Abstract:A 400-year dust-storm history in Daihai Lake area, Inner Mongolia, Northern China, was reconstructed on the basis of high-resolution grain-size analysis of the lake sediments, in combination with reconstructed historical data of regional precipitation from tree ring, frequency of dust storms in China and historical documentary records.The Daihai Lake is located at a climatically transitional zone between semi-arid and semi-humid where front position and intensity of the East Asian summer monsoon and winter monsoon chiefly control the climate change.Both the median grain size and coarse grain content indicate that dust-storm events were controlled mainly by the intensity of the summer and winter monsoon in the past 400 years.Major dust-all events are generally associated with dry and cold climate during the Little Ice Age, when the median grain size of the lake sediments is larger with high contents of coarse grain (> 100μ m)-At time of warm conditions after the Little Ice Age, dust-storm events were limited, both the contents of coarse grain (> 100μ m) and the median grain size also decreased-During the last one to two decades, however, dust-storm events increased gradually, related partly with more desertificated soil by human activity.

Abstract:Through analysis of the physical, social, economic situation of Taihu Basin, some problems of flood control of the whole basin are recognized, i.e.the flood control standard is lower, the construction of flood control system can not meet the rapid development of economics in the Basin, etc.In view of practicability and possibility, the future flood control standards should be re-examined in three levels city, regional and whole basin.The immediate flood control standard is put forward according to the rule of unified planning, couple flood detention with storage, improvement of Flood Regulation Scheme of Taihu Basin, and scientific regulation, etc.

Abstract:According to the high resolution sediment data reveal by a core in deep water area in Qinghai Lake, the fluctuation of lake level in the last 600 years is reconstructed.The results show that the fall of Qinghai Lake level was more than 9m in the first half of 18th century. Moreover, there is a close relationship between lake level and climatic fluctuations in century time scale.The rises and falls of lake level are more or less in line with the wet and dry stages in the last 600 years.Wavelet analysis results indicate that the environment in Qinghai Lake has a quasi 180 year cycle during the research period.

Abstract:Some evidences from geomorphy, pollen and sediment have shown paleolake Qinghai has undergone at least three high-level stages since 40kaBP i.e.30-40kaBP, 11-13kaBP, 7.5-5kaBP.The second high lake-level stage was relevant to ice melting and wet/warm climate, while the other two stages are relevant to the whole global wet/warm climate.Using M.N.Byduko's equation of heat and water balance, and J.E.Kutzbach's equation of energy balance to compute the ground evaporation, the hydrological and energy balance of paleo-lake Qinghai as well as the water balance model of the whole closed basin, is estimated, i.e., the paleoprecipations of paleolake Qinghai are 645+/-5mm/a during 30-40kaBP, 595+/-15 mm/a during 7.5-5kaBP, which are 280mm and 235+/-15mm higher than current precipitation in Qinghai Lake area respectively-As a result, the corresponding high lake-level stages are deduced. During 30-40kaBP, 11-13kaBP and 7.5-5kaBP in Paleolake Qinghai, the paleo-lake level might be 104m, 104m and 45m higher than current Qinghai Lake level respectively.

Abstract:Fifteen One-meter-deeped cores were drilled in West Lake, Hangzhou, in 1991.The vertical distribution of microfossil algae in the sediment were analyzed, in order to study the algae succession and trophic developing process of West Lake.Three zones were divided as follows (1) Epiphytic algae zone (Eunotia spp.-Cymbella spp.-Gomphonema spp.assem.):-85cm to-45cm deep, mainly made up of acidobiotic and acidophilous species which were suitable for the bog stage in 2000 years ago.(2) Transitive zone from epiphytic algae to phytoplankan (Aphanizomenon flos-aquae-Melosira spp.assem.): usually existed in a depth between-30cm to-40cm, consisted of indifferent species combining with some alkaliphilous species, indicating that the lake had entered into mesotrophic stage-(3) Phytoplankton zone (Fragilaria construens var.venter-Scenedesmus quadricauda-Lyngbya contorta assem.): At the depth of-30cm and above alkaliphilous species became the dominant species and its density were increased indicating that the lake had been entered into eutrophic stage.Around the depth of-10cm, the density of microfossil algae reached the peak value, representing a hypertrophic stage of West Lake.At the depth of-10cm and above, the density of microfossil algae were decreased, which maybe relative to the government's comprehensive control of eutrophication after 198Q

