2014—2019年东江干流氮磷通量传输特征与源解析

Temporal and spatial dynamics of nitrogen and phosphorus flux in the Dongjiang River mainstream(2014-2019)

东江是华南地区主要水源地之一,其河流氮、磷通量变化对珠江口富营养化和重要城市供水安全具有重要影响.针对东江干流氮、磷通量的复杂变化及其来源贡献不清问题,基于LOADEST模型对2014—2019年东江干流上下游氮、磷逐日通量进行模拟,结合LAM模型解析氮、磷来源与贡献,评估东江干流氮、磷通量的时空演变规律及其多尺度污染源结构特征.结果表明:①2014—2019年东江氮、磷年均通量分别为1890 kg·km^(-2)和77 kg·km^(-2),位居国内外主要江河的高位;②东江氮、磷通量从上游到下游呈指数增长趋势,氮、磷通量的时间累积关系呈凸弧曲线,具有显著的瞬时高通量特征;③东江干流的氮、磷输入以非点源为主,76.8%以上的氮和94.7%以上磷来源于非点源,虽然汛期和非汛期有所差异,但非点源是东江干流氮、磷的主导来源.

The Dongjiang River,a crucial water source in the southern China,plays a pivotal role in influencing eutrophication of the Pearl River Estuary and ensuring water security for vital urban areas.To study the complex changes in nitrogen and phosphorus flux in the main stream of Dongjiang and the uncertainty about their sources,we employed the LOADEST model to simulate the daily flux of nitrogen and phosphorus in the upstream and downstream of Dongjiang from 2014 to 2019.Additionally,we utilized the LAM model to analyze the sources and contributions,the spatiotemporal evolution patterns,and the multi-scale pollution source characteristics of nitrogen and phosphorus flux in Dongjiang's main stream.Results showed several key insights:①The annual average flux of nitrogen and phosphorus in Dongjiang peaked at 1890 and 77 kg·km^(-2),during 2014 to 2019,which is significantly higher than that of other major rivers in the world.②The flux of nitrogen and phosphorus in Dongjiang exhibited an exponential growth trend from the upstream to the downstream,with a convex curve representing the cumulative relationship between time and flux,characterized by notably high outputs within condensed time frames.③Non-point sources predominantly contributed to the input of nitrogen and phosphorus in the main stream of Dongjiang.over 76.8%of the nitrogen and 94.7%of the phosphorus loading.Although there were differences between the flood season and non-flood season,non-point sources remained the dominant contributors to nitrogen and phosphorus levels in Dongjiang’s main stream.