Estimating benthic Fe and reactive solute fluxes
Estimating benthic Fe and reactive solute fluxes
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DOI：
10.1016/j.marchem.2023.104221
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发表时间：
2023-02
期刊：
影响因子：
3
通讯作者：
R. Aller;I. Dwyer;D.A. Swenson Perger;C. Heilbrun;N. Volkenborn;L. Wehrmann
中科院分区：
文献类型：
--
作者：
R. Aller;I. Dwyer;D.A. Swenson Perger;C. Heilbrun;N. Volkenborn;L. Wehrmann
沉积物中溶解铁(FED)通量是生物地球化学铁循环的重要组成部分。估算这些通量的一般方法是根据底孔水剖面的模拟，或利用海底洞室或取回的岩心培养沉积物和上覆水。沉积物最上层的孔隙水Fe剖面分辨率不足和Fe2+的快速氧化会极大地损害这些方法。这些限制可能是报告的底栖生物通量在给定值的独立控制变量(如沉积Corgremination速率)时出现较大差异的部分原因。进行了一系列实验室实验，以比较估算铁通量的方法，并证实在含氧室水中，Fe2+在几分钟内被氧化为Fe3+。生成的Fe3+胶体不会通过0.2%μm孔径的过滤器，也会从悬浮液中迅速失去。停产造成的损失是部分可逆的。大多数海底洞室研究没有纠正这种损失，很可能严重低估了联邦通量。在助熔剂测量过程中，与沉淀铁氧化物有关的其他活性成分，如磷和痕量金属，也必须遭受类似的重大损失。我们修改了标准的孵化方法，通过铁萃取器循环上覆水，并在已知时间内在恒定的O2和pH下累积释放到室内的FeD。我们在一系列实验条件下发现，在圆柱形容器中，在饱和O2(∼270μM)和海水pH(∼8；NBS)下，通常可以在蓄电池上回收70-93%的引入Fe2+。我们建议以反应性溶质(如Fe、P)为目标的助熔剂培养池应配置直流式萃取器，并针对特定于腔室设计、腔室水停留时间和部署条件(例如O2、pH)的损失进行预校准。
The flux of dissolved Fe (Fed) from sediments is a critical component of the biogeochemical Fe cycle. Common approaches to estimating these fluxes are based on modeling of Fedporewater profiles or incubating sediment and overlying water using benthic chambers or retrieved cores. Inadequate resolution of pore water Fe profiles in the uppermost mm of sediments and rapid Fe2+oxidation can greatly compromise these approaches. These limitations may be partially responsible for large variations in reported benthic Fedfluxes at given values of independent controlling variables such as sedimentary Corgremineralization rates. A series of laboratory experiments were conducted to compare methods to estimate Fe fluxes and confirmed that Fed2+is oxidized to Fe3+within a few minutes in oxygenated chamber water. The resulting Fe3+colloids do not pass through 0.2 μm pore size filters and are also rapidly lost from suspension. Loss from suspension is partially reversible. Most benthic chamber studies do not correct for such losses and likely significantly underestimate Fedfluxes. Additional reactive components such as P and trace metals that associate with precipitated Fe-oxides must be subject to similar major losses during flux measurements. We modified the standard incubation methods by circulating overlying water through Fe extractors and accumulating Fedreleased into chambers over a known period at constant O2and pH. We found using a range of experimental conditions that in cylindrical chambers ∼70–93% of introduced Fe2+is typically recovered on accumulators at saturated O2(∼270 μM) and seawater pH (∼8; NBS). We recommend that flux incubations that target reactive solutes (e.g., Fe, P) be configured with flow-through extractors, and pre-calibrated for losses specific to chamber designs, chamber water residence times, and deployment conditions (e.g., O2, pH).