Abstract:Qinghai Lake is the largest one of inland lakes in China. Some issues about water level drop, lake area shrinking and lake separateies have brought to broad attentions in recent years. Remote sensing researches for these issues were discussed in this paper. Landsat MSS, TM, ETM⁺ images and Chinese FY-1C, FY-1D, HY-1A satellitic data from 1975 to 2002 were applied to this study. Furthermore, we collected some useful data including relief map, water depth map and hydrological data. Those satellitic data, combined with useful data, were processed and analyzed, some results revealed that the lakeshore physiognomy have greatly changed from 1975 to 2000. The region changed mostly located in the west shore near the Bird Island and Buha River, in the north shore-Shaliu River and the east shore-Sha Island and Haiyan Bay. Due to rich land-carriage materials from Buha River and lake currents action, the west shore of lake is progressing towards lake. The famous Bird Island and Haisepi Island become the part of land; Also, the east shore was accumulated eroded by the removal of sand dune. Shadao Lake and Haiyanwan Lake were gradually separated from Qinghai Lake. On basis of lakeshore line change, we estimated that lake water level dropped about 2 m from 1975 to 2000, by the approach to matching two images and contrasting water depth data. This numeric value estimated was close to hydrological observation value 1.71 m. Also, this study estimated that the area of Qinghai Lake was 4405.64 km² in 1975, and was 4256.04 km² in 2000. FY-1D image on June, 2002 and field investigating results revealed that Haiyanwan Lake with an area or 100 km² has been separated from Qinghai Lake. Water level drop and lake variation were the main cause of lake shrinking. In addition, we carried through field investigating and lake water depth measuring in the south-easters lakeshore of Qinghai Lake in Sep., 2002. The study indicated that the relativity of the grey scale of TM1 band image and water depth was very high in this lake. As a result, the water depth retrieval model was established.

Abstract:The Little Ice Age is the latest and the most typical case of cold climate event, which is significant for the research of centennial climate change. The existing results of study show that, solar and volcanic activities are the main reasons for the climate change of Little Ice Age. In this paper, by using an AGCM+SSiB model, modeling experiments are made to understand the effects of the changes of solar radiation, volcanic dust, vegetation to the change of temperature and precipitation of LIA, respectively. The result shows that:the effect on LIA temperature of changing vegetation has the same scale to that of changing solar radiation and volcanic dust, while the effect on LIA precipitation of changing vegetation is greater than that of changing solar radiation and volcanic dust. This means the effect of vegetation feedback can't be neglected for centennial climate change. It is helpful to understand the mechanism of LIA climate change deeply, and it provides a new thought and method for research of centennial climate change and forecast of climatic scenario at the same time.

Abstract:The study on the sediment transport due to waves is necessary for prediction of deposition of waterway. Owing to the lack of appropriate formula for calculation of suspended sediment load in Taihu Lake under wave action, an experimental study on transport of silt collected from Taihu Lake is conducted by using a wave flume. In this paper, the process of entrainment and suspension of silt is quantitatively described, and detailed measurements of suspended sediment profiles are carried out for each run of the experiments. Based on the test results, an empirical relationship for calculation of the mean suspended load on waves is presented. The verification results of a case study show that the present equation is satisfying to be used in prediction of sediment deposition of waterway in Taihu Lake.

Abstract:Erosion loss is one of the most important problems in the ecological system. For the heavily silt loaded river, it is necessary to allocate a certain amount of ecological water demand for the maintenance of the ecological system balance. Taking the heavily-silt loaded river as the research object and based on the sediment transport kinetic theory, the river sediment discharge and sand carrying capacity were analyzed in this paper. Therefore, the calculation method for the critical river flow rate in the no scouring and no sanding status was proposed in this paper. This method is exactly the calculation method for the lowest ecological water demand to prevent the river sediment accumulation. Using an actual example, the application of the proposed calculation method was carried out and illustrated. It is noteworthy that this study will be beneficial for water resources proper allocation and ecological balance maintenance.

