摘要
Nitrogen pollution in the shallow groundwater in Changxing county of the Taihu basin was investigated.A total of 43 groundwater samples were collected and their ammonia,nitrate and nitrite concentrations were analyzed.The results show that 13.95%,16.27%,and 16.27% of ammonia,nitrate and nitrite concentrations exceeded the standard.Nitrate pollution is serious in the agricultural areas near Jiapu,Xiaopu,Hongqiao and Hongxingqiao towns among which the Hongxingqiao town is the most serious with the maximum value of nitrate of 22 mg/L.A geostatistic method was used to quantify the spatial variation and correlation of the ammonia,nitrate and nitrite concentrations based on 43 groundwater samples.The result show that the spatial pattern of the nitrate-and nitrite-nitrogen concentration data can be described with a spherical model while that of the ammonia concentrations with a Gaussian model.The correlation distances of the ammonia-nitrogen,nitrate-nitrogen,nitrite-nitrogen concentrations were 9.98,1.51 and 3.82km,respectively.The results also show that nitrate-nitrogen concentrations in groundwater in this region were positively correlated to the rate of fertilizer application.The average of the groundwater nitrate-nitrogen concentrations is 6.7 mg/L in the areas where the annual fertilizer application was 300 kg/hm2(N) and 2.2 mg/L in the area where the annual fertilizer application was 100 kg/hm2(N);Groundwater nitrate-nitrogen concentrations were related to the depth to the water table: the shallower the water table,the higher the nitrate-nitrogen concentrations.Groundwater nitrate-nitrogen concentrations were also positively correlated to population density when the land use types are similar.