潮汐作用下盐沼孔隙水流动及溶质运移模拟
Modelling of tide induced pore water flow and solute transport in a salt marsh
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摘要: 滨海盐沼是重要的陆地-海洋交界带生态系统。目前国际上存在关于盐沼的两大假设:盐沼系统输出养分和盐沼植物带状分布。为验证这两大假设,增强对盐沼湿地的了解,盐沼孔隙水流动及溶质运移研究至关重要。为模拟复杂盐沼系统孔隙水流动及溶质运移,改进了美国地质勘测局编制的SUTRA程序。基于假定的潮沟横断面物理条件,对孔隙水流动及溶质运移过程进行了模拟分析。结果表明潮沟附近孔隙水及溶质交换较快,潮水浸淹会减缓潮沟附近出现物质集结。落潮时潮沟附近有明显垂向流和水平流,远潮沟地带主要为水平流。潮沟附近土壤通气条件较好。这些模拟结果较好的吻合了潮沟附近较盐沼内部盐沼植物长势较好的现象。Abstract: Coastal salt marshes are the important intertidal ecosystems at the land-ocean interface.The investigation of the complex flows and the associated solute transport in marsh soils is made in order to improve our understanding of these wetland systems,particularly the relation to the important hypotheses in the marsh ecology:the nutrient outwelling and the plant zonation.In this paper,we modify the SUTRA code to simulate the complex pore water flows and the associated solute transport in marsh soils.We simulate the pore water flow and the associated solute transport in a salt marsh based on an imaginary creek section.The results show that the pore water flow and the associated solute exchange near the tidal creek are more intensive than in the inner marsh,which prevents pore water solute near the creek from concentrating or accumulating.During the ebb tide,the pore water flow near the tidal creek is both vertical and horizontal,while it is primarily horizontal far from the creek. The optimal aeration condition is also found occurring near the tidal creek.These results are consistent with the observation that the salt marsh plants often grow better near tidal creeks than in the inner areas.