【作者】 侯立军；

【导师】 许世远； 刘敏；

【作者基本信息】 华东师范大学 ， 自然地理学， 2004， 博士

【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。同时，河口滨岸潮滩又是地球表面圈层结构中物质循环最为活跃的区域之一，营养元素的生物地球循环对维持河口生态系统高生产力和高生物量具有极其重要的生态意义。因此，研究这一复杂巨系统内营养盐的迁移转化过程及其影响机制已经成为当前自然地理学和河口近岸环境地球化学等领域内的热点问题之一。 近年来，在国家自然科学基金项目：“长江口滨岸潮滩复杂环境条件下物质循环研究”与“长江口滨岸沉积物-水界面氮磷动态交换机制及环境效应”，以及教育部高等学校骨干教师计划项目“长江口滨岸环境污染物动态交换、模型及环境效应”的资助下，围绕“长江河口滨岸潮滩界面营养盐的环境生物地球化学过程及其生态效应”这一重大科学问题，开展了一系列的研究工作，取得了以下主要认识和研究成果： (1) 长江河口潮滩沉积物有机质中稳定碳、氮同位素具有明显的季节性变化，7月份稳定碳同位素值普遍低于2月份的稳定碳同位素值，其变化范围分别为-29.8‰～-23.7‰和-27.3‰～-25.6‰；7月份和2月份稳定氮同位素分别为1.0‰～5.5‰和1.7‰～7.8‰。研究区域内，稳定碳、氮同位素的地区分布和季节变化特征揭示，有机质中稳定碳、氮同位素组成不仅受陆源和海源有机质输入量之间消长变化的影响，同时一系列的生物地球化学过程、人为有机质的输入和沉积物粒度与叶绿素含量对碳、氮同位素组成均存在一定的改造作用。此外，利用稳定碳同位素质量平衡混合模型，还对陆源有机质输入量的贡献率进行了初步定量估算，结果表明，研究区域内沉积物中有机质的陆源输入量略高于海源输入量，约占有机质总输入量的54.85％，而且有机质的陆源输入也存在明显的时空变化差异，在浒浦与白龙港之间的淡水区域内大部分岸段有机质的陆源输入明显高于海源输入，其中7月份和2月份有机质的陆源输入量分别占总输入量的7:3.670rk和52.45%，反映了洪水季节(7月份)陆源输入占绝对优势，这与长汪径流量和年输沙量的季节分配相吻合;而在朝阳农场与奉新之间的咸水区域内，大部分岸段有机质的陆源输入低于海源输入，其中7月份和2月份有机质的陆源输入量分别占有机质总输入量的40.57%和46.140k。 (2)潮滩沉积物一水界面附近营养盐的时空分布与累积特征揭示了，在理化因子变化剧烈的长江口滨岸潮滩环境系统内，因受长江径流、滨岸带河流及工业废水、生活污水排放的影响，沉积物一水界面附近营养盐的时空分布与累积变化比较复杂。利用潮滩沉积物一水界面间营养盐的浓度梯度，并依据Fick，S第一定律对沉积物的源一汇效应进行了研究和探讨。结果表明，NHn+一N扩散通量的时空分布比较复杂，孔隙水中NH.+一N的再生过程是控制其界面扩散通量的主要因素。在潮滩环境系统内，NH4+一N的界面扩散以负通量为主，即NH4+一N主要由沉积物向l几覆水中扩散，反映了沉积物是上覆水中NH#+一N的重要来源之一。对Nox一N而言，其界面扩散以正通量为主，即Nox一N主要自上覆水向沉积物中扩散，说明沉积物是上覆水中Nox一N的重要蓄积库(汇)，对削减上覆水中高含量的Nox一N具有重要的环境意义。Nox一N界面扩散通量的空间分布显示，在浒浦至石洞口采样岸段，N()户N的界面扩散通量较小，而在吴淞口至芦潮港采样岸段，Nox一N的界面扩散通量普遍较高，并且研究发现上覆水与孔隙水之间的Nox一N浓度梯度是控制N。、一N界面扩散时空变化差异的主要因素。研究区域内，TDP的界面扩散以负通量为主，并且发现潮滩表层孔隙水中TDP含量是影响TDP界面扩散的控制性因素。在淡水区域内，D工P的界面扩散为正通量，而在较高盐度区域内DIP的界面扩散为负通量，其中水体盐度和孔隙水中的DIP含量共同控制着DIP的界面扩散过程。 (3)实验模拟研究了长江河口滨岸潮滩表层沉积物对上覆水体中P叮一P的吸附特征，结果表明沉积物对P043一P的吸附是一个复合动力学过程，可划分为快吸附和慢吸附两个过程，其中快吸附过程主要发生在O一10h内，尔后基本上达到了一种慢吸附的动态平衡过程，在O一0.sh之内沉积物对P叮一P的吸附速率最大，达到10.14一56.40mg·kg一‘.h一‘，且其吸附速率与细颗粒物含量之间存在明显的正相关关系，反映了在快吸附过程中以物理吸附为主。沉积物对P043一P的等温吸附曲线符合Langmuir方程，根据Langmuir等温吸附方程计算，潮滩表层沉积物中P叮一P的吸附容量为26.32一204.08mg/kg，且TOC和F广含量是控制PO43一P吸附容量的主要因素。沉积物对P氏3一P的吸附效率为21 .55一248.30L/kg，并且P叮一P的吸附效率主要取决于沉积物中TOC的含量。此外，研究还发现，环境因子(PH、盐度和温度等)对沉积物吸附P043一P的作用影响比较显著。随pH变化，沉积物对P0护一P的吸附量呈“U”形变化曲?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. In addition, the estuarine and coastal tidal . flat is one of important regions where the biogeochemical cycling is very intense within the ecosystems on the earth’s surface. The biogeochemical cycling of nutrient has the important ecological significance to sustaining higher productivity and biomass in the estuarine and coastal tidal ecosystem. Therefore, to study the nutrient biogeochemical cycling in the complex ecosystem has recently become one of headline scientific problems in the fields of physical geography and estuarine and coastal environmental geochemistry. In recent years, the important scientific problem on environmental geochcmical processes across the intertidal sediment-water interface and ecological significance in the Yangtze Estuary has been studied, which was funded by the National Natural Science Foundation of China and the Foundation for University Key Teacher by the Ministry of Education. The main findings are as following.