| Summary: | 碩士 === 國立東華大學 === 自然資源管理研究所 === 93 === Water body can be divide into flow and stand water according to dynamic differentiates. For example rivers and streams are flow water , lakes and ponds are stand water. No matter what kind of water body all belong to a link of the aquatic environment, which participate in nature hydrologic cycle and becomes the surface water interaction with natural environment at time. Dong Lake is part of the ecosystem of stand water. Although it is a imitation lake, it still interact with natural environment. We can forecast the change of the Dong Lake ecosystem by study the nature’s lentic environment. We research on the Dong Lake’s water quality by analyse the physical factors (water temperature, suspended solid, DO), pollutants (BOD, nitrate, amonia nitrogen), the parameters of eutrophication (phosphorus, Chlorophyll a, transparency), hydrologic chemistry (pH, conductivity), cations in water (Ca2＋、Mg2＋、Na＋、K＋）, anions in water（SO42－、Cl－、F－、Br－、NO2-、NO3-、PO43－) and so on of Dong Lake’s water to understand the probably effect factors to the water quality. Through these analyses we can study and monitor the influence of these pollutants on Dong Lake and conjecture it’s polluted load according to different space and period. And these data will provide the basis for deal with lentic ecosystem in the future. We use noparametrics one way wilcoxon test to analyse data, the results show that space (sampling locations) is not a variable of these measured (Pr＞0.05) but time is（Pr＜0.05）. The influence of groundwater sources on average ionic concentrations are critical, SO42－（30.46 mg/L）＞Ca2＋（30.03 mg/L）＞Mg2＋（9.88 mg/L）＞Na＋（6.57 mg/L）＞Cl－（5.43 mg/L）＞K＋（2.14 mg/L）＞NO3－（0.0974 mg/L）＞F－（0.0774 mg/L）＞Br－（0.0092 mg/L）＞NO2－（0.0039 mg/L）＞PO43－（0.0008 mg/L）, except atmospheric fallout. Ten months continuously examine results show that terrestrial water class and water quality locate between class B to class E and this result is out of an expected value 60%. There is no filthy water be discharged into Dong Lake so the water quality index is between 57.43-79.90, it means water quality is not good enough still need to improve. The increasing and depositing of nutrients during a long period, Carlson Trophic status index is between 56.04-65.55, show that the situation of eutrophication becomes seriously and have to adopt some measures to control eutrophication.
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