【作者】 刘俊；

【导师】 田学达；

【作者基本信息】 湘潭大学 ， 环境科学工程， 2019， 硕士

【摘要】 洞庭湖是我国第二大淡水湖泊,位于长江中游段,其水体交换与长江来水具有重要的关联性。由于其地理位置关键性、生态功能及航运等相关社会经济价值,近三十年来,洞庭湖沉积物重金属铜、锌、铅、镉等元素向湖体输入量增加显著,同时相应的风险和毒性水平也持续提高。为反映洞庭湖重营养盐、金属污染水平、空间分布特征以及风险评价等问题,本论文完成了洞庭湖表层沉积物、入湖河流和湖心区沉积柱芯的调查及分析工作,研究结果具体如下:(1)洞庭湖表层沉积物中总有机碳含量均值为13.26 mg/g,总氮含量均值为1046 mg/kg;总磷含量均值为242.19 mg/kg。空间分布总体呈自西向东浓度递减的分布格局。有机指数和有机氮评价洞庭湖沉积物环境状况表明,洞庭湖沉积物存在有机氮污染情况,有机指数评价结果显示所有点位无严重污染,符合或优于尚清洁水平。通过比对污染源同位素特征值得出,土壤有机质是洞庭湖表层沉积物有机质的主要污染源。(2)沉积物中重金属浓度空间分布呈现自西向东递减趋势,重金属元素空间部分特征显示出入湖河流区域浓度高于湖心区。此外,地积累指数法和潜在生态安全指数对洞庭湖沉积物重金属评价结果显示:单一元素污染程度依次为Cd>Cr>Pb>Cu>Zn,单项潜在生态风险程度大小顺序为Cd>Pb>Cu>Cr>Zn,其中Cd对洞庭湖沉积物综合潜在生态风险指数贡献较大,为主要的生态风险贡献因子。(3)湖心区柱状沉积物中,南湖心区和西湖心区沉积物中陆源性有机质输入显著,而东湖心区则为内源性来源。在历史沉积特征上,营养盐历史沉积变化不显著,重金属历史沉积具有明显的增加趋势,有机质与总磷,总氮具有同源性,重金属Cu,Zn,Pb,Cd,Cr均显示出同源特点,且陆源的输入对营养盐和重金属的累积增加具有重要作用。更多还原

【Abstract】 Dongting Lake is the second largest freshwater lake in China.It is located in the middle reaches of the Yangtze River,and its water exchange has an important correlation with the Yangtze River.Due to its geographical location,ecological function,shipping,other related social and economic values.In the past 30 years,the input of heavy metals such as copper,zinc,lead and cadmium into the Dongting Lake,the corresponding risks and toxicityhas increased significantly,and its level also continued to increase.In order to reflect the heavy nutrient salt,metal pollution level,spatial distribution characteristics and risk assessment of Dongting Lake,this paper completed the investigation and analysis of the sediment cores of the Dongting Lake,the sedimentary cores into the lake and the lake center,and the research results are specific.as follows:(1)The average total organic carbon content in the surface sediments of Dongting Lake was 13.26 mg/g,the total nitrogen content was 1046 mg/kg,and the total phosphorus content was 242.19 mg/kg.The spatial distribution generally shows a decreasing distribution from west to east.The organic index and organic nitrogen evaluation of the environmental conditions of the Dongting Lake sediments indicate that organic nitrogen pollution exists in the sediments of Dongting Lake.The organic index evaluation results show that there is no serious pollution at all points,which is consistent with or better than the cleanliness level.It is worthwhile to compare the isotope characteristics of the pollution source.Soil organic matter is the main source of organic matter in the surface sediments of Dongting Lake.(2)The spatial distribution of heavy metal concentration in sediments showed a decreasing trend from west to east.The spatial characteristics of heavy metal elements showed that the concentration of rivers in the lake was higher than that in the lake center.In addition,the results of the evaluation of heavy metals in the Dongting Lake sediment by the cumulative index method and the potential ecological safety index show that the single element pollution degree is Cd> Cr> Pb> Cu> Zn,and the order of single potential ecological risk is Cd> Pb> Cu> Cr> Zn,in which Cd contributes a lot to the comprehensive ecological risk index of Dongting Lake sediments,and is the main ecological risk contribution factor.(3)In the columnar sediments of the lake center,the input of terrigenous organic matter in the sediments of the South lake center and the West lake center is significant,while the East lake center is an endogenous source.In the historical sedimentary characteristics,the historical sedimentary changes of nutrient salts are not significant,and the historical deposition of heavy metals has a significant increasing trend.The organic matter has homology with total phosphorus and total nitrogen.The heavy metals Cu,Zn,Pb,Cd and Cr all show homology.Characteristics,and the input of terrestrial sources plays an important role in the cumulative increase of nutrients and heavy metals.更多还原