Molecular organic geochemical evidence for paleoenvironmental changes at 11.87–12.28 m in GS-1 sedimentary core, Gucheng Lake, East China

Organic lipids with different occurrence modes in a sedimentary core in a subtropical freshwater lake, Gucheng Lake, were sequentially extracted, separated and analyzed. The down-core variations of OEP index of alkanes, C_18:2/C_18:0 ratios of fatty acids, ratios of bound, fatty acids to free fatty acids, thermo-maturity indices of hopanoid hydrocarbons and rerative concentrations of sedimentary minerals revealed an evident increasing in allochthonous input from rock detritus below 12.28 m in the sedimentary profile. The distribution pattern of tightlybound β-hydroxy fatty acids indicated a difference in bacterial communities above and below the boundary, as well as the gammacerane index may assign a significant change in lake water salinity. The evidence, in general, suggested that a significant paleoenvironmental change had taken place in ca. 9.6 kaBP on the regional basis.     

Molecular organic geochemical evidence for paleoenvironmental changes at 11.87-12.28 m in GS-1 sedimentary core, Gucheng Lake, East China

Organic lipids with different occurrence modes in a sedimentary core in a subtropical freshwater lake, Gucheng Lake, were sequentially extracted, separated and analyzed. The down-core variations of OEP index of alkanes, C18:2/C18:0 ratios of fatty acids, ratios of bound, fatty acids to free fatty acids, thermo-maturity indices of hopanoid hydrocarbons and relative concentrations of sedimentary minerals revealed an evident increasing in allochthonous input from rock detritus below 12.28 m in the sedimentary profile. The distribution pattern of tightly-bound β-hydroxy fatty acids indicated a difference in bacterial communities above and below the boundary, as well as the gammacerane index may assign a significant change in lake water salinity. The evidence, in general, suggested that a significant paleoenvironmental change had taken place in ca. 9.6 kaBP on the regional basis.     

137Cs tracing of lacustrine sediments in the Dalian Lake, Qinghai Province, China

Based upon the analysis of Cs and grain-size parameters, the total amounts of ¹³⁷Cs deposition by wind and water in the Dalian Lake of Gonghe Basin, Qinghai Province are defined. The vertical profile of ¹³⁷Cs in the lacustrine sediments exhibits three ¹³⁷Cs activity maxima and one minimum. The major maximum corresponds to the global ¹³⁷Cs fallout in 1963; the two secondary maxima correspond to the leakage of the Chernobyl reactor in 1986 and complete desiccation of the lake in 1994, respectively. The minimum corresponds to aeolian deposition caused by extensive reclamation in the late 1980s and early 1990s. The 137Cs data set was used to evaluate average sedimentation rate of the Dalian Lake since 1963. The deposition was stable in 1963-1986 and 1994-1998, and it was rapid during 1986-1994. This preliminary study reveals that l37Cs has the same potential to trace environmental changes introduce by human interference in arid/semiarid regions as in humid regions.     

Molecular organic geochemical peculiarities of lacustrine core sediments in Fildes Peninsula, King George Island, Antarctica

The peculiarities of lipids in lacustrine core sediments from Fildes Peninsula, King George Island, Antarctica, are reported. The origin of high-molecular-weight n-alkanes, alkenes,fatty acids, alcohols is supposed to be related to the abundant moss occurring in the sediments.Abundant iso-and anteiso-fatty acids that occur in the sediments indicate a relatively strong bacterial activity in non-ice-cover zone than in other regions in Antarctica. The C18:2 unsaturated fatty acids mainly originate from autochthonous algae in the sediment pool, and the C18:2/C18:0ratios in the profile are controlled more by paleotemperatures than source assemblies. Long-chain alkenones were identified in freshwater lacustrine sediment in Antarctica for the first time, of which Prymnesiophyceae is assumed to be the source organism. High relative abundance of C37:4honologue in long-chain alkenone well correlates to the severely cold climate in Antarctica.     

