Distributions of heavy metal(Pb,Cr,Cu,Ni,Mn,and Zn)speciation in surface sediment of the Wei he River(Xianyang Section)were studied by using the modified four step sequential extraction(BCR method).Results show that Cr,Ni,and Zn mainly occurred as residual fraction,which were 97.91%,66.36%,and 73.68%,respectively.Pb and Mn indicated some bioavailability and potential ecological risks because the extraction of acid was 27.66%and 38.49%for Pb and Mn.The total"labile"f ractio natio next racted for heavy metals was highest in the upper confluence of Fenghe River and Weihe River,then higher in the third bridge of Weihe River,and the lowest in the downstream confluence of Fenghe River and Weihe River.