Abstract:

Assessment of groundwater vulnerability is a prerequisite to protect groundwater resources. It can provide a reference to city planning and construction and has a strong practical significance. The DRASTIC, which is a commonly used for groundwater vulnerability assessment model, had an extensive application in various countries since it is simple and easy to operate. However, the model just gives an overall consideration of general pollutants, and does not take into account biochemical processes of specific pollutants occurring in the vadose zone. It gets the score based on expert experience, which has a certain shortage. The LPI assessment model, which includes adsorption and biodegradation processes of ammonia and nitrate in the vadose zone, is selected to assess groundwater vulnerability to ammonia and nitrate in Changping area of Beijing. Results show that groundwater vulnerability to ammonia and nitrate has a good distribution trend in this area. From the alluvial fans to the flat plain, groundwater vulnerability enhances gradually. The vulnerability to ammonia is greater than nitrate. Besides, the decrease in groundwater table caused by exploitation lowers groundwater vulnerability. The groundwater vulnerability in 2005 is lower compared with 2009 due to the consistent groundwater exploitation. The assessment result is well consistent with groundwater quality data, indicating that the LPI model can be used for groundwater vulnerability assessment.

Key words:  groundwater vulnerability, ammonia, nitrate, Changping, Beijing