颤蚓生物扰动对水—沉积物界面附近理化特征的影响

发布时间：2018-03-26 04:43

本文选题：生物扰动　切入点：颤蚓　出处：《吉林大学》2016年博士论文

【摘要】：沉积物是自然水体的重要组成部分,水-沉积物界面附近的物理化学特征变化会对水体环境质量、营养组成以及环境污染物的迁移转化过程等方面产生显著的影响。在水-沉积物界面生活着数量巨大的水体底栖生物,它们的摄食、排泄、筑穴和呼吸等生命活动,会直接或间接地对水-沉积物界面附近的理化特征以及污染物的环境行为产生影响。因此,生物扰动是影响自然水-沉积物体系和其中污染物的环境行为的重要因素。正因为如此,生物扰动作用受到广泛的关注,在水体污染物、水环境营养组成、沉积物生物地球化学特征和水生生态系统等多方面的科学研究工作中,生物扰动都被视为重要的研究对象。在自然淡水水体当中,寡毛纲底栖生物颤蚓的生物扰动具有很强的代表性,颤蚓在全球范围内分布非常广泛,虽然生物个体较小,但生物密度较高。在相对平静的水体环境中,如湖泊、水库、池塘以及水流较缓的河流等,颤蚓生物扰动作用对水体的理化特征和污染物的环境行为会产生不可忽视的影响。目前,颤蚓生物扰动对水体中部分污染物迁移转化过程的影响已经基本明确,但作用机制尚未清楚。因此,本论文以颤蚓作为扰动生物,从以下几方面内容进行研究。为了研究颤蚓扰动对沉积物内部物理结构的影响,研究了在颤蚓存在的条件下,沉积物孔穴和孔隙结构的变化规律。在实验室内建立微宇宙模拟实验体系,在保持沉积物的完整性不受到破坏的前提下,利用X射线连续断层扫描(CT)技术和数码图像技术,研究颤蚓孔穴和沉积物内部较大孔隙结构的分布和变化特征;通过添加人工污染沉积物,研究在重金属污染的沉积物体系中,沉积物孔穴和孔隙的变化情况。结果表明,沉积物孔穴和孔隙结构的截面积所占沉积物断层面积的比例,会随颤蚓扰动时间的延长而增加,同时孔穴和孔隙结构也随着生物密度的增大而增加。不同深度范围内沉积物中的孔穴和孔隙分布同样与颤蚓的扰动时间密切相关:在颤蚓扰动初期0-10 mm深度范围内的孔隙比例较高,0-30 mm范围内孔穴较多,在11-19 d时30-60 mm深度范围内孔穴和孔隙都有明显增加;且孔隙分布与颤蚓孔穴的分布密切相关。颤蚓扰动还使沉积物的氧化带厚度增加。在颤蚓扰动体系中,受到重金属污染沉积物的氧化带厚度减小,颤蚓孔穴结构的截面积减小,但孔隙截面积增加。在Cu、Cd和Pb单一重金属污染物当中,Cu对颤蚓生物扰动体系中孔穴和孔隙的影响最强,三种重金属联合污染的影响大于单一重金属污染。为了研究颤蚓对水-沉积物体系中物质交换作用的影响,通过对分层填加含有Ba SO4标记物的沉积物进行CT扫描,研究了不同深度范围的沉积物颗粒在颤蚓扰动作用下的迁移规律;通过在指定深度添加重金属污染沉积物层,研究颤蚓对重金属污染物在沉积物内部迁移作用的影响。实验结果表明,颤蚓扰动使沉积物内部的颗粒物发生迁移,特别是使20-50 mm深度范围内的沉积物颗粒向上迁移,并不断沉积于水-沉积物界面附近,原有的水-沉积物界面在这种沉积作用下向下迁移,出现在20-50 mm深度范围,从而使沉积物颗粒在一定深度范围内持续循环。在含有重金属Pb和Cd污染的沉积物中,颤蚓的扰动在促进沉积物表层的污染物向上覆水释放的同时,会使Pb和Cd随沉积物颗粒一起向沉积物内部迁移。在颤蚓扰动下,20-50 mm深度范围的重金属污染向沉积物表层迁移。在单位时间内,重金属污染物的迁移量会随颤蚓扰动强度的增大而增加,但两者并不存在明显的比例关系。为了探究颤蚓对水-沉积物体系化学成分的影响,以颤蚓孔穴为中心,研究孔穴附近微环境的部分化学特征指标的分布和变化规律。通过室内模拟实验,使用剖面微电极工作系统,研究了颤蚓孔穴附近微环境的p H、DO和氧化还原电位值,在水平和垂直方向上的分布和变化规律。研究结果表明,上覆水和沉积物的p H会随时间的延长,呈现出先升高再降低随后趋于稳定的变化趋势,而在颤蚓扰动下,p H的降低会出现滞后性。在水平方向上,颤蚓扰动使沉积物表面的p H以颤蚓孔穴为中心出现下降(最多达0.3 p H单位),这种下降作用可影响孔穴周围半径1 mm的范围。扰动时间相同时,颤蚓孔穴处的p H在垂直方向上变化较小。在无颤蚓的体系中,上覆水的DO浓度和氧化还原电位值变化较小,但沉积物DO浓度和氧化还原电位值均随时间的延长而逐渐降低。颤蚓扰动降低了上覆水DO浓度和氧化还原电位值,但且使颤蚓孔穴附近沉积物表面DO浓度和氧化还原电位的升高,与无颤蚓的体系相比,颤蚓孔穴附近DO浓度可升高9.2-17.0μmol/L。同时,颤蚓增加了DO在沉积物中的渗透深度,使最大渗透深度从3 mm增加到5 mm。颤蚓孔穴附近沉积物的氧化还原电位与DO浓度的变化规律相似。因此,沉积物中颤蚓的存在可通过改变上覆水和沉积物微环境的p H、DO和氧化还原电位的分布特征,进而影响水-沉积物界面附近污染物的环境行为。为了了解颤蚓扰动的生物化学作用,研究了颤蚓产生的溶解性有机物(DOM)溶液对重金属污染在沉积物上吸附作用的影响。在室内对颤蚓生物样品进行培养,获取其产生的DOM溶液样品,测量其TOC含量,并采用紫外-可见吸收、三维荧光和同步荧光光谱技术,对不同培养时间的DOM溶液进行表征。在具有颤蚓DOM溶液的条件下,进行Pb和Cd在沉积物中的吸附动力学和吸附热力学实验。研究结果表明,颤蚓产生的DOM中很可能含有色氨酸和酪氨酸结构,且DOM中色氨酸和酪氨酸结构会随培养时间的延长而增加。颤蚓产生的DOM抑制了沉积物颗粒对重金属Pb和Cd的吸附作用,并且对Pb的抑制作用更加明显。
[Abstract]:Sediment is an important part of natural water, water physical and chemical characteristics of sediments near the interface will change on water quality of the environment, have a significant effect of nutrition composition and environmental pollutants migration and transformation process. A large number of water benthic organisms living in the water sediment interface, their feeding, excretion, and nest breathing and other life activities, environmental behavior will influence directly or indirectly on the physicochemical characteristics of water sediment near the interface and pollutants. Therefore, biological disturbance is an important factor affecting the natural water sediment system and the pollutant environmental behavior. Because of this, bioturbation is widely concerned in water pollution water environment, nutrition, scientific research work on sediment biogeochemistry characteristics and aquatic ecosystems, biological disturbances are considered As an important research object. In natural freshwater bodies, Oligochaeta benthic tubifex bioturbation strongrepresentative, tubifex is widely distributed in the global