2014—2019年青铜峡灌区入黄干沟水质时空分布及污染源解析

SPATIOTEMPORAL DISTRIBUTIONS OF WATER QUALITY OF DRAINAGE DITCHES AND ITS POLLUTION SOURCE ANALYSIS FROM 2014 TO 2019 IN QINGTONGXIA IRRIGATION DISTRICT

关键词:  水质  输出系数法  时空分布  污染源解析  青铜峡灌区

Key words:  water quality  export coefficient method  spatiotemporal distribution  pollution source analysis  Qingtongxia irrigation district

摘要:

目的 为了解黄河中上游青铜峡灌区入黄干沟水质时空变化特征，揭示典型污染物来源及空间分布。方法 文章针对2014—2019年灌区12条入黄干沟水体中总磷（TP）、氨氮（NH₃-N）、化学需氧量（COD）与高锰酸盐指数（COD_Mn）浓度的时空变化规律进行探究，并采用输出系数法揭示灌区污染物来源。结果 （1）时间尺度上，研究期间入黄干沟整体水质为Ⅳ至劣V类，氨氮和总磷浓度超标严重，受灌溉影响，污染物浓度在非灌溉期高于灌溉期；（2）空间分布上，12条干沟的污染物浓度沿黄河水流方向呈现出先降低后升高再降低的趋势，银古公路桥附近的银新干沟、中干沟、永二干沟污染较为严重（劣V类）；（3）污染物来源上，灌区总磷入河负荷主要来自面源污染（占比86.7%），集中在青铜峡市、贺兰县与平罗县，氨氮入河负荷主要来自点源污染（占比66.8%），COD入河负荷点源和面源分别占比48.1%和51.9%，集中在银川市区和利通区。结论 青铜峡灌区入黄干沟治理应重点关注银新干沟、中干沟和永二干沟，严格控制冬季点源排放是灌区干沟水质提升的关键，种植源污染防控优先考虑青铜峡市、贺兰与平罗县，畜禽养殖源污染防控优先考虑利通区，城镇生活源污染防控优先考虑银川市区。

Abstract:

To understand the spatiotemporal variation characteristics of water quality of the main drainage ditches in the Qingtongxia Irrigation district in the middle and upper reaches of the Yellow River, and reveal the pollution sources and spatial distribution of typical pollutants. The spatiotemporal distributions of total phosphorus (TP), ammonia nitrogen (NH₃-N), chemical oxygen demand (COD) and permanganate index (COD_Mn) concentrations in the 12 main drainage ditch of irrigation district from 2014 to 2019 were explored. The pollution sources and its spatial distribution in the region of drainage ditches were revealed by the output coefficient method. The results were showed as follows. (1) The overall water quality of the drainage ditches in the irrigation district was the surface water quality grade Ⅳ standard and some even worse than the grade Ⅴ during study period. The concentrations of ammonia nitrogen and total phosphorus exceeded the standard seriously. The concentration of pollutants in the non-irrigation period was significantly higher than the irrigation period. (2) On the spatial scale, the water quality of drainage ditch along the direction of the Yellow River first decreased, then increased and then decreased. The water quality of Yinxin ditch, Zhong ditch and Yonger ditch near Yingu Bridge was worse than the grade Ⅴ standard. (3) On the source of pollutants, the total phosphorus load into the river in the study area mainly came from non-point source pollution (86.7%) and concentrated in Qingtongxia, Helan county and Pingluo county, while the ammonia nitrogen load mainly came from point source pollution (66.8%). COD load into the river was concentrated in Yinchuan city and Litong district and from point source and non-point source accounting for 48.1% and 51.9%, respectively. Therefore, the study area should focus on Yinxin ditch, Zhong ditch and Yonger ditch in drainage ditch control. Strictly controlling of point source discharge in winter is the key to improving the water quality of main ditches in irrigation areas. Qingtongxia, Helan and Pingluo cities are given priority in the planting source pollution prevention and control, while Litong district is given priority in the livestock and poultry breeding source pollution prevention and control. Yinchuan city is given priority in the urban living source pollution prevention and control.