| In this paper,multiple varieties of aquatic plants,growing in artificial wetland of the Shifo Temple,have been chosen to study the effects of aquatic plants on the nutrient contents in wetland.During the death and decay stage,in order to analyze and discuss the influence affected by four kinds of aquatic plants on the nutrition contents associating with the quality of water and bottom sediment,relevant laboratory simulation experiments were conducted.Considering the influence of aquatic plants on the contents variation within the entire wetland,the corresponding and pollution-controlled measures were put forward to prevent the eutrophication of the wetland to establish the environment-friendly wetland system.The main results were as follows:(1)During the rapid growth stage,there was a relatively better purification effect with aquatic plants on water quality,while during the nutrition accumulation stage and the decomposing and death stage,its effect was more stable and greater volatile respectively.Besides,the main purification mechanism of aquatic plants contained assimilation and absorption functions,rhizosphere effect,interception adsorption and biochemical functions,and there was a certain relationship between purification effect and plant biomass.It increased yearly with the increasing of the plant biomass in water.During the nutrient accumulation period,rapid growth period and smooth growth stage,the plants had significant removal effects on inorganic salts contents in water,and within the period of death wither,the aquatic plants could increase the content of inorganic salts in water.Therefore,within the decomposing and death period,the dead and rotten plants need to be removed in time for wiping off the inorganic salts contents and preventing secondary pollution.(2)Microorganism,external contamination and aquatic plants are the main factors which affect the content of nutrient in sediment.These factors have different effects in different vegetation period on the nutrient content in sediment.In fast growth period:plant absorbing is the head factor that affects the content of nutrient substance in sediment;In stationary phase:extraneous is the determinant factor that affects the content of nutrient substance in sediment;In decomposition stage:plant decomposition is the main factor that affects the content of nutrient substance in sediment.Temperature has different effects on microorganism and then it will affect the content of nutrient substance in sediment.According to the results of our study,it is concluded that the changes of nutrient substance content in sediment is mainly affected by the plants.(3)There was a small impact on the PH?DO?CODcr?TN?TP change trend in water and the sediments with treatments of the four kinds of aquatic plant decomposition,but in different stages of decomposition,the impact on the variation of different index values in water is different.In this study,the decomposition rate of four life-type aquatic plants was exhibited in the following order:Trapa Japonica(floating leaf-type plant)?Salvinia Natans(floating type plant)>Hydrilla Verticillata(submerged plant)>lotus plant(emergent macrophytes).There is different influence on water environment with different life-type aquatic plant decomposition,the process of decomposition will result in a greater volatility to water quality,but at the end of the experiment compared to the original status,pH of water has a small increase while TN and TP in water significantly increased.The influence of TN content on the water quality was the most significant among the emergent macrophytes plants.The submerged macrophytes had the greatest influence on TP in the process of decomposition.The influence of decomposition process on the DO and CODcr content in water is different.Decomposition promoted the outward release process of TC and TN resulting in reducing the sediment TC and TN contentand preventing the deposition of nutrients in sediment,but the effects of decomposition on TP was completely contrary to that on TC and TN. |
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