Fate and transport of heavy metals is controlled by the biogeochemical processes in the environment. Reactive transport modeling is particularly important for capturing the complex interplay between the microbial community dynamics and redox-stratified environments. The focus of this study is to investigate the impacts of (i) multicomponent diffusion (MCD) and (ii) electrical double layer (EDL) on reactive diffusive transport of heavy metals at Lake Coeur d’Alene (LCdA) sediments. The solute benthic fluxes at LCdA sediments are controlled by diffusion, and therefore, the biogeochemical model is focused purely on diffusive transport. In diffusive transport-dominated multicomponent systems, species-specific multicomponent diffusion (i.e., Nernst-Planck representation of diffusion) and the explicit treatment of electrostatic effects can play an important role on the overall dynamics of biogeochemical cycling of metals in the system. The results of this study demonstrate that the use of single uniform diffusion coefficient for all species in purely diffusion-dominated sediments may underestimate the mobility of heavy metals undergoing complex reaction network. This outcome is further signified when explicit treatment of EDL effects is considered in addition to MCD. The simulation results also illustrate the importance of aqueous metal (bi)sulfide complexes, especially when MCD and EDL effects are implemented in reactive transport simulations, impacting the solubility and dynamics of heavy metals in diffusion-dominated systems. The competitive effects of Fe-reducing bacteria FRB and sulfate reducing bacteria SRB activities on pH and overall biogeochemical processes are also demonstrated with multispecies diffusion and explicit treatment of electrostatic effects in the system.

中文翻译：

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湖泊沉积物中重金属的生物地球化学循环：多物种扩散和静电效应的影响

重金属的命运和运输受环境中生物地球化学过程的控制。反应性传输模型对于捕获微生物群落动力学与氧化还原分层环境之间的复杂相互作用特别重要。这项研究的重点是研究（i）多组分扩散（MCD）和（ii）电双层（EDL）对Coeur d'Alene湖（LCdA）沉积物中重金属的反应性扩散传输的影响。LCdA沉积物的溶质底栖通量受扩散控制，因此，生物地球化学模型仅关注扩散运移。在以扩散运输为主的多组分系统中，特定物种的多组分扩散（即 扩散的能斯特-普朗克表示法和静电效应的显式处理可以在系统中金属生物地球化学循环的整体动力学中发挥重要作用。这项研究的结果表明，在单一以扩散为主的沉积物中，所有物种均采用单一的均匀扩散系数可能会低估经历复杂反应网络的重金属的迁移率。如果除了MCD之外还考虑对EDL效果进行明确治疗，则进一步表明这一结果。模拟结果还说明了水性金属（双）硫化物配合物的重要性，特别是当在反应性运输模拟中实现MCD和EDL效应时，这会影响重金属在扩散主导系统中的溶解度和动力学。