Holocene climate reconstructions of Ulungur Lake (Xinjiang,China) inferred from ostracod species assemblages and stable isotopes     

Qingfeng JIANG  Ji SHEN  Xingqi LIU  Enlou ZHANG 《Frontiers of Earth Science》2008,2(1):31-40

In this paper, the data on the paleoclimatic and paleoenvironmental changes during the Holocene are presented and a discussion is made on a 225-cm-long sediment core from Ulungur Lake, located in Northwest China. The chronology is constructed from six AMS radiocarbon dates on the bulk organic matter. On the basis of the analysis of ostracod assemblages and the shell stable isotopes, the core is divided into three paleoclimatic and paleoenvironmental evolution stages: 9 985–5 250 cal.aB.P. stage is the wettest phase of the core section. The climate changed from moderate-dry to cool-wet, and then to warm-wet in turn, and the lake level rose accordingly, showing the characteristic of a high lake level. 5 250–1 255 cal.aB.P. stage was the driest phase of the core sediment. The climate turned from the early warm-dry to the late warm-wet and the lake level fell and rose again. Finally, the 1 255 cal.aB.P. stage was the medium stage of the section. The temperature was low and then increased after the 1920s and the climate was dry. The whole climatic and environmental evolution records of Lake Ulungur were not only in agreement with the sporopollen record of the same core but also in agreement with the record of environmental changes of adjacent areas. It responded to regional environmental changes and global abrupt climate events, following the westerly climate change mode on 100-year-scale, primarily with cold-wet and warmdry characteristics. __________ Translated from Quaternary Sciences, 2007, 27(3):382–391 [译自:第四纪研究]  相似文献   

浅谈太湖流域饮用水安全与地下水保护     

肖裕生  钟华平  谢石连 《上海国土资源》2008,(1):18-20,43

太湖流域经济发达,人口稠密,如管理不善将引发水污染严重、水环境恶化和水质型缺水等水问题,对饮用水安全构成威胁。因此,地下水在保障太湖流域饮用水安全中的作用就显得特别重要,提出了太湖流域地下水保护的对策措施。  相似文献   

Influence of submerged aquatic vegetation on size class distribution of perch (Perca fluviatilis) and roach (Rutilus rutilus) in the littoral zone of Lake Geneva (Switzerland)     

Olivier Rossier  Emmanuel Castella  Jean-Bernard Lachavanne 《Aquatic Sciences - Research Across Boundaries》1996,58(1):1-14

The abundance of different size classes of perch and roach in the littoral zone of Lake Geneva was compared between submerged aquatic vegetation and unvegetated zones. Samples were taken with gillnets during four periods between June and October 1993. During the vegetation period (June to September), perch 9 cm and roach 10 cm were more abundant in vegetation whereas roach > 20 cm were more abundant in open water. Perch larger than 18 cm and medium roach were equally distributed in both habitats whatever the period, whereas medium perch distribution fluctuated according to the period. In October, after the decline of the vegetation, no more differences in fish distribution were observed except for small roach, which were always more abundant in the vegetated sites.  相似文献   

Pesticide residues in birds at Lake Nakuru,Kenya     

J. K. Kairu 《International Journal of Salt Lake Research》1994,3(1):31-48

Specimens of three species of birds were collected from Lake Nakuru, Kenya, between September and October 1990. Samples of liver, kidney, muscle, fat and brain tissue were removed and analyzed for organochlorine pesticide residues. Fat was extracted and the content of three lindane (BHC/HCH) isomers (, and ), aldrin, heptachlor, heptachlorepoxide, endrin, dieldrin, DDD, DDE and DDT was determined. The samples contained varying residue levels of 12 organochlorine pesticides. No residues of 0, p'-DDD were detected. The most prevalent compounds were DDE and -BHC, found in 95.5 per cent and 66.4 per cent of the samples, respectively. The highest median residue concentration was 207 mg kg^–1×10^–3 of DDE in pelican fat tissue. White pelicanPelecanus onocrotalus, and the white-necked cormorant,Phalacrocorax carbo, showed greater concentrations of organochlorine residues than the lesser flamingo,Phoenicopterus minor. The mean DDE concentrations in pelican liver samples in 1970 and 1990 were 64 mg kg^–1×10^–3 and 274 mg kg^–1×10^–3, respectively. In cormorant liver samples the mean DDE concentration was 15 mg kg^–1×10^–3 in 1970 and 52 mg kg^–1×10^–3 in 1990. The mean DDE concentration in flamingo liver remained more or less similar at 2 mg kg^–1×10^–3 in 1970 and 1990.  相似文献   