Spatial distribution and stratigraphic characteristics of surface sediments in Taihu Lake,China

A geophysical survey was carried out for Taihu Lake, one of the largest shallow lakes in China. The StrataBox™ Marine Geophysical Instrument was applied for the first time to obtain high-resolution seismic data (in the form of vectorgraphs) of the lake sediment. Data were then interpreted by SonarWiz.Map acoustics software. Data were correlated with core stratigraphy from the lake as well as an outcrop on the northern side of the lake at Yao Bay. Results show that the upper 10 m sediment (beneath the interface of the sediment and the overlying lake water) is characterized by laminated sediments, which can be classified into two stratal types, i.e. lacustrine sediment stratum (U1) and underlying hard loess stratum (U2). The contact of these two lithologies is not continuous, and part of it is absent in the lake basin. Unequally spread over the lake basin, the lacustrine sediment (mainly consisting of sludge and muddy-clay) is found in areas along the western bank, to the northwest of the Xishan Mountains and along the northwestern side of the lake. In the rest of the lake basin, the hard loess stratum is exposed in outcrops. The depth of the lacustrine sediment ranges from 1 to 2 m, while the depth of the sludge (closely related to the modern lacustrine environment) varies from 0.03 to 1.0 m. The spatial distribution of lacustrine sediments in Taihu Lake is primarily influenced by transportation and sedimentation of riverine materials, as well as the hydrodynamics of lake currents.     

Paleosandstorm characteristics and lake evolution history deduced from investigation on lacustrine sediments——The case of Hongjiannao Lake, Shaanxi Province

Sediment cores from desert lakes serve as good records of the frequency and intensity of sandstorms in history. By multi-proxy analysis of grain-size, magnetic susceptibility, TOC and Rb/Sr ratio, the paleosandstorm characteristics and lake evolution history in Yulin Area for the past 80 years, are discussed in this article. It is revealed that Hongjiannao Lake formed in about 1928 A.D. and in its initial stage sandstorms were prevalent with three extremes taking place in 1936 A.D., 1939 A.D. and 1941 A.D.. During the expansion period of 1952-1960 A.D., inflow waters to the lake increased sharply and a lot more weathered materials were carried into the lake. The frequency and intensity of sandstorms have reduced a lot since 1960s and the ＂double peaks＂ feature of the grain-size frequency curve has changed into the ＂single peak＂ feature. Study on the catchment ecology of the lake shows that the occurrence of sandstorms has been effectively restrained by the forest plantation and water and soil conservation.     

Spatio-temperial variations of the bacterioplankton community composition in Chaohu Lake, China

Despite considerable attention paid to Chaohu Lake in China, the dynamics of bacterioplankton community composition （BCC） on spatial and seasonal scales are poorly understood. In this study, water samples were collected from autumn 2006 to summer 2007 at five positions in Chaohu Lake with different trophic status. BCC of these samples was determined by both the PCR amplification of the 16S rDNA gene and the denaturing gradient gel electrophoresis （DGGE）. The abundance and diversity of bacterioplankton communities at different sampling positions showed similar seasonal patterns. The BCCs in the samples varied substantially, and the pattern of changes indicated that the seasonal difference might have a significant impact on the BCC＇s structure in the lake. Canonical correspondence analysis （CCA） on the DGGE patterns and physicochemical parameters indicated that the temperature and the levels of 5-d biochemical 02 demand （BODs）, NH3-N, CODMn, total nitrogen, total phosphorous, and dissolved oxygen significantly influenced the BCC, and four of the seven variables were related to the level of eutrophication. Our results indicate that eutrophic status and season are the most influ- ential factors in determining BCC in Chaohu Lake.     

滇池浮游植物的生物多样性调查研究

 根据2001年9月至2002年7月6个月滇池浮游植物种类和数量的调查结果,分析了该湖浮游植物的物种组成,通过Shannon指数、Pielou均匀度指数、Berger-Parker指数计算,从不同侧面研究了滇池的生物多样性水平.结果表明:调查期间共鉴定浮游植物106种及变种;浮游植物生物多样性在3月最高,而其他月份差别不明显,平面分布上南部高于北部,东部高于西部.     