(1)Based on the analysis of stable carbon and nitrogen isotopes in the surface tidal flat sediments from the Yangtze estuary, it was found that the ratios of stable carbon and nitrogen isotopes were respectively 29.80% ~ -23. 7% and 1.0% ~ 5.5% in the flood seasons, while they were -27.3% ?-25. 6% and 1.6% ~ 7.7% in the dry seasons respectively,indicating the seasonal distribution of discharges from theYangtze river has significantly affected the seasonal variation of stable carbon and nitrogen isotopes in sedimentary organic matter. In general, the distribution of stable carbon and nitrogen isotopes revealed the mixing inputs of terrigenous and marine organic matter controlled the stable carbon and nitrogen isotope compositions in sedimentary organic matter. However, a series of physical, chemical and biogeochemical processes occurring in the local environments had also the significant influence on the stable carbon and nitrogen isotope compositions in organic matter. In addition, the contribution of terrigenous input to sedimentary organic matter was quantitatively estimated in light of the mixing balance model of stable carbon isotope. It was revealed that the inputs of terrigenous organic matter occupying about 54.85% of total organic mater inputs was slightly higher than marine inputs in the intertidal sediments, and had the apparent seasonal and spatial difference in the study area. Terrigenous inputs far exceeded marine inputs in the freshwater areas from Station Xupu to Bailonggang, and were respectively 73. 67% and 52. 45% of total organic matter inputs in July and February, which was consistent with the seasonal distribution of water discharge and sediment discharge from the Yangtze River. However, terrigenous inputs obviously decreased in the saltwater areas from Station Chaoyang Farm to Luchao, and were 40. 57% and 46.14% of total organic matter inputs in July and February, respectively.(2)The spatial and temporal distribution of nutrients showed that due to the effects of water discharge from the Yangtze Estuary, coastal rivers and industrial and domestic sewage, there was complex spatial and temporal distribution of nutrient near the intertidal sediment-water interface in the Yangtze estuarine and coastal ecosystem. The diffusive fluxes of nutrient across the intertidal sediment-water interface in the Yangtze Estuary were estimated, using Pick’s first law. The spatio-temporaldistribution of NHLf-N diffusive flux was very complex which was dominated by NH-N production. NH/-N mainly diffused from the sediments into the overly waters in the Yangtze estuarine and tidal system, indicating sediments was one of potential sources of N更多还原