基于排水单元的流域农业面源污染时空分异性研究

为了揭示流域内各排水单元农业面源N、P污染的总量和组成特征，揭示各排水单元间农业面源污染的时空变异特征，以湖北四湖流域为例，选取流域内24个排水单元，运用ENVI 4.7和GIS技术提取出研究区土地利用现状，并建立基础数据库，通过对排水单元出水口水体的多时段定点采样测试，分析四湖流域排水单元农业面源污染的时空变化特征。结果表明：各排水单元面源污染空间分布格局总体上呈现上、下区排水单元污染较轻、中区表现严重的态势，这与流域内湿地和旱地等土地利用分布格局有关。在时间变异方面，农业面源年内变异明显，TN、TP在不同季节存在着显著差异，主要表现在冬、春季的浓度明显高于夏、秋季，这与流域内降水和径流的季节性差异有关。

Temporal and Spatial Change of Agricultural Non-point Source Nitrogen and Phosphorus Pollution in Four Lakes Region Based on Drainage Unit in Hubei Province

In order to analyze the amount and form of surface pollution in Four Lakes Region on drainage units in Hubei Province, reveal the temporal and spatial change characteristics of agricultural source nitrogen and phosphorus pollution, Four Lakes Region was selected as the study area, the land use in 24 drainage units selected from the area was classified based on Remote Sense image interpretation of HJ-1AB, water samples taken from the outlet of ditches in 24 drainage units in multi-period. Using GIS as a tool, spatial information was analyzed to demonstrate the temporal and spatial characteristics of nitrogen and phosphorus source pollution of the study area. The results showed that: the water pollution space distribution pattern was general to be good in the upper and lower area drainage unit and bad in the middle, this basin on the land use distribution pattern. In the time variation, there was significant difference of concentration on TN, TP in different seasons, the concentration in winter and spring were higher than in summer and autumn, this concerned with the seasonal difference of rainfall and runoff.