Cu²⁺ Adsorption Characteristics And Electric Charge Oropertv Changes Before And After Removal Of Active Organic Carbon In Vellow-brown Soils

Four yellow-brown soils were graded into particle-size fractions, then an stable organic C andN of the different particles were gained by oxidation of HCl、H₂O₂、NaClO、Na₂S₂O₈. Soilorganic C and N and stable organic C and N were tested to compare the capacity of removingactive organic carbon among the four different approaches. Then The effect of active organiccarbon on Cu adsorption was studied. And then zata potential was test. The major results obtainedwere summarized as follows：1Soil total organic carbon and nitrogen and stable soil organic carbon and nitrogen wereconcentrated on <2μm of soil particles and the amount was generally decreased with the soil depth,mainly in0¹0cm>10²0cm>20³0cm.2After removing active organic carbon by different approaches, the amount of stable organiccarbon was HCl>NaClO>H₂O₂>Na₂S₂O₈. The availability of removing active organic carbon wasNa₂S₂O₈> H₂O₂>NaClO> HCl. The amount of stable organic nitrogen was NaClO <HCl <Na₂S₂O₈<H₂O₂. The availability of removing active organic nitrogen was H₂O₂>Na₂S₂O₈> HCl>NaClO.3After removing active organic carbon by different approaches, the ratial of C/N was NaClO>HCl>原土>H₂O₂>Na₂S₂O₈。The ratial of C/N increased after dealing with NaClO and HClcompared to the original soil, and decreased after dealing with H₂O₂and Na₂S₂O₈. This indicatesthat the removal capacity of organic nitrogen was greater than organic carbon by NaClO and HCl.However, the removal capacity of organic carbon was greater than organic nitrogen by NaClO andHCl.4Before and after removal of active organic carbon, Cu adsorption by yellow brown soil couldbe fit well with both Langmuir and Freundlich equations and reached a significant correlation（p<0.01）. After removing AOC, the maximum adsorption capacity obviously reduced in every layersof yellow brown soil, and was about10%³0%of original soil.5Cu adsorption capacity of active organic carbon was higher than the non-active organiccarbon. The rate of Cu adsorption reduced quickly after removal of active organic carbon.6Removal rate of organic carbon was between30%and75%with HCl acidification inyellow brown soils, and Cu adsorption rate reduced between54%and86%. Before and afterremoval of active organic carbon, the linear correlation was very significant between organiccarbon contents and Cu adsorption capacities. Furthermore, there was an extremely significantlevel between the removal percentages of organic carbon and decrement rate of Cu adsorption inyellow brown soil. 7The amount of organic carbon in yellow brown soil was sand<original soil<silt<clay, andbetween them the difference was extremely significant. It was significantly positively relatedbetween soil organic carbon content and clay content. Cu adsorption capacity increased with theparticles becoming thin, sand<original soil<silt<clay, and Cu adsorption capacity reached aextremely significant correlation （p<0.01） between clay and silt, and reached a significantcorrelation （p<0.05） between sand and original soil, and it was not significant between silt andoriginal soil.8From the parameters Q （maximum adsorption capacity） of the Langmuir adsorption equationand the K （adsorption capacity） of Freundlich equation, garden soil> forest soil> paddy soil>upland.9The linear correlation was very significant between organic carbon contents and Cuadsorption capacities in yellow brown soil. The linear coefficients were upland （R²=0.9792）>garden soil （R²=0.9549）> paddy soil（R²=0.8472）> forest soil（R²=0.7694）. Cu adsorption capacitygradually increased with organic carbon content increasing in yellow brown soil.10Colloidal particles surface potential was-5mv^-35mv in yellow brown original soil.Colloidal particles surface potential increased at pH2⁴and reduced at pH4¹0after removal ofactive organic carbon, range of-5mv^-50mv. However, Colloidal particles surface potentialreduced at pH2¹0after Cu adsorption, range of-5mv^-50mv.11The range of variation of the amount of variable charge of four differentuse of theyellow-brown: garden soil0³0cmol kg^-1, woodland soil0⁴5cmol kg^-1, paddy soil0⁴4cmolkg^-1,dry cropland soil0⁴1cmol kg^-1.Soil surface charge volume increased after organic matterwas removed or copper was adsorpted.Variable amount of charge （Qv） is dependent on the pH ofsoil suspensions, the3-point model applies to describing the relationship between the amountof variable charge soils with pH changes. the pK（i）shows the strong regularity.pK1ranges from3.5to4.7, pK2ranges from6.1to7.3pK3ranges from9.3to9.8.When pH ranges from3to8.5,Qv1and Qv2accounted for the major part of the surface charge, and Qv3will play a major role inthe higher pH value.