| Land use is one of the most important factors that determine the occurrence and pattern of non-point source pollution. This study selected 15 catchments of Hujiashan watershed to examine the effect of land use on non-point source pollution. Land uses of these 15 catchments were classified from Resources Satellite No.2 images. The total nitrogen and nitrate content of discharge were monitored from Jan.to Dec.of 2008. The relations between nitrogen export and land use were analyzed using the hydrological modeling and spatial analysis extensions of ArcGIS 9.2. The results showed that dry land and residential area exported significant amount of nitrogen, whilst forest and grassland could be considered as nitrogen sinks. Land use was a controlling factor that determined the amount of nitrogen export, although the effects varied with time. Annually, dry land was the top nitrogen producer. However, seasonally, top producers were dry land, residential, residential and dry land in spring, summer, autumn and winter, respectively. Rainfall, temperature and human activity are also important for influencing the nitrogen export. |
