Silicon isotope compositions of dissolved silicon and suspended matter in the Yangtze River, China

Silicon isotope compositions of main channel samples of the Yangtze River were systematically investigated along with their chemical compositions. The concentration of suspended matter in the Yangtze River tends to decrease from the upper reaches to the lower reaches, corresponding to settling of the sediments in the lakes and reservoirs due to reduction of the velocity of water flow. The silica contents of suspended matter vary from 52.1% to 56.9% and their δ³⁰Si values vary from 0 to −0.7‰, both similar to those of shales. From the upper to lower reaches, the silica contents of suspended matter tend to increase, whilst their δ³⁰Si values tend to decrease. Both trends reflect the increase of clay minerals and decrease of carbonates in suspended matter.The concentrations of dissolved silicon vary from 97 to 121 μmol/L and their δ³⁰Si values vary over a wide range from 0.7 to 3.4‰. From the upper to lower reaches, dissolved silica concentrations tend to decrease and their δ³⁰Si values tend to increase. These trends mainly reflect the change of chemical and isotopic characteristics of the tributaries from the upper to lower reaches. The major factors responsible for these changes may be the high meteoric precipitation and significant silicon absorption by grass (in wetlands) and rice (in paddy fields) in drainage areas of the middle and lower reaches.There is no correlation between δ³⁰Si of dissolved silicon and that of suspended matter. The Δ³⁰Si_Diss-SPM values vary over a wide range of 1.0-3.7‰, indicating that (1) they are out of isotopic equilibrium, (2) dissolved silicon and the associated suspended matter do not belong to one physico-chemical system, and (3) isotopic exchange rate between them is very slow.The δ³⁰Si value of dissolved silicon output from the Yangtze River to the East Sea is estimated to be 3.0‰, much higher than the values reported for the Amazon and Congo rivers. This increases the δ³⁰Si range of dissolved silicon in the world’s rivers from 0.4-1.2%; to 0.4-3.4%.     

气象灾害与作物种植

利用历年气象资料和作物观测资料,分析了驻马店各季的气象条件和气象灾害对作物生长的影响,提出了现有作物种植的弊端,分析了改进作物种植方法的必要性和紧迫性,并提出了改进措施.     

气象地理信息系统的设计与实现

微软.NET平台上采用C#语言编程, 从低层开发成功面向气象应用的专题型地理信息系统———气象地理信息系统 (MeteoGIS)。该系统以满足气象防灾减灾工作对GIS功能的迫切需求为目标, 实现了一个拥有自主版权的独立GIS内核, 不依赖于任何商业GIS系统及其二次开发接口。介绍了该系统开发的背景、目的、意义与若干关键技术, 简述了该系统的结构、功能与推广应用前景。     

北京地区小震活跃与首都圈地区中等地震活动关系研究

通过研究北京地区的小震活跃与首都圈地区中等地震活动的关系，发现1999年到2003年间频度异常与首都圈地区Ms4．0以上地震具有一定对应关系，但频度异常对未来地震地点判定的意义不大，需要将北京地区小震频度异常和首都圈及附近地区小震活动的有序性特征有机结合起来，才能更好地把握中等地震发生的时间和地点，最后指出，频度异常指标具有一定的时间性特征。     

ANSYS/LS-DYNA在地震工程中的应用

近年在国内很流行的大型通用程序ANSYS不但具有强大的前后处理功能、丰富的单元类型和材料库,而且该软件中有一个LS-DYNA模块采用了粘性边界（viscous boundary）来模拟无限域的影响,从而可以方便地、较准确地进行地基动力作用分析.国外利用ANSYS/LS-DYNA进行地基动力作用分析非常普遍,而国内还未见到将ANSYS/LS-DYNA用于地震工程.本文将介绍如何利用ANSYS/LS-DYNA进行地基动力作用分析,同时,由于软件中用于模拟无限域的粘性边界精度较低,本文提出采用精度较高的粘-弹性边界替换粘性边界,从而改善了计算结果.     

