Lake In Eastern China Research Articles

Distribution and characterisation of nitrogen-utilising bacteria in a eutrophic shallow lake in eastern China

To elucidate the roles of microorganisms in the nitrogen geo-chemical cycle, the distributions of nitrogen-utilising bacteria were studied in a small eutrophic lake. Ammonifiers, nitrogen fixers and nitrate reducers were more concentrated at the severely polluted Xili sub-area than at the Centre of Outer (CO), whereas the contrary was true for autolithotrophic nitrifiers. Molecular identification of predominant ammonifiers and nitrogen fixers showed that two of the ammonifiers were γ-Proteobacteria, two were β-Proteobacteria, one was CFB group and the other three were low G+C% Gram positive Bacillus. Among four nitrogen fixers, one belonged to α-Proteobacteria, and the other three were γ-Proteobacteria.

A bio-optical model based method of estimating total suspended matter of Lake Taihu from near-infrared remote sensing reflectance

Total suspended matter is an important water quality parameter, and plays a key role in water quality evaluation, especially of inland waters. Many different methods have been developed to estimate TSM from remote sensing data, in which empirical methods and model-based methods are two types of commonly used methods. Compared with empirical methods, model-based methods have the advantages of definite physical meanings, high robustness and retrieval accuracy. In model-based methods, matrix inversion method is commonly used in monitoring water qualities of inland waters. However, matrix inversion method has to predetermine some optical parameters by empirical values or simplified optical model, which may introduce some errors in retrieved water quality parameters. In order to overcome the shortcomings of matrix inversion method and increase the estimating accuracy of total suspended mater, in this paper, a bio-optical model based method is developed, which estimates total suspended mater by using remote sensing reflectance of two near-infrared bands. This method is validated by in-situ experiment data measured in Lake Taihu, a big turbid lake in eastern China. The results show that this method has better performance than matrix inversion method. The average relative error of the estimated total suspended matter by this method is only 13.0%, which is much smaller than the errors by matrix inversion method (32.7%). This method has the advantages of definite physical meaning, easiness to carry out, and high estimating accuracy. However, the applicable scope of this method has limitations: it can only be applied to optically deep waters with high concentrations of total suspended matter.

Stable isotopic composition of nitrate in Lake Taihu, China, and major inflow rivers

Identification of sources of nutrient pollution is a first step towards remediation of eutrophication in aquatic ecosystems. The stable isotope nitrogen-15 (15N) is a natural indicator of nitrogen (N) source and biogeochemistry. We sampled Lake Taihu, a hyper-eutrophic lake in eastern China, and major inflow rivers during winter and spring of 2004 to determine concentration and δ15N of nitrate (NO 3 − ). Nitrate concentrations in rivers and the lake were higher, in most cases, in spring than in winter. δ15N of NO 3 − was not correlated with NO 3 − concentration, indicating that concentrations alone are insufficient to describe N sources. Results show that riverine N inputs in winter are influenced by discharge of human sewage into rivers and the lake. In spring, however, wastewater inputs to the lake appear to be balanced by fertilizers, atmospheric, and/or N2 fixation sources. Rain NO 3 − concentrations were seasonally high and isotopically enriched compared to potential sources, indicating that rain may be a significant or even dominant source of N to the lake during the rainy season. δ15N values show that urbanized areas of the lake have more sewage-derived N than those areas dominated by agriculture, aquaculture, or industry. This observation has important implications for human health, since Lake Taihu is a source of drinking and irrigation water as well as fish for human consumption.

Record for Long-range Transport of Fly-ash Particles during Past 100 Years in the Pond Sediments in Oki Islands, Japan Sea

Fly-ash particles such as spheroidal carbonaceous particles (SCPs) and inorganic ash spheres (IASs) in sediments indicate modern fossil fuel combustion. A lake or pond away on the leeward of industrialized areas accumulates these particles in sediments to record the temporal change of fossil fuel combustion in the industrialized areas. The authors analyzed the fly-ash particles in a sediment core from Oike Pond in Oki Islands in the Japan Sea. The age of the core covers the last 100 years. The amount of both SCPs and IASs gradually increases from 1950s to the present. SCPs appear for the first time around the 1950s, while IASs have appeared around the 1920s. The profiles of lead and mercury concentration are similar to the profiles of the fly-ash particles. This evidences the increase of air-pollutants by coal combustion. The primary source of the IASs and SCPs is supposed to be coal combustion. The SCPs profile from Oike Pond resembles to that of Taihu Lake in eastern China after 1950s. Therefore the IASs deposited in Oike Pond after 1950s are inferred to have derived from China following increased coal consumption.

