Study On The Influencing Factors Of Transformation-transpotration Processes For Nitrogen In Hyporheic Zone

In recent years, the contamination of nitrogen with the nitrogen in surface waterand groundwater has been more serious.It has caused more and more attention of thepeople. The hyporheic zone is water saturated sediment layer,and it locates under theriver bed and extends to srteamside zone. It plays an important role in the riverecosystem. The microorganisms in the hyporheic zone play a major role fortransportation transformation processes of nitrogen. Therefore, studying on the theoryof transportation transformation of nitrogen in the hyporheic zone can provide thetheoretical basis for the development of new denitrification technology.Based on investigating relevant documents,the paper designed the simulativeinstrument of hyporheic zone and simulated transportation transformation of nitratenitrogen in the surface water that through the hyporheic zone. the paper researches theinfluence of the medium of hyporheic zone、the type and content of carbon source ofsediment layer for transportation transformation of nitrogen. The specificexperimental content and results are as follows:（1） By studying the influence of three type of mediums（coarse sand、fine sand、mealy sand） for transportation transformation of nitrate.Results show that:①Without added plus carbon source, the decrease of the concentration of NO₃⁺-N is themost in the column of mealy sand, and next is the column of fine sand followed by thecolumn of coarse sand. The concentration of NH₄⁺-N is the highest in the column ofmealy sand, and next was the column of fine sand followed by the column of coarsesand. According to these,water environment in the column of mealy sand is better forthe denitrification and the dissimilation deoxidization of nitrate than that in thecolumn of coarse sand and fine sand.The smaller the mediums size and the more theorganic content,the better the removing of NO₃⁺-N.②After adding carbon source,column sufficient carbon source, the carbon source is enough.The concentration ofNO₃⁺-N is very low in three columns, below the detection limit.It indicates thatcarbon sources plays an important role on nitrate removal.（2） By studying the influence of the type of carbon source （glucose、citric acid、 humic acid and the mix of the three） in the sediment layer fortransportation transformation of nitrate.Results show that:①、the concentration ofNO₃⁺-N is the lowest in the column of mixed carbon sources.The decrease of theconcentration of NO₃⁺-N is the most.The concentration of NH+4N is highest. Thedecrease of the concentration of NO₃⁺-N is near in the column of glucose and thecolumn of humic acid. The concentration of NH+4N is also near in them.But,thedecrease of the concentration of NO₃⁺-N is the least in the column of citric acid. Theconcentration of NH+4N is lowest. According to these,we can know that it generate aenvironment that pH is low and ORP is high in the column of citric acid.Theenvironment is not good for the denitrification and the dissimilation deoxidization ofnitrate. The denitrification and the dissimilation deoxidization of nitrate is theweakest in this column.So, the decrease of the concentration of NO₃⁺-N is the least.②、By analyzing the curves of total inorganic nitrogen and NH+4N,the denitrificationis stronger than the dissimilation deoxidization of nitrate in four column. It shows thatthe denitrification plays the major role on the decrease of the concentration ofNO₃⁺-N.（3） By studying the influence of the content of humic acid （the content of theTOC is0、1%、5%and10%） in the sediment layer for transportation transformationof nitrate.Results show that:①、The decrease of the concentration of NO₃⁺-N is themost in the column which the content of the TOC is10%in the sediment layer. Thelargest decline of the concentration of NO₃⁺-N is22.7mg/L, and next is the TOCcontent of5%followed by the TOC content of1%,the last is the TOC content of0,The decrease of the concentration of NO₃⁺-N respectively are21.9mg/L、19.2mg/L、14.6mg/L. It shows that the more the organic content,the more the decrease of theconcentration of NO₃⁺-N.②、By analyzing the curves of total inorganic nitrogen andNH+4N,the denitrification is also stronger than the dissimilation deoxidization ofnitrate in four column.It shows that the denitrification still plays the major role on thedecrease of the concentration of NO₃⁺-N for different content of carbon source in thesediment layer.