Abstract:Acid-volatile sulfides (AVS), which can form insoluble sulfides complexes with minimal biological availability with a number of cationic metals, is a key partitioning phase controlling metal bioavailability in the sediments. Toxic effects were found to be absent for SEM/AVS ratios smaller than one, but appeared to be present at SEM/AVS ratios exceeding one. This study investigated the vertical distribution of SEM (Cu, Zn, Pb, Cd, Ni, Co, Ag, Cr) and SEM/AVS ratio in the sediments cores of three different polluted stations in Lake Donghu, Wuhan. It was found that the metal concentrations were in the order of Zn > Cr > Cu > Ni≈Pb>>Ag≈Cd. Among heavy metals, Zn, Cr and Cu were the dominating species, accounting for nearly 90% of SEM. At Station I and Ⅱ, AVS was the key factor to control the bioavailability of metals, and SEM/AVS ratios were less than one. Significant linear relationship between AVS and metals at Station I and Ⅱ confirmed that AVS had a great effect on the vertical distribution of metals. However, at Station Ⅲ, SEM/AVS ratios were larger than one, and no significant linear relationship between AVS and metals was found. The sediments in Station Ⅲ have potential metal toxicity. Significant linear relationships were observed between trace metals (Cr, Ni, Ag, Cd) and AVS at Station I and Ⅱ, indicating that these metals were associated to the AVS phase in the sediments more than other metals. Especially there was a close relationship between SEM-Ag and AVS in the sediments at both stations (r=0.6973, Station I;r=0.7786, Station Ⅱ). Our results also show that there was a higher SEM-Cr/AVS ratio in the sediment with high AVS (Station I, r=0.7129) than in the sediment with low AVS (Station Ⅱ, r=0.4114) while SEM-Cr level did not differ significantly in both stations. It seems likely that Cr is strongly influenced by complex redox reaction pathways rather than simple substitution reactions, and tends to be absorbed on, or coprecipitate with iron sulfide phases in an anoxic environment more than a slight anoxic environment.

Abstract:In laboratory, by using the water from Taihu Lake after filtrated as background experimental sample, and the experimental environmental condition simulate to the algae growth quickly status of Taihu Lake. In the background experimental sample the phosphates, detergent and dominance algae were used, then the algae growth for 12 days were surveyed. The algae growth results show that the phosphorus in detergents has a significant effect on algae growth in some degree. Especially, when the phosphate concentration less then 0.08mg/L, the phosphate in detergents are the main factor affecting the algae growth.

Abstract:Traditionally, it is absolutely difficult to collect SSC data(suspended sediment concentration) in the whole lake and impossible to decide the time derivation of SSC with small time interval either. Based on acoustic backscatter theory, this paper presents the denary logarithmic relationship between SSC and the emended ADP signal strength in Lake Taihu on condition that the components of suspended sediment do not change dramatically. Verification is also conducted based on the observation made at Wugui island in July 2002. The satisfactory results suggest the method is available in Lake Taihu and has bright prospect in determining SSC.

Abstract:Three layers of a sediment core collected from Meiliang bay of Taihu Lake in December of 2002, were examined under microscope to identify algae species composition and cultured axenically in MA medium to find the living cells and its vertical distribution in sediment. Many species of algae were found in the surface of the core sample(0-3cm) and three of them (Microcystis aeruginosa Kutz, Cyclotella bodanica Eul, Scenedesmus obliquus(Turp) Kutz) were able to develop in culture 8 them. Less algae species could be found in the layer (10-13cm) of the core sample and only two of them(Microcystis aeruginosa Kutz, Cyclotella bodanica Eul) were developed in culure. Two algae species could be identified in the layer(20-23cm) of the core sample and no algae cell could be developed in culture. It showed that Microcystis aeruginosa Kutz, and Cyclotella bodanica Eul, the dominant phytoplankton populations in summer bloom, could be survive the environment of the sediment in Taihu Lake during the winter period.

