Sedimentary Records and the late Pleistocene-Holocene climatic changes in Tai Co,Tibet (Xizang)     

ZHENG Mianping  LIU Junying  PANG Qiqing  MA Zhibang  WANG Hailei  MA Nina 《地质学报》2012,86(1)

西藏西部台错湖T1阶地的两个剖面沉积中,除下部10余厘米含炭化植物和50～70 cm处为暗色碳酸盐粘土及粘土外,中、上部全系粘土碳酸盐层,含丰富的介形类和轮藻类.据碳酸盐、介形类、轮藻类的碳、氧稳定同位素值与微体古生物群落生态特征等提供的环境气候变化指标,指示该区距今41.4～4.5 ka BP间气候变化为:在41.4～26.2 ka BP气候较湿润;26.2～25.5 ka BP偏暖稍干;25.5～22.5 ka BP气候暖湿;22.5～21.0 ka BP气候偏冷湿;20.5～17.5 ka BP气候骤冷、偏湿,反映本区处于末次冰期盛冰期;17.5～16.0 kaBP偏冷偏干;16.0～11.8 ka BP气候偏暖湿,为全球间歇性暖事件的响应;11.8～10.4 ka BP气候较冷干,大致相当于新仙女木期,10.4 ka BP气温开始回升;10.4～9.4 ka BP气候偏暖湿;9.4～8.5 ka BP气候呈现短暂暖湿颤动;8.5～7.9 ka BP气候偏干冷,为冰后期强烈降温偏干事件;7.8～6.3 ka BP气候偏暖湿;6.3～4.5 ka BP气候趋向冷干,4.5 ka BP记录了晚更新世晚期以来最大的干燥期.  相似文献   

Eigen analysis of tree-ring records: Part 1, a limited representativeness of regional curve     

Bao Yang  Dmitry M. Sonechkin  Nina M. Datsenko  Nadezda N. Ivashchenko  Jingjing Liu  Chun Qin 《Theoretical and Applied Climatology》2011,106(3-4):489-497

Based on a set of very long-living (2,000?years) Qilian junipers (Sabina przewalskii Kom.) from the north-eastern part of the Tibetan Plateau (the region of Dulan), we carefully consider the regional curve standardization (RCS) technique. For this goal, we correlate deviations of individual tree-ring width records from their regional mean age-dependent curve (RC). It turns out that these correlations keep their positivity for almost all shifts between ages compared (up to 500?years and even more) evidencing each Dulan juniper to be a unique ??thermometer??. Just the unification of these ??thermometers?? in the form RC creates a spurious positive trend in the Dulan chronology. We modify the RCS technique to closer attach RC to these ??thermometers?? in order to construct a new chronology in which the trend is absent.  相似文献   

Regional Temperature Forecast for the Next Day in Hong Kong          下载免费PDF全文

LAM Hil  SHUM Karen Kit-ying  TANG Julian Shu-yan 《Acta Meteorologica Sinica》2011,25(6):725-733

For a century or so, the Hong Kong Observatory (HKO) has been providing temperature forecast for the whole of Hong Kong with the HKO Headquarters as the reference location. In recent decades, due to spreading of population from the main urban center to satellite towns, there is an increasing demand for regional temperature forecasts. To support such provision, the HKO has developed a regression model to provide objective guidance to forecasters in formulating forecasts of maximum and minimum temperatures for the next day at various locations in Hong Kong. In this paper, the regression model is presented, together with the assessment of its performance. Based on the verification of one year of forecasts, it is found that the root mean square errors (RMSEs) of maximum (minimum) temperature forecasts are from about 1.3 to 2.1 (1.1 to 1.4) degrees, respectively. The regression model is shown to have generally out-performed the operational regional spectral model then operated by HKO. Regional temperature forecast methods of other meteorological or research centers are also surveyed. Equipped with the regression model, the HKO has launched an online regional temperature forecast service for the next day in Hong Kong since March 2008.  相似文献   

A whole life cycle assessment on effects of waterborne PBDEs on gene expression profile along the brain-pituitary-gonad axis and in the liver of zebrafish     

Han XB  Lei EN  Lam MH  Wu RS 《Marine pollution bulletin》2011,63(5-12):160-165

Polybrominated diphenyl ethers (PBDEs) are now found ubiquitously in the aquatic environment and biota, and there is a growing concern that PBDEs may disrupt endocrine systems, leading to reproductive impairments of aquatic animals. In our study, zebrafish (Danio rerio) were exposed to the 5 ng/L, 1 μg/L and 50 μg/L of DE-71 for the duration of the whole life cycle (120 days, from eggs to adults). The expression of selected genes along the brain-pituitary-gonadal (BPG) axis and liver, and the levels of plasma sex hormones were examined. In male fish, up-regulation of GnRH in brain, FSHβ and LHβ in pituitary, FSH-receptor, LH-receptor, and CYP19a in testis was clearly evident, while down-regulation of CYP11a and 3β-HSD was found in testis. In female fish, a 2.4-fold up-regulation of 3β-HSD was found in ovary upon exposure to 50 μg/L of DE-71. GnRH in brain, FSHβ and LHβ in pituitary were also up-regulated, while ERβ, TH and TPH in brain and GnRH-receptor in pituitary were significantly down-regulated. Hepatic ERα, AR and VTG in males were all down-regulated, while hepatic ERα and AR in female were up-regulated. Serum estradiol (E2) was reduced in both male and female upon exposure to DE-71, while significant increases in serum testosterone (T) and 11-keto-testosterone (11-KT) were only found in male but not female fish. The ratio of T/E2 as well as the ratio of 11-KT/E2 in male fish increased in a dose-dependent manner upon exposure to DE-71. Our overall results showed that whole life exposure of DE-71 altered the expression of regulatory genes and receptors at all three levels of the BPG axis in zebrafish, and the responses are sex dependent. The observed disruption of GnRH and GtHs can be further related to the subsequent disruption in both levels and balance sex steroid hormones.  相似文献   

