【作者】 薛红喜；

【导师】 何江；

【作者基本信息】 内蒙古大学 ， 生态学， 2007， 博士

【摘要】 黄河包头段水体集高含沙水流水质环境和工业污染于一体，拥有宏大的沉积物群体比表面与周围水介质构成的微界面体系，具有独特的水动力学过程，同时包头市的工业污水排放使黄河包头段重金属污染严重。开展黄河包头段重金属在水-沉积物界面的吸附机制及其在环境中的时空分布、迁移转化和污染迭加等研究具有典型性和代表性。本研究以环境地球化学、生物地球化学、污染生态学及现代沉积学的理论和方法为指导，注重环境污染载体有关信息的综合获取及时空变化规律的对比，以重金属的地球化学特性及其吸附机制为主线，深入开展了黄河包头段沉积物粒径和水体常见离子对重金属吸附的影响、重金属间的竞争吸附及矿物组成对重金属形态分布的影响等一系列重金属吸附解吸机制研究，探讨了黄河包头段重金属的时空分布、迁移转化、污染迭加等动态过程；首次开展了黄河包头段天然鱼群及沿岸植物对重金属富集能力的研究，为重金属生物有效性、生物地球化学循环及生态风险评价积累了基础数据。本研究取得了如下主要成果和进展。1．推导了不同粒级沉积物的表面分形分维计算公式，计算了不同粒级沉积物的表面分形分维值、黄河包头段沉积物整体的表面分形分维值（1.91）和＜63μm沉积物的表面分形分维值（1.36）；获得了Cu＞Pb＞Zn≈Cd的粒径对四种重金属吸附影响程度的序列，Cu、Pb在大粒径颗粒物中的平衡吸附量有一定的升高，Zn、Cd则随粒径增大，平衡吸附量减小：分形校正吸附模型较Freundlich和Langmuir吸附模型对重金属在不同粒径沉积物中的吸附具有更好的适用性。2．不同浓度范围的Na⁺、K⁺、Mg²⁺、Ca²⁺、Cl^-、SO₄^2-等离子对重金属吸附作用的影响机制不同。因离子强度增大而引起的重金属离子活度减小或双电层压缩作用和结构或物理化学性质相似的环境阳离子与重金属间的竞争作用及环境阴离子与重金属的络合作用等均可引起溶液内重金属吸附与解吸平衡的移动。3．重金属离子间竞争吸附存在于重金属离子浓度的各个阶段，无论吸附反应体系是否达到饱和吸附。竞争吸附不是简单的以占据吸附点位形式存在的“零和效应”过程，重金属浓度不同，相互间竞争吸附的主导机制也不同。此外，据竞争吸附实验得出了Pb²⁺＞Cu²⁺＞Zn²⁺≥Cd²⁺的水-沉积物环境中重金属离子间竞争吸附能力的一般序列。4．伊利石和绿泥石是黄河包头段颗粒物中携带重金属的主要粘土矿物，同时该两种矿物对重金属次生相的形态分布也具有重要影响；碳酸钙（方解石）则通过对水环境CO₃^2-浓度的调节，间接影响重金属的形态分布及其运移能力；石英、正长石、斜长石及钠闪石等对可交换态重金属影响较大。5．黄河沉积物在不同水期所起的源／汇功能与强度不同。因枯水期和平水期利于悬浮物的沉积和重金属在水-沉积物微界面的吸附，沉积物对重金属具有汇的功能；而丰水期由于黄河流量和含沙量增大，对底层沉积物的冲刷作用较强，使其发生再悬浮，导致吸附在沉积物中的重金属重新释放进入上覆水体，形成二次污染，对上覆水体中的重金属起到源的作用。各水期沉积物对重金属的富集能力排序为，枯水期＞平水期＞丰水期。6．首次开展了黄河包头段天然鱼群及沿岸植物对重金属富集能力研究，为重金属的生物有效性、生物地球化学循环及生态风险评价奠定了基础并积累了第一手资料。研究揭示，沿岸植物和天然鱼群对重金属的富集能力具有元素差异性、点位差异性、物种差异性、营养部位差异性及鱼龄差异性。更多还原

