The Investigation On The Effect Of Redox Condition On The Release Of The Sediment Phosphorus In Lake

Lake eutrophication is one of the main ecological environment problems about lakes,and phosphorus is the control factor to most of the lake eutrophication.When the exogenous input was controlled, endogenesis had become an important source of nutrients for lake water body.Due to the release of internal phosphorus is strongly influenced by many environmental factors, Including pH, temperature, dissolved oxygen, disturbance and so on The deep water of plateau in yunnan-guizhou in china,the unique geographical conditions and the natural environment of lake lead to the change such as pH, temperature is small in sediment, dissolved oxygen changes are the main factors, so deep understanding of different environmental factors on the sediment endogenous phosphorus release have great significance,And can provide scientific guidance for the prevention and control of eutrophication of lakes.In this paper, Hongfeng Lake, located in Guizhou Province, was chosen to study the release process of the sediment phosphorus under the natural, aerobic and anaerobic conditions. Microscale observation of the physical and chemical properties of sediment-water interface by microelectrode technology was used, together with traditional P-speciation analysis, to explore the P-releasing mechanisms. The main conclusions were summarized are as follows:1. Different oxidation-reduction environment created bigger difference in sediment-water surface.In the Anaerobic condition,the dissolved oxygen content of sediment and water interface is reduced, only 70.0μmol/L, the penetration depth of dissolved oxygen is only 0.9 mm or so, but the highest of hydrogen sulfide can reach 47.3μmol/L.Under aerobic condition, the dissolved oxygen of sediment and water interface is about 280.0 μmol/L, penetration depth is 4.2 mm, the highest content of H2 S is only 9.0 μmol/L.Through the study of difference places and the two seasons in winter and in summer in Dam and in Houwu,found that under the condition of natural sediments dissolved oxygen, hydrogen sulfide, and pH are affected by season and location, the Dam in winter and summer, the interface between sediment and water dissolved oxygen were 186.4 μmol/L, 28.4μmol/L, Houwu in winter and summer,both of the two seasons of dissolved oxygen are about 200.0μmol/L, the produce of the concentration of hydrogen sulfide is in big difference all the same in the Dam in winter and in summer, the respectively of the peak are 135.0μmol/L and 11.0μmol/L, and Houwu are all less than 10.0μmol/L. Peak in summer than in winter.2. Under the condition of natural,the average of total phosphorus content of Hongfeng lake is 1474.0 mg/kg, but under the condition of nitrogen is 1039.9 mg/kg, under the condition of aeration is 1483.7 mg/kg, under anaerobic conditions,the total content of phosphorus in the sediment in Hongfeng Lake decreased significantly, which was mainly caused by the reduction of NaOH-P and rest-P, indicating that the aerobic condition promoted the phosphorus release in sediments. Through monitoring about Hongfeng lake in winter and summer found that the sediment can release higher phosphorus, and have a greater risk of phosphorus release.3. The aerobic condition promoted the phosphorus release in sediments,and the concentrations of phosphate in the pore water of sediment increased greatly under anaerobic condition, and the trend was contrary to that under aerobic condition. Under the anaerobic condition, concentrations of dissolved oxygen decreased and sulfate reduction was enhanced, which released NaOH-P in the sediment. Decrease of O2 accelerated the sediment reducing processes and produced a large amount of H2 S, which combined with ferrous icon to form the precipitation-ferrous sulfide, resulting in release of NaOH-P(Fe-P) into the pore water. The conversion of aerobic to anaerobic condition could promote the release of rest-P by changing the distribution of pH value in the sediment as well as microbial activities. Under the anaerobic condition, anaerobic microorganisms could not only contribute to the sulfate reduction and H2 S production, leading to pH decrease, but also consume organic matter and convert organic phosphorus into inorganic phosphorus.4. On the analysis of phosphorus forms in Dam and in Houwu, found that whether the dam or Houwu, winter or summer, the proportion of NaOH- P is the highest, followed by a rest- P, the least is NH4Cl- P. Different forms of phosphorus under the influence of oxidation-reduction environment is different, with HCl-P and NH4Cl- P less affected by the dissolved oxygen;BD- P, NaOH- P, rest- P are greatly influenced by dissolved oxygen.Different oxidation-reduction environment impact sediment phosphorus release may influence the migration and release of BD- P, NaOH- P, rest- P.The research results show that the redox environment of sediment-water interface could affect the penetration depth of sediment-oxygen, pH distribution, microbial activity, sulfur cycle as well as organic matter degradation process, which controlled the speciation transformation and release of sediment phosphorus. Microelectrode technology, together with traditional P-speciation analysis, is an effective way to reveal the release mechanism of sediment phosphorus as well as the control factors.