Distributions And Seasonal Variations Of Dissolved Inorganic Arsenic, Selenium And Antimony And Their Speciations In The Changjiang Drianage Basin And Yellow River Estuary And Its Coastal Area

Changjiang Drianage Basin and Yellow River are the largest rivers in China. Inrecent years, anthropogenic activities in the drainge basins become more and moreserious and there are lots of dams to be constructed to control the water and sedimentdischarge regularly, which surely will conduce huge impacts on the ecosystems of therivers and estruaries. The concentrations of total dissolved inorganic arsenic (TDIAs,sum of arsenate [As(V)] and arsenite [As(III)]), As(III), total dissolved inorganicselenium (TDISe, sum of selenate [Se(VI)] and selenite [Se(IV)]), Se(IV) totaldissolved inorganic antimony (TDISb, sum of antimonate [Sb(V)] and antimonite[Sb(III)]), Sb(III) were measured by Hydride Generation-Atomic FluorescenceSpectrometry (HG-AFS). The distributions, seasonal variations and effect factors ofdissolved inorganic arsenic, selenium and antimony and their speciations in theChangjiang Drianage Basin, Yellow River Estuary and its coastal area are primarilystudied in this dissertation.The observations were carried out in the main stream and major northern andsouthern tributaries of the Changjiang were investigated during August and October2009to evaluate the impact of The Three Gorges Dam (TGD) and to assess the impactof anthropogenic activity on the concentrations of dissolved inorganic arsenic,selenium and antimony in the Changjiang Drianage Basin. The results show that thedominant species are arsenate, selenate and antinmonate in the Changjiang DrianageBasin respectively. The concentrations of TDIAs, As(III), TDISe, Se(IV), TDISb,Sb(III) in the downsteam are higher than upstream as a result of weathering andanthropogenic activities. The concentrations of dissolved inorganic arsenic, seleniumand antimony in groundwater are lower than the mainstream and northern andsouthern tributaries of Changjiang, which indicateds that the concentrations ofmetalloids in the groundwater of Changjiang still remaind at the natural level. Theflux calculations indicate that Changjiang transports380.3×106mol/a of TDIAs, 6.0×106mol/a of TDISe,3.0×106mol/a of TDISb to the East China Sea, whichindicates that Changjiang plays sighifiant part of the element’s annual transport intothe sea. Compared with the precious results of TDIAs and TDISe of our lab which thefield observations were carried out before, during and after the construction of TGD(spring1997, spring2003, winter2008, and this study, respectively), the impact ofcongstruction of TGD on the metalloid elements in the Changjiang can be drawn.There is no significant variation of TDIAs concentrations in the downstream ofChangjiang Drianage Basin between the results of spring1997and spring2003.However, the average concentrations of TDIAs in the downstream of ChangjiangDrianage Basin in autumn2009are significantly higher than spring2003, whichindicates the impact of the construction of TGD. The construction of TGD has nosignifiant impacts on the annual variations of TDISe in the downstream ofChangjiang.The river water sampes were collected monthly at Station Kenli (72kmdownstream from Yellow River Estuary) in the Yellow River during January2009toDecember2011. During this period, the concentrations’ range are18.99~36.67,0.27~7.47,5.70~13.62,1.17~3.11,4.40~9.09nmol/L are for TDIAs, As(III), TDISe,Se(IV), TDISb, respectively. Sb(III) is not detectable in all the samples. Conparedwith the previous results, anthropogenic activities have no sighifiant impacts on theconcentrations of TDIAs in the Yellow River. The concentrations of As(III) show nosignificantly seasonal variations. The concentrations of TDIAs in spring, summer andautumn are higher than winter which is samilar to Se(IV). The concentrations ofTDISe in spring are higher than summer, autumn and winter. The concentrations ofTDISb in summer are higher than spring and winter. The monthly fluxes of As, Sb insummer and autumn are higher than spring and winter. The monthly fluxes of Se insummer are higher than spring and winter. The concentrations of TDIAs in2009areequal to2010and are lower than2011.During the period of water-sediment regulation event in the summer of2009,daily observation were conducted at Station Kenli from June19to July15in2009.The concentrations range of TDIAs are16.67~33.02nmol/L, which correlatenegatively with runoff and SPM. The flux of TDIAs during these27days represents25.5%contribution in the whole year, which indicates that the water-sedimentregulation has sighifiant impacts on the element’s annual transport into the Bohai Sea.Moreover, three cruises were carried out in the Yellow River Estuary on15June,1 July and19July, respectively, which were before, during and after the regulationevent. Each cruise in the estuary covers six sections. The results show that theconcentrations of TDIAs have highest value in the northern Yellow River Estuary.The concentrations of TDIAs in the middle period of water-sediment regulation are1.5times higher than the beginning as a result of water-sediment regulation event.After water-sediment regulation, the concentrations of TDIAs are lower.