Cation concentrations during benthic weathering of calcite and dunite in benthocosm experiments@en

Enhanced benthic weathering has been proposed to serve as a efficient negative emission strategy. The precise weatherig behaviour of calcite and dunite was investigated in leng-term experiments in benthocosms. These experiments were conducted between Sept. 2022 and Sept. 2023 ashore at the Kiel Fjord. The latter are large plastic containers (~0.8 m²) that are partly filled with sediments, with constant flow-through of Baltic Sea bottom water. The sediments, obtained from Boknis Eck in the Eckernförde Bay in March 2022, were amended with calcite and dunite in triplicate (22 mol/m² equivalent) . Three additional benthocosms were left unamended to serve as controls. The used materials were obtained from Sibelco (dunite) and from the german Lime Stone Association (calcite). Samples were obtained using benthic chambers (chamber volume of 400 ml) that were placed on the sediment for three hours. Samples were taken at the beginning (_in) and at the end of the deployment (_out). All samples were filtered through a 0.2 µm cellulose membrane filter and refrigerated in 25 ml ZinsserTM scintillation vials. Acidified sub-samples (30 μl suprapure HNO3- + 3 ml sample) were prepared for analyses of major and trace elements (Si, Na, K, Li, B, Mg, Ca, Sr, Mn, Ni and Fe) by inductively coupled plasma optical emission spectroscopy (ICP-OES, Varian 720-ES).强化底栖风化被提出作为一种高效的负排放策略。本研究通过底栖宇宙模拟系统（benthocosms）开展长期实验，探究方解石（calcite）与纯橄榄岩（dunite）的精准风化行为。实验于2022年9月至2023年9月期间在基尔峡湾（Kiel Fjord）沿岸开展。该系统为大型塑料容器（表面积约0.8 m²），内部部分填充沉积物，并持续通入波罗的海底层海水。沉积物于2022年3月采自埃克恩弗尔德湾的博克尼斯埃克海域（Boknis Eck），以每份当量22 mol/m²的比例，分别添加方解石与纯橄榄岩，设置三组平行样。另外设置3组未进行改性处理的底栖宇宙模拟系统作为对照组。实验所用材料分别购自Sibelco公司（纯橄榄岩）与德国石灰石协会（German Lime Stone Association，方解石）。采用底栖采样舱采集样本，将采样舱放置于沉积物表面静置3小时。分别在采样舱部署初始时刻（_in）与结束时刻（_out）采集样本。所有样本均经0.2 µm纤维素微孔滤膜过滤后，分装于25毫升Zinsser™闪烁瓶中并冷藏保存。制备酸化分样（取30微升超纯硝酸与3毫升样本混合），用于通过电感耦合等离子体光学发射光谱法（inductively coupled plasma optical emission spectroscopy，ICP-OES，Varian 720-ES）分析常量与微量元素（硅、钠、钾、锂、硼、镁、钙、锶、锰、镍与铁）。