Carbon and phosphorus processing in a carbonate karst aquifer and delivery to the coastal ocean
Carbon and phosphorus processing in a carbonate karst aquifer and delivery to the coastal ocean
复制标题
DOI：
10.1016/j.gca.2019.10.040
复制
发表时间：
2020-01
影响因子：
5
通讯作者：
A. Pain;Jonathan B. Martin;C. Young;A. Valle‐Levinson;I. Mariño‐Tapia
中科院分区：
文献类型：
--
作者：
A. Pain;Jonathan B. Martin;C. Young;A. Valle‐Levinson;I. Mariño‐Tapia
在硅质岩系统中，海底地下水排放（SGD）提供了一部分输送到沿海沃茨的淡水和营养物质，但在许多碳酸盐岩溶地形中，SGD是陆地水和溶质的主要来源。地下河口的反应可能会改变水的成分，通过SGD改变化学通量。在碳酸盐环境中，有机碳再矿化与碳酸钙矿物质（CaCO 3）溶解和沉淀之间的反馈可能会改变二氧化碳（CO2）和磷（P）浓度以及与SCD相关的通量。为了评估这些影响，我们从尤卡坦半岛东海岸沿着的多个海底泉水，以及内陆的天然井和沿海的地下水井中取样。我们测量铵（NH4），磷酸盐（PO4），主要元素，溶解无机和有机碳浓度（DIC和DOC），荧光特性的有色溶解有机物（CDOM）和模拟方解石饱和指数（SIcal）和溶解CO2分压（PCO2）。这些数据表明，反应沿着一个假设的流动路径到海岸控制陆地淡水进入地下河口的组成。微咸水和泻湖水之间的非保守混合反映了地下河口内的地下水成分的变化，从CO2产生的有机质矿化和CaCO3溶解。虽然有机质矿化和碳酸盐溶解释放P，摩尔N：P的比例在春季排放高于Redfield比16：1，表明封存的矿化P通过吸附到碳酸盐矿物内的STE。这一结果表明，SGD，水和营养盐的主要来源，这一海岸带，在沿海水域的P限制的结果，是一个来源的CO2，尽管缓冲CaCO3溶解。这一结果也强调了地下河口内土壤地球化学反应的重要性，以估计SGD溶质输送到海洋和沿海碳循环的影响。
In siliciclastic systems, submarine groundwater discharge (SGD) provides a fraction of freshwater and nutrients delivered to coastal waters, but in many carbonate karst terrains SGD represents the predominant source of terrestrial water and solutes. Water compositions may be modified by reactions in subterranean estuaries, altering chemical fluxes via SGD. In carbonate settings, feedbacks between organic carbon remineralization and calcium carbonate mineral (CaCO3) dissolution and precipitation may alter carbon dioxide (CO2) and phosphorus (P) concentrations and fluxes associated with SGD. To assess these effects, we sampled water from multiple submarine springs along the east coast of the Yucatan peninsula, as well as inland cenotes, and a coastal groundwater well. We measured ammonium (NH4), phosphate (PO4), major element, dissolved inorganic and organic carbon concentrations (DIC and DOC), fluorescent characteristics of colored dissolved organic matter (CDOM) and modeled calcite saturation indices (SIcal) and the partial pressure of dissolved CO2(PCO2). These data indicate that reactions along a hypothetical flow path to the coast control the composition of terrestrial fresh water entering the subterranean estuary. Non-conservative mixing between brackish groundwater and lagoon water reflect changes to groundwater compositions within the subterranean estuary from CO2produced during organic matter remineralization and CaCO3dissolution. Although both organic matter remineralization and carbonate dissolution should liberate P, molar N:P ratios in spring discharge are higher than the Redfield Ratio of 16:1, suggesting sequestration of remineralized P through sorption to carbonate minerals within the STE. This result indicates that SGD, the primary source of water and nutrient to this coastal zone, results in P limitation in coastal water and is a source of CO2despite buffering by CaCO3dissolution. This result also emphasizes the importance of biogeochemical reactions within subterranean estuaries for estimates of SGD solute delivery to the oceans and impacts to the coastal carbon cycle.