[Assessment of groundwater vulnerability to nitrate in He'nan Province of China based on principal component regression].

According to the hydrological and morphological characteristics, He'nan Province was divided into mountainous region and plain region. The level of rich water, infiltration modulus of precipitation, fertilization level per unit area, proportions of vegetable planting area, and soil texture were selected as the common indices, and the slope and groundwater depth were selected as specific indices to assess the groundwater vulnerability to nitrate. Principal component regression analysis was adopted to determine the index weights, and the spatial distribution of groundwater vulnerability to nitrate in He'nan Province was assessed with ArcGIS 9.2. In the Province, the groundwater vulnerability to nitrate was mainly at low and medium level, and the region with this vulnerability level accounted for 68.4% of the total. The high vulnerability region accounted for 19.8%, and the extremely high vulnerability region occupied 11.8%. The main factors affecting the groundwater vulnerability to nitrate in plain region were soil texture, fertilization level, and infiltration modulus of precipitation, while those in mountainous region were fertilization level, soil texture, and slope. This study provided a theoretical basis for reasonable fertilization and agricultural environment management.