[Distribution Characteristics and Influencing Factors of Nitrate Pollution in Shallow Groundwater of Liujiang Basin]

Taking the nitrate in shallow groundwater of Liujiang basin as the research object, a total of 215 groups of shallow groundwater samples were collected during the wet period in July 2014 and the drought period in April 2015 on the basis of groundwater pollution investigation. The characteristics of spatial and temporal variability and the account of nitrate pollution were analyzed based on the model of semivariogram, the geostatistics of ArcGIS and factor analysis, respectively. The results showed that the study region in the southeast was the main nitrate-polluted area, with concentrations of up to 30-120 mg · L⁻¹, in both wet and drought periods, while the nitrate-contaminated area in drought period was about 1. 4 times higher than that in wet period. The spatial distribution of nitrate was primarily influenced by human activities and the geological conditions, and secondarily by Eh, DO, pH and landform conditions. The nitrate concentration was less than 20 mg · L⁻¹ in north. Pollution in local middle area was rather serious, due to human activities and the loss of nitrogen fertilizer in agricultural cultivation; the area to the south, which was confined by impervious boundary, was seriously contaminated, as indicated by the nitrate accumulation effects.