Carbon and Oxygen Stable Isotope Values and Microfossils at 41.4–4.5 ka BP in Tai Co, Tibet, China, and Their Paleoclimatic Significance     

ZHENG Mianping  LIU Junying  MA Zhibang  WANG Hailei  MA Nina 《《地质学报》英文版》2011,85(5):1036-1056

Two sedimentary sections were measured at Tai Co (Co means lake in Tibetan) in western Tibet, China. The two sections are almost all composed of clay carbonate beds except in their lower parts where there are carbonized plants at >10 cm depths and dark-colored carbonate clay and clay at 50–70 cm depths, yielding abundant gastropods, ostracods, and charophytes. The carbon and oxygen stable isotope values of carbonate, ostracods, and charophytes and ecological features of microfossil communities indicate the following climatic change in the area from 41.4 to 4.5 ka BP: at 41.4–26.2 ka BP, the climate was relatively wet; at 26.2–25.5 ka BP, it was slightly warm-dry; at 25.5–22.5 ka BP, it was warm-wet; at 22.5–21.0 ka BP, it was slightly cold-wet; at 20.5–17.5 ka BP, it became cold abruptly and slightly wet, implying the climate of the last glacial maximum; at 17.5–16.0 ka BP, it was slightly cold-dry; at 16.0–11.8 ka BP, it was slightly warm-wet; at 11.8–10.4 ka BP, it was relatively cold-dry, roughly equivalent to the climate of the Younger Dryas, and at 10.4 ka BP, the temperatures began to rise again; at 10.4–9.4 ka BP, it was slightly warm-wet; at 9.4–8.5 ka BP, there occurred short warm-wet oscillations; at 8.5–7.9 ka BP, it was slightly dry-cold, representing a strong temperature-lowering and drying event in the postglacial stage; at 7.8–6.3 ka BP, it was slightly warm-wet; at 6.3–4.5 ka BP, the climate tended to be cold-dry. 4.5 ka BP recorded the maximum aridity since the late part of the late Pleistocene.  相似文献   

A review of the equations used to predict the velocity distribution within a ship’s propeller jet     

W. Lam  G.A. Hamil  Y.C. Song  S. Raghunathan 《Ocean Engineering》2011,38(1):1-10

Predicting the velocity within the ship’s propeller jet is the initial step to investigate the scouring made by the propeller jet. Albertson et al. (1950) suggested the investigation of a submerged jet can be undertaken through observation of the plain water jet from an orifice. The plain water jet investigation of Albertson et al. (1950) was based on the axial momentum theory. This has been the basis of all subsequent work with propeller jets. In reality, the velocity characteristic of a ship’s propeller jet is more complicated than a plain water jet. Fuehrer and Römisch (1977), Blaauw and van de Kaa (1978), Berger et al. (1981), Verhey (1983) and Hamill (1987) have carried out investigations using physical model. Current paper reviews the state-of-art of the equations used to predict the time-averaged axial, tangential and radial components of velocity within the zone of flow establishment and the zone of established flow of a ship’s propeller jet.  相似文献   

Neoarchean suprasubduction zone arc magmatism in southern India: Geochemistry,zircon U-Pb geochronology and Hf isotopes of the Sittampundi Anorthosite Complex     

M. Ram Mohan  M. Satyanarayanan  M. Santosh  Paul J. Sylvester  Mike Tubrett  Rebecca Lam 《Gondwana Research》2013,23(2):539-557

