Speciation And Distribution Of Phosphorus In Aquatic Environment In Tuo River

In aquatic systems,phosphorus is considered as an important nutrient for its role in relating to the growth of phytoplankton,but its excessive input will lead to the occurrence of ecological disasters such as eutrophication and vast phytoplankton bloom.Sediments in aquatic systems can be a source or a sink to make substance exchange at sediment-water interface(SWI)when the depositing environment changes.So studying the migration and transformation process as well as the behavior of biogeochemistry of phosphorus at the sediment-water interface is essentialIn this thesis,the phosphorus species in the sediments and porewaters in the Regions of Jintang and Jianyang,Tuo River were systematically determined,and the vertical distributive behaviors of phosphorus in SWI were demonstrated.The speciation changes of the nitrogen and phosphorus in the two regions before and after ten years were also compared.(1)In the overlying waters of the two sites,the soluble reactive phosphorus(SRP)was the main form existed in the total dissolved phosphorus(TDP).The water qualities of overlying water body in both sites belong to the standard of inferior V.In Jingtang,the content of SRP and TDP were decreased generally and the soluble un-reactive phosphorus(SUP)was increased.While in Jianyang,SRP and TDP were increased firstly and then decreased,and the SUP was decreased in the first and then increased.(2)As to the porewater of sediments in both sites,the vertical distributions of different species of phosphorus were fluctuated,while SRP was the main form exsited in TDP.In Jintang site,the content of SRP at the depth of-6 cm?-9 cm and-9 cm?-13 cm was increased firstly and then decreased,while the contents of SUP and TDP at the depth of-6 cm?-9 cm and-12 cm?-14 cm were increased firstly and then decreased;In Jianyang site,the contents of SRP,SUP and TDP below the depth of-9 cm were increased firstly and then decreased.(3)As to the sediments in both sites,the inorganic phosphorus(TIP)was the main form existed in the total phosphorus(TP),and the inorganic phosphorus mainly existed as in the form of calcium bound phosphorus(Ca-P).In Jintang site,the contents of exchangeable phosphorus(Exc-P),calcium bound phosphorus(Ca-P),refractory phosphorus(Res-P),TIP and TP were the highest,and then decreased gradually with the increasing of the depth.In the contrast,the content of aluminum bound phosphorus(Al-P)was increased with the increasing of depth;In Jianyang site,the content of Exc-P in the surface was the highest,and then was decreased firstly and then increased below the depth of-7 cm,while the content of Al-P was increased gradually with the increasing of depth,and the content of Res-P was increased firstly and then decreased at the depth of-9 cm?-14 cm(4)A comparison of phosphorus species in overlying waters,porewaters and sediments between the two sites,it was found:in the overlying water,the content of SUP in Jintang than that in Jianyang,while the contents of SRP and TDP were higher in Jianyang than those in Jintang;in the porewaters,the contents of SRP,SUP and TDP were higher in Jintang than those in Jianyang;in the sediments,in addition to Exc-P,the contents of the other phosphorus forms were higher in Jintang than those in Jianyang,indiacting that phosphorus in iupstream was mainly concentrated in the sediments.The content of TDP in the overlying waters in downstream was high,indicating that there was phosphorus pollution in downstream.(5)A comparison of phosphorus species existed in both sites before and after ten years,it was found:Firstly,in the overlying water,the contents of SRP and TDP were all reduced and the content of SUP was increased in Jintang;the contents of SRP,SUP and TDP were increased in Jianyang.Secondly,the contents of SUP and TDP were increased and the content of SRP was reduced in porewaters of Jintang while the content of SRP,SUP and TDP were increased in porewaters of Jianyang.Thirdly,as to the sediments,although the phosphorus pollution status was remised generally in Jingtang site,the content changes of different phosphorus species is probable due to the release of phosphorus from sediment to porewater and then to overlying water body;However,in Jianyang site,phosphorus pollution status gets worse either in overlying water body or in the sediments,which is probable due to the exogenous pollutio.