Abstract:Cluster analysis, principal component analysis and correlation matrix analysis were used to analysis the nitrogen and phosphorus release risks from sediments in 18 lakes located in the middle and lower reaches of the Yangtze River, as well as the nitrogen and phosphorus forms and related geochemical parameters from sediments, pore waters and overlying waters. The ecological difference of macrophyte and algae dominated lakes was the main reason of the difference of nitrogen and phosphorus release. The release risks were well correlated with the iron-bound phosphorus (FeP), algae available phosphorus (AAP), total nitrogen (TN), total phosphorus (TP) in sediment, the content of nitrogen and phosphorus in overlying and pore waters, porosity and organic matter content of surficial sediment. The AAP and FeP was the main phosphorus forms deciding the phosphorus release risk and other forms were in less effect on it due to the lower contents or lower transformation ability. The sediment organic phosphorus was not directly related to the phosphorus release risks but remarkably positively correlated to organic matter contents in sediment.

Abstract:According to compare the content of phosphorus (P) fraction, P sorption ability of water-sediment in ponds polluted by sewage from a hoggery and a rearing-pond, the influences of sewage from hoggery and fishery on P behavior in water-sediment system were studied. The results indicated that sewage from hoggery and fishery could significantly increase P contents in water, and sewage from hoggery increased more significantly dissolved P in water than fishery. Sewage from hoggery had no significant influence on sediment P concentration and P sorption properties, whereas fishery could significantly increase total inorganic P, Fe bound P (Fe-P) in sediment and maximum P sorption capacity and decrease P absorptive capability of sediment. The P sorption properties of sediment had some relationship with organic matter content in sediment.

Abstract:The West Lake, a famous scenic spot for tourists in China, is a small shallow eutrophic lake. However, the lake has been suffering from eutrophication from year to year and its beauty is marred by low transparency of the water. To control its eutrophication, a great deal funds had been invested and some projects had been organized by the government in the past twenty years. The effects of these projects were not satisfactory and the eutrophication is still progressing. Thus, the average depth 0.5m of silt on the bottom of the West Lake was dredged largely from 1999 to 2002. During the Jan. 1999 to Dec. 2000, the N and P of the sediment and water quality were surveyed, the phytoplankton, zooplankton and benthos communities (including species composition and density biomass) were investigated in the West Lake. To compare the investigated result with previous results and data (before the dredging), the succession of the communities was discussed. Further, the ecological effect of the dredging and the present trophic state of the lake were evaluated. The results showed that the N and P content in the sediment were decreased after the dredge, the water quality had been improved obviously, and the density in the phytoplankton community and the chlorophyll-a concentrations had decreased obviously comparing those in 1999, and the trophic level also had decreased in main lake areas.

Abstract:This paper analysed the existence of long-chain alkenones from the surface sediments in the Lake Qinghai and lakes in Qaidam Basin. The ratios of C₃₇to C₃₈alkenone is observed larger than 1 in both freshwater and saline lakes, while less than 1 in salt lakes. The calculated temperatures based on U ^K'₃₇ equation reported in literatures can fall within the observed temperature ranges for the Lake Qinghai, but are lower than air temperatures observed for lakes in the Qaidam Basin. The abundances of the long-chain alkenones in the saline lakes are found higher than those in freshwater and salt lakes, with the highest abundance of 86.09g/L in Lake Gahai with salinity of 103.2g/L. Such characteristics suggest that the algal precursors might prefer to live in water bodies with intermediate salinity but do not grow well either in freshwater or salt lakes. Thus the fluctuation of long-chain alkenone abundance might indicate variations of freshwater or saline environments.

