Fractionation of hydrogen and oxygen isotopes of gypsum hydration water and assessment of its geochemical indications

Fundamental knowledge of the isotopic fractionation between the hydration water and the mother solution and whether the primary information recorded in hydration water can be preserved or not in deposits or mines have long been unclear. In order to calculate the accurate hydrogen and oxygen isotopic fractionation factors between gypsum hydration water and its mother solution with new methods, to understand the mechanism of fractionation and synthetically assess the record-keeping abilities of the isotopic composition of hydration water during the process of diagenesis after deposition, experiments on the hydrogen and oxygen isotopic compositions of gypsum hydration water and its mother solution at different isothermal temperatures from 5 to 50°C were systematically conducted. In addition, samples from two typical gypsum deposits formed in different environmental conditions were also determined. Results show that during gypsum crystallisation, both hydrogen and oxygen isotopes show significant fractionation between the hydration water and the mother solution. The calculated hydrogen isotopic fractionation factors are <1, while the oxygen isotopic fractionation factors are >1 at temperatures from 5 to 50°C. The fractionation factors show no functional relationships with temperature. Isotopic compositions of gypsum hydration water in arid lake sediments can be used to trace the source of water and primary deposit environmental information. However, the isotopic composition of the gypsum hydration water can easily be altered by dissolution and secondary precipitation of gypsum during later diagenesis, particularly in areas with humid climate and abundant groundwater. A very careful assessment on record-keeping abilities of the primary isotopic composition of hydration water in gypsum during later diagenesis must be considered before application.     

风暴潮灾害风险评估研究综述

我国是受风暴潮影响最严重的少数国家之一,风暴潮灾害致灾机理的研究在过去几十年取得了极大的进展,而风暴潮脆弱性评估和综合风险评估还不能满足风暴潮灾害风险管理的需求.系统总结了风暴潮危险性、脆弱性、综合风险评估及其应用的研究进展,重点分析了典型重现期风暴潮估计、可能最大风暴潮计算、风暴潮物理脆弱性和社会脆弱性评估以及风暴潮风险评估及其应用的研究进展及不足,并对我国风暴潮风险评估急需解决的问题以及未来的研究重点进行了展望,指出了风暴潮灾害风险评估的模型化、系统化、定量化是未来风暴潮风险评估研究的发展趋势,风暴潮灾害的未来风险评估还需考虑全球气候变化以及海平面上升等因素的影响,而风暴潮灾害承灾体脆弱性的定量评价是风暴潮综合风险评估的重点和难点.     

南极威德尔海西北区域的冰-气拖曳系数和脊帆形拖曳力分析

基于机载激光高度计测得的南极威德尔海西北区域冬季海冰表面起伏数据,结合脊帆形态参数和空间分布对中性条件(大气层处于中性平衡态)下对应10m高度处风速的冰-气拖曳系数Cdn(10)和脊帆形拖曳力Fd的参数化方案进行了改进,并探讨了冰-气拖曳系数Cdn(10)和脊帆形拖曳力对总拖曳力的贡献随脊帆强度(脊帆高度与间距的比值,其中脊帆高度是指脊帆顶点到平整冰面的垂直距离,脊帆间距是指相邻两个脊帆顶点之间的距离)和冰面粗糙长度的变化情况。结果表明,冰-气拖曳系数Cdn(10)随脊帆强度增大呈递增趋势,对较小的脊帆强度,Cdn(10)随粗糙长度的增大而增大,但脊帆强度较大时,Cdn(10)随粗糙长度减小而增大,即存在某一脊帆强度阈值,使Cdn(10)在该阈值两侧随粗糙长度的变化趋势相反;脊帆形拖曳力对总拖曳力的贡献随脊帆强度减小而减小,随着粗糙长度增大而减小。通过分析发现,造成以上不同变化趋势的主要原因是:随着脊帆强度的增大,摩拖曳力在总拖曳力中的优势地位逐渐由形拖曳力代替。     

我国低硒带典型景观植物硒的研究

本研究在我国低硒带的东北端和西南端分别选取了针阔叶混交林景观和云南松林景观,并且在低硒带内的克山病和大骨节病非病区与东南非病带选取了落叶阔叶林景观和马尾松林景观为对照景观,系统地采集了上述各不同景观的主要植物和土壤,对硒进行了分析。结果发现,在我国低硒带的东北瑞和西南瑞景观的主要植物含硒量显著地低于对照景观,同时景观内土壤硒也明显地低于划分我国低硒生态景观的阈值,从天然植物的角度进一步对我国低硒带客观存在这一科学论断进行了补充。     

