【作者】 欧冬妮；

【导师】 刘敏； 许世远；

【作者基本信息】 华东师范大学 ， 自然地理学， 2004， 硕士

【摘要】 河口滨岸潮滩是一个典型的海陆交互作用地带，是一个多功能的复杂生态系统，具有独特的生态价值和资源潜力。由于受海陆交互作用的影响，河口滨岸潮滩环境中的各种物理、化学和生物因子复杂多变，具有径流、波浪和潮流等水动力作用强烈、泥沙运移和物质交换频繁、理化要素梯度变化大、生物多样性丰富等独特的环境特征，其中，由潮汐作用引起的滩面周期性的淹没与暴露过程显得尤为特别。本文以长江口滨岸潮滩为典型对象，研究营养元素磷在上覆水体、沉积物及其孔隙水中的时空分布规律，分析不同形态磷在潮滩大型植物根际环境中富集、迁移的生物地球化学过程及主要控制因素，并采用野外采样与室内模拟相结合的方式，研究了“干湿交替”模式下，系统中磷的迁移过程与转移机理。 对长江口潮滩沉积物中磷的赋存形态进行了深入研究，发现输入源差异和水动力条件是影响潮滩沉积物中TP时空变异的主要因素。在沉积物-水界面物理化学因子的控制下，各形态磷之间进行着一定的相互转化，然而，受沿岸各类污染源输入的复合影响，磷在沉积物中的分配平衡遭到破坏。沉积物中Fe-P的沿程分布与长江口近岸水体盐度的分布模式相吻合，认为长江口区确实存在“盐度效应”影响营养盐磷的环境地球化学行为；相反，由于潮滩周期性的淹没和暴露，沉积物的颗粒组成与晶体结构发生变化，使不同地貌单元中沉积物磷的分布受“粒径效应”的影响程度明显减弱；此外，还发现沉积物中活性铁的存在也对磷在界面间的迁移转化产生作用。引入生物有效性概念，在长江口潮滩表层沉积物各形态磷定量分析的基础上，估算出长江口潮滩潜在地能够被生物所利用的磷约占TP的32.75％。 对长江口潮滩生长植物的表层沉积物（SP）与根际沉积物（S_R）中磷的赋存形态进行对比，发现S_R中各形态磷之间、不同物化因子之间的相互关系较S_P弱，表明了磷循环中植物根际效应的存在；同时，作为评价沉积物质量重要指标之一的Fe-P并未表现出在污染严重地区S_R中的富集，显示了植物根际对污染物的降解能力，同时也体现了植物根系的吸收作用。另一方面，以活性Fe³⁺和活性Fe²⁺之间比值的相对大小来表征潮滩植物根际环境的氧化还原状态，结果显示长江口潮滩大多数岸段根际沉积物的Fe3+用矛十值小于1，表明潮滩植物根际环境趋于还原一弱氧化状态，与实际测得的氧化还原电位基本吻合。在这个还原一弱氧化状态下，Fe一P所包含的磷酸盐与孔隙水中的磷酸盐发生交换，使沉积物（孔隙水）和上覆水体之间建立了一种联系，并因此影响了磷酸盐的生物有效性;而org一P在SP和SR间的分配则与磷的吸收和再矿化有关，且可通过食物链构成一套生物小循环。 对长江口潮滩柱样沉积物的研究发现，沉积物形态磷、活性铁、有机质、含水量、粒度之间表现出相当复杂的相互关系，明显地反映了在潮滩干湿交替的物理格架下，沉积物组成、含水量等物化参数对磷、铁和有机质在沉积过程中的地球化学“活性”的重要性。通过对潮滩典型柱样沉积物不同磷形态沉积速率差的估算，发现存在两种机制使磷滞留于潮滩沉积物中:一为有氧一缺氧层边界，FeOOH与活性磷酸盐的多价态鳌合，二为沉积过程中，CFAP十Ca一P的形成。建立了早期成岩作用下沉积物孔隙水中磷酸盐的“扩散一平流一反应”模型，认为在长江口滨岸带有机磷分解、磷酸盐的吸附和沉淀都符合一级动力学特征，它们控制了孔隙水中磷酸盐的转移反应。 利用实验模拟技术，以长江口崇明东滩自然状态下、经过不同程度暴露的沉积物为对象，研究了海水再浸没时，长江口滨岸潮滩环境系统内磷的迁移、转化过程，发现不同程度的暴露将使沉积物的物理、化学性质和微生物的活动习性发生改变，影响沉积物的释磷量，控制着系统内的长期磷平衡。在对暴露程度不同的沉积物磷的吸附动力学研究中发现，长时间暴露于空气中的沉积物，受氧化作用和铁的熟化过程的影响，表现出对磷的弱亲和力，反映在被潮水浸没的过程中吸附容量的减少。检验了不同化学物质对处于“干湿交替”模式下的沉积物释放磷酸盐的影响程度，推断出发生在沉积物中不同细菌过程的重要性，特别研究了不同沉积物在不同环境中释放磷酸盐的差异，认为厌氧环境下沉积物释放磷酸盐的能力要高于有氧环境。更多还原

