Nitrogen Argon Measurements for the Quantification of Surface Water Nitrogen Fixation in the Baltic Sea (NArrFix )

用于量化波罗的海地表水固氮的氮氩测量 (NArrFix)

• 批准号: 450156712
• 负责人: Dr. Oliver Schmale
• 金额: --
• 依托单位: Leibniz-Institut für Ostseeforschung Warnemünde (IOW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/450156712?language=en
• 关键词: Nitrogen; Argon; Measurements; Quantification; Surface

Nitrogen fixation by cyanobacteria is a common phenomenon in the Baltic Sea. It occurs in the absence of dissolved inorganic nitrogen (DIN) during mid-summer (June – August) mainly in the central Baltic Sea and the Gulf of Finland. The contribution to the N budget is significant and enhances the eutrophication of the Baltic Sea. Current input estimates range between 300 kt-N/yr and 800 kt-N/yr and are in the same order of magnitude as the sum of the riverine and airborne DIN input. The huge range of the different estimates is a consequence of both the considerable interannual variability of the N2 fixation and huge uncertainties associated with the different approaches (15N incubation; total N budget; pCO2 records; phosphate excess) for the quantification of the N2 fixation and with extrapolating the results from local studies to entire basins.Our approach is based on large-scale records of the surface water N2 depletion during a cyanobacteria bloom, complemented by Ar measurements to account for the air-sea N2 gas exchange. The N2 and Ar concentrations will be determined semi-continuously by means of mass spectrometric analysis of N2 and Ar in air equilibrated with a continuous flow of surface water (MIMS, Membrane Inlet Mass Spectroscopy). The measurement device will be attached to an established fully automated measurement system for the analysis of surface water trace gases (CO2, CH4, O2, N2O, CO) on a voluntary observation ship (VOS, “Finnmaid”). Through this the N2 and Ar concentration between the Mecklenburg Bight and the Gulf of Finland will be obtained with a temporal resolution of 2 – 3 days.Two intense measurement periods will be performed (2021 and 2022) in order to quantify the N2 fixation during the cyanobacteria high season from June to August. Through this we are aiming to identify the factors which trigger and possibly limit the cyanobacteria growth such as temperature, P availability and meteorological/hydrographic conditions. Concurrent records of the pCO2 by the existing measurement system will be used for independent estimations of the cyanobacteria biomass production and thus of the associated N2 fixation. Likewise, measurements of total N and total P will be available through cooperation with the Finnish Environment Institute (SYKE) and facilitate nitrogen budget calculations for consistency tests with our direct N2 fixation measurements.To estimate the total N2 fixation, the rates obtained for the upper surface layer must be integrated over depth. This will be achieved by numerical modelling (GETM) of the mixed layer depth which will be defined by different criteria. Extrapolation of the N2 fixation obtained along the Finnmaid route to entire basins is a more challenging task. In cooperation with the remote sensing group of the Federal Maritime and Hydrographic Agency (BSH), we will make an attempt to use remote sensing data for an extrapolation procedure.

蓝藻固氮是波罗的海的一种常见现象。它发生在没有溶解的无机氮（DIN）在仲夏（6月至8月），主要在波罗的海中部和芬兰湾。氮预算的贡献是显着的，并提高了波罗的海的富营养化。目前输入的估计范围在300 kt-N/年和800 kt-N/年之间，与河流和空气中DIN输入的总和处于相同的数量级。不同估算值的巨大范围是N2固定的显著年际变化和与不同方法相关的巨大不确定性的结果（15 N培养;总N收支; pCO 2记录;磷酸盐过量）的N2固定的量化和外推的结果，从当地的研究，整个流域。我们的方法是基于大-蓝藻水华期间地表水N2消耗的尺度记录，补充Ar测量，以解释空气-海洋N2气体交换。将通过对用连续地表水流平衡的空气中的N2和Ar进行质谱分析（MIMS，膜入口质谱法），半连续测定N2和Ar浓度。该测量装置将连接到一艘自愿观测船（VOS，“Finnmaid”）上的一个既定的全自动测量系统上，用于分析地表水痕量气体（CO2、CH 4、O2、N2 O、CO）。通过这一点之间的梅克伦堡湾和芬兰湾的N2和Ar浓度将获得时间分辨率为2 - 3 day.Two密集的测量期间（2021年和2022年）将进行，以量化的N2固定在蓝藻高发季节从6月至8月。通过这一点，我们的目标是确定触发和可能限制蓝藻生长的因素，如温度，磷的可用性和气象/水文条件。由现有的测量系统的二氧化碳分压的并发记录将用于独立的估计蓝藻生物量的生产，从而相关的N2固定。同样，通过与芬兰环境研究所（SYKE）的合作，可以获得总氮和总磷的测量结果，并促进氮收支计算，以便与我们的直接N2固定测量结果进行一致性测试。为了估计总N2固定，必须对上表面层获得的速率进行深度积分。这将通过混合层深度的数值模拟（GETM）来实现，混合层深度将由不同的标准定义。将沿着芬梅德路线获得的N2固定外推到整个流域是一项更具挑战性的任务。我们将与联邦海洋和水文局遥感小组合作，尝试利用遥感数据进行外推。