Sediment resuspension in the Lake Taihu, China

In order to examine the intensity of surficial sediment resuspension in Lake Taihu, a large shallow lake in eastern China, suspended sediment concentrations (SSCs) were measured on the basis of analysis of water samples collected using an innovative multi-level water sampler. The results show that under calm weather conditions, the SSC is relatively homogenous through the entire water column. However, when strong winds occur, the SSC in the bottom layer is 1–2 orders of magnitude greater than in the surface layer; thus, in this case, the amount of total suspended matter in the water column cannot be estimated using the SSC values of the surface layer alone. Furthermore, the depth of disturbance, or the thickness of the sediment layer that is set in motion by wind-wave induced currents, is of the order of 100 mm.

Extract enclosure culture in lakes based on remote sensing image texture information

Most lakes in eastern China are exploited in the form of enclosure culture. The high density enclosure culture area is easy to cause lake eutrophication and deteriorate the water quality. So the lake enclosure culture area is focused by people and is usually extracted by using the multi-temporal remote sensing data and the multi-spectral classification or the manual digitization means. The multi-spectral classification is easy to confuse enclosure culture area with the natural water area and the manual digitization demands much time. This paper suggests a new method using the image texture information to extract lake enclosure area. The result is more accurate and the method demands less expense. Lake Baima is the study area and the image of the area is multi-spectral data of China Brazil Earth Resources Satellite 02. First the water area、the man-made area and the bare soil which has the similar spectral characteristics with the water are extracted by using the normalized difference water index. Then the principal component analysis was used to compress the multi-spectral data of the study area and enhance the texture information of the image. The third step Grey Level Co-occurrence Matrix (GLCM) was used to analyze the image, select a proper threshold of mean value which quantifies the GLCM. Finally, the lake enclosure culture area was extracted by using the decision tree.

Protein and Amino Acid Composition of Chinese and North American Wild Rice

Chinese wild rice (Zizania latifolia Griseb.) Turcz from five lakes in Eastern China and North American wild rice (Zizania aquatica) from the United States of America and Canada were analysed for protein content and amino acid composition. Protein (N × 6.25) content was respectively 13.22, 13.02, 13.24 g/100 g in Chinese. American and Canadian wild rice. The amino acid compositions of the wild rice varieties from the three countries were quite similar with the exception of methionine which was present in lower amounts in Chinese wild rice. Threonine and lysine were the first and second limiting amino acids in all samples of wild rice.

The limnology and paleolimnology of a shallow eutrophic lake in Eastern China

Xuanwu Lake (3.7 km2) is a shallow (mean depth 1.4 m) hypereutrophic lake (annual productivity greater than 600 g cm−2) located in East China's flood plain near the N end of Nanjing, China's ninth largest city. Paleolimnological data based on a 16 cm long sediment core removed from near the center of the lake indicated that nutrient pollution tolerant diatoms have replaced pollution intolerant taxa which were common near the base of the core (approximately 35 years before present). These paleolimnological observations support the hypothesis that progressive eutrophication is occurring in Xuanwu Lake. This conclusion is corroborated by direct comparisons of the present day phytoplankton and zooplankton species composition within the lake and published accounts of its species composition during the mid 1970's.

A preliminary study on the water temperature and freezing of Lake Suwa in Japan and shallow lakes in eastern China.

Based on the assumption that the extent of winter ice in lakes in Japan and central-eastern China may be correlated, the water temperature and condition of freezing were examined. Equilibrium temperature and estimated eplimnion temperature were used for the prediction of annual variation of lake temperature and explanation of the formation of ice cover. Lake Suwa freezes almost every year due to its high altitude, whereas the possibility of lake freezing in central-eastern China varies meridionally. January air temperature at Nanjing fluctuates in parallel with the temperature at Suwa, and appears to be correlated with the extent of ice cover in Lake Suwa.