Assessment and validation of groundwater vulnerability to nitrate in porous aquifers based on a DRASTIC method modified by projection pursuit dynamic clustering model.

The groundwater vulnerability assessment has been identified as an important tool of groundwater pollution prevention. In this study, the DRASTIC method was modified to estimate the groundwater vulnerability of porous aquifers to nitrate. The parameter system was optimized by replacing the original parameters of aquifer media, soil media, impact of the vadose zone and hydraulic conductivity with quantitative parameters of aquifer thickness, nitrate attenuation intensity, hydraulic resistance and groundwater velocity and adding pollutant input intensity to develop the DRANTHVP method. In addition, the rating scale of the DRASTIC method was revised, and the weight and influence degree of each parameter were determined using the projection pursuit dynamic clustering (PPDC) model. The DRANTHVP method was applied to the plain area of western Jilin Province, and the vulnerability index map of groundwater to nitrate pollution was established. The DRANTHVP method improved the correlation coefficient between vulnerability index and nitrate concentration to 0.720, which was more than three times that of the original DRASTIC method. And the high variance of the (ANOVA) F statistic indicated that there was less overlap between the nitrate values in different vulnerability classes. Furthermore, the DRANTHVP method produced a more uniform distribution of vulnerability classes. In short, the DRANTHVP method using the PPDC model was suitable to assess the groundwater vulnerability of porous aquifers to nitrate in the study area. Hence, the mapping of groundwater vulnerability to nitrate can provide a scientific and reasonable basis for the formulation of groundwater resource protection plan.