The Study On Forms Of Nitrogen-Phosphorus And Ecological Remediation Simulation In Shiwuli River

Eutrophic water body restoration principles and technical studies is the hot research field in domestic and foreign environment and ecology. In a variety of methods to repairing eutrophic water, the plant floating bed repair is a low power way, it acquires obvious effect new technology, that uses aquatic plants to absorb nutrients to purify eutrophic water. It has attracted domestic and foreign academic circles attention.In this paper, we screen of plant species for floating bed in the eutrophic water, and we study on the purification effect to water of these plant which we have selected. First of all, we have studied nitrogen and phosphorus speciation in water body and sediment of a typical inflow rivers named Shiwuli River. According to eutrophication of water bodies, we select the part of the aquatic plants, to study the absorption and transformation mechanism of inorganic nutrients such as nitrogen and phosphorus in water under natural conditions. Taking into account the plant growth conditions, we choose to adapt to the status of river water quality and has a high nutrient removal plant species as a pioneer species that construct floating bed.Taking into account the process of eutrophication of water bodies, in addition to exogenous nutrient inputs, the endogenous release of sediments is also an important reason. In the medium-term, through the different environmental conditions (temperature, DO, pH, organic content, etc.), we monitored the release form and quantity of nitrogen which is released from sediment to overlying water, and we studied the release mechanism and the law, then we come to the best conditions for the release of the inhibitory.Later, we use water spinach, canna floating bed for engineering applied research. We have studied the change in plant species, plant biomass,plant density effects on water purification in the outdoor pool to simulate Shiwuli River. Conclusions were as follows:⑴Plants chosen for the experiment can be quickly adapted to the eutrophic water. They removal of nitrogen and phosphorus all have a certain effect, in which water spinach, canna and altemanthera philoxeroides has a strong cleaning ability to remove nitrogen and phosphorus. Canna has some landscaping features, water spinach as a vegetable varieties have some economic value, altemanthera philoxeroides is prevalent in the natural environment, and easy access, can be processed into animal feed. These plants can be a candidate in the ecological restoration of species to build floating bed. Oenanthe stolonifera likes the cool, is sensitive to heat, easily wither in the summer. It grows well in the fall, and the absorption of nutrients is better. Water spinach grows significantly in summer and it can withstand high temperatures. However, the growth of it in the fall slow. So we use water spinach and oenanthe stolonifera to construct artificial floating bed in the summer and fall seasons.Comprehensive consideration factors such as plant survival, growth amount of biomass, absorption of nitrogen and phosphorus, we have come to: mainly use water spinach and altemanthera philoxeroides, mixed-use canna, oenanthe stolonifera and other plants is a more reasonable community structure to build floating bed in Shiwuli River.⑵The release of ammonia nitrogen in sediments over time showed the law of logarithmic equation. Control of DO on nitrogen release from sediments is an important factor. Under aerobic conditions, the release of ammonia nitrogen in sediment is inhibited. Phosphorus released from sediments is based on iron phosphate as the main form. When the soluble phosphorus concentration was 0.01~0.5mg/L in the overlying water, sediment phosphorus released into the overlying water. At the same time high concentrations of phosphate inhibited ALP activity in the overlying water. The release of phosphorus is small in weak acid to neutral range.Acidic and alkaline conditions are conductive to the release of phosphorus, elevated temperature, anaerobic conditions may increase the release of phosphorus in sediments. Therefore, to maintain high DO and pH in the neutral range of fluctuation in the river water can inhibit the release of ammonia nitrogen and phosphorus from the sediment effectively.⑶Because a large number of aquatic plants absorb nitrogen, phosphorus and other nutrients in the water, and change the water body environmental factors, leading to the phosphorus in sediment is more easily fixed, that is, it slows down the release of phosphorus in sediment and reduce the concentration of total phosphorus in water of river.⑷In the experiment, oxygen increased and the activity was enhanced in the plant root zone. It may lead to the enhanced role of nitrification and denitrification and an increase in phosphorus intake, also it can contributes to microbial degradation of COD in the eutrophic water body. Aquatic plants can effectively control nitrogen and phosphorus and other nutrients in water during their growing period. Through experiments, inorganic nitrogen were decreased by 70%,ammonia nitrogen index fell 85%,total phosphorus index has declined by 50%,water transparency has improved, and other water quality indicators showed a smooth fluctuations in the state. Under suitable conditions,the biomass of aquatic plant increases several times,creating significant economic value.