乐安河流域入鄱阳湖营养盐通量及溯源分析

Estimation of Nutrient Fluxes of Le’an River Watershed into Poyang Lake and Traceability Analysis

该文选取鄱阳湖典型入湖河流乐安河为研究对象,构建SWAT模型模拟了流域1990-2020年入湖营养盐通量。基于子流域营养损失状况对入湖TN和TP通量进行溯源分析,确定主要贡献区域和排放源。结果表明,入湖营养盐通量存在明显年际变化,分别在1995年和2011年达到峰值(TN:31.22 Gg;TP:7.75 Gg)和谷值(TN:5.90 Gg;TP:1.62 Gg)。下游区域TN和TP损失强度明显高于中上游区域,其中子流域15、22和23为高损失强度区域。溯源分析发现,流域下游为入湖营养盐主要贡献区域且越靠近流域出口贡献权重越高。河口断面TN和TP主要来源区域均为子流域13、22和27,且耕地和森林为非点源营养损失的主要排放源。

Le’an River,a typical stream flowing into Poyang Lake,was selected as the study object in this paper,and the SWAT model was constructed to simulate the nutrient fluxes into the lake from the River watershed during the period of 1990-2020.Based on the sub-catchment nutrient loss,traceability analysis of TN and TP fluxes into the Lake was conducted to identify the main contributing areas and discharge sources.As a result,the study showed that there was significant inter-annual variation of nutrient fluxes to the Lake,the nutrient flux used to reach the peak(TN:31.22 Gg;TP:7.75 Gg)in 1995,while dipped into the trough(TN:5.90 Gg;TP:1.62 Gg)in 2011.The intensity of TN and TP losses in the downstream area of the River watershed was markedly higher than that in the mid/upstream areas,where the sub-catchments 15,22 and 23 were the areas where the intensity had been much more lost.Additionally,the traceability analysis revealed that the downstream of the watershed was the major contributor region of nutrients flowing into the Lake and the closer to the outlet of the River,the higher the weight of nutrients contribution;and the main source regions of TN and TP in the estuary cross-section were subcatchments 13,22 and 27,and the arable land and wood land were the dominant emission sources in terms of the nonpoint source nutrient loss.