Abstract:Grain size analysis is a conventional method to explore paleo-environmental changes, but its environment significance has various explanations. Especially for the lake sediments preserved in dry-land area close to Gobi and desert, it is still unclear if the grain size represents the intensity and frequency of the dust weather or the other environmental indicators. Based on the¹³⁷ Cs and ²¹⁰ Pbex activities from a short-length Glew core drilling from the center of Lake Bosten, the largest inland freshwater lake in China, grain size analysis of the past 50 years of lake sediments suggests that the average grain size and coarse grains content coincide with the maximum one-day runoff and the flood peak runoff at Dashakou station of Kaidu River, and with the annual precipitation of Bayinbuluke Station in the Tianshan Mts. However, the peaks of grain size curves were not consistent with lake level variations or wind speed changes (from March to June) of the Yanqi Station near to Lake Bosten. Therefore, the coarse grains content and average grain size can generally represent intensity and frequency of flood events of the Kaidu River and strong precipitation in the surrounding Tianshan mountainous area, but do not indicate lake level variations nor wind speed changes. A millennial multi-proxy record of Lake Bosten also suggests that the environmental significance from grain size at centennial or multi-centennial timescales is the same as that at annual to decadal timescales.

Abstract:Lake Hongfeng is a reservoir located in the center of Guizhou Province, which was built in 1960. A 35cm sediment core HF1-2 was sampled from the lake for analysis in 2004. Some mineral magnetism parameters such as SIRM, χ_lf, IRM_20mT, χ _ARM, Hard, χ_fd% are measured, furthermore HIRM, ARM/SIRM, IRM_20mT/SIRM, ARM/χ_lf, SIRM/χ_lf are calculated from them. Based on magnetic measurements of the core, we can find the changes of magnetic properties influenced by soil erosion in the catchments during the past 43 years from 1960 to 2003. Combination with the results of analyses of¹³⁷Cs, grain size, TOC(%)and C/N, we divide the changes of soil erosion in the drainage area into several periods during these 43 years, the most seriously soil-erosion periods are during 1977 to1980 and 1987 to 1997. Compared with the rainfall data, we find the precipitation, especially summer precipitation may be the major reason of soil-erosion during 1977-1980, and there are some other unknown complex factors to affect the serious soil-erosion during period of 1987 to 1997.

Abstract:A 32cm long sediment-core was sampled from Kechou reservoir located in Karst area of central Guizhou Province. According to study on grain size pattern and ¹³⁷ Cs dating in the profile, comparing with precipitation records, we determined the sediment ages in different depth of this core. Using the cumulative mass depth, we also calculated the deposit rates in different stages from 1960 to 2004. We improved the traditional ¹³⁷ Cs dating method which only relied on the position of peaks in profile. By analyzing the ¹³⁷ Cs depositing transportation and sedimentation, we found that the absolute values of ¹³⁷ Cs in the certain small catchment often appear in the low level. We believe that the soil erosion, which was caused by precipitation and other reasons, should intensively affect the amount of ¹³⁷ Cs depositing from soil to the sediment in reservoir. That should be the main reason of different pattern of ¹³⁷ Cs distributions in the sediment-core.

Abstract:Availability of phosphorus forms of submerged plant in the sediment and soil has been studied using the submerged plant Hydrilla verticillata culturing in different trophic sediments and soil. Different phosphorus forms in sediments and soil were separated by the chemical sequential extraction methods, at the same time the biomass of Hydrilla verticillata, concentrations of phosphorus in overlying water and in interstitial water were also analyzed. Amount of the bioavailable particular phosphorus was estimated by the formula of age available particular phosphorus. The results showed that labile phosphorus (P) and reducible soluble phosphorus (RSP) were the main phosphorus forms for Hydrilla verticillata utilization. The sediment is beneficial for the growth and fade of Hydrilla verticillata at the growth early stage. Phosphorus concentrations of the overlying water and interstitial water were affected mainly by the RSP concentrations in sediments. Phosphorus concentrations of interstitial water in soil were affected mainly by its labile P concentrations. The submerged plant Hydrilla verticillata promoted available phosphorus transforming, and its utilization rate for available particular phosphorus in soil is lower than that in sediments.