Abstract:The samples of zooplankton taken from 24 stations of 8 sections in Poyang lake in two seasons, spring and autumn in 1999, were identified. The 150 species of zooplankton was found, the most of which were rotifers. The species number of rotifer was found 96, reached to 64.0% in the total species, which showed that rotifers were preponderant genus. The protozoan took place in the second. The distribution of the quantities of the four genus, Protozoan, rotifer, cladocera and copepoda differed a lot in each stations, those of which No.10, 12, 13 and 23 station were in higher level, more than 100ind/L. The highest level appeared in No.13 station, whose quantities were 1101.60ind/L. The amount of zooplankton changed with seasons apparently, while rotifers fluctuated more. The quantities of rotifer and cladocera were more in spring than in autumn, while protozoan and copepode were just opposite.

Abstract:According to the investigations in Kaitan reservoir area of Oujiang river, Zhejiang Province from July 2001 to June 2002, 82 species of phytoplankton were identified, which belongs to 7 division and 40 genera. The dominant species were Bacillariophyceae and Chlorophyceae. The type of phytoplankton community is Chlorophyceaetype and Bacillariophyceaetype. The speaies and numbers of phytoplankton in different seasonals and water areas showed marked variation. The nutritive peculiarity belongs to responding type of phytoplankton. The development tendency of mesotrophic condition for water body were clear with part of water body suffering in some degree from pollution.

Abstract:Mycosporine-like amino acids (MAAs) strongly absorb UVR and protect cells against harmful UVR. Using spectroscopic and HPLC analysis, two MAAs were detected, i.e. shinorine and porphyra-334, in the pure culture of Microcystis aeruginosa isolated from Lake Taihu and in the phytoplankton samples of Lake Taihu dominated by Microcystis. Synthesis of MAAs could be one of the adaptive strategies to high solar radiation including UVR and one of the bloom-forming mechanisms in Microcystis aeruginosa.

Abstract:The growth of Potamogeton pectinatus and P. malaianus in waters with a great number of cycanobacteria was studied through some micro-ecosystems and a large enclosure (6667 m²). The results of the micro-ecosystems experiment showed that influence of cycanobacteria on P. pectinatus was not Significant. Biomass of P. pectinatus only decreased 8.4% when it grew in waters with a great number of cycanobacteria in 22 days, but biomass of P. pectinatus increased 27.7% in waters without cycanobacteria. And that of cycanobacteria on P. malaianus was Significant. Biomass of P. malaianus decreased 57.1% when it grew in waters with a great number of cycanobacteria in 22 days, whereas Biomass of P. malaianus in waters without increased 24.1%. The results of the large enclosure experiment showed that the cover rate of was up to 60% under the condition of pressure with a great number of cycanobacteria. However, P. malaianus diedont under the same condition. Therefore, the results of above indicated that impact of cycanobacteria on P. pectinatus was less pronounced than that on P. malaianus.

Abstract:Little Ice Age (LIA) is the global cold event nearest to modern time, having an important effect on the development of society and economy throughout the world and in China. As a key period, it is now being used to explore the relationship between historical climate and human activity. Based on historical documents and the result of high resolution proxies (ice core, tree-ring, lake sediment, stalagmite) in recent years, incorporating with part of the foreign researches, several characteristics of LIA are discussed in this paper, including the climatic evolutional process from high-latitude and high-altitude regions to mid-latitude and low-altitude regions and how the monsoon influences the universal temperature decrease of wide range in 17th century, the maximum of LIA, and the variation and distribution of precipitation. By verifying the climate simulations with these results, palaeo-analogue can be obtained to predict the cold oscillation in the global warming background.

Abstract:This paper describes the progress of Chaohu Lake eutrophication research in the past 20 years. In the light of characters of different researches in different periods, the study progresses are divided into three stages:initial investigation, detailed research and applied research. Eight main research areas are summarized in the paper including fact findings for natural and social environmental background, lake ecological investigation and assessment, investigation and evaluation for waste water sources in the lake basin, Chaohu eutrophication mechanical study, water function planning and its allowance pollution load study, non-point sources pollution research, study on ecological environmental status and internal loading pollution control. Since no any fundamental research for Chaohu lake eutrophication has been undertaken in recent 10 years, the results obtained decades ago can not satisfied the requirement of present eutrophication prevention and control. According to recent monitoring results, eutrophication issue still besets the lake. The paper points out that further study must start urgently and new countermeasures could be found consequently. Finally some main research facets are given for further study reference.