漳江口海气二氧化碳交换通量的无人机遥感研究

Recent research has highlighted the valuable role that vegetated coastal ecosystems play in sequestering carbon dioxide (CO2). The carbon sequestered in these systems, such as mangrove forests, has been termed “blue carbon”. However, part of the organic carbons releasing from the systems may not be able to escape from recycling in the downstream estuaries, leading to degassing of CO2. Therefore the blue carbon may not be as significant as expected. Since the waters adjacent to the vegetated ecosystems are highly heterogeneous, it is hard to get to know the detailed patterns .of the CO2 degassing. New approaches are advocated. We have developed an UAV (unmanned aerial vehicle) based remote sensing approach. Here in this study, we propose to study a mangrove adjacent estuary-Zhangjiang river estuary, using. Inherent optical properties (IOPs) will be measured using an imaging spectrometer onboard the UAV, and are used to indicate the chemical and biological factors influencing the variation of surface water partial pressure of CO2(pCO2w). An IOPs dependent algorithm to estimate pCO2w will be developed. Using this algorithm, we may investigate the variabilities of pCO2w and CO2 fluxes at fine scales. Spatial gradients and diurnal variations will be particularly studied.Mechanisms controlling the observed variabilities will also be discussed. The technique output of this study may facilitate future studies in vegetated coastal ecosystems, because the novel UAV-based approach has the resolution of about 1 m and can avoid the drawbacks of satellite remote sensing resulted from cloud cover.Better understanding of the CO2 degassing in mangrove adjacent estuaries will be achieved and benefit the assessment of blue carbon on global scale.

沿海植被生态系统（如红树林）可高效、长期封存碳，引发“蓝碳”概念得到强烈关注。但该系统水平输出之有机碳可能在其下游河口再循环，使下游水体成为二氧化碳（CO2）的源。植被系统与河口水体一并总体衡算，封存碳的量可能低于预期。因河口水体时空异质性强，实测数据匮乏，CO2 释放规律仍不清楚。本研究组在国家基金一年期项目资助下已建立可克服云干扰、具米级空间分辨率的无人机海色遥感系统，对一个典型红树林河口-漳江口水体实施了遥感与现场观测，取得技术突破。在此基础上，我们提出，仍选择漳江口，采用结合无人机遥感与实测的技术路线，以具有高遥感反演精度的固有光学特性指示生物与化学控制因子，完善针对目标区的海水二氧化碳分压遥感算法，进而开展 CO2 通量时空变化的观测研究，着重揭示河口水域通量空间变化的精细特征，探讨控制机制。研究结果可为探讨全球尺度蓝碳的显著性提供科学依据及方法支持。

沿海植被生态系统（如红树林）可高效、长期封存碳，引发“蓝碳”概念得到强烈关注。但该系统水平输出之有机碳可能在其下游河口再循环，使下游水体成为二氧化碳(CO2)的源。植被系统与河口水体一并总体衡算，封存碳的量可能低于预期。因河口水体时空异质性强，实测数据匮乏，CO2释放规律仍不清楚。故本研究提出，针对一个典型红树林河口-漳江口水体，采用结合无人机遥感与实测的技术路线，以具有高遥感反演精度的固有光学特性指示生物与化学控制因子，完善针对目标区的海水二氧化碳分压遥感算法，进而开展 CO2通量时空变化的观测研究，着重揭示河口水域通量空间变化的精细特征，探讨控制机制。在本研究执行的四年内，开展了41个航次的现场调查与8架次无人机高光谱同步飞行，在国际上率先实现技术突破，获得了可靠的无人机遥感反射率，实现水华无人机定量遥感；并且在国际上首度实现10分钟时间分辨的藻华卫星遥感，未来两种技术结合可能弥补无人机在时间密集观测上的缺陷；建立了目标区全新的、基于固有光学特性的pCO2算法，实现了CO2通量估算，得到观测期间通量在-4-23 mmol CO2 m-2 day-1，最高值出现在冬季，假若仅仅根据分散有限的现场pCO2观测，所得到的结果为-3-12 mmol CO2 m-2 day-1。项目所取得的成果，将为探讨全球尺度蓝碳的显著性提供科学依据及方法支持。