The Mechanism Of Microbial Influence On Iron-Sulfur Interface Behavior

Iron and sulfur are common elements that are widely involved in the geochemical cycle,the interfacial behavior of the two elements tend to occur simultaneously and interact with each other.In this paper,in view of the long-term ice-covered period of Mongolian plateau lakes,taking the sediments in Wuliangsuhai which is on the typical cold and arid area as the research object,mainly researched the interaction behaviors of iron and sulfur under the conditions of ice-covered and non-freezing period,deeply discussed the mechanism of synergistic effect of DFeRB/SRB on iron and sulfur behaviors in sediment-water interface,illustrated the coupling relationship of sulfur and iron,so as to reveal the environmental changes of lakes in the cold and arid regions during the freezing period and to evaluate the contribution of low-activity microorganisms in the ice-sealing period to the iron/sulfur geochemical cycle,thus providing basic data and scientific basis.This paper draws the following conclusions:?1?Although the iron/sulfur reduction degree and release intensity during the ice-covered period are lower than the non-freezing period,and the change trend is more stable,the frozen state still has a certain degree of influence on the occurrence and transformation of iron/sulfur in natural lakes.?2?In the iron-sulfur non-coexistence system,DFeRB and SRB have the same effect on iron reduction,but DFeRB promotes sulfur reduction more strongly than SRB.In the iron-sulfur coexistence system,both bacteria are more inclined to exchange electrons with sulfate.And the total amount of iron and sulfur electrons is larger when DFeRB participates in the reaction.It reveals the difference in reducing tendency and bioavailability of different microorganisms.?3?There is a correlation between the release rate of Fe and S and the rate of reduction product formation,but the release rate of Fe has a significant hysteresis compared with S.It is confirmed that there are different degrees of coupling between Fe-S and there are stage differences.?4?Under the condition of adding reducing bacteria,the reduction of sulfate is more obviously than the reduction of ferric iron,revealing a reduction mechanism that the induction in the reaction product in combination with the direct action of microorganisms.?5?The concentration of Fe²⁺in the non-freezing period of the undisturbed sediment group increased slightly from the upper layer to the lower layer.The distribution of iron/sulfur in other systems is also different in the vertical direction,indicating that the iron/sulfur vertical interface also has migration and conversions.