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Organic colloids can enhance the movement of strongly sorbing contaminants,a phenomenon called colloid-facilitated contaminant transport.Organic colloids may interact with the original soil colloids,enhance or inhibit the colloid facilitated transfer of heavy metals in different regional soil.It is our scope to show that the information obtained for Cu and Zn vertical mobility in silty sandy loam acid soil(in Guizhou province,N25°30′E105°0)and Ca-dominant silty clay alkalinity soil(in Shandong province,N37°8′E115°53′)affected by pH and water-dispersible organic colloids from swine manure.Swine manure were sequentially centrifuged to obtained 0.45-10 μm organic colloid sample.We used a glass chromatography column 2.6 cm in diameter and 10 cm long.Eight columns were filled with 40 g of both soils in duplicate.Columns were saturated from below with the distilled water to prevent air inclusion,using a peristaltic pump to control the steady state upward flow.After saturation and 48 h incubation,the flow direction was changed into downwards.The top of the column was connected via a tube to the influent solution.The influent solution was prepared with 150 mg/L organic colloids and 10 mg/L Cu and Zn at pH 4.5 and pH 6.5 condition individually.The influent solution without organic colloids was used in contrast test.A fraction collector was used to collect the effluent samples of about 25 mL.Besides total Cu and Zn,we measured soluble and colloidal Cu and Zn,the EC,pH and turbidity in the effluent.Some effluent samples was also selected to measured the size distribution.And Synchrotron radiation X-ray fluorescence spectrum(SRXRF)was used to analyze the trace metals in effluent colloids.The result showed that the transport of Cu and Zn could not be affected by the organic colloids in acid condition.However,in neutral pH condition,the water-dispersible organic colloids can facilitated the transport of heavy metals in the higher pH condition.The concentration of metals in effluent was positively correlated to the content of colloids.Fifty percent of Cu was found transport as colloidal combination,while Zn was mainly transport as dissolved.In Ca-dominant alkalinity soil,Cu probably transport as organic colloidal-complex,carbonate or hydroxide precipitate.And Zn seemed to react with Fe-and Mn-oxides or mineral,and then co-transport through soil.The colloid facilitated transport of heavy metals might be affected by the dynamic adsorption of colloids on metals,chemical disturbance of soil solution,physicochemical characteristics of soil matrix and the nature of heavy metals.With high affinity for metals and facilitated transport,organic colloids might provide significant risks for groundwater contamination in areas receiving heavy application of agriculture solid wastes amendment.This research was supported by Zhejiang Provincial Natural Science Foundation of China under Grant No.LQ13B070003 and the National Natural Science Foundation of China No.40771101.