三峡库区澎溪河重金属迁移转化规律研究

发布时间：2018-01-19 11:16

本文关键词： 澎溪河三峡库区沉积物重金属迁移转化藻类　出处：《重庆交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：重金属污染一直是全世界关注的热点,而河流中大量的重金属排入对水环境造成了严重后果。重金属污染是物无机有毒物质,其难以被降解,还会在生物体内富集,对生物造成持久性影响。因此,研究水体重金属污染特征并评价其对水体的影响程度具有重要意义。本文以澎溪河水体、未淹水沉积物和淹水沉积物为研究对象,测定了其中Fe、Mn、Cr、Pb、Cu、Cd六种重金属的含量分布、形态特征;通过模拟实验研究了水位涨落影响下沉积物重金属的迁移转化规律,以及沉积物中Cd的释放对水体藻类生长情况的影响。研究取得的主要成果如下:①澎溪河枯水期水体中各重金属含量普遍高于平水期和丰水期,且在平水期变化较稳定,总体上重金属含量大小顺序为FeMnCuCrPbCd。六种重金属元素中仅Pb和Cu在枯水期含量分别超过了国家II类水质标准限值和I类水质标准限值。②沉积物中重金属含量大小顺序为FeMnPbCuCrCd,其中Cu的变异系数最大,沿程变化最大,其受到人类活动影响比其它重金属严重。六种重金属中Cr、Pb、Cu主要以残渣态形态存在,对环境危害较小。采用地积累指数法对河流沉积物重金属污染情况的评价结果表明,沉积物受到Cd、Pb和Cu的污染。③水位涨落模拟实验发现,淹水时沉积物中重金属含量大小顺序为FeMnPbCrCuCd,污染程度大小顺序依次为CdPbMnCuCrFe;水位退缩后出露的沉积物中重金属含量大小顺序为FeMnPbCrCuCd,污染程度大小顺序依次为CdPbMnCuCrFe。研究表明,水位退缩后的沉积物中重金属的含量有所降低,而不同元素的形态变化各异,Cr、Pb和Cu在淹水前后重金属形态百分比顺序保持不变。④沉积物中Cd释放模拟实验发现,上覆水中N/P比平均大于100,呈较强富营养条件,磷成为影响藻类生长的限制因子;藻类总数和叶绿素a含量呈先减少后增加的趋势。未进行遮光处理的样本中藻类总数和叶绿素a整体呈下降趋势,这与总磷、总氮浓度变化趋势一致;而遮光样本的藻类很难生长繁殖,因此其氮、磷含量一直呈增长趋势。水体中重金属Cd的含量和藻类总数、叶绿素a的相关分析表明,它们之间存在较弱相关性或者拮抗作用,水体中的Cd促进部分藻类生长。
[Abstract]:Heavy metal pollution has been the focus of attention all over the world, and the discharge of a large number of heavy metals in rivers has caused serious consequences to the water environment. Heavy metal pollution is inorganic toxic substance, which is difficult to be degraded. Therefore, it is important to study the characteristics of heavy metal pollution and evaluate its influence on the water body. The content distribution and morphological characteristics of six heavy metals in unflooded sediments and flooded sediments were determined. The migration and transformation of heavy metals in sediments under the influence of water level fluctuation were studied by simulation experiments. And the effect of CD release from sediment on algae growth in water body. The main results are as follows: 1. The heavy metal content in water during the dry period of Penghuihe River is generally higher than that in the normal and high water periods. And the change is stable in the mean water period. As a whole, the order of heavy metal content is FeMnCuCrPbCd.The contents of Pb and Cu of the six heavy metal elements in the dry season exceed the national water quality standard limit of class II and the water quality standard limit of class I, respectively. The order of heavy metal content in sediment is FeMnPbCuCrCd. Among them, the variation coefficient of Cu is the largest and the variation along the course is the biggest, and the influence of human activities is more serious than that of other heavy metals. The assessment results of heavy metal pollution in river sediment by the method of accumulation index show that the sediment is polluted by CD Pb and Cu in the simulated experiment of water level fluctuation. During flooding, the order of heavy metal content in sediment is FeMnPbCrCuCdd, and the degree of pollution is CdPbMnCuCrFe. The order of heavy metal content in sediment after water level retreat is FeMnPbCrCuCdCdand the degree of pollution is CdPbMnCuCrFe. The contents of heavy metals in sediments after water level receding were decreased, while the morphological changes of different elements were different. The CD release simulation experiments of Pb and Cu in sediments before and after flooding showed that the N / P ratio in overlying water was higher than 100 on average, showing strong eutrophic conditions. Phosphorus is the limiting factor of algae growth. The total number of algae and the content of chlorophyll a decreased first and then increased. The total amount of algae and chlorophyll a in the samples without shading showed a decreasing trend, which was consistent with the change trend of total phosphorus and total nitrogen concentration. However, the algae in shaded samples are difficult to grow and reproduce, so the contents of nitrogen and phosphorus have been increasing. The correlation analysis of heavy metal CD and the total amount of algae, chlorophyll a in water shows. There was a weak correlation or antagonism between them, and CD in water promoted the growth of some algae.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X52

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