| Agricultural non-point source pollution?ANPS?plays an important role in water eutrophication and quality deterioration,has been hot issues,many domestic and international scholars paid attention to it.The processes of phosphorus migration and transformation have been not yet made clear and were complex because of unique hydrogeological structure in karstic basin.To clarify the pollution process of phosphorus from ANPS in karstic basin,we studied on the karst agricultural watershed in Guiyang county,Guizhou province,southwest China.The ?18O and ?D values of waters,the concentration of TP and TDP in surface water and underground water were detected in normal season and dry season,respectively.The pH,organic matter,exchangeable acid,total phosphorus,Olsen-p,Al-P,Fe-P,O-P,Ca-P contend of soil were measured,at the same time,TDP/TP of Soil exudate and water around soil profile were tested.The variation features of TP and TDP and relation of different water were discussed,the processes of phosphorus migration and transformation in soil profile were analyzed.Different waters in basin were mainly supplied by local atmospheric precipitation,the variation d-excess was small,which illustrated single vapor source in the basin.Temporally,the ?18O and ?D values of waters were higher in normal season than dry season.Spatially,the ?18O and ?D values of underground water were higher in northwest of study area than south,which of moon lake was higher than Huaxin reservoir.The hydrogen and oxygen isotopic values of surface water and groundwater were in good consistency,and there was a strong hydraulic relationship between them.Land use type had an impact on hydrogen and oxygen isotopic values of waters,the hydrogen and oxygen isotopic values of waters around paddy field were higher than dryland and forest.The TP concentration of surface water and underground water were 0.087 mg·L-1 and 0.067 mg·L-1,and TDP concentration were 0.029 mg·L-1 and 0.022 mg·L-1 in normal season,the TP concentration of surface water and underground water were 0.032 mg·L-1 and 0.025 mg·L-1,and TDP concentration were 0.018 mg·L-1 and 0.019 mg·L-1 in dry season.The TP and TDP concentration of surface water and groundwater were almost the same,there was a certain hydraulic relationship between them.The proportion of Particulate P was about 60%,output form was Particulate P.The soil in the study area was acidic,and exchangeable H+content was the main cause of soil acidification.TP,Olsen-P and Al-P mainly existed in topsoil?0?30cm?,and it is difficult to migrate in soil depth below 30cm,O-P and Ca-P were winding change along the depth in vertical direction.O-P was the main form for inorganic phosphorus in A1,B1,C1 and C2 soil profile.In B2 soil profile,Fe-P was the main form in soil depth ranging from 0 to 30 cm,however,O-P was the main form within the range of 0 to 30cm.Fe-P was the main form in B3,B4,C2 and C3 soil profile.Organic phosphorus was main form for total phosphorus in soil profile except C1 soil profile,inorganic phosphorus was main form within the range of 20 to 60cm in C1 soil profile.Phosphorus transform from Al-P and Fe-P to O-P and Ca-P with soil depth gradients.pH and Olsen-P/Fe-P/Al-P showed strongly negative correlation,organic matter and TP,Olsen-P/Fe-P/Al-P showed strongly positive correlation,soil Olsen-P/Fe-P/Al-P content would been increased by adjust the value of pH and organic matter.The water quality of Huaxin river watershed was ? water body,the soil with better viscosity can protect phosphorus from riparian zone migrating reservoir,because of adsorption.TDP/TP of Soil exudate which include S2 and S3 was 14.56%and 9.02%respectively,indicating the ratio of particulate P was very high. |
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