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首页> 外文期刊>Clays and clay minerals >ROLE OF MICROBIAL Fe(III) REDUCTION AND SOLUTION CHEMISTRY IN AGGREGATION AND SETTLING OF SUSPENDED PARTICLES IN THE MISSISSIPPI RIVER DELTA PLAIN, LOUISIANA, USA
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ROLE OF MICROBIAL Fe(III) REDUCTION AND SOLUTION CHEMISTRY IN AGGREGATION AND SETTLING OF SUSPENDED PARTICLES IN THE MISSISSIPPI RIVER DELTA PLAIN, LOUISIANA, USA

机译：美国密西西比河三角洲平原微生物的Fe（III）还原和固溶化学在悬浮颗粒聚集和沉降中的作用

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River-dominated delta areas are primary sites of active biogeochemical cycling, with productivity enhanced by terrestrial inputs of nutrients. Particle aggregation in these areas primarily controls the deposition of suspended particles, yet factors that control particle aggregation and resulting sedimentation in these environments are poorly understood. This study was designed to investigate the role of microbial Fe(III) reduction and solution chemistry in aggregation of suspended particles in the Mississippi Delta. Three representative sites along the salinity gradient were selected and sediments were collected from the sediment-water interface. Based on quantitative miheralogical analyses 88-89 wt.% of all minerals in the sediments are clays, mainly smectite and illite. Consumption of SO_4~(2-) and the formation of H_2S and pyrite during microbial Fe(III) reduction of the non-sterile sediments by Shewanella putrefaciens CN32 in artificial pore water (APW) media suggest simultaneous sulfate and Fe(III) reduction activity. The pH_(PZNPC) of the sediments was ≤3.5 and their zeta potentials at the sediment-water interface pH (6.9-7.3) varied from -35 to -45 mV, suggesting that both edges and faces of clay particles have negative surface charge. Therefore, high concentrations of cations in pore water are expected to be a predominant factor in particle aggregation consistent with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Experiments on aggregation of different types of sediments in the same APW composition revealed that the sediment with low zeta potential had a high rate of aggregation. Similarly, addition of external Fe(II) (i.e. not derived from sediments) was normally found to enhance particle aggregation and deposition in all sediments, probably resulting from a decrease in surface potential of particles due to specific Fe(II) sorption. Scanning and transmission electron microscopy (SEM, TEM) images showed predominant face-to-face clay aggregation in native sediments and composite mixtures of biopolymer, bacteria, and clay minerals in the bioreduced sediments. However, a clear need remains for additional information on the conditions, if any, that favor the development of anoxia in deep- and bottom-water bodies supporting Fe(III) reduction and resulting in particle aggregation and sedimentation.
机译：河流占主导的三角洲地区是活跃的生物地球化学循环的主要地点，陆地养分的投入提高了生产力。这些区域中的颗粒聚集主要控制悬浮颗粒的沉积，但是在这些环境中控制颗粒聚集和导致沉积的因素知之甚少。这项研究旨在调查微生物的Fe（III）还原和溶液化学在密西西比三角洲悬浮颗粒聚集中的作用。选择沿盐度梯度的三个代表性地点，并从沉积物-水界面收集沉积物。根据定量的矿物学分析，沉积物中所有矿物的88-89 wt。％是粘土，主要是绿土和伊利石。在人造孔隙水（APW）介质中腐殖酸希瓦氏菌CN32对非无菌沉积物的微生物Fe（III）还原过程中SO_4〜（2-）的消耗以及H_2S和黄铁矿的形成表明同时有硫酸盐和Fe（III）还原活性。沉积物的pH_（PZNPC）≤3.5，且其在沉积物-水界面pH（6.9-7.3）处的ζ电位在-35至-45 mV之间变化，表明黏土颗粒的边缘和表面都带有负表面电荷。因此，与Derjaguin-Landau-Verwey-Overbeek（DLVO）理论相一致，孔隙水中的高浓度阳离子有望成为颗粒聚集的主要因素。在相同的APW组成中对不同类型的沉积物进行聚集的实验表明，ζ电位低的沉积物具有较高的聚集速率。类似地，通常发现添加外部Fe（II）（即不是来源于沉积物）可增强所有沉积物中的颗粒聚集和沉积，这可能是由于特定的Fe（II）吸附作用导致了颗粒表面电位的降低。扫描和透射电子显微镜（SEM，TEM）图像显示了天然沉积物中主要的面对面粘土聚集以及生物还原的沉积物中生物聚合物，细菌和粘土矿物的复合混合物。但是，仍然明确需要有关条件的其他信息，如果有的话，这些条件有利于深水和底水体内形成缺氧，从而支持Fe（III）还原并导致颗粒聚集和沉淀。

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