| There are many lake-bays in Long-jing Lake. The hydrodynamic force in CentreLake and Lake Bay were different. Experiment study on water environment inLong-jing Lake to find the water quality difference in Centre Lake and Lake Bay. Themaximum water depth in Long-jing Lake is25m, seasonal thermal stratification is oneof the most important limnology characteristics in deep lakes and reservoirs, which isof great importance for theproductivity of ecosystems, biological community structureand water quality. Regarding the climate characteristics and limnology characteristicsin mountainous city, the characteristics of the seasonal thermal stratification and itseffect on vertical water qualityweresystematically researched.Aiming at the problem ofdeep and slow moving water, poor water self-purification ability and small waterenvironment capacityin mountainous deep landscape lake, which may causeeutrophication in the lake-bay area in spring and summer, combined with the landscaperequirement of Garden Export, fountain aeration systems werefield test researched inTingyu Bridge lake-bay.The conclusions are as follows:①Experimental study on the water-quality in lake bay area was launched.Theresults showed that: the comprehensive nutrition state index of bay area was higherthan that in the centre Lake. The current eutrophic state in the bay area had generallyachived medium nutritional level in spring and summer, which could be proved byhigh chl-a and low transparency presented in the water column.②Based on analysis and investigation of thermal stratification and its effect onwater-quality parameters in Long-jing Lake, results indicate that thermal stratificationinLong-jing Lake could be classified as warm monomictic lakes. During the monitoringyear, the Lake had three periods: the thermal stratified period started from March toDecember, stratified transitional period lasted from September to October, andisothermally mixed period is relatively short (from November to February).Stratification during the summer acts as a barrierrestraining mixing of the water columnso that the difference of water-quality across the vertical water column was significant.Hypolimnion was in aerobic state, which could indicate by lowDO, pH and ORP in thebottom water. A strong smell of H2S was detectedbelow the4m level. EC, nitrogen andphosphorus were low in the upper layers, whereas high in the deeper layers. WhileChl-a was the opposite, which presented high in the upper layers and low in the deeper layers.The comprehensive nutrition state index was the heighest during stratified period,which indicate the eutrophic state had generally achived medium nutritional level.During theisothermally mixed period, no significant difference in the water-qualityparameters of vertical water column, pH, DO, EC and ORP becomes homogeneous inthe vertical water. According to the experiment study on the seasonal thermalstratification and its effect on water-quality parameters, we could deeply understand theseasonal variance of water temperature, DO, nitrogen and phosphorous across thevertical water,which wouldprovide important references for the installation andoperation of artificial aeration equipment in mountainous urban lake.③Experimental study on the efficacy of fountain for artificial aeration in the bayarea was launched.The results showed that: under the mixing and aeration conditions,the thermal stratification structure was not successfullydestroyed, and the thermoclinestill existed.Theseasonal aerobic state was withheld at bottom of the bay,theconcentration ofDO increased significant in the upper layers and maintained above1.5mg/L at the sediment surface.The concentrations of TP, Ammonia and TN in theoverlying water on sediment surface decreased significant. In winter, the effect offountain aeration was not significant, The difference of DO conditions in fountain bayand contrast bay was not siginificant, while DO conditions of bottom water in fountainbay maintained3.5mg/L. Chl-a decreased mainly attribute to the great disturbance offountain.④The effect of spray height, pump depth, sprinkler type and operation mode onaeration was studied by the method of single factor experiment.It is found that thereaeration capability of spray height1m and5m improved than that of8m. Integratereaeration capability and energy consumption,1m was the optimumspray height. DO ofbottom water increased when pump water depth increased, but nitrogen andphosphorous would increase in the surface water due to the nutrients in the bottomwatter were mixed to the upper layers.Integratereaeration capability andwater-quality,3m was the optimum pump water depth in summer, while7m in winter.Fireworks nozzle had good atomizing effect, and jet stream had large flow, which hadthe best disturbance effect. These two nozzleshad better reaeration capability. Thereaeration capability of fountain tended to be stable after5hours operation in spring.⑤In spring and summer, DO super-saturation is frequently observed at thesurface water, then it should be taken measures to reaeration to the bottom water.Increasing pump water depth to break thermal stratification, accelerate mixing, improve DO conditions across diffusion process that well aerated surface water down toward thebottom. In autumn and winter, during the isothermally mixed period, on account oftemperature and low light penetration, DO concentration is relatively low throughoutthe water column resulting from low rates of photosynthetic O2production. It isoptimum to use fireworks nozzle, a further research on the spray height and pump depthto aeration should be taken, so the reaeration capability and DO concentrationincreased.The researches of thermal stratification and its effect on water-quality parameters inLong-jing Lake would provide theriod basis for thermal stratification and its effect onwater-quality parameters in mountainous landscape deep lakes. Fountain aerationsystems werefield test researched in Tingyu Bridge lake-bay have important meanningsin improve present situation that low DO conditions across the bottom waters, poorwater mobility, and algae growth too fast in the bay area, to prevent the occurrence ofeutrophication. It also provides important references for the installation and operation offoutain aeration equipment in mountainous urban lake... |
PDF Full Text Request