旋链角毛藻对中肋骨条藻化感作用的影响因素

在已知旋链角毛藻对中肋骨条藻具有化感作用的前提下,进行了温度、生长时期、光照、细菌等因素对旋链角毛藻化感作用的影响、化感物质的萃取及粗提物对中肋骨条藻的化感效应检验等实验,研究了旋链角毛藻化感物质的性质、降解特点,并初步测定了化感物质的结构。结果表明:旋链角毛藻化感作用与生长时期有关,指数期滤液化感作用强于衰亡期;旋链角毛藻的化感物质在50℃以下保持稳定,光和细菌均引起旋链角毛藻化感物质的降解,且细菌降解强于光降解;旋链角毛藻的乙酸乙酯萃取物具有明显的化感活性,该萃取物在255～260 nm处有特征吸收峰。综合以上结果,推测旋链角毛藻化感物质可能为分解温度在50℃以上的易被光和细菌降解的苯衍生物,从极性上看较易溶于乙酸乙酯。     

Enhanced Arctic Ice Concentration Estimation Merging MODIS Ice Surface Temperature and SSM/I Sea-Ice Concentration

Ice concentration data from passive microwave sensors are not reliable during the summer melt season. In this study passive microwave ice concentration estimates are improved upon through the assimilation of ice surface temperature data from the Moderate-Resolution Imaging Spectroradiometer (MODIS). Ice concentration from the analysis is converted to ice extent and compared with data from the Interactive Multisensor Snow and Ice Mapping System (IMS). Ice concentration analysis from data assimilation is in better agreement with the IMS data than the original passive microwave data, with the largest improvements occurring during sea-ice melt.     

Evolution of meteorological drought characteristics in Vietnam during the 1961–2007 period

The drought conditions over the seven sub-climatological regions in Vietnam are examined using three meteorological drought indices: de Martonne J, PED, and Standardized Precipitation Index (SPI). According to the seasonal probabilities of drought occurrence estimated by the de Martonne index, droughts mainly occur between November and March in all the sub-regions. The PED index and the SPI index generally show high probabilities of drought occurrence from April to August and from May to October, respectively. In the southern sub-regions of Vietnam, droughts more frequently occur in El Niño years and wet conditions are more frequently observed in La Niña years. However, such El Niño–Southern Oscillation influences are not clearly observed in the northern sub-regions. During 1961–2007, droughts significantly increased in the northern part of Vietnam. In the southern regions, PED shows increasing drought conditions while J and SPI show decreasing drought trends for almost all the stations.     

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???????У???????????????????μ????б??????á?????????????е?VP??б?????У???????????????9.414 mV/ms??     

Effect of dietary potassium on growth,nitrogen metabolism,osmoregulation and immunity of pacific white shrimp (Litopenaeus vannamei) reared in low salinity seawater

An 8 weeks feeding experiment was conducted to determine the effect of dietary potassium on the growth and physiological acclimation of Pacific white shrimp(Litopenaeus vannamei) reared in diluted seawater(salinity 4). Six semi-purified practical diets containing 0.59, 0.96, 1.26, 1.48, 1.74, and 2.17+ g potassium K per 100 g diet were formulated, respectively. The survival and feed conversion rate did not show significant difference among groups of shrimps given these diets(P0.05). The shrimps fed the diets containing 0.96-1.48 g K+ per 100 g diet gained the highest weight, specific growth rate, and protein efficiency ratio. Their ammonium-N excretion rate as well as hemolymph concentration of Na+ and Cl- were significantly lower than those of the control(P0.05), but a reverse trend was observed for their gill Na+/K+-ATPase. Moreover, the shrimps fed with 1.48 g K+ per 100 g diet were the highest in hemolymph urea level, and the phenoloxidase and lysozyme activities were significantly higher than those of the control(P0.05). The growth and physiological response of the test shrimps suggested that diet containing 1.48 g K+ per 100 g diet improved the growth of L. vannamei in low-salinity seawater, and enhanced the physiological acclimation of the organism.