文摘
Little information about the nitrogen (N) deposition in the lower Liaohe River Plain (LRP) of Northeast China was available. A continuous 5-year observation (from 2004 to 2008) was conducted to determine the nitrogen deposition in precipitation collected by a standard rain gage, and then we assessed its ecological consequences. The mean inorganic nitrogen concentrations were 1.82 mg N L−1 for NH4+–N and 0.89 mg N L−1 for NO3−–N. On an annual basis, the averaged amounts of N deposition were 14.5 kg N ha−1 year−1, which were much lower than that of hotspots in China. However, the amount of deposited N should still be taken account into the N fertilizer management of the agroecosystems. Compared with the critical loads (CL) of N deposition, the deposited N would likely threaten the natural ecosystems in LRP. The N concentrations in rainwater and the amount of N deposition showed a clear seasonal pattern, and precipitation played an important role in regulating the N concentration. Furthermore, the seasonal fluctuation of NH4+/NO3− ratio reflected that the deposited N originated from both fertilizer application and fossil fuel combustion, and environmental factor (soil temperature, lightning and sunshine) might also contribute to the seasonal cycles of NH4+/NO3− ratio. The high annual NH4+/NO3− ratio (2.05) compared with the more developed region suggested that N deposition in this region was mostly affected by agricultural activities rather than industrial activities.