scope, although individual small, but the biological density is higher. In the water environment is relatively calm, such as lakes, reservoirs, ponds and water a gentle River, the environmental behavior of Tubificid bioturbation on water physicochemical characteristics and pollutant effects will influence can not be ignored. At present, tubifex bioturbation effects on the part of the process of migration and transformation of pollutants in water has been basically clear, but the mechanism is not clear. Therefore, this paper takes t.tubifex as a biological disturbance, are studied from the following aspects. In order to study the effect of disturbance on t.tubifex physical structure of sediments, studied in tubifex under the condition of the existence of cavities and pore structure change of sediment The establishment of simulation experiment system of law. The micro universe in the laboratory, in the premise of maintaining the integrity of the sediment not damaged, using X ray continuous tomography (CT) technology and digital image technology, the characteristics of distribution and variation of t.tubifex cavities and internal pore structure of large sediment; by adding artificial contaminated sediments, research in the pollution of heavy metals in sediment systems, changes of sediment and pore cavity. The results showed that the cross-sectional area of the cavity and the sediment pore structure for sediment fault area ratio, with the extension of Tubificid bioturbation increasing time. At the same time, aperture and pore structure also increases with increasing the density of biological cavities and pore distribution of sediment. Different depth in the same time is closely associated with the disturbance of tubifex tubifex: perturbation in the initial pore ratio within the depth of 0-10 mm high 0-30 M The range of M cavity more, at 11-19 D and 30-60 mm within the depth of cavities and pore has increased significantly; and the distribution of pore distribution and t.tubifex cavities are closely related. The sediment disturbance t.tubifex oxidation zone thickness increases. In t.tubifex disturbed system, by oxidation of heavy metal pollution of sediments decreases with the thickness of the cross-sectional area, t.tubifex cavity structure decreases, but the pore area increased. In Cu, Cd and Pb single heavy metal pollutants, the influence of Cu on tubifex bioturbation cavities and pore system in the strongest effect of three kinds of heavy metal combined pollution is greater than that of single heavy metal pollution. In order to study the influence of water sediment t.tubifex material in the system of exchange, CT scan through the sediments on layered filling containing Ba SO4 markers, the study of sediment particles in different depth of the disturbance migration under the action of tubifex; by referring to Add depth heavy metal contaminated sediment layer, effects of tubifex on migration of heavy metal pollutants in the sediments inside. The experimental results show that the sediment particles of Tubificid bioturbation internal changes, especially the sediment particles within the depth of 20-50 mm upward migration, and continuous deposition in the vicinity of the sediment water interface, the original the water sediment interface in the sedimentation of downward migration, appeared in 20-50 mm depth, so that the sediment particles in continuous circulation in a certain depth range. In sediments containing heavy metals Pb and Cd pollution, t.tubifex