4VRBA J, ZAPOROZEC A. Guidebook on mapping groundwater vulnerability[ M]. Hanover: Heise, 1994:131.
5National Research Council (U. S. ). Ground water vulnerability assessment-predicting relative contamination potential under conditions of uncertainty [ M ]. Washington D. C. : National Academy Press, 1993:204.
6ALLER L, BENNET T, LEHR J H, et al. A standardized system for evaluating ground water pollution potential using hydro geological settings [ M ]. Oklahoma: U. S. Environmental Protection Agency, 1987.