Estimation of the nonpoint source nitrogen load in a strongly disturbed watershed of the North China Plain.

Identification of nonpoint source (NPS) pollution is a great challenge in the North China Plain, which has modified rivers and insufficient data. In this study, a simple and reasonable method was developed to estimate the total nitrogen (TN) load in rural areas of the North China Plain. The method was found to work well and produce results consistent with monitoring data when considering various TN sources and transfer mechanisms. The annual TN loads from rural living, livestock and the farmlands were 121.9 × 10(3), 45.6 × 10(3) and 78.5 × 10(3) kg/yr, respectively. The TN load in the region along the river contributed much more to the NPS pollution than that in areas far from the river, with average TN loads of approximately 3394 and 602 kg km(-2) yr(-1), respectively. Overall, the results indicate that this method is suitable for NPS load estimates in severely disturbed watersheds with insufficient data.