Abstract:Particle settling fluxes, phytoplankton biomass and concentrations of HCHs and TOC, sampled from a small blocked lake, were monitored from spring to autumn in 2006. The results showed that biomass of phytoplankton was high at the end of spring and autumn. The same change trend was found with phytoplankton biomass, chlorophyll concentrations and suspended particulate materials, and a closely relationship found between suspended particulate materials and phytoplankton biomass. Particle settling fluxes were high in spring in which there was a lag period with suspended particulate materials and chlorophyll concentrations, and kept lower in summer and autumn. HCHs settling fluxes were high in spring which was consistent with the change trend of organic carbon settling fluxes. This indicated that HCHs settling fluxes were mainly controlled by organic carbon settling fluxes.

Abstract:The hydrophyte has an important effect on removing nitrogen in the wetland system. This paper studied the nitrogen removal rate of the simulated wetland systems with Phragmites communis, Scirpus tabernaemontani cv.Zebrinus. and Vallisneria spiralis L. respectively. The hydrophytes had changed the redox condition markedly, however no significant discrepancies were found on the nitrogen removal rate. For the low nitrogen load (2.85mg/L for NH₄⁺_-N and 1.07mg/L for NO₃^-_-N), the ten-day removal rate of Ammonium and Nitrate of the wetland systems with and without hydrophytes were 39.32% and 21.91%, 34.68% and 13.86% respectively. In contrast, for the high nitrogen load (5.50mg/L for NH₄⁺_-N, and 3.37mg/L for NO₃^-_-N), the ten-day removal rate of Ammonium and Nitrate of the wetland systems with and without hydrophytes were 66.87% and 78.92%, 40.62% and 31.77% respectively. The hydrophyte could promote the process of nitrous transfer and shorten the time of the nitrous stay in the wetland.

Abstract:Based on the systematic measurment of nitrogen (N) and phosphorus (P) concentrations in lake water, the main river water, partial agricultural drainage, groundwater and urban sewage, we analyzed the present situations of N and P pollution at the Lake Poyang Basin, and discussed the sources of the pollution primarily. Lake Poyang Basin was polluted by N and P at some extent, while especially Rao River was polluted by N seriously and Xin River was polluted by P badly. The concentrations of total nitrogen and total phosphorus were 1.06±0.28mg/L and 0.067±0.042mg/L respectively in the Lake Poyang water and the lake has subjected to eutrophication status.

Abstract:The effects of different foods on growth of snail Radix swinhoei were examined at experimental station from July to August in 2006. The results showed that, for survival rates, snail consumed Vallisneria spiralis at the lowest rate, periphyton and Hydrilla verticillata at lower rate and compound foods at the highest rate. The specific growth rates of snail grazing two submersed plants were significant lower than that of grazing periphyton and compound foods. At the same time, snail size also affected its growth. The snail shell length increased slowly, only 0.01mm/d for V. spiralis and 0.02mm/d for H. verticillata, and increased significantly (0.05mm/d) for both periphyton and compound foods. The results suggestted that snail gazing submersed plants may very well be due to little abundance of periphyton in our experiment.

Abstract:Diaphanosoma dubia is one of the dominant species in most tropical reservoirs, however, how it becomes dominant and whether food concentration plays a key role are unclear. In order to study the effects of algal food concentration on the growth and reproduction of D. dubia and to understand the possible causes for this small animal to be one of the dominant species in the tropical water bodies, the animals were fed by Chlorella pyrenoidosa as food with five organic carbon concentrations: 0.05mg/L, 0.1mg/L, 0.3mg/L, 0.6mg/L and 1.0mg/L, respectively. The survival rate was quite low and no reproduction at the food concentration of 0.05mg/L. The somatic growth rate and longest body length increased with the organic carbon concentrations of Chlorella pyrenoidosa, the longest body length was 1.087mm, 1.125mm, 1.225mm and 1.313mm, respectively. Food concentration showed no significant effect on embryonic and juvenile development periods, lifespan and the number of the cumulative eggs for each adult. The size at maturity and the mean number of eggs per brood both increased with the increasing organic carbon concentrations of Chlorella pyrenoidosa, but the duration of reproduction decreased. The intrinsic rate of increase increased with the increasing organic carbon concentrations of Chlorella pyrenoidosa. The net reproduction rate and the intrinsic rate of increase showed peak values at the food concentration of 0.6mg/L. Under the maximal food concentration of 1.0mg/L, the generation time was shortest and the intrinsic rate of increase was closed to the peak value. The proper concentrations for the growth of D. dubia were 0.6mg/L and 1.0mg/L. The D. dubia is smaller than many species in cladocerans such as Daphnia galeata and has lower number of eggs per female. Its small body size and few eggs seems not be caused by low food concentration. The maximal sized animals cultured in the high food concentration is close to the animals found in natural water bodies, this means that predation doesn't significantly reduce its body size. Small size, transparent body and quickly moving enhance its advantages to dominate in tropical water bodies.

