Aeolian sandy soils are an important carbon sink for dissolved inorganic carbon (DIC), however, the underlying mechanisms are still mystery. To solve this issue, the adsorption of HCO3− and CO32− on aeolian sandy soil particles was studied using molecular dynamics simulation and adsorption experiments. Both HCO3− and CO32− can be adsorbed, albeit with varying adsorption capacity, distributions, and local environment, which was influenced by the pH value and concentration. The adsorption mechanisms of DIC were though hydrogen bonds or cation bridges, as well as in the form of single or multiple molecular clusters, which were regulated by the pH level. At pH=7.5, HCO3− was mainly captured by hydrogen bond and in a form of single molecule; at pH=9.5 and 11, both HCO3− and CO32− were mainly adsorbed as DIC clusters through the linkage of Na+ bridge. The HCO3− cluster mainly found at pH=9.5, comprising of HCO3−−Na+−CO32− complex, whereas the CO32− cluster mainly observed at pH=11, comprising of CO32−−Na+−CO32−. The CO32− cluster exhibited greater stability compared to the HCO3− cluster. These results are valuable in enhancing our understanding of the carbon cycle process and carbon balance dynamics in arid and semi-arid regions.

中文翻译：

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破译风沙土作为溶解性无机碳汇的机制：分子动力学模拟与实验研究


风沙土壤是溶解无机碳 （DIC） 的重要碳汇，然而，其潜在机制仍然是个谜。为了解决这个问题，采用分子动力学模拟和吸附实验研究了风沙土壤颗粒上 HCO3− 和 CO32− 的吸附。HCO3− 和 CO32− 都可以被吸附，尽管吸附容量、分布和局部环境不同，这受 pH 值和浓度的影响。DIC 的吸附机制是通过氢键或阳离子桥，以及单个或多个分子簇的形式，它们受 pH 值调节。当 pH=7.5 时，HCO3− 主要被氢键以单分子形式捕获;在 pH=9.5 和 11 时，HCO3− 和 CO32− 主要通过 Na+ 桥的键合以 DIC 簇的形式吸附。HCO3− 团簇主要在 pH=9.5 时发现，由 HCO3−−Na+−CO32− 络合物组成，而 CO32− 簇主要在 pH=11 时观察到，由 CO32−−Na+−CO32− 组成。与 HCO3− 簇相比，CO32− 簇表现出更高的稳定性。这些结果对于增强我们对干旱和半干旱地区碳循环过程和碳平衡动态的理解具有价值。