干旱区生态环境知识资源中心

Pollutants released to the land surface have to pass through the unsaturated zone (UNZ) before entering the ground-water system. This paper carried out the groundwater nitrate pollution through isotope investigation both on groundwater and soils in Shijiazhuang City in China. The results show that nitrate concentrations were higher in areas irrigated with sewage than in non-sewer irrigated areas and in general nitrate concentrations are lower in the northern part of the study area and higher in the southern part of the study area. The groundwater for village water supply has delta(15) N values little higher than those of chemical fertilizer soil and lower than those of manure and sewage irrigated soil. This indicates the nitrogen is mainly from human waste and partly from chemical fertilizer. The natural soil nitrate with low delta(15) N values is not the main cause of nitrate contamination of groundwater in the area.