【Abstract】 The estuarine and coastal tidal flat, as a typical transitional zone between land and ocean, is a multifunctional and complex ecosystem with special ecological values and potential resources. Due to the interaction of land and ocean, the estuarine and coastal tidal flat is characterized by intense hydrodynamic conditions, frequent sediment transport and material exchange, steep physiochemical gradients and high biodiversity, especially the periodical change process of "exposure-immersion" in the tidal flat that is raised by tidal ebb and flood. Taking the Yangtze estuarine and coastal ecosystem as an example, the temporal and spatial distribution of phosphorus in the overlying water columns, sediments and its pore waters have been discussed, and the biogeochemical processes of phosphorus speciation in the rhizospheres of macrophytes involving accumulation and transfer, and its key effects have been analyzed. Meanwhile, the transfer processes and transformation mechanisms under the "exposure-immersion" pattern have also been discussed through the field sampling and the laboratory simulation.The results had shown that the different input sources and the hydrodynamic conditions were the main factors controlling the spatio-temporal variations of total phosphorus. By the controls of physico-chemical parameters, there were inter-transformations among the different forms of phosphorous near the sediment-water interface. However, there was an unbalance of sedimentary phosphorus distribution due to the impact of various pollutants input. The coastal distribution of Fe-P in the sediments was similar to the distributional pattern of salinity in the overlying waters, which indicated that salinity could influence the biogeochemical behaviors of phosphorus. On the contrary, the influence of grain size was relatively weak because the particle compositions and crystal structures of sediments had been changed by periodical "exposure-immersion" in the tidal flat. In addition, the reactive iron also affected the transfer and transformation of phosphorus in the sediment-water interface. Based on the quantitative analysis for the contents ofphosphorus species, the potentially bioavailable phosphorus was assessed by introducing the notion of bioavailability. The assessed results showed that about 32.75% of total phosphorus could be utilized by organisms.By comparison of phosphorus species in the sediments where had plats(Sp) with them in the rhizospheric sediments(SR), the relationships among different forms of phosphorus in SR was weaker than that in Sp, which demonstrated the rhizospheric effects on phosphorus cycle, as well as the relationships among physico-chemical parameters. Moreover, Fe-P in SR, as one of indicators for sediment quality, could not accumulate in the severe polluted areas, maybe indicating that the root system was able to degrade the pollutants and had uptake ability. On the other hand, Fe3+ to Fe2+ ratios which was used to represent the redox status suggested that the rhizosphere of tidal flat was under the reduction-less oxidation status, which was almost equal to the measured redox potentials. In this redox status, the phosphate adsorbed by iron oxyhydroxides could exchange with anther phosphate in the pore waters, which built a good relationship between sediments (pore waters) and overlying waters, and influence the bioavailability of phosphate. As for Org-P, the distribution between Sp and SR was controlled by phosphorus assimilation and remineralization, which constructed a biological cycle through food chain.There were quite intricate relationships among sedimentary phosphorus, reactive iron, organic matters, water contents and grain sizes of core sediments, which indicated that the physico-chemical parameters were important for phosphorus, iron and organic matters to enhance their activities in the process of sedimentation. Through the assessment of difference in accumulation rates between surficial and deep sediments, two retention mechanisms of phosphorus were discovered. One was the sequestr更多还原