Submarine Groundwater and River Discharges Affect Carbon Cycle in a Highly Urbanized and River-Dominated Coastal Area
Submarine Groundwater and River Discharges Affect Carbon Cycle in a Highly Urbanized and River-Dominated Coastal Area
复制标题
DOI：
10.3389/fmars.2021.817001
复制
发表时间：
2021-12
期刊：
影响因子：
--
通讯作者：
Xuejing Wang;Yan Zhang;C. Zheng;Manhua Luo;S. Yu;Meiqing Lu;Hailong Li
中科院分区：
文献类型：
--
作者：
Xuejing Wang;Yan Zhang;C. Zheng;Manhua Luo;S. Yu;Meiqing Lu;Hailong Li
在估算沿海碳收支时，河流向海洋的碳通量一直被考虑，但海底地下水排放（SGD）长期以来一直被忽略。以粤港澳大湾区（GBA）为例，研究了SGD和河流排放对碳循环的影响。利用镭模型估算出SGD排放的硝酸盐（NO3-）、溶解有机碳（DOC）和溶解无机碳（DIC）通量分别为（0.73-16.4）× 108 g/d、（0.60-9.94）× 109 g/d和（0.77-3.29）× 1010 g/d。SGD引起的DOC和DIC通量是河流输入的1.22倍，但SGD引起的NO3-通量是河流输入的1/4。额外的硝酸盐和碳输入可以刺激新的初级生产力，提高生物泵效率，并影响海水碳酸盐系统的平衡。结果表明，在干旱的冬季，SGD是大气CO2的潜在净源，其通量为1.46 × 109 gC/d，而河流是大气CO2的潜在净汇，其通量为3.75 × 109 gC/d。提出了两个概念模型，说明了主要的潜在过程引起的SGD和河流排放的碳循环。这些研究结果表明，SGD，作为重要的河流，在碳循环中起着重要的作用，并应考虑在区域和全球范围内的碳预算估计未来。
Riverine carbon flux to the ocean has been considered in estimating coastal carbon budgets, but submarine groundwater discharge (SGD) has long been ignored. In this paper, the effects of both SGD and river discharges on the carbon cycle were investigated in the Guangdong-HongKong-Macao Greater Bay Area (GBA), a highly urbanized and river-dominated coastal area in China. SGD-derived nitrate (NO3–), dissolved organic carbon (DOC), and dissolved inorganic carbon (DIC) fluxes were estimated using a radium model to be (0.73–16.4) × 108 g/d, (0.60–9.94) × 109 g/d, and (0.77–3.29) × 1010 g/d, respectively. SGD-derived DOC and DIC fluxes are ∼2 times as great as riverine inputs, but SGD-derived NO3– flux is one-fourth of the riverine input. The additional nitrate and carbon inputs can stimulate new primary production, enhance biological pump efficiency, and affect the balance of the carbonate system in marine water. We found that SGD in the studied system is a potential net source of atmospheric CO2 with a flux of 1.46 × 109 g C/d, and river, however, is a potential net sink of atmospheric CO2 with a flux of 3.75 × 109 g C/d during the dry winter season. Two conceptual models were proposed illustrating the major potential processes of the carbon cycle induced by SGD and river discharges. These findings from this study suggested that SGD, as important as rivers, plays a significant role in the carbon cycle and should be considered in carbon budget estimations at regional and global scales future.