Dissolved carbon dynamics and exchange in a high permeability beach aquifer
Dissolved carbon dynamics and exchange in a high permeability beach aquifer
复制标题
DOI：
10.1016/j.gca.2024.01.014
复制
发表时间：
2024-01
影响因子：
5
通讯作者：
Yan Zhang;Yifan Guo;Junjian Wang;D. Maher;Xiaolong Geng;Qianqian Wang;Kai Xiao;Hu Ding;Hailong Li;Chunmiao Zheng;Zhenyan Wang;Xuejing Wang
中科院分区：
文献类型：
--
作者：
Yan Zhang;Yifan Guo;Junjian Wang;D. Maher;Xiaolong Geng;Qianqian Wang;Kai Xiao;Hu Ding;Hailong Li;Chunmiao Zheng;Zhenyan Wang;Xuejing Wang
潮滩溶解碳的地球化学转化影响着海岸带碳循环和碳收支。然而，地下水流对溶解碳和CO2通量在这些动态海滩系统中的不同界面的行为的影响仍然知之甚少，特别是在深海滩含水层。研究了南海陆架高渗透性海滩含水层（9-13 m）中溶解碳的地球化学反应和来源，并定量评价了海底地下水排放（SGD）驱动的CO2释气。结果表明，溶解无机碳（DIC）和总碱度（TA）表现出非保守性的增加跨越盐度梯度。过量的DIC和TA最有可能是由于有机碳分解在半咸水和盐碱区。有氧呼吸（上盐羽区），厌氧反应和潮汐混合被确定为主导过程控制DIC和TA动态。通过海滩沉积物-空气界面的平均CO2释气通量估计为1.05 g m−2d−1，明显高于通过海-气界面的CO2通量。地下水CO2从海滩含水层的释气模式似乎是由潮汐抽水驱动。考虑到SGD产生的溶解碳和营养盐的综合影响，我们认为SGD产生了净CO2通量，占海-气界面CO2通量的45%。SGD直接和间接地从海滩含水层向大气输送了大量的CO2，沿76.2 km长的桑迪海岸沿着约输送（4.89-9.21）× 103 t CO2。这些研究结果表明，潮间带海滩含水层，作为活跃的地球化学反应器有很强的潜力，加强CO2排放到大气中通过海滩沉积物-空气和海-气界面。这项研究提供了一个更好的了解碳地球化学循环和水文过程之间的联系在海岸带。
The biogeochemical transformation of dissolved carbon in tidal beaches affects the coastal carbon cycle and budget. Yet, the influence of groundwater flow on the behavior of dissolved carbon and CO2flux across the different interfaces in these dynamic beach systems remains poorly understood, especially in deep beach aquifers. In this study, we investigated the biogeochemical reactions and origins of dissolved carbon and quantitatively evaluated CO2outgassing driven by submarine groundwater discharge (SGD) in a high permeability beach aquifer (9–13 m depth) located in the South China Sea shelf. Results revealed that both dissolved inorganic carbon (DIC) and total alkalinity (TA) exhibited non-conservative additions across the salinity gradient. The excess DIC and TA most likely resulted from organic carbon decomposition in the brackish and saline zones. Aerobic respiration (upper saline plume zone), anaerobic reactions, and tidal mixing were identified as the dominant processes controlling DIC and TA dynamics. The mean CO2outgassing flux across the beach sediment-air interface was estimated to be 1.05 g m−2d−1, significantly higher than the CO2flux across the sea-air interface. The outgassing pattern of groundwater CO2from beach aquifer appeared to be driven by tidal pumping. Considering the combined effects of SGD-derived dissolved carbon and nutrients, we suggest that SGD yielded a net CO2flux, contributing to 45 % of the CO2flux across the sea-air interface. SGD directly and indirectly delivered substantial CO2from the beach aquifer to the atmosphere, approximately (4.89–9.21) × 103tons of CO2per year along the 76.2 km long sandy coast. These findings demonstrate that intertidal beach aquifers, as active biogeochemical reactors have the strong potential to intensify CO2emissions to the atmosphere through both beach sediment-air and sea-air interfaces. This study provides a better understanding of the links between carbon biogeochemical cycles and hydrologic processes in the coastal zones.