Papers by Keyword: Eutrophication

Abstract: Temporal distribution phytoplankton community structure in a shallow lake, Lake Taihu, China, was investigated from 2010 to 2011 on a monthly basis at 9 sampling stations. The results showed that phytoplankton communities primarily consist of cyanobacteria, chlorophyta and bacillariophyta in Lake Taihu. A significant change in phytoplankton community was observed in both years: cyanobacteria hold an overwhelming dominance in summer and autumn, chloraphyta and bacillariophyta occupied the certain proportion only when the cyanobacterial bloom was declined in winter and early spring. The maximum abundance value of cyanobacteria, chlorophyta and bacillariophyta appeared at June, 2010, July, 2011 and Feb, 2011, respectively. The present study is a continuation and complement in long-term research of Lake Taihu, which provides scientific foundation for further research of the lake.

Abstract: Considering the fuzzy and stochastic feature in assessment, a new assessment model based on cloud theory is proposed. The new model can realize greatly the conversion from qualitative conception to quantitative model. Taking the new model into evaluating water quality of lake eutrophication, the evaluation model based on cloud theory can not only show the fuzzy feature of grade, but also indicate random attribute of membership. The method is developed to evaluate lake eutrophication status, and the results show that the new evaluation model is feasible and can effectively evaluate eutrophication level.

Abstract: In this paper, taking Laohutan reservoir in Huzhou city of Zhejiang province as an example, we systematically discussed the variation trends of trophic status in the early impoundment period of newly built reservoir and the dominant factor of eutrophication. It has been proved that the reservoir’s nutrition index in the early stage is on rise and the water body has a trend of eutrophication. According to actual situation, the outbreak of cyanobacteria and deterioration of water quality in September have showed the features of eutrophication. The dominant factors of eutrophication are total phosphorus, total nitrogen and dissolved oxygen, among which total phosphorus matters most to the trophic status. The results have laid great important foundation for people to explore evolution process of new reservoir ecosystem and the influences of hydraulic engineering construction to ecological environment, and they also provide reference for construction and management of other new reservoir.

Abstract: The objective of this research is to construct an efficient way of monitoring water quality and assessing trophic state using remote sensing techniques in Qinshan Lake of Hangzhou, China. Two Landsat ETM+ images were acquired and simultaneous in situ measurements, sampling and analysis were conducted. Results of the study indicated that the ratio of ETM+1/ETM+3 was the most effective single band in estimating chlorophyll-a (Chl-a), followed by normalized ratio vegetation index (NRVI). Two multiple regression models with determination coefficients were further constructed between logarithmically transformed Chl-a and the combination of ETM+1/ETM+3, ETM+2/ETM+3, and ETM+3/ETM+4 of ten sample sites. The resulting models, Log (Chl-a)=1.65 + 0.87*(ETM+1 / ETM+3) 3.39*(ETM+2 / ETM+3) + 0.89*(ETM+3 / ETM+4), and Log (Chl-a)=2.94 1.37*(ETM+1 / ETM+3) + 0.40*(ETM+2 / ETM+3) 0.20*(ETM+3 / ETM+4), both showed strong ability to evaluate the distribution of Chl-a, with R² of 0.72 and 0.92, respectively. Then two trophic state maps generated for Qinshan Lake using this model could identify zones with a higher potential for eutrophication, which turned out to be an appropriate method for synoptic monitoring of water quality in lakes. Similar modeling can be made for any given subtropical lake, to provide rapid and long term assessment of water quality and also useful information for decision making.

Abstract: Water eutrophication has become a worldwide environmental problem, and understanding the causing factors of water eutrophication will help for prevention and remediation of water eutrophication. The major causing factors of water eutrophication and purifying technologies were reviewed in this paper. There are many factors causing water eutrophication, including human activities, air deposition, precipitation, fertilizer runoff, animal waste and rural household pollution. Therefore, it is difficult to remediate eutrophic water. Constructed wetlands and floating beds have proven to be promising treatment alternatives in developing countries. Moreover, the biomass from phytoremediation ecological engineering can be used bioenergy feedstocks or animal feeds.

Abstract: Bosten Lake was the largest inland freshwater lake in China. It is facing with a series of ecological problems nowadays. The phytoplankton and water samples of seventeen sampling sites in Bosten Lake were collected in September 2012. Results show that sixty-four species (genera) of phytoplankton, which belong to six phyla, are identified. The community structure of phytoplankton is dominated by Chlorophyta. The mean cell density of phytoplankton in whole lake is 8179.01×10⁴cells·L^-1 and Cyanophyta accounts for 94.71%. The dominant species are Chroococcus sp. and Synedra acus. In terms of Shannon-Wiener diversity index, Margalef richness index, Pielou evenness index and total nitrogen content, it is ascertained that trophic state of water body in Estuary and Pumping Station is between mesotrophication and eutrophication. While in the other districts, the water body is eutrophic. In addition, the eutrophic degree of water body in District IV is higher.

Abstract: Erlongshan Reservoir water quality was evaluated for Class Ⅳand Class Ⅴby monitoring continuously indexes and was unable to meet the requirement of central drinking water source due to higher COD_Mn, TN and TP and eutrophic environment. The treatment measure including pollution source control and pollutant reduction was put forward for the sake of water quality improvement.

Abstract: This study investigated the relation between seasonal stratification and sediment phosphorus release in a seasonally stratified lake. Lake quality monitoring was conducted for 10 months from April 2010 to January 2011 in Lake Hongfeng, southwestern China. Destratification generated strong mixing from surface to bottom waters in the early autumn. The lake water was well-mixed vertically within 3 days and became anoxic within next few months. Total phosphorus concentrations of the whole water column increased by 15-20% as a result of high surface sediment concentrations of total phosphorus and reactive phosphorus. In seasonally stratified lakes, high reactive phosphorus content in sediments may form a larger flux of dissolved phosphorus in the sedimentwater interface following turnover. Technical measures should be taken to increase dissolved oxygen concentration and control the water circulation in this lake, especially during the cooling period, to weaken the effect of destratification and prevent sediment phosphorus release.

Abstract: This inoculation method inputting photosynthetic bacteria, nitrifying bacteria, compound bacteria etc into the water, to degrade pollutants of the urban lakes in this paper. The results show that, the removal rates of organic substance, chlorophyll-a and nitrogen compounds were 60%, 90% and 50% respectively .Moreover, dissolved oxygen (DO) content increased from 1 to 7 mg/L by adding microbes. The conclusion can be drawn that its feasible for adding microbes into eutrophication water to decontaminate water.

Abstract: The comprehensive trophic level index has been applied to assess eutrophication status of QiXing Wetland. The five subzones of QiXing Wetland with different vegetation pattern have different eutrophication status. The comprehensive trophic level index is mainly affected by TN and TP at high concentration of nitrogen and phosphorus. Therefore, the plant communities can significantly influence on eutrophication status of the wetland through removing nitrogen and phosphorus in water. Three mainly dominant plants in wetland are Phragmites australis, Nelumbo nucifera and Typha orientalis Presl. The ability to remove nitrogen and phosphorus of these three plant communities were investigated. Typha orientalis Presl community has the maximum efficiency in removing nitrogen and phosphorus in water. Therefore, Typha orientalis Presl is more suitable for the purification of the water.