9Ramos L,Hernqndex L M,Gonzalez M J. Sequential fractionation of copper,lead, cadmium and zinc in soils from or near Donana National Park . J. Environ. Qual. 1994, 23:50 ~ 57.
10Lena Q Ma, Gade N Rao. Chemical fractionation of cadmium, copper, nickel, and zinc in contaminated soils. J. Environ.Qual. , 1997, 26:259-264.