Abstract:The origins cases of the lakes along the middle-lower reaches of the Yangtze River are complicated.Lakes formed mainly by tectonic subsidence are of large scale and depth.But most of the lakes are tributary-mouth depressions, fan-edge depressions and interchannel depressions.The water level of the lakes is controlled by the water level of the main stream of the Yangtze River.During the glacial age and lower sea-level age, the main stream of the Yangtze River had eroded downward, and the lakes along the Yangtze River had dried up.During the postglacial age, the water level of the Yangtze River had risen from the river mouth to upper reach in succession, and in this case, the depressions along the Yangtze River had stored water and lakes came into being.The evolution trend of the lakes along the Yangtze River is that the lakes are filled by silt deposition and their static volumes decrease which lead to the annual change range of the lake level increasing and flood level keeping on rising.This is the main cause of the unceasing flood disasters along the middle-lower reaches of the Yangtze River.

Abstract:This paper presents a concise computer simulation which utilizes thermodynamic relationships coupled with mass balance and electroneutrality constraints to investigate the buffering function of aluminum in acidic natural waters euqilibria with mineral kaolinite-Various factors affecting theoretical prediction of the pH values are discussed, such as the concentration of dissolved silica, concentration of dissolved inorganic carbon and temperature-The model is verified by analyzing practical water samples-The pH calculated is in good agreement with the experimental results-The uncertainties in thermodynamic constants and measured input data are evaluted by the Monte Carlo simulation.

Abstract:In this research Spirulina subsala was firstly pretreated by paraquat (10μmol° L^-1) and H₂O₂ (2mmol° L^-1) to induce its antioxidant enzymes, then were treated under Pb₂₊ stress (40mg° L^-1).The results showed that the decreases of both grow th yield and photosynthesic rate of pretreated Spirulina subsalsa were less than those of the non-pretreated.Although the activities of SOD and CAT were also decreased, they were higher than those of the non-pretrea ted, and they inhibited the accumunation of O2 and M DA effectively.The range of POD increase was between those of the non-pretreated and the control.It could be concluded that induction could increase the antioxidant capacity, and could help Spirulina subsala resist Pb₂₊'s toxity.

Abstract:The chlorophyll of phytoplankton in saline-alkaline ponds in Zhaodi an Fish Farm (Latitude 37°17'N,Longitude 117°55'E), Gaoqing County, Shandong Province, during April 1997 to September 1998, was measured.319 samples were collected.The results indicated that the mean concentration of chlorophyll in experimental ponds were 115.12μ g° L^-1, mean concentration of chlorophyll-a were 79.90(μ g° L^-1.The percentage of the content of Chla, Chlb and Chlc to total concentration of chlorophyll was 61.76%, 12.97% and 25.2%, respectively.The concentrations of Chla had obvious seasonal dynamics, and have a peak value in summer and early autumn.The concentratio nof Chla in control ponds was much smaller than that fish-culture ponds.The temporary and spatial changes of Chla were greater, but the pattern of dynamics is not unit.The concentration of Chla in experimental ponds have significant positive correlation to the biomass of phy to plankton, water temperature, total nitrogen, total phosphorus and silicon, and negative correlation to water transparency.No regular correlation of Chla concentration to salinity, alkalinity, pH, hardness and conductivity is found.

Abstract:Biodegradation process is an economical and effective way to degrade organic chemicals in remediation sites-Based on the intensity study about chemical s degradation processes, a comprehensive mathematical model, which describes chemicals diffusion, sorption/desorption, sequestration, and biodegradation in soil-water-microbes system, has been developed in this paper-A sensitivity analysis was performed to assess the effect of several parameters on model behavior-It is noteworthy that the chemical s concentrations in soil, in particle water phase, in bulk water, as well as the necessary remediation time can be predicted by using this model.

Abstract:From 1997 August to September, 25 typical surafce surface features were investigated in the field and the reflectivities of 10 channels of them were determined on the spot in.llantai Salt Lake, Inner mongolia and its periphery.Based on geological characteristics of Jilantai Salt Lake, 25 typical surface features can be divided into 5 types which are vegetation, base rocks, waters, chemical sediments and loose deposits-Through studying the characteristics of the reflectivities of typical surface features and their influencing factors and according to the formation principle of infrared aerial photo and LANDSAT Thematic Mapper (TM) image, the authors established symbols of remote sensing interpretation in Jilantai Salt Lake.

