浅海Mg^(2+)和SO_4^(2-)对微生物诱导形成锰碳酸盐的影响

Effects of Mg^(2+) and SO_4^(2-) on Mn-Carbonate Mineralization Induced by Microorganisms in Shallow Seas

为了模拟浅海环境下锰氧化物微生物还原作用诱导碳酸盐沉淀的过程,选取最常见的锰氧化物-水钠锰矿(K_(0.33)Mn_7O_(14)·7H_2O)为研究对象,在不同种类与浓度盐离子(Mg^(2+)、SO_4^(2-))存在条件下开展异化锰还原菌Dietzia cercidiphylli 45-1b好氧还原水钠锰矿的实验研究.通过测试体系蛋白、Mn^(2+)等离子浓度变化,利用X射线衍射(XRD)和X射线吸收谱(XAS)表征反应前后矿物结构变化,来探讨不同初始Mg^(2+)和SO_4^(2-)浓度对于菌株45-1b还原水钠锰矿及诱导碳酸盐矿物沉淀的影响.结果显示体系pH值在4天内从7.0迅速上升至9.3,Mn^(2+)浓度在2天内迅速上升至166μmol/L,随后迅速下降至8μmol/L(第4天),其好氧还原产物为菱锰矿(MnCO3),且其产生量随Mg^(2+)浓度的升高而降低,随SO_4^(2-)浓度的升高而升高.上述实验结果表明好氧环境下菌株45-1b能够利用乙酸为电子供体,水钠锰矿为电子受体还原水钠锰矿释放Mn^(2+),最终转化有机碳为无机碳酸盐矿物菱锰矿.Mg^(2+)通过影响微生物生长和菱锰矿成核对水钠锰矿的还原及菱锰矿沉淀产生抑制作用,而SO_4^(2-)可以缓解Mg^(2+)的抑制作用并促进水钠锰矿的还原及菱锰矿沉淀.

In order to simulate bio-reduction of manganese oxides and coupled carbonate precipitation induced by microbes in shallow sea environments, we took one of the most common manganese oxides-birnessite（K（0.33）Mn7O（14）·7H2O） as an example and carried out experiments under different Mg^2＋and SO4^2-concentrations, where dissimilatory manganese-reducing bacteria Dietzia cercidiphylli 45-1 b reduced birnessite under aerobic conditions. By analyzing variations of the concentrations of protein, Mn^2＋, etc., alongside X-ray powder diffraction（XRD） and X-ray absorption spectroscopy（XAS） for mineralogical transformations analyses, we discussed the impact on birnessite reduction and carbonate precipitation by Strain 45-1 b under different initial concentrations of Mg^2＋and SO4^2-. Results show that the pH in our experimental systems quickly increased from7.0 to 9.3 during the course of four days, and Mn^2＋concentrations increased to 166 μmol/L in two days and rapidly decreased to 8 μmol/L on the fourth day with rhodochrosite（MnCO3） as reduction products under aerobic conditions.The production of rhodochrosite decreased with increasing Mg^2＋concentrations and increased with rising SO4^2-concentrations. These results indicate that Strain 45-1 b can utilize acetate as the electron donor and birnessite as the electron acceptor under aerobic conditions, causing birnessite reduction and Mn^2＋releasing and ultimately conversing organic carbon into inorganic carbonate minerals as rhodochrosite. Mg^2＋inhibited microbial growth and the presence of rhodochrosite nucleation sites to affect birnessite reduction and rhodochrosite precipitation, and SO4^2-mitigated Mg^2＋inhibition and promoted birnessite reduction and rhodochrosite precipitation.