【Abstract】 The Yellow River contains large amounts of sands, resulting in a peculiarhydraulic condition which is characterized by a magnificent interface between theparticulates and water. In addition, Baotou section of the Yellow River suffers fromsevere heavy metal pollution receiving the industrial discharges from the Baotou city.Therefore, this study was carried out on Baotou section of the Yellow River based onits representativeness on the mechanism of heavy metal adsorption on water-sedimentinterface, and on the heavy metal spatial distribution, mobilization, transformation,and accumulation effects in sediments.Because of their persistence in the environment, heavy metals often pose threatsto aquatic lives and plants in the environment. Based on the theories and methods ofenvironmental geochemistry, biogeochemistry, pollution ecology and modernsedimentology, the adsorption mechanisms and the geochemistry characters of theheavy metals in Baotou section of the Yellow River are researched in this paper. Tosay concretely, the adsorption-desorption mechanisms of the selected heavy metalsonto the sediments in the Yellow River are studied, which includes the impacts of thegrain sizes of the sediments and the usual ions in aquatic environment on theadsorption of the selected heavy metals, the competitive adsorption of the selectedheavy metals and the impact of the mineral composition of the sediments on thespecies distribution of the heavy metals. Meanwhile, spatial distribution, mobilization,transformation, and accumulation effects of the selected heavy metals in Baotousection of the Yellow River are discussed. In addition, it can be worth notice that the biological enrichment of heavy metals in coastal plants and natural fishes in Baotousection of the Yellow River is also analyzed for the first time, which may providevaluable database for the studies of biological availability, biogeochemical cycle andecological risk assessment of heavy metals in Baotou section of the Yellow River.The results are described as follows:1. The expression of surface fractal dimension （SFD） for size fractions of theYellow River sediment was deduced. Based on the expression, the SFD value ofdifferent size fractions of the sediment was calculated. The SFD value of thesediment in the Baotou section of the Yellow River is 1.91, and the SFD value of thesediment smaller than 63μm is 1.36. The variation extents of equilibrium adsorptioncapacity influenced by different grain size are ranked as Cu＞Pb＞Zn≈Cd. The Cu andPb present higher adsorption capacity at relatively large grain sizes; whereas, for Znand Cd, the adsorption capacity decreases with increasing grain size. The modifiedfractal model, Freundlich model and Langmuir model are used in this study, and themodified fractal model is found to fit the data of heavy metal （Cu, Pb, Zn and Cd）adsorption well compared to Freundlich model and Langmuir model.2. The heavy metals in the water system are affected by usual ions (such as Na⁺,K⁺, Mg²⁺, Ca²⁺, Cl^- and SO₄^2-) through different adsorption and desorptionmechanisms, which is caused by different dominant mechanism in different usual ionconcentration ranges. According to the results of the experiments, with the increasingof the ionic strength of the additional ions in the solutions, the adsorption capacitiesof the heavy metals increase when the compression of the electric double layerdominates on sediment-water interface, whereas decrease when the ionic activities ofthe heavy metals dominate; there is competitive adsorption between the heavy metalsand the additional cations when the structures or physicochemical properties of theadditional cations are similar to the heavy metals’; the complexations between theanions and the heavy metals lead to decrease of ionic activities and the valence statesof the heavy metals, and have influence on physical adsorption of the heavy metalswhich is caused by electrostatic attraction. 3. The competitive adsorption exists in different concentrations of heavy metalsolution and is not simply as occupying adsorption sites. The competitive adsorptionmechanisms are different in different concentration gradient of heavy metaladsorption reaction systems. And the competitive adsorption abilities of heavy metalson sediment-water interface in Baotou section of the Yellow River are ranked as:pb²⁺＞Cu²⁺＞Zn²⁺≥Cd²⁺.4. The illite and chlorite which are important minerals of carrying the heavymetals via particulates in Baotou section of the Yellow River have significantinfluence on species distribution of the heavy metals in secondary phase. And theregulation effect of calcium carbonate （calcite） on the concentration of CO₃^2- hasindirect influence on the species distributions of the heavy metals in sediment inaquatic environment, and further impact on the mobility of the heavy metals withother minerals. Furthermore, the quartz, orthoclase, plagioclase and riebeckite havesignificant influence on exchangeable form of the heavy metals.5. The sediments in the Yellow River have different functions as sink or source indifferent periods. The sediments can function as sink in low-water period andmedium water period, in which it is propitious of suspended matter deposition inwater system and heavy metal adsorption on sediment-water interface; whereas it canfunction as source in high-water period, in which the heavy metals adsorbed bysurface sediments would be transferred into the water phase again, then cause thesecondary pollution. The enrichment abilities of heavy metals in different periods areranked as: low-water period＞medium water period＞high-water period.6. The concentrating abilities of coastal plants and natural fishes to heavy metalsin Baotou section of the Yellow River are investigated for the first time. This papernot only lays foundations but also provides valuable firsthand database for the studiesof biological availability, biogeochemical cycle and the ecological risk evaluation.The concentrating abilities of coastal plants differ in different elements, samplingsites, plant species, and different nutritive organs. And the concentrating abilities ofnatural fishes differ in different elements, fish ages, fish species and different nutritive organs.更多还原