Abstract:Many Chinas lakes are facing with serious eutrophication problem.Although some deterioration tedndency of water quality has not been controlled efficiently-Lake sediuments are rich in nutrients, which usually have a higher concentration than that of in the water-Therefore, as one of the possible measures, dredging is applied for controlling eutrophication in some lakes around the world.This measure needs a great deal of funds.In fact, there are no obvious samples, which indicate the efficiency of dredging, as the key measure for controlling the lake eutrophication.Can we control eutrophication in (usually shallow) lakes by dredging? Theoretical analysis shows that there are some basic problems limiting the effciency of dredging for lake eutrophication control (1) The lake bottom is a reservoir of nutrients, not a source of that in the long run, for example, a couple of months or years.The self-purification capacity of lakes usually functions-In the water-sediment interface, the total nutrient fluxes are shown downwards, not upwards, even when the liquid nutrient flux is upward sometimes, but the solid (including inorganic and organic substance) flux is downward.(2) The high concentration of nutrients in the water-sediment interface is formed mainly by decomposition of recent detritus of organisms.The liquid and diluted mud are movable and easy for re-suspension, forming fractional" pollutant cloud", as main internal source of pollution in lakes.(3) Experiments in laboratory show that nutrients are released from sediment just in the first few days.The release may become less and negative for longer periods of 20-40 days.Self-puiification dominates as time goes on.Laboratory experiments also show that the nutrient release decreases at the beginning after dredging, and after several months it differs little with those in the period before dredging.(4) The nutrient concentration in the sediment is of 1C4 orders more than that in the water body, and 10 orders more than that for algae bloom (when all the nutrients would be released from the phytoplankton).Dredging can decrease the nutrient in sediment only 10 times, and could not be the key factor for controlling eutrophication and the algae bloom.To cut off the pollutant loading into lake and to improve the environment of aquatic ecosystem should the key approaches instead.(5) The efficiency of dredging is related with the dredging method.Attentions should be paid to the negative influences, which may occur by dredging on ecological restoration.(6) The water quality problem, such as the algae bloom, could be solved alternatively through ecological endeavors.To improve the environment of aquatic ecosystem, approaches such as Physico-Ecological Engineering (PEEN) and Bio-Environmental Enterprise (BEEN) are favored in lakes step by step from local to all the open water system.

Abstract:One of the most obvious characters of freshwater ecosystems is their heterogeneity, namely, their disconnected structure and isolated functions, as comparing with terrstrial environments.However, this character is usually neglected by most traditional statistical methods, so using these tools can t describe these ecosystems correctly.In this paper, the authors recommend geostatistics to solve this problem-Based on regionalized variable theories, geostatistics is one kind of spatial statistical theory used to explore the correlativity and dependence between spatial variables.The first character of this method is its emphasis on the importance of spatial dependence of variables-In practical research, semivariance values of ecological factors or other indices can be calculated from the semivariance formulate according to the theory, and then, semivariogram can be drawn, distribution character of the research object (such as clumped or uniform pattern) can be found from the graph-Mathematical models simulation should be used in quantification of this character.Fractal dimension (D) obtained by double-logarithm semivariogram (D=(4-m)/2, where m (the slope of the graph) shows its heterogeneity character as well.The lower the value is, the higher heterogeneity the distribution of object.Kriging is another quantifying tool deduced from the theory.By kriging, the spatial concentration (density and so on) pattern of the variables can be known, values of unkown points also can be estimated, and this calculation value is more creditable because of its concern for regional property of the variables.In view of its accuracy, geostatistics would be widely used in freshwater ecology research such as density or spatial pattern of float grass, nitrogen, phosphorus and their ability of spatial occupation and so on.

Abstract:The "Appendage Shaking Disease" (ASD) of Eriocheeir sinensis has been one of the most serious disease in the farmed freshwater crabs of China in the past five years.The ultrastructural study on the affected crabs sampled from Huaiyin district, Jiangsu Province indicated th at massive Richettsia-like organisms (RLO) had been found in all th e affected crabs.However, no RLO was found in healthy crabs sampled from East Taihu Lake, Jiangsu Province where there was no epidemic of ASD.The RLO that have mainly infected the periopod muscle organization and blood cell of crabs and amage th periopod muscle fiber of muscle cell and, hence, be harmful to the locomotion system of crabs.This was identical with the symptom of ASD.So we come to the conclusion that RLO is probably the pathogen of ASD.