Nitrogen biogeochemistry of groundwater fluxes to the estuaries in the northern Gulf of Mexico

墨西哥湾北部河口地下水通量的氮生物地球化学

• 批准号: 446330207
• 负责人: Dr. Dini Adyasari
• 金额: --
• 依托单位: Department of Geological Sciences
• 依托单位国家: 德国
• 项目类别: WBP Fellowship
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/446330207?language=en
• 关键词: Nitrogen; biogeochemistry; groundwater; fluxes; estuaries

The Gulf of Mexico hosts some of the most diverse ecosystems in the world; however, its ecological diversity is currently threatened by poor water quality and water resource scarcity. Currently, the largest hypoxic zone in U.S. coastal waters is found in its northern part and it is correlated with freshwater nitrogen (N) flux, which originates from the Mississippi River Delta. Nevertheless, recent studies indicate that river water is a minor contributor to the local hypoxia problem; instead, they point to potential contribution of nutrient-rich groundwater discharge into the coastal water. In this study, I aim to (1) quantify groundwater-derived N fluxes, (2) determine freshwater N sources, and (3) assess N transformation in the organic-rich coastal sediment found in the northern Gulf of Mexico. Specifically, I propose to focus on several smaller estuaries along coastlines, in which groundwater discharge has not been studied due to their proximate locations to the Mississippi River Delta, the largest delta in the continental U.S. I hypothesize that groundwater-derived N fluxes are partially responsible for the hypoxia problem in the northern Gulf of Mexico, and the organic-rich coastal sediment acts as a sink of anthropogenic N through a combination of biogeochemical processes. To test my hypotheses, I propose to do a combination of field and laboratory works, including measurements of radon, radium, dissolved organic and inorganic N concentration, and microbial sequencing. The results of this study can be used to assess the contribution of groundwater to total regional N budget, determine the role of subterranean estuary in transforming or/and attenuating anthropogenic N transport, and further contribute to better fundamental understanding of the drivers and remediation of water quality in the Gulf of Mexico. On a broader scale, the knowledge obtained by this project will improve our predictive ability of the contribution of groundwater to the global nutrient marine budget.

墨西哥湾拥有世界上最多样化的生态系统;然而，其生态多样性目前受到水质差和水资源短缺的威胁。目前，美国沿海沃茨中最大的缺氧区位于其北方部分，它与源自密西西比河三角洲的淡水氮（N）通量相关。然而，最近的研究表明，河水是造成当地缺氧问题的一个次要因素;相反，他们指出，富含营养的地下水排放到沿海水域的潜在贡献。在这项研究中，我的目标是（1）量化地下水来源的N通量，（2）确定淡水N的来源，（3）评估在墨西哥湾北方富含有机物的沿海沉积物中的N转化。具体来说，我建议把重点放在几个较小的河口沿着海岸线，其中地下水排放尚未研究，由于其接近的位置，以密西西比河三角洲，最大的三角洲在美国大陆我假设，地下水衍生的N通量是部分负责缺氧问题，在墨西哥湾的北方，富含有机物的沿海沉积物通过生物地球化学过程的组合充当人为氮的汇。为了验证我的假设，我建议做现场和实验室工作相结合，包括测量氡，镭，溶解有机和无机氮浓度，和微生物测序。 本研究的结果可用于评估地下水的区域总氮预算的贡献，确定地下河口在改造或/和减弱人为N运输的作用，并进一步有助于更好地从根本上了解墨西哥湾水质的驱动因素和补救措施。在更广泛的范围内，该项目获得的知识将提高我们对地下水对全球海洋营养物收支的贡献的预测能力。