Age dating of lacustrine sediments in Lake Tianshuihai of the Tibetan Plateau by using U-series isochron method and its significance

The age of the clastic-clay sediments with varied content of carbonate in core TS95 taken from the Lake Tianshuihai in the northwest of the Tibetan Plateau was determined successfully by using the total sample dissolution U-series isochron method for the first time. With this method, the serial absolute timescale (isotope time scale) covered the last 240 ka in the main body of the Tibetan Plateau with a sea level up to 4000 m is also established for the first time, thereby laying the foundation for the research on the paleoclimate and palaeoenvironment in the Lake Tianshuihai region as well as the relationship between evolution of the Tibetan Plateau and global changes. In addition to a brief introduction of the basic principles, the procedures of experiments, and the results, this note also presents the adaptability and superiority of this method as well as its possible problems.     

太湖现代沉积物的物质组成和形成条件分析

对太湖现代沉积物进行了X射线衍射分析、粒度分析和常量元素分析，由此推断它们的矿物成分、化学风化程度差异，并分析了不同的水动力条件和物源。太湖沉积物的主要矿物组成是石英、云母、正长石和钠长石，粘土矿物为伊利石、绿泥石、高岭石和蒙脱石。化学组成显示，太湖沉积物的烧失量较高，与上部陆壳平均化学成分相比，Na、Na、K、Mg亏损，Mn、Ti富集，上部陆壳成分标准化图表明其风化程度明显强于下蜀土。化学风化程度指标CIA、Na/K值和Fe/Mg值的变化也表明太湖沉积物的化学风化作用比下蜀土强，，并存在地域的差别。太湖沉积物的CaCO3含量明显较低，反映了太湖流域本身的特点。所有这些特征表明，太湖沉积物的形成不仅与物源、地域位置有关，而且明显受人类活动的影响。     

Spatio.temporal variations of the bacterioplankton community composition in Chaohu Lake,China

Despite considerable attention paid to Chaohu Lake in China,the dynamics of bacterioplankton community composition(BCC) on spatial and seasonal scales are poorly understood.In this study.water samples were collected from autumn 2006 to summer 2007 at five positions in Chaohu Lake with different trophic status.BCC of these samples was determined by both the PCR amplifieation of the 16S rDNA gene and the denaturing gradient gel electrophoresis (DGGE).The abundance and diversity of bacterioplankton communities at different sampling positions showed similar seasonal pattems.The BCCs in the samples varied substantially,and the pattern of changes indicated that the seasonal difiefence might have a significant impact on the BCC'S structure iU the lake.Canonical correspondence anal-ysis(CCA)on the DGGE patterns and physicochemical parameters indicated that the temperature and the levels of 5-d biochemical O2 demand(BODs),NH3-N,CODMn,total nitrogen,total phosphorous,and dissolved oxygen significantly influenced the BCC,and four of the seven variables were related to the level of eutrophication.Our results indicate that eutrophic status and season are the most inttu-ential factors in determining BCC in Chaohu Lake.     

Identification and significance of 3β-alkyl steranes in the Eogene lacustrine sediments and petroleum of China

The study on steranes with substitution at C-2, C-3 or C-4 positions in ring-A has become a hot field for their specific precursors in recent years[1-15]. Summons et al. firstly identified C28-C30 3β-methyl steranes in Michigan Basin and found that the p…     

南海中部表层沉积物中脂肪酸的组成、分布及来源

对5个采自南海中部地区的表层海洋近代沉积物样品的脂肪酸的组成进行了测试．测试结果表明,南海中部近代沉积物中脂肪酸由正构饱和脂肪酸、一元不饱和脂肪酸、多元不饱和脂肪酸及带支链的异构、反异构脂肪酸组成．较高含量的C12：C20短链脂肪酸和较丰富的一元不饱和脂肪酸以及其它细菌标志脂肪酸的出现表明,细菌等海洋微生物是脂肪酸的主要贡献者,海洋浮游生物对南海近代沉积物脂肪酸的贡献仅占次要位置．     

Climatic changes documented by stable isotopes of sedimentary carbonate in Lake Sugan, northeastern Tibetan Plateau of China, since 2 kaBP

