胶州湾大沽河口潮滩重金属分布机理室内模拟实验研究

发布时间：2018-01-12 14:24

  本文关键词：胶州湾大沽河口潮滩重金属分布机理室内模拟实验研究　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

  更多相关文章： 河口 重金属 铁 铬 Zeta电位

【摘要】：胶州湾属半封闭海湾,有相对独立的自然条件。大沽河为胶州湾最大河流,其河口属于封闭程度较高的海湾河口潮间带类型,是开展潮间带调查的理想场所。本文通过相关性分析得出:Fe是影响河口潮滩重金属分布的最主要因素,并选择与Fe相关性最高的重金属Cr共同作为研究对象。通过实验室模拟实验,探究在pH和盐度显著变化的河口地区Fe对于Cr分布的影响;并辅以XRD、SEM-EDS、XPS的表征手段,为河口区沉积物重金属分布影响机理提供科学依据。得出如下结论:(1)由于pH增大和盐度提高,进入河口地区的铁会发生水解,并完全生成氢氧化铁;Fe的水解速率随pH的增大而增大,而受盐度的影响不大。(2)河口区近河水端向近海水端过渡,pH从弱酸性向弱碱性过渡,氢氧化铁对于铬的去除率随pH增大而减小;这是由pH改变氢氧化铁的Zeta电位引起的。(3)河口区近河水端向近海水端过渡,盐度由0变化到30的过程中,氢氧化铁对铬的去除率先降低后增加。由于Na+进入氢氧化铁胶体滑动面使Zeta电位升高,胶体稳定性提高,因胶体聚沉卷吸过程被去除的Cr减少,同时Cl-与CrO42-/HCrO4-形成竞争吸附,因而盐度为10组的Cr去除率仅不到10%。(4)河口区生成的氢氧化铁会经历絮体生成,絮体生长以及絮体变小三个阶段,盐度越大,生成絮体的速度越快,粒径越大,絮体之间的结合更紧密越不容易进入絮体变小阶段,且絮体变小后的颗粒粒径越大,分布越均匀。(5)Cr(Ⅵ)通过静电引力吸附到氢氧化铁絮体表面,Cr(Ⅲ)通过卷吸进入絮体内部和共沉淀在絮体表面被去除,卷吸进絮体内部的铬会因絮体变小释放出来,不易生成Fe-Cr氧化物或氢氧化物。
[Abstract]:Jiaozhou Bay is a semi-closed bay with relatively independent natural conditions. The Dagu River is the largest river in Jiaozhou Bay, and its estuary belongs to the intertidal zone type of estuary with higher closure degree. It is an ideal place to carry out intertidal investigation. Through the correlation analysis, it is concluded that: Fe is the most important factor affecting the distribution of heavy metals in estuarine tidal flat. The heavy metal Cr which has the highest correlation with Fe was chosen as the research object. The effects of Fe on the distribution of Cr in estuaries where pH and salinity changed significantly were investigated by laboratory simulation experiments. With the help of XRDX SEM-EDSU XPS, this paper provides a scientific basis for the distribution mechanism of heavy metals in sediment in the estuary. The conclusion is as follows: (1) because of the increase of pH and salinity. Iron entering the estuary area will hydrolyze and form iron hydroxide completely. The hydrolysis rate of Fe increases with the increase of pH, but is not affected by salinity. The removal rate of chromium from ferric hydroxide decreases with the increase of pH. This is caused by the change of Zeta potential of ferric hydroxide in the estuary. The transition from the end of the river to the near end of the sea water and the change of salinity from 0 to 30. The removal of chromium by ferric hydroxide firstly decreased and then increased. Because Na entered the sliding surface of ferric hydroxide colloid, the potential of Zeta increased, the stability of colloid increased, and the Cr removed by colloid entrainment process decreased. At the same time, Cl- and CrO42--HCrO4- form competitive adsorption, so the Cr removal rate of 10 groups of salinity is less than 10%) the ferric hydroxide formed in the estuary will undergo floc formation. In the three stages of floc growth and flocs becoming smaller, the higher the salinity, the faster the speed of floc formation, the larger the particle size, the closer the combination between the floc is, the less easy it is to enter the floc becoming smaller stage. The larger the particle size of the flocs is, the more uniform the particle size is, and the more uniform the particle size is, the more uniform the particle size is. The surface of Fe (OH) _ 3 floc is adsorbed by electrostatic gravity. The Cr (鈪，

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