Monitoring and Loading Estimation on Non-point Sources Nitrogen Pollution of Crop Production
|School||Chinese Academy of Environmental Science|
|Keywords||Crop Production Non-point Sotlrces Nitrogell Pollution Morlitoringtechnologies of Non-point sources pollution Isotope Tracing Loading Estimation|
Non-point source nitrogen pollution of crop production monitoring technology is an important way to estimate the total amount of non-point sources nitrogen pollution and research on the mechanism and characteristics of crop production pollution. This technology is not only built through research and analysis about the process of Non-point source nitrogen pollution of crop production, but also combined the classic field investigation. Focusing on that nitrogen retarded in crop production field and dissolved non-point source nitrogen pollution in water, pollution loading estimation method were proposed and applied to the Ashi River Basin.This thesis has achieved the following results:(1) Formation processes and pollution characteristics of non-point source nitrogen pollution were analyzed, through basic data collection, summary and research, monitoring method on non-point source pollution of crop production was established. It is mainly focusing on monitor index selection, analytical method, monitor point setting method and monitor frequency. Meanwhile, non-point source pollution isotope analytic detection technology is applied in order to achieve monitoring the system:non-point source pollution origin-migration and transformation-into water.(2) We monitored basin non-point source nitrogen pollution through Ashi River Basin. According to the investigation, measuring and the formation characteristics of river runoff, we investigated the characteristic and source of basin nitrogen pollution during normal water period, rich water period and low water period, respectively. The results show that the total nitrogen concentration is higher than ammonia-nitrogen concentration in Ashi River Basin. The ammonia-nitrogen concentration kept in III level in most area except the area that affected by agricultural and industrial production.The amount of sampling point for III level ammonia-nitrogen concentration raised by the water decreasing. We obtained that upstream of river possessed better water quality and worse in middle and down stream by analyzing the general index value from Ashi River Basin source to the downstream.(3)Combined with15N isotope tracer technique, we analyzed the origin of basin nitrogen pollution. Among them, the planting of non-point source nitrogen pollution as the main sources of pollution areas are mainly distributed in the middle and lower reaches, soil organic nitrogen pollution mainly caused by artificial fertilizers and farm recession, and high correlation with the land use types. In wet period, non-point source nitrogen pollution to planting the area of the main sources of pollution more, the upper reaches of artificial fertilizers as the main sources of pollution, mainly the middle and lower reaches of erosion by rain and irrigation planting area soil and the formation of soil organic nitrogen sources. There are some areas as artificial fertilizers as the major sources of nitrogen pollution in the dry season, mainly due to the rainy season, artificial fertilizers, nitrate infiltration into the ground, when the dry season, underground runoff rivers, nitrate retention in the river caused by pollution.(4) We obtained that the TN content of topsoil possessed the highest volume after crop harvest, the content of TN during growing period of plants had less and during thesowing time it drop button, this results were received by monitoring the nitrogen content in soil of12typical planting area in Ashi River Basin during sowing time, growing period and after crop harvest, which was1.36×106t,1.37×106t and1.59×106t. The conclusion proved that nitrogen content of topsoil in Ashi River Basin is closed related to fertilization for plants.(5)According to the monitor dissolved and adsorbed nitrogen content results of typical planting area of Ashi River Basin basin and experimental site rainfall, we calculated the export coefficient of non-point source nitrogen pollution of crop production is2.96t/km2-a, then the output load was achieved by using export coefficient method:4847.26t/a, amount into river was2210.52t/a, which account for54.01%to the whole non-point source nitrogen pollution in Ashi River Basin. The middle and lower reaches of Ashi River Basin possess higher output load.