Abstract:Investigation on the zooplankton of Huizhou West Lake which composed of five small connected lakes were carried out for three times from January to September 2005. 55 species of zooplankton including 38 species of Rotifers, 10 species of Cladocerans and 7 species of Copepods were found. The dominant species included Polyarthra trigla, Filinia longiseta, Brachionus diversicornis, B. forficula, B. angularis, B. calyciflorus, Asplanchna priodonta, Trichocerca capucina, Moina micrura and Mesocyclops thermocyclopoides which mostly were the indicator species of eutrophication. The abundance of zooplankton were between 147.3and 726.10ind./L and the abundance of Rotifer were on predominance. It showed that the distribution of zooplankton were related closely to the water quality combined with correlative analysis of abundance of zooplankton and chemical and physical index of water.

Abstract:Referring to the different water body function, the survey of water quality was carried out on major urban lakes of Beijing monthly in 2006. According to TLI method, the state was evaluated on the basis of measurement result: lakes of drinking water source were mesotropher; lakes of major landscape water were light-middle eutropher; lakes of ordinary landscape water were middle-hyper eutropher. The eutrophic characteristics and its changing trend were analyzed. The causes were analyzed. The measures and suggestions were expounded on different water body function for improving water quality and reducing eutrophication.

Abstract:Based on the continuous six-year MODIS data (from 2001 to 2006), changes of lakes in Maduo County were continuously monitored in recent years. The results showed that there were 35 lakes in 2006 more than that in 2001, and the lakes' area in 2006 was 56.59km² larger than that in 2001. The lake numbers and areas kept decreasing from 2001 to 2003 and were the least in 2003, but yearly increased from 2003 to 2006. Each lake presented the different change tendency, and was not consistent with general trend of lake changes of the county. The correlation coefficient between annual precipitation and the lakes' area was the most significant which indicated that the annual precipitation had important effect on the lakes' area of the county. Climatic elements had different effects on main lakes.

Abstract:Along with the industrialization and the urbanization approaching rapidly, regional spatial development turned to environmental sensitive area, for example, sloping field, lakeshore etc., which has affected regional sustainable development. Carrying on the natural geographical features of Suzhou city, to classify the type of environmental sensitive area and to make a clear distinction boundary of the future regional development and protection has a vital practical significance for realizing the region economy sustainable development. From ecological protection, water source safeguard, pollution, farmland zoology and disaster prevention etc., the environmental sensitive area in Suzhou city will be divided into the ecological sensitive area, surface water source sensitive area, contaminated sensitive area, high quality farmland sensitive area as well as the latent disaster sensitive area——five kinds. In the foundation of being clear about its spatial scope, comprehensive evaluation of environmental sensitive area had been made and many kinds of sensitive environment protections and the development suggestions had been pointed out.

