Analysis of spatial variability of nitrate content in groundwater and its factors in Huaitai county in North China plain

584 observed wells were sampled in Huantai County in North China Plain and the NO₃-N content in every phreatic water were measured.The geostatistics and GIS technique are used to analyze the data.The results indicate that NO₃-N concentration shows a lognormal distribution.The Kriging method is used to estimate the unobserved points and the distribution map of NO₃-N concentration is generated.The areas of NO₃-N content in phreatic water for each category are calculated according to the National Quality Standard for Ground Water in every town of Huantai County.The correlative analysis shows that there is a significant correlation between the annual total nitrogen input,wastewater irrigated and NO₃-N concentration in phreatic water.It is showed that the wastewater irrigation contributed much to NO₃-N content in phreatic water and the total nitrogen input should be considered in the region evaluation.