【作者】 张媛；

【导师】 罗平平； 孙长顺；

【作者基本信息】 长安大学 ， 环境工程， 2020， 硕士

【摘要】 沣河流域位于陕西省西安市西南部,对渭河水环境及关中区域人民的生产和生活起着非常重要的作用。本文在对沣河水环境背景资料及水污染现状调查的基础上,设立了8个监测断面,监测了15种水质因子。通过分析2018年9月至2019年8月水质数据,探讨了沣河在这一水文年中丰水期、枯水期、平水期的指标化学特征、水质变化规律;采用单因子指数法、内梅罗指数法、模糊综合评价法和灰色关联分析法等方法评价了流域水质类别和污染程度;解析了流域主要污染因子与污染源;分析了流域中下游断面富营养化爆发风险;提出了流域水环境污染防治措施。主要的研究成果有:（1）PO₄-P和NO₂-N对流域水质变化影响很小。N类指标和P类指标相关性较高,对水质变化影响较大。同一时期站点水质污染状况为上游<下游<中游,主要原因是城市化发展与人口密度的影响;按不同水期来看,丰水期污染最轻,平水期次之,枯水期污染最严重,主要原因是低径流的枯水期水体停留时间长,对水体中各种元素有富集作用。（2）综合来看,监测点的污染状况从优到劣依次为沣峪、高冠峪、严家渠、三里桥、秦渡镇、太平峪、沣河口、潏入沣。单因子指数法评价结果为三个水质时期中12.5%的断面水质为IV类水质,87.5%为V类水质;传统的内梅罗指数法评价水质12.5%为IV类和V类水质,87.5%为劣V类水质;传统的模糊综合评价法评价流域V类水比例高达91.8%,这三种方法评价结果都较悲观,主要原因是评价结果很大程度上取决于污染最严重的因子-TN。改进的内梅罗指数法削弱了TN对水质的影响,评价结果显示12.5%为II类和III类水质,54.2%为IV类水质,33.3%为V类水质。灰色关联分析法评价流域I类水质占比75%,V类水质占比25%,与其他方法判定类别不同的主要原因是评价因子标准化处理方式不同。改进的模糊综合评价法结合了层次分析法与熵权法的优点,削弱了TN的影响,均衡了COD_Mn和DO的占比,权重分配更合理,I类水、II类水和III类水占比49.9%,IV、V类水占比50.1%。本研究认为改进的模糊综合评价法评价结论更合理。（3）根据富营养化风险评价,沣河中下游有轻度甚至中度富营氧化的风险,水体中的浮游植物生长很可能受到了N、P,DO和水温的限制。表层水中的N含量与沉积物中的N含量有较强的相关性,主要是由于内源氮对表层水的影响较大。（4）通过污染源分析,流域上游主要污染来源为生活污水和农业污染,中下游主要的污染来源包括生活污染、工业污染和农业污染。流域主要污染要素是TN、NH₃-N和TP。流域水质保护工作的重点方向为控制营养盐污染。为了打造更适宜的人居和水文环境,在进行水环境宣传工作的同时,针对性的污染防控措施包括:养殖业中开发利用绿色饵料和优良苗种进行生态养殖;农业上科学合理施肥,同时进行水土保持工作;工业上以清洁生产、节能减排为主要手段,辅以奖惩、经济扶持,在配套建设污水收集管网的前提下,结合建设湿地工程,防止大规模散排现象的发生。更多还原

【Abstract】 The Fenghe Basin is located in the southwestern of Xi’an City,Shaanxi Province.It plays an important role in the water environment of Weihe Basin and the production and livelihood of the local residents.Based on the investigation of environment background and water pollution status of the Fenghe Basin,8 sections and 15 evaluation indexes were monitored.The chemical characteristics of the indexes,the trends and regulars of the wet season,dry season and normal season in this hydrological year were discussed by analyzing the data from September 2018 to August 2019.The methods such as Single-factor exponential method,Nemerow method,Fuzzy Comprehensive Evaluation（FCE）and Grey Correlation Analysis（GRA）were used to describe the degree of polluted water for each section.They were also performed to analyze main pollution factors and sources.In addition,eutrophication risk analysis was carried out on middle and downstream sections.According to the assessment results and the analysis of its pollution sources,measures to prevent and control water environment pollution in the Fenghe Basin are proposed.The main research results are:（1）The influences of PO₄-P and NO₂-N on the change of water quality were very slight.There was a strong correlation between N and P which have large influence on water quality.The pollution status of the sections during the same period was upstream<downstream<midstream,the section Fengyu in the upstream had the best water quality,while the section Yurufeng in the midstream was polluted seriously.Compared to different water periods,the wet season was least polluted than the normal season,with the dry season was polluted the most serious.（2）Generally speaking,the pollution status of sections from light to heavy were Fengyu,Gaoguanyu,Yanjiaqu,Sanliqiao,Qinduzhen,Taipingyu,Fenghekou,Yurufeng.The Single-factor index method evaluated that 12.5%sections were level IV and 87.5%were level V in Fenghe Basin.The traditional Nemerow method evaluated that 12.5%sections were level IV and V,and 87.5%were inferior level V.The proportion of level V water in the traditional FCE is as high as 91.8%.The evaluation results of these precious three methods are pessimistic,for the reasons of evaluation results depend largely on the most polluted factor-TN.The improved Nemerow method which reduces the effects of TN,evaluated that 12.5%were level II and III,54.2%were level IV,and 33.3%were level V.The GRA evaluated the water quality that 75%were in level I and 25%were in level V.The main difference of this method from others may be the evaluation factors were standardized in different ways.The improved FCE has both advantages of Analytic Hierarchy Process（AHP）and entropy weight method,weaken the influencing factors of TN,balance the proportion of COD_Mn and DO,and make the weight distribution more reasonable.The level I,II and III were accounted for 49.9%,while levels IV and V were accounted for 50.1%.Take the characteristics of these methods into account,the conclusion of this study chose the result of improved FCE.（3）According to the assessment of eutrophication risk,the midstream and downstream of the Fenghe Basin had the risk of mild or even moderate eutrophication.The growth of phytoplankton is likely to be restricted by N,P,DO and water temperature.There was a strong correlation between the N content in surface water and sediment,mainly for the reason of endogenous N has a great influence on the surface water.（4）The main pollution sources in the upstream were domestic sewage and agricultural pollution,while the midstream and downstream included domestic sewage,industrial sewage and agricultural pollution.The main pollution indexes are NH₃-N,TP and TN.The key direction of water quality protection is to control nutrient pollution.To create a more suitable living environment,while carrying out the publicity work about water environment,the targeted pollution prevention and control measures include:the development and use of green bait and excellent seedlings for ecological breeding in the aquaculture industry;applying fertilizer scientifically and rationally in agriculture,carrying out soil and water conservation at the same time;energy conservation and emission reduction are the main means in industry;on the premise of supporting the construction of sewage collection pipe network,combining with the construction of wetland project to prevent the large-scale scattered discharge of sewage.更多还原