Variation Characteristics And Influencing Factors Of Silicon Composition And Transport In The Surface Water Of The Lower Reaches Of Min River

Silicon is one of the most important elements in the study of global environmental change.The transport of silicon from land to sea and its effect on marine environment is the key fields in the study of land-sea interaction.In view of this,we studied the variation characteristics and influencing factors of composition and transport on dissolved silicon(DSi),biogenic silica(BSi),lithogenic silica(LSi)in the lower reaches of Min River which is located at the southeast of China in 2019(July and November)and 2020(January and July)through field investigation and laboratory experiment analysis methods.The influencing factors of silicon composition and transport was synthetically analyzed,estimating the flux of silicon including DSi,BSi,LSi,particulate silica(PSi)and reactive silica(RSi),in the lower reaches of Min River in different seasons,and assessing the ecological efficiency of the silicon transportation in the lower reaches of Min River.The main research results are as follows:(1)The average content of DSi,BSi and LSi in the surface water of the lower reaches of Min River was 5.25 mg/L,2.41 mg/L and 4.48 mg/L,respectively.Contrary to DSi,the content of BSi and LSi in dry season were higher than that in wet season,and the content of DSi and LSi gradually decreased to the estuary.(2)The results of statistical analysis shown that the DSi content of the surface water in the lower reaches of Min River was mainly affected by temperature,p H and salinity,the BSi content was mainly affected by water temperature and salinity,and the LSi content was mainly affected by water temperature.In addition,the spatial and temporal distribution of silicon was also affected by river flow,SPM matter concentration and diatom growth,and human activities such as dam construction,agricultural activities and construction also interfered with the silicon transport in the lower reaches of Min River.(3)The average content of PSi and RSi in the lower reaches of Min River was 6.89mg/L and 7.66 mg/L,respectively,and the contents of dry season were higher than those in wet season.Contrary to RSi,the content of PSi increased gradually to the Min River estuary.In the wet season of the lower reaches of Min River,the content of the silicon was all falling in the order:DSi>BSi>LSi,while during the dry season,the PSi accounted for a large proportion of the total silicon.(4)The average monthly transported fluxes of DSi,BSi and LSi in the surface water of the lower Min River were 3.97×10~4t/month,1.70×10~4t/month and 2.83×10~4t/month,respectively.The average annual transported fluxes of RSi was(474.09±9.90)×10~3t/a,respectively.Under the influence of runoff,the silicon flux of the lower reaches of Min River in wet season is greater than that in dry season,the DSi flux is greater than that of PSi,and the RSi flux is greater than that of LSi..