Lake Sugan at the northern edge of the Qaidam Basin was selected as the research object. The temporal sequence of sedimentary cores retrieved from Lake Sugan since 2 kaBP was reconstructed using the ^210Pb, AMS 14C and conventional 14C dating methods. Carbon and oxygen isotopes of carbonate in the fine-grained lake sediments were analysed. Combined with the changes of 8180 values of surface water and air temperature observation data in the study area, it might be thought that the δ^18O value of the carbonate indicates effective moisture, and the changes in δ^13C values are related to annual freeze-up duration of the lake and indirectly indicate air temperature changes in winter half year. From the above, the sequence of climatic changes in the region since 2 kaBP was established. The climatic changes experienced five stages： Warm-dry climate during 0-190 AD： cold-dry climate during 190-580 AD; warm-dry climate during 580-1200 AD （MWP）; cold-wet climate during 1200-1880 AD （LIA）; cold-dry climate during 1880-1950 AD： and climate warming since 1950s. The air temperature changes in winter half year reflected by carbon isotope since 2 kaBP are in good agreement with the historical literature records and other geologic records, which shows that the climate changes recorded by the stable isotopes from Lake Sugan since 2 kaBP are of universal significance.     

Preservation of black carbon in the shelf sediments of the East China Sea

Concentrations and carbon isotopic(14C,13C) compositions of black carbon(BC) were measured for three sediment cores collected from the Changjiang River estuary and the shelf of the East China Sea. BC concentrations ranged from 0.02 to 0.14 mg/g(dry weight) ,and accounted for 5% to 26% of the sedimentary total organic carbon(TOC) pool. Among the three sediment cores collected at each site,sediment from the Changjiang River estuary had relatively high BC contents compared with the sedi-ments from the East China Sea shelf,suggesting that the Changjiang River discharge played an im-portant role in the delivery of BC to the coastal region. Radiocarbon measurements indicate that the ages of BC are in the range of 6910 to 12250 years old B.P.(before present) ,that is in general,3700 to 9000 years older than the 14C ages of TOC in the sediments. These variable radiocarbon ages suggest that the BC preserved in the sediments was derived from the products of both biomass fire and fossil fuel combustion,as well as from ancient rock weathering. Based on an isotopic mass balance model,we calculated that fossil fuel combustion contributed most(60%―80%) of the BC preserved in these sediments and varied with depth and locations. The deposition and burial of this "slow-cycling" BC in the sediments of the East China Sea shelf represent a significant pool of carbon sink and could greatly influence carbon cycling in the region.     

茶叶中的糖苷类香气前体物质研究进展

分析了近年来国内外茶叶中糖苷类香气前体的研究现状.对茶叶中糖苷类香气前体的种类、茶叶中糖苷类香气前体的研究方法以及糖苷与茶叶香气形成的关系等内容进行了综述,在此基础上探讨了茶叶中糖苷类香气前体物质研究中存在的问题及今后可能的研究方向.     

长期口服小剂量胺碘酮对老年人甲状腺激素及糖、脂质水平的影响

目的：观察长期口服小剂量胺碘酮对老年人甲状腺激素及糖、脂质水平的影响。方法：对１８例需长期服用胺碘酮（平均剂量０．１８±０．０３ｇ／ｄ）的老年心律失常患者,于治疗前及治疗期间定期测定甲状腺激素Ｔ３、Ｔ４、ｒＴ３、ＴＳＨ及血糖、血脂水平。结果：服胺碘酮１年后,Ｔ４、ｒＴ３、ＴＳＨ分别增加１７．１％（Ｐ＜０．０５）、４０．３％（Ｐ＜０．０１）和１５．６％（Ｐ＞０．０５）,而Ｔ３减少２８．２％（Ｐ＜０．０５）,除ｒＴ３外均在正常范围内波动,无一例出现甲状腺功能异常的临床症状。血糖、甘油三酯无明显变化,总胆固醇增加９．１％,但无统计学意义（Ｐ＞０．０５）。结论：长期口服小剂量胺碘酮对老年人是安全的,对甲状腺激素水平及糖、脂质的代谢均无明显影响。