【作者】 李红；

【导师】 辛卓航；

【作者基本信息】 大连理工大学 ， 水利工程（专业学位）， 2022， 硕士

【摘要】 流域强人类活动增加了点源和面源污染输入,影响了营养盐、重金属等物质的产出和输移过程,自然水体经流域、河口入海,给海洋生态环境也带来了严重的威胁。污染物在流域-近海河口中的分布输移和治理调控等已成为国家新时期陆海统筹生态环境保护的重要任务,这其中,污染物在河流和近海河口的分布和协同演变关系是制定近海环境污染物管控的重点内容。基于此,本文选择辽河流域的大辽河-双台子河-辽河口为研究区域,选取河流-近海河口28个代表性点位(河流18个,河口10个),以沉积物中As、Cu、Pb、Cd、Cr、Zn、Mn、Ni常规重金属为代表性污染物,在2019年9月、2020年6月、2021年4月开展调查分析,以揭示丰、平、枯水期沉积物中重金属的时空分布特征;基于此,量化评估河流、河口不同重金属元素的生态风险与污染程度,进一步解析人为要素对沉积物重金属分布的影响,以期为流域-近海河口的生态环境治理与保护提供科技支撑。主要的研究成果如下:(1)沉积物重金属时空分布特征。沉积物中重金属Cu、Pb、Zn的含量在三个观测水文期均未有超标点位,而重金属Ni在各时期超标现象均较严重,多集中在大辽河与河口。其他指标在不同水文条件下的超标情况有所差异:在丰水期Cd存在超标点位,在平水期与枯水期As、Cr与Mn均存在超标点位,在枯水期Cr有27个采样点位存在超标现象。丰水期重金属As、Cd、Cr、Ni在近海区含量较高,重金属Cu、Pb、Zn在双台子河含量较高;平水期重金属As、Cu、Pb、Cd、Zn、Mn、Ni在大辽河含量较高,重金属Cr在近海区含量较高;枯水期重金属As、Cd在近海区含量较高,Cu、Pb、Cr、Zn、Mn、Ni在大辽河含量较高。各重金属含量在枯水期高于平水期,且均高于丰水期。(2)沉积物重金属生态风险和污染程度量化分析。基于单因子污染指数的评估结果表明,Ni在丰水期呈现重度污染水平,Cr在枯水期呈现中度污染水平,此外,各沉积物重金属在三个水文期的所有采样点均处于无污染水平;基于内梅罗指数的评价结果表明,丰水期各点位处于IV级中度污染水平,平水期和枯水期各点位则处于II级警戒水平;基于地质累积指数的评价结果表明,枯水期Cr的指数均值处于II级未污染-中度污染状态,丰水期、平水期Ni污染较严重;基于污染负荷指数和潜在生态风险指数的评价结果表明,三个水文条件下所有点位均处在未污染状态,且处于轻微风险水平。(3)沉积物重金属污染来源分析。基于相关性分析和聚类分析,明晰Cu、Zn、Mn来源于同一污染源;通过对比人类活动与重金属分布特征,明晰城镇化水平与流域重金属As含量呈现出相关性,As、Cu、Mn含量与第三产业发展相关,Cu、Cd、Zn与工业发展水平相关;农业化肥施用是Cd、Cr、Pb等重要来源,农药使用是Cu、Pb的重要来源;此外,交通发展,城镇、水田等土地利用类型也是影响重金属含量的因素。综上,本文在大辽河-双台子河-辽河口区域开展了沉积物重金属分布、评价及影响因素分析的系统研究,将为流域-近海河口连续体的生态环境保护、生态环境风险管控提供基础信息和科学参考。更多还原

【Abstract】 Strong human activities in the river basin have increased the input of point source and nonpoint source pollution,affecting the output and transport process of nutrients,heavy metals and other substances.Natural water bodies enter the sea through the river basin and estuaries,which also poses a serious threat to the marine ecological environment.The distribution,transport,control and regulation of pollutants in the river basin offshore estuaries have become an important task for the country to coordinate the land and sea ecological environment protection in the new era.Among them,the land sea distribution and coevolution relationship of pollutants is the key content of formulating the management and control of pollutants in the offshore environment.At present,there is a lack of systematic research,which has brought great uncertainty to the offshore environmental governance.Based on this,this paper selects the Daliao River Basin,Shuangtaizi River Basin,Offshore Coastal-estuary area as the study area,selects 28 representative points(18 in the land and 10 in the sea)from the river mainstream and coastal estuary,and takes the conventional heavy metals As,Cu,Pb,Cd,Cr,Zn,Mn and Ni in the sediments as representative pollutants.The investigation and analysis will be carried out in September 2019,June 2020 and April 2021 to reveal that spatial and temporal distribution characteristics of heavy metals in sediments during wet,normal and dry season and their coevolution in river basin and offshore estuary;Based on this,the ecological risk and pollution degree of different heavy metals in rivers and estuaries are assessed,and the impact of human factors on the distribution of heavy metals in sediments is further analyzed,so as to provide scientific and technological support for the ecological environment treatment and protection of river basins and offshore estuaries.The main research results are as follows:(1)Spatial and temporal distribution characteristics of heavy metals in sediments.The contents of heavy metals Cu,Pb and Zn in sediments did not exceed the standard in the three observed hydrological periods,while the heavy metal Ni exceeded the standard seriously in each period,mostly concentrated in the Daliao River Basin.The exceedance of other indicators under different hydrological conditions is different: there are exceedance points for Cd in high water period,as,Cr and Mn in normal water period and low water period,and there are 27 sampling points for Cr in low water period.In the wet season,the contents of heavy metals As,Cd Cr and Ni are higher in the offshore area,and the contents of heavy metals Cu,Pb and Zn are higher in the Shuangtaizi River Basin;In normal season,the contents of heavy metals As,Cu,Pb,Cd,Zn,Mn and Ni in Daliao River Basin are higher,and the contents of heavy metal Cr in offshore area are higher;In the dry season,the contents of heavy metals As and Cd are higher in the offshore area,and the contents of Cu,Pb,Cr,Zn,Mn and Ni are higher in the Daliao River.The content of heavy metals in the samples collected in the dry season is higher than that in the normal season,and higher than that in the wet season.(2)Quantitative analysis on ecological risk and pollution degree of heavy metals in sediments.The assessment results based on the single factor pollution index show that Ni presents a heavy pollution level in the wet season and Cr presents a moderate pollution level in the dry season.In addition,all sampling points of heavy metals in the sediments in the three hydrological periods are at a pollution-free level;The evaluation results based on Nemero index show that each point is at level IV moderate pollution level in wet season,while each point is at level II warning level in normal and dry seasons;The evaluation results based on geological accumulation index show that the average value of Cr index in dry season is in level II unpolluted-moderately polluted state,and Ni pollution is more serious in wet season and normal season;The evaluation results based on pollution load index and potential ecological risk index show that all the points are in a non-polluted state and at a slight risk level under the three hydrological conditions.(3)Source analysis of heavy metal pollution in sediments.Based on correlation analysis and cluster analysis,it is clear that Cu,Zn and Mn come from the same pollution source;By comparing the distribution characteristics of human activities and heavy metals,it is clear that the urbanization level is related to the content of heavy metals As in the watershed,the content of As,Cu,Mn is related to the development of the tertiary industry,and Cu,CD,Zn is related to the level of industrial development;The application of agricultural chemical fertilizers is an important source of Cd,Cr,Pb,and the use of pesticides is an important source of Cu and Pb;In addition,traffic development,land use types such as towns and paddy fields are also factors affecting the content of heavy metals.更多还原