的分析。     

深圳大鹏湾表层沉积物碎屑矿物空间分布特征

立足样品测试数据,利用空间分析、空间插值、地质统计以及景观生态学方法,深入分析了深圳大鹏湾表层沉积物碎屑矿物的空间分布特征,并使用球状模型对相应半变异函数进行理论建模。结果表明,碎屑矿物分布的Hurst分维数为0.28～0.97,空间几何分维数为1.03～1.72;Moran Ⅰ型空间自相关系数-0.15～0.53。在此基础上,以等值线分布所包围范围作为划分尺度,以Shannon-Wiener信息指数作为度量,得到的矿物分布所反映出的信息量或者富集程度指数为0.88～1.85。     

一种程控增益低噪声水声接收机的设计

本文介绍了一种数字测深仪的接收机的具体设计，其特点是低噪声、增益程序控制，可以输出高质量的回波信号。稍加调整，即可用作其它声纳的接收机。     

重金属锌,铅对菲律宾蛤仔的急性毒性试验

本文研究了必需元素Ｚｎ及非必需元素Ｐｂ对菲律宾蛤仔的急性毒性作用，得到Ｚｎ对其的４８ｈＬＤ５０和９６ｈＬＤ５０分别为１４７．９１、１６．４０ｍｇ／ｄｍ＾３；Ｐｂ对其的４８ｈＬＤ５０和９６ｈＬＤ５０分别为３１．６２、１４．２８ｍｇ／ｄｍ＾３。估算得到Ｚｎ、Ｐｂ对菲律宾蛤仔的安全浓度分别为０．８２、０．７１ｍｇ／ｄｍ＾３。