洪涝灾害遥感监测研究   总被引：10，自引：3，他引：7  

周成虎 《地理研究》1993,12(2):63-68

本文讨论了利用陆地卫星、气象卫星和航空侧视雷达等遥感技术进行洪涝灾情监测的技术方法,并应用于1991年江淮地区特大洪涝灾害的快速调查与分析。  相似文献   

Intrinsic sample methods for mineral exploration and resource assessment     

DeVerle Harris  Guocheng Pan 《Natural Resources Research》1993,2(2):113-121

We report on an objective methodology, referred to as intrinsic sample methodology, for the delineation of exploration target areas or resource areas for assessment. Important features of the methodology include (1) identification of recognition criteria for critical genetic factors, (2) synthesis of new variables from enhanced geodata, (3) estimation of logit probability models, and (4) cutting of estimated logit probabilities to delineate exploration targets or resource areas. The methodology is demonstrated on the Walker Lake quadrangle of Nevada and California.  相似文献   

The role of sediments in the phosphorus cycle in Lake Lugano. I. Geochemical approach     

D. Span  J. Dominik  M. A. Lazzaretti  J. -P. Vernet 《Aquatic Sciences - Research Across Boundaries》1992,54(3-4):277-284

The bottom sediment from three coring stations in Lake Lugano (Lago di Lugano) show major differences in their role in the P-cycles related to their geochemistry and characteristics of sedimentation. In the northern basin, the deepest sediment may be considered practically inactive, due to a permanently reduced condition at the sediment-water interface. In the southern basin, the sediments are active with respect to P-recycling with strong seasonal variations. One of the sites (Figino) behaves as a sink for P due to a high iron content and an important rate of detrital sedimentation.  相似文献   

衡水湖湿地水环境分析及保护对策   总被引：3，自引：0，他引：3  

刘振杰 《湿地科学与管理》2006,2(2):41-44

衡水湖是华北平原惟一保存完整的内陆淡水湿地生态系统,生物多样性十分丰富,本文通过对衡水湖湿地水环境监测资料的收集整理,分析了衡水湖湿地水环境质量现状。结果表明:衡水湖在建立国家级自然保护区后,通过实施一系列严格的保护措施,目前水质仍保持较好。为了进一步保护衡水湖良好的生态环境,充分发挥衡水湖的生态功能,结合衡水湖的实际,提出了水环境保护建议。  相似文献   

Weathering and climate change since l820 AD in Hoh Xil, Qinghai-Xizang Plateau, China——Evidence from element geochemistry of lake sediments of Gulug Co Lake     

吴艳宏李世杰  夏威岚 《中国地球化学学报》2006,25(1):56-61

Element geochemistry of lake sediments has been widely used to detect climate change because element composition and ratios can reflect the weathering degree in the source area. Given the dement composition of lake sediments from Gulug Co Lake, Hoh Xil, Qing- hai-Xizang Plateau, chemical index of alteration （CIA）, index of composition variability （ICV） and other element ratios have been used to establish the weathering sequence of this area since 1820 AD. The weathering is so weak that the element composition change is more sensitive to climate change and autochthonous processes. From 1820 to 1984 AD, there were two drier periods with a wetter interval from 1870 to 1945 AD. After 1984 the weather showed a tendency of becoming wet.  相似文献   

Paleoenvironmental records of water level and climatic changes from the middle to late Holocene at a Lake Erie coastal wetland, Ontario, Canada   总被引：2，自引：0，他引：2  

Sarah A. Finkelstein  Anthony M. Davis 《Quaternary Research》2006,65(1):33-43

Pollen and diatom assemblages, and peat stratigraphies, from a coastal wetland on the northern shore of Lake Erie were used to analyze water level and climatic changes since the middle Holocene and their effects on wetland plant communities. Peat deposition began 4700 cal yr B.P. during the Nipissing II transgression, which was driven by isostatic rebound. At that time, a diatom-rich wild rice marsh existed at the site. Water level dropped at the end of the Nipissing rise at least 2 m within 200 yr, leading to the development of shallower-water plant communities and an environment too dry for most diatoms to persist. The sharp decline in water level was probably driven primarily by outlet incision, but climate likely played some role. The paleoecological records provide evidence for post-Nipissing century-scale transgressions occurring around 2300, 1160, 700 and 450 cal yr B.P. The chronology for these transgressions correlates with other studies from the region and implies climatic forcing. Peat inception in shallow sloughs across part of the study area around 700 cal yr B.P. coincides with the Little Ice Age. These records, considered alongside others from the region, suggest that the Little Ice Age may have resulted in a wetter climate across the eastern Great Lakes region.  相似文献