The Sittampundi Anorthosite Complex (SAC) in southern India is one of the well exposed Archean layered anorthosite-gabbro-ultramafic rock associations. Here we present high precision geochemical data for the various units of SAC, coupled with zircon U-Pb geochronology and Hf isotopic data for the anorthosite. The zircon ages define two populations, the older yield a concordia age of 2541 ± 13 Ma, which is interpreted as the best estimate of the magmatic crystallization age for the Sittampundi anorthosite. A high-grade metamorphic event at 2461 ± 15 Ma is suggested by the upper intercept age of the younger zircon population. A Neoproterozoic event at 715 ± 180 Ma resulted in Pb loss from some of the metamorphic zircons. The magmatic age of the anorthosite correlates well with the timing of crystallization of the arc-related ~ 2530 Ma magmatic charnockites in the adjacent Salem Block, while the metamorphic age is synchronous with the regional metamorphic event. The geochemical data suggest that the rocks were derived from a depleted mantle source. Sub-arc mantle metasomatism of slab derived fluids and subsequent partial melting produced hydrous, aluminous basalt magma. The magma fractionated at depth to produce a variety of high-alumina basalt compositions, from which the anorthositic complex with its chromite-rich and amphibole-rich layers formed as cumulates within the magma chamber of a supra-subduction zone arc. The coherent initial¹⁷⁶Hf/¹⁷⁷Hf ratios and positive εHf values (1.7 – 4.5) of the magmatic zircons in the anorthosite are consistent with derivation of a rather homogeneous juvenile parent magma from a depleted mantle source. Our study further confirms that the southern part of the Dharwar Craton was an active convergent margin during the Neoarchean with the generation and emplacement of suprasubduction zone arc magmas which played a significant role in continental growth.  相似文献   

Hydrological characteristics of karstic groundwater in the northeast Viet Nam as studied by isotopic techniques   总被引：1，自引：0，他引：1  

Dang Duc Nhan  Nguyen Van Lam  Ha Chu Ha Long  Dao Dinh Thuan  Dang Anh Minh  Vo Thi Anh 《Environmental Earth Sciences》2013,70(2):521-529

The stable water isotopic composition (δ²H and δ¹⁸Ο), tritium (³H) activity, dissolved organic carbon, alkalinity, as well as the composition of carbon 13 (δ¹³C) in dissolved inorganic carbon (DIC) of 36 water samples taken from 16 resurgences in the northeast provinces of Viet Nam in the dry (Mar 2008) and rainy (June 2008) seasons were analyzed to elucidate hydrological characteristics of the karstic aquifers in the area. The stable water isotopic composition of the water samples collected clearly demonstrated that the karstic groundwater in the region was recharged from the local meteorological water. The tritium activity in the samples was found to be in between 3 and 4 TU, falling in the range of the ³H activity in the local precipitation and thus meaning that the traveling of recharge water to the resurgences was very short. Concentrated and diffuse allogenic recharges seem to be important sources of karstic groundwater in the study region. Water in the karstic aquifers could be classified into three types as: (a) water from karstic areas with dense vegetation cover that causes DIC be depleted in carbon 13 (¹³δ<?12‰ vs. Pee Dee Belemnite standard of Vienna, VPDB); (b) water from karstic areas with poor vegetation cover that originates DIC with carbon 13 composition ranging from ?11 to ?12‰; and (c) surface water from lakes, springs and rivers that has DIC with enriched carbon 13 (δ¹³C >?10‰). This implies that there are several sources of carbon dioxide contributing to the DIC in water of the karstic aquifers in the study region. Among other potential sources, the atmospheric CO₂, CO₂ from carbonate rock dissolution, biomineralization of soil organic matters and plant roots respiration seem to be important sources of the DIC in the waters of this region. The results show high vulnerability towards anthropogenic contaminants of karstic groundwater in the study region.  相似文献   

Trace element residues in eggs of Little Egret (Egretta garzetta) and Black-crowned Night Heron (Nycticorax nycticorax) from Hong Kong, China     

Lam JC  Tanabe S  Wong BS  Lam PK 《Marine pollution bulletin》2004,48(3-4):390-396

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Toxicities of antifouling biocide Irgarol 1051 and its major degraded product to marine primary producers     

Zhang AQ  Leung KM  Kwok KW  Bao VW  Lam MH 《Marine pollution bulletin》2008,57(6-12):575-586

Irgarol 1051 (2-methythiol-4-tert-butylamino-6-cyclopropylamino-s-triazine) is an algaecide commonly used in antifouling paints. It undergoes photodegradation which yields M1 (2-methylthio-4-tert-butylamino-6-amino-s-triazine) as its major and most stable degradant. Elevated levels of both Irgarol and M1 have been detected in coastal waters worldwide; however, ecotoxicity effects of M1 to various marine autotrophs such as cyanobacteria are still largely unknown. This study firstly examined and compared the 96 h toxicities of Irgarol and M1 to the cyanobacterium Chroococcus minor and two marine diatom species, Skeletonema costatum and Thalassiosira pseudonana. Our results suggested that Irgarol was consistently more toxic to all of the three species than M1 (96 h EC50 values: C. minor, 7.71 microug L(-1) Irgarol vs. > 200 microg L(-1) M1; S. costatum, 0.29 microg L(-1) Irgarol vs. 11.32 microg L(-1)M1; and T. pseudonana, 0.41 microg L(-1) Irgarol vs. 16.50 microg L(-1)M1). Secondly, we conducted a meta-analysis of currently available data on toxicities of Irgarol and M1 to both freshwater and marine primary producers based on species sensitivity distributions (SSDs). Interestingly, freshwater autotrophs are more sensitive to Irgarol than their marine counterparts. For marine autotrophs, microalgae are generally more sensitive to Irgarol than macroalgae and cyanobacteria. With very limited available data on M1 (i.e. five species), M1 might be less toxic than Irgarol; nonetheless this finding warrants further confirmation with additional data on other autotrophic species.  相似文献