滨海小流域湿地“DOC流”关键过程及机理研究

Dissolved organic carbon (DOC) plays an important role in the carbon cycle. At present, studies on the DOC of wetland are focused on the micro scale, and mainly centralize on the internal cycle of wetland systems. The quantities and structures of internal DOC in wetland closely are related to the exogenous import, hydrological migration, and output process. However, few studies have examined the DOC flow between wetland system and the adjacent ecosystems at the macro-scale. As sea-land transitional zone, the coastal wetland has remarkable characteristics of DOC flow. In this project, coastal wetland in Jiaozhou Bay is selected as study area. Its DOC flow on watershed scale will be researched based on RS and GIS techniques. The source of DOC will be identified by using δ13C and C/N isotope tracer analysis methods, and the percentages of exogenous import of DOC will be further estimated. The impacts of landscape pattern, land use structure, and precipitation-hydrological processes on the transport processes of DOC will be analyzed. The output coefficient model of DOC will be set up, which is used to calculate the lateral hydrological fluxes of DOC from the coastal wetland to offshore in Jiaozhou Bay. This project aims to reveal the flow process of DOC and its mechanism on watershed scale. The anticipated results of this project will improve the wetland carbon cycle theories, and make a further useful exploration for costal wetland carbon cycle and its relationship with the ocean environment.

溶解性有机碳（DOC）在湿地碳循环中重要作用已得以明确。当前对湿地DOC研究局限于微观尺度，且侧重内部循环。而湿地系统内部DOC数量、结构等要素与其外源输入、水文迁移和输出过程密切相关，但当前宏观尺度将湿地与相邻系统间作为一个碳流共同体，充分考虑该共同体内“DOC流”关键过程的研究尚未开展。滨海湿地作为海陆过渡带，其“DOC流”有显著特点。项目以胶州湾滨海小流域湿地为研究对象，开展流域内湿地“DOC流”关键过程研究，利用δ13C和C/N双同位素示踪法识别湿地DOC源，判断不同外源输入对DOC相对贡献率；分析景观格局、土地利用结构及降雨-水文过程对DOC水文迁移过程影响；构建DOC输出系数模型，核算滨海小流域湿地向近海水文输出DOC横向通量。本研究旨在揭示宏观尺度上小流域湿地DOC的流动过程及机理。研究在完善湿地生态系统碳循环基础上为滨海湿地碳循环及其与海洋环境之间联动关系做出有益的探索。

溶解性有机碳（DOC）容易随水发生运移，使宏观尺度上的湿地与相邻系统形成一个“DOC流”共同体，该共同体将“DOC流”从陆地输送到海洋，构成全球碳循环的重要一环。项目以胶州湾滨海小流域湿地为研究对象，开展 “DOC流”关键过程研究。主要研究内容与成果如下：.（1）分析和评估胶州湾滨海典型流域湿地DOC的外源及相对贡献。大沽河口沉积物DOC属于海陆混源物质，C/N值在0.39~21.10之间，δ13C值为-20.93‰~-26.55‰。所选多种主要陆源中，养殖池和农村地区贡献率比较大，农田和林地贡献率小，人类活动是DOC的重要影响因素。.（2）分析和探讨胶州湾滨海典型流域湿地DOC含量、结构及水文迁移特征。典型流域湿地DOC 含量均表现出从表层到底层逐渐降低的变化趋势，FI值均接近于1.9，说明腐殖质成分主要源于内源性生物降解；降水和景观差异性是影响大沽河流域DOC水文横向迁移的主要因素，水文输出通量集中在7月份。.（3）探究胶州湾滨海典型流域特征变化，并利用RDA分析DOM含量、组分与流域特征因子之间的关系，解释变异数为87.2%。结果认为土地利用和景观格局是影响流域出口沉积物DOC含量和组分的两个主要因素。流域特征对DOC组分的影响大于其对含量的影响。.（4）研究水盐梯度、潮汐循环与互花米草对DOC含量和结构特征的影响及潜在生态风险。含水量和含盐量均会改变土壤DOC的含量，影响DOC结构，并通过影响土壤吸附重金属增加其潜在生态风险；潮汐循环促进了沉积物中DOC的释放，释放量最大达到15.18 QSU，同时潮汐循环对DOC荧光强度也有较大的影响；互花米草入侵使土壤 DOC含量由35.67增加到168.99mg/kg，分子量也呈增加趋势，结构更趋于复杂，并且DOC含量随入侵时间延长增加。.研究结果补充和完善湿地系统碳循环理论，揭示流域尺度上DOC流的产生、归趋与生态风险，并为滨海湿地碳循环及其与海洋环境之间的联动关系做出有益的探索。