Abstract:We assume that the measurement errors of absorption coefficient and remote sensing reflectance are zero in October 2004, Lake Taihu. Then we can employ the optimization algorithm to simulate the backscattering coefficient by the most appropriate bio-optical model especially in the optically deep waters, where the bottom has no influence on remote sensing reflectance. Finally, the possibly real backscattering probability of suspended particulate matter may be approximately calculated by the quantitative relationship between the tested backscattering probabilities and their corresponding backscattering coefficients of suspended particulate matter. The results show that the backscattering probability of suspended particulate matter is not a constant and can be expressed as a quadratic function of wavelength, and the values are 0.017, 0.017, 0.027, 0.033, 0.054 and 0.094 at 442, 488, 532, 589, 676 and 852 nm, respectively; with a mean of 0.041±0.030.

Abstract:Based on the underwater photosynthetically active radiation (PAR) profile measurement and the concentrations of the optically active substances, the spatial patter and affecting factors of euphotic depth in Lake Taihu are discussed. Phytoplankton primary production (PP_eu) of all the lakes in autumn 2004 is estimated using the vertically generalized production model (VGPM) based on measured surface chlorophyll-a (Chl.a) concentration, euphotic depth, water temperature, PAR at the water surface, photoperiod and water depth. Euphotic depth ranges from 0.37 to 5.27m with a mean value of 1.52±1.06 m. The higher euphotic depth appears in the macrophyte-dominated lake regions such as East Lake Taihu, Xukou Bay and water area between Xishan and Dongshan Islands. In contrast, the lower euphotic depth is found in algal-dominated lake region such as Meiliang Bay and the southwestern open water. The regression analyses show that euphotic depth is mainly controlled by nonpigment particle matter, next to phytoplankton and chromophoric dissolved organic matter (CDOM). Nonpigment particle matter can explain 96.7% variation of euphotic depth. The ranges of Chl.a concentration and estimated PP_eu are 1.21-53.59μg/L, 77.4-2484.9mg/(m²·d), respectively. The estimated daily mean PP_eu distribution coincides closely with that of Chl.a concentration. Higher Chl.a and PP_eu values are recorded in Meiliang Bay and lower values are found in Xukou Bay or southwestern open water. There is a good correlation between VGPM PP_eu and primary production from the empirical model (PP_em)(r² = 0.79, p<0.0001). Daily mean_eu and PP_em of all the lakes are 694.5±492.0, 719.8±315.4mg/(m²·d), respectively. Although the ranges of the two methods differ, the mean values are very close. PP_eu more accurately captures spatial variation by considering the effect of euphotic depth, water temperature, surface PAR and photoperiod on PP.

Abstract:Based on water inherent optical properties using AC-S and BB9, which were developed by WETlabs Inc, the backscattering and scattering coefficients of Lake Taihu waters had been obtained from Oct. 24th to Nov. 2rd, 2006. Based on data analysis, the models between backscattering coefficients and scattering coefficients had been established. Two kinds of curve functions had been used to simulate, i.e. S curve at blue waveband and inverse function at green and red wavebands. And the change ranges of MAPE and RMSE are 0.027-0.156 m^-1 and 0.005-0.050m^-1, which indicated higher accuracy. Meanwhile, marked spatial distribution differences of the backscattering and scattering coefficients were found in Lake Taihu. As far as the entire lake was concerned, the scattering and backscattering coefficients in wester lake regions were higher than those in eastern lake regions. Strong scattering and backscattering were found in Meiliang Bay, center region of lake, western and southwestern lake region, while weak values were in East Lake Taihu and Xukou Bay.

Abstract:2008年3月21日是我国著名的自然地理学家施雅风院士九十华诞.3月20日,"地理环境变化研究"学术研讨暨施雅风院士九十华诞座谈会在中国科学院南京地理与湖泊研究所隆重举行.应邀出席座谈会的为在宁部分与施老有长期科研合作关系的著名学者,包括赵其国院士、王颖院士、朱大奎教授、王富葆教授、朱诚教授、徐琪研究员、唐领余研究员、王建教授、张忍顺教授、李世杰研究员、屠清瑛研究员、佘之祥研究员、沈道齐研究员、王苏民研究员、朱季文研究员、季子修研究员、陈家其研究员等老同志,以及施老在南京培养的部分学生等30多人.