滨海盐沼水动力机制和物质传输特征多维实验和数模研究

Salt marsh is an important ecosystem at the land-ocean interface. The hydrodynamic process and associated soil conditions in salt marsh determine the growth of wetland plants. The movement of sediments, water and solute in the marsh system is considered to be the main factors affecting the salt marsh formation and evolution. Based on the analysis of field observations at the study site, two-dimensional and three-dimensional salt marsh models were established in the laboratory to simulate the role of the main factors (tides, the hydrological factors, the morphology of salt marsh and soil properties) in controlling the salt marsh hydrodynamic and mass transport processes under controlled conditions, and to obtain a relatively complete set of experimental data. The data will be used for the development and validation of a coupled surface-subsurface model. Based on laboratory experiments and numerical simulation results, is the study aims to reveal the hydrodynamic mechanism and mass transport characteristics of salt marsh. The research outcomes will form a scientific basis for determining accurately mass exchange fluxes between land and ocean, and contribute to better understanding of the essential functions of the salt marsh, utilizations of the salt marsh resources, and protection of the offshore environment.

盐沼是重要的陆地-海洋交界带生态系统。盐沼水动力过程以及由此过程影响的土壤特性决定着湿地植物生长，泥沙、水分及溶质运移，被认为是决定盐沼形成和演变的主要因素。本研究拟通过分析野外观测取得的盐沼形态数据，在实验室分别建立一个二维和三维盐沼物理模型，在可控条件下模拟主要因子（潮汐、水文因子、盐沼形态、土壤特性）作用下盐沼水动力和物质传输过程，取得一套相对完整的实验数据。该数据将用于开发和验证地表水-地下水耦合模型。借助室内实验和数值模拟结果，揭示盐沼湿地水动力机制和物质传输特征。研究成果将为海洋－陆地物质交换通量的准确计算提供科学依据，有助于深入认识盐沼基本功能，合理利用盐沼资源，保护近海环境。

盐沼是位于陆地-海洋交界带的湿地系统并拥有诸多生态功能，为水生动植物提供栖息地从而维持滨海生物多样性、通过拦截过滤陆源生物化学物质以净化沿海水质、吸收存储二氧化碳进而缓解全球变暖现象等。盐沼水动力过程以及受此过程影响的土壤特性决定着盐沼植被生长，泥沙、水分及溶质运移，被认为是影响盐沼形成和演变的主要因素。因此，开展滨海盐沼水动力机制的研究不仅有助于为海洋-陆地物质交换通量的准确计算提供科学依据，还能帮助人们深入认识盐沼基本功能，合理利用盐沼资源以及保护近海环境。本项目主要开展的研究内部包括：（1）开展了大量滨海水动力条件下海水入侵机理物理模型实验，结合数值模拟手段分析了潮汐、地下水位波动等滨海水动力作用对海水入侵混合带入侵距离和混合带宽度的影响机理；（2）优化地下水数值模型SUTRA，按照物理实验设置模拟混合带的入侵距离和混合带宽度，并与实验结果进行对比，揭示了水动力作用下盐沼湿地盐分混合过程；（3）通过物理实验及数值模拟探讨了正盐度梯度（地表水盐度高于孔隙水盐度）和负盐度梯度（地表水盐度低于孔隙水盐度）对盐沼孔隙水动力过程的影响；（4）通过室内实验及数值模拟研究了非稳定指流对保守性污染物在盐沼土壤中运移的影响；分析复杂水动力作用下海岸水库脱盐及盐分输运机制。