disturbance released to the overlying water and surface sediments of the pollutants in the promotion, will make Pb and Cd together with sediment particles to the sediment internal migration. In t.tubifex perturbations, the migration of heavy metal pollution in the depth of 20-50 mm to the sediment surface. In the unit time, weight The migration amount of metal contaminants will increase with the strength of Tubificid bioturbation increased, but the two are not obvious. In order to explore the relationship between the proportion of t.tubifex impact on water sediment system of chemical composition, the tubifex hole as the center, distribution and variation of some chemical indexes of cavities near the micro environment. Through indoor simulation experiments using microelectrode system profile, studied the micro environment near t.tubifex hole DO and P H, redox potential, distribution and variation in horizontal and vertical direction. The results show that the overlying water and sediments of P H with time, showing the first increase and then decrease then tends to be stable, while in tubifex disturbance, decrease P H will appear lag. In the horizontal direction, the disturbance of the sediment surface tubifex tubifex in P H as the center hole decreased (up to 0.3 p This decline, H units) effect can influence surrounding the hole radius is 1 mm. The disturbance at the same time, the P H t.tubifex hole changes in the vertical direction is smaller. In the absence of t.tubifex system, DO concentration and oxidation reduction potential of overlying water changed little, but the sediment concentration and oxidation of DO the reduction potential gradually decreased with time. T.tubifex disturbance reduced the DO concentration of the overlying water and the redox potential values, but make t.tubifex hole sediment near the surface DO concentration and redox potential increased, compared with no tubifex tubifex system, cavity near the DO concentration can be increased by 9.2-17.0 mol/L. at the same time, tubifex increased the permeability of DO in sediment in depth, variation of the maximum penetration depth increased from 3 mm to 5 mm. tubifex hole near the oxidation reduction potential and DO sediment concentration is similar. Therefore, the sediment of tubifex in there by The change of overlying water and sediment micro environment of P H, DO and redox potential distribution, thereby affecting the environmental behavior of the water sediment interface near the pollutants. In order to understand the biochemical effects of tubifex tubifex disturbance, dissolved the organic matter (DOM) on the effect of solution on the adsorption of heavy metal pollution in sediment. In the interior of t.tubifex biological samples were cultured to obtain DOM solution samples from the measurement of the content of TOC, and UV Vis absorption, fluorescence and synchronous fluorescence spectroscopy, DOM solution of different culture time were characterized. With tubifex DOM solution under the condition of adsorption kinetics and thermodynamics experiments of Pb and Cd in sediments. The results show that t.tubifex produces a DOM may contain tryptophan and tyrosine, tryptophan and tyrosine and DOM structure with culture The DOM produced by the vermis inhibited the adsorption of sediment particles on heavy metal Pb and Cd, and the inhibition of Pb was more obvious.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X174;X52

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