Ionic Strength and Species Drive Iron–Carbon Adsorption Dynamics: Implications for Carbon Cycling in Future Coastal Environments,Environmental Science & Technology Letters

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Ionic Strength and Species Drive Iron–Carbon Adsorption Dynamics: Implications for Carbon Cycling in Future Coastal Environments
Environmental Science & Technology Letters ( IF 8.9 ) Pub Date : 2021-07-19 , DOI: 10.1021/acs.estlett.1c00432
E. J. Tomaszewski ₁ , E. K. Coward ₁ , D. L. Sparks ₁

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In coastal environments, sea level rise (SLR) will likely alter reactions between organic matter (OM) and iron (Fe) minerals. A molecular understanding of OM–Fe reactions in complex ionic matrices such as seawater is lacking. We investigated the temporal molecular composition and adsorption of coastal OM to ferrihydrite (Fh) over 24 h in low-ionic strength water (LIW) (I = 0.0009 M), mid-ionic strength water (MIW) (I = 0.003 M) (freshwater proxy), and high-ionic strength water (HIW) (I = 0.6 M) (seawater proxy). Adsorbed OM concentrations significantly (p < 0.05) decreased in HIW (2.12 ± 0.03 mg C/g Fh), compared to those in MIW (3.24 ± 0.56 mg C/g Fh) and LIW (3.74 ± 0.36 mg C/g Fh). In combination with adsorbed ions in HIW (9–195 mg/g Fh) compared to adsorbed ions in MIW and LIW (0.02–0.9 mg/g Fh), an ionic strength threshold is evident. This threshold effect was reflected in the dynamic molecular composition of OM, characterized via Fourier transform ion cyclotron mass spectrometry. In LIW and MIW, rapid sequential adsorption of polycyclic aromatic and phenolic compounds occurred, followed by increasing adsorption of highly unsaturated compounds. Conversely, OM in HIW did not exhibit observable selective adsorption. Overall, limited OM adsorption and indiscriminate fractionation as a result of SLR will likely impact carbon cycling.

中文翻译：

离子强度和物种驱动铁碳吸附动力学：对未来沿海环境中碳循环的影响

在沿海环境中，海平面上升 (SLR) 可能会改变有机物 (OM) 和铁 (Fe) 矿物质之间的反应。缺乏对复杂离子基质（如海水）中 OM-Fe 反应的分子理解。我们研究了 24 小时内沿海 OM 在低离子强度水 (LIW) ( I = 0.0009 M)、中等离子强度水 (MIW) ( I = 0.003 M) (淡水代理）和高离子强度水（HIW）（I = 0.6 M）（海水代理）。吸附的 OM 浓度显着 ( p< 0.05) 与 MIW (3.24 ± 0.56 mg C/g Fh) 和 LIW (3.74 ± 0.36 mg C/g Fh) 相比，HIW (2.12 ± 0.03 mg C/g Fh) 降低。结合 HIW 中的吸附离子 (9-195 mg/g Fh) 与 MIW 和 LIW 中的吸附离子 (0.02-0.9 mg/g Fh) 相比，离子强度阈值很明显。这种阈值效应反映在 OM 的动态分子组成中，通过傅里叶变换离子回旋质谱法表征。在 LIW 和 MIW 中，多环芳香族和酚类化合物的快速连续吸附发生，随后高度不饱和化合物的吸附增加。相反，HIW 中的 OM 没有表现出可观察到的选择性吸附。总体而言，由于 SLR 导致的有限 OM 吸附和不分青红皂白的分馏可能会影响碳循环。

更新日期：2021-08-10

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