我院在我省水利信息化建设中应如何发挥作用

水利信息化是水利行业走向现代化的措施和手段,水利信息化是一个系统工程,不仅涉及的部门多,业务范围广,而且技术复杂、投资大。我院应该充分利用自己的优势,深入开发和广泛利用水利信息资源,积极参与水利信息化建设,为我省的水利信息化建设作出自己的贡献。     

Effects of intracellular structural associations on degradation of algal chloropigments in natural oxic and anoxic seawaters

To understand the effects of intracellular structural associations on degradation of algal chloropigments, we conducted a series of microcosm experiments by incubating Emiliania huxleyi cells (a marine haptophyte) in natural oxic and anoxic seawaters collected from a stratified water column in the Cariaco Basin. The incubated cell detritus were sequentially treated with two buffer solutions to separate pigment components into soluble and insoluble fractions. By using non-denaturing gel electrophoresis, several chlorophyll-complexes, free chlorophyll, and another unknown chlorophyll-containing component were further separated from the soluble fraction. The chlorophyll-complexes included those bound with high molecular weight core-proteins (CP-I and CP43+CP47) and low molecular weight polypeptides (LHC-I and LHC-II) in the cellular photosystems PS-I and PS-II. Overall pigment recovery from these fractions and gel bands was well equivalent to the total amount from direct acetone extraction of the cells. We followed the time-dependent concentration changes of chlorophyll-a (Chl-a), phaeophorbide-a (Ppb-a), and phaeophytin-a (Ppt-a) in all fractions and complexes to estimate the degradation rate constants of chloropigments in natural oxic and anoxic seawaters. Our experimental results demonstrated that the intracellular structural associations had important influences on degradation of chloropigments under different redox conditions. In general, total Chl-a degraded faster (∼4X) in oxic seawater than in anoxic seawater. However, the rate differences between oxic and anoxic conditions varied among the fractions and complexes. Degradation rate constants of Chl-a in soluble fraction were much higher (>10X) than those in insoluble fraction under both oxic and anoxic conditions. Chl-a bound with the complexes in PS-II appeared to be more reactive (∼2X) than that in PS-I under oxic conditions but the difference in degradation rate constants between two photosystems became indistinguishable under anoxic conditions. Variations of Ppb-a in different fractions and complexes during incubation showed different patterns, implying that cellular Chl-a could degrade through two different pathways: (1) internal degradation into Ppb-a within insoluble pool and polypeptide complexes; and (2) release first from protein complexes and followed by external degradation.     

基于因子分析法的县域土地利用 程度时空变异分析 ——以河北省曲周县为例

本文基于多元统计的因子分析法,以河北省曲周县为例,对县域尺度下土地利用程度进行时空变异分析。通过对1985、1995和2000年三个时间点的研究,表明：(1)1985～2000十五年间,曲周县的土地利用程度得到明显提高,其中以槐桥乡最为显著;(2)曲周土地利用程度具有明显的空间分异特征,中东部、西部地区明显高于南部及东南部地区。最后,文章结合区域实际,从自然、社会、经济、区位特征和科学技术五个方面对曲周县土地利用程度的时空变异进行驱动力分析,为调控区域土地利用提供借鉴。     

Geochemical evidence for the variation of historical seabird population on Dongdao Island of the South China Sea

From a rare freshwater lake characteristic of alkalescence, named “Cattle Pond”, on the Dongdao Island of South China Sea (16°39′–16°41′ N, 112°43′–112°45′ E), we collected two undisturbed sediment cores that contain seabird droppings. In this paper, we determined the concentration-versus-depth profiles of the geochemical elements in the ornithogenic sediment layers of the two cores, analyzed these profiles by various statistical methods, and studied their geochemical characteristics. The concentration profiles of As, Cd, Cu, Se, Zn, P and S are significantly correlated with each other and with loss on ignition (LOI) at 550°C, the measure for the abundance of organic matter. Similar geochemical characteristics, however, were not observed in the upper sediment layer of the Cattle Pond notably affected by cattle excrements, as well as in the bottom sediment layer compositionally dominated by coral sand and gravel. This shows that these “bio-elements” are mainly derived from seabird feces and their geochemical composition is an important geochemical characteristic of the lacustrine ornithogenic sediments. By Q-mode factor analysis (QFA) on the concentration profiles of these bio-elements, we reconstructed the historical seabird population on Dongdao Island between 1350 and 350 year B.P., and observed significant fluctuations in the calculated population. The fluctuations seem to be related to the change of sea surface temperature (SST) in the Southern China Sea. This study provides new paleoenvironmental information of past seabird population changes in low latitude areas using an indirect geochemical method.     

航空摄影测量在道路测量工作中的应用探讨

本文通过工程实践,对航空摄影测量的方法在道路测量中的应用进行了探讨,并通过大量的实验数据对于GPS拟合高程的精度、航空摄影测量的精度进行了探讨和验证.