Study On The Oxygenation And Environmental Effects Of ONBMMs On The SWI In Deep Water

Sediments are an important part of the ecosystem of natural water bodies?such as lakes?.It can be the"sink"or"source"of pollutants in water.The sediment-water interface?SWI?in contact with water is a key environmental factor.Because multiple reactions involving protons took place at the SWI of lakes,strong biochemical changes may occur at the millimeter scale of the SWI.Phosphorus is generally considered to be a major limiting factor for lake primary productivity.Excessive phosphorus input into lakes?reservoirs?will aggravate the eutrophication of water,resulting in serious destructions to global freshwater resources.The sources of phosphorus in lake water can be divided into exogenous phosphorus and endogenous phosphorus.With the continuous strengthening of water environmental protection,the input of exogenous phosphorus decreased obviously,but the contribution of endogenous phosphorus release to lake water phosphorus continued to increase.Therefore,it is urgent to control the release of endogenous phosphorus in the lake from the SWI to the overlying water,which is of great significance for the restoration of eutrophic lakes.Effectively improving the oxygen content of SWI is an important way to control the release of endogenous phosphorus in lakes.The existing deep-water aeration technology,due to its lack of pertinence to SWI aeration,has limited its application in the restoration project of endogenous pollution of lakes.Oxygen nanobubbles have good oxygen supply effect,long duration and low environmental risk,and have great potential in application of lakes SWI to oxygen addition and control of endogenous phosphorus pollution.In this study,mineral screening,bubble preparation and effect characterization were used to develop the aerobic technology of oxygen nano-bubble modified mineral particles?ONBMMs?specially designed to add oxygen to the SWI,and its oxygenation efficiency and control effect on the release of endogenous phosphorus were evaluated under anaerobic conditions.The main results are as follows:?1?the surface microtopography of natural mineral materials?mica,sericite,zeolite,diatomite?was analyzed by SEM,and it was found that mica presented flat flake structure,while sericite,zeolite,and diatomite all presented irregular massive or flocculous structure.Therefore,it was recommended that mica be the optimal substrate for nano-bubble materials.?2?taking natural mineral materials as the substrate,oxygen nanobubbles were prepared by the alcohol-water substitution method.Under the condition of indoor simulation,they were added to the SWI to conduct an experimental study on oxygen enhancement.The results showed that ONBMMs had an obvious oxygenation effect on the anoxic SWI.The interfacial oxygenation effects of different minerals and materials with different particle sizes of the same mineral were significantly different.The modified mineral white mica showed better oxygenation performance.In addition,the finer the mineral particle size,the better the interfacial oxygenation effect and the longer the continuous oxygenation time.?3?ONBMMs is equivalent to an oxidizing layer,which changes the redox conditions of the SWI,oxidizes Fe²⁺to Fe³⁺,and strongly adsorbs phosphate,thus reducing the content of both active Fe and active P near the SWI,significantly reducing the concentration of total phosphorus?TP?and soluble reactive phosphorus?SRP?in the overlying water,resulting in a decrease of 97.9%in the overlying water SRP,and 78.9%in the release flux of DGT-P in the sediments.The release of phosphorus from sediments to overlying water was significantly inhibited.?4?ONBMMs has obvious effect of oxygen and phosphorus enhancement and inhibition.This technology has many advantages,such as convenient operation,strong pertinence,good effect of oxygen enhancement,low price and low environmental risk,etc.It is expected to become an effective technical means of accurate oxygen enhancement and endogenous pollution control in deep-water anoxic lake SWI.