| Gypsum and anhydrite sulfate minerals were widely distributed in various salt sedimentary environment, when the local layer was in the anaerobic environment, under the action of sulfate reducing bacteria (SRB), these minerals were easily decomposition,then migration of elements and mineral transformation were taken place, finally caused an important impact on the environment. By conducting simulation experiment, this paper discusses the SRB reduction on several issues in the process of decomposition of sulfate minerals, including:(1) in salt sedimentary environment, the effects of high salinity conditions were taken the activity of SRB which focus on studying the effect of Na, Mg and Ca ion concentration; (2) adopt the method of dialysis to examines SRB and the contact between different molecular and mineral to weight the influence of the reductive decomposition; (3) the geochemical impact on the element As with themineral decomposition process by SRB. The obtained results in the paper are as follows:Cation concentration has a great influence on activity of SRB. PH and ORP in low concentration of Na system are fall in SRB growth period, at the same time appear a little precipitation; When Na concentration increased to more than 35‰, pH in system rised lower rarely, ORP in system kept elevating, precipitation is no longer present at the same time, shows that the high Na conditions restrict the growth of SRB. In this study set of Ca, Mg concentration range (<1‰ and 4‰), pH and ORP in solution are keep falling during the growth of SRB, and precipitation increased with the increasing of the concentration of two elements, show that Ca and Mg has a promoting effect on the growth of SRB.SRB - sulfate mineral system, pH was rising during the experiment, Eh was continuing to fall, the two indicators which has bacterium experiments raised or droped were of less influenced by experimental condition. The S2 - concentration in the sterile system remains the same, in the bacteria system continued to rise, and contact experiment rise which is greater than the dialysis, dialysis experiment dialysis bag S2 - high concentrations of aperture is large. Under the same experimental conditions, the elevated degree about S2 - in gypsum and anhydrite has the similar degree, barite is about one order of magnitude smaller than the gypsum and anhydrite. Research results show that the SRB and its metabolic product and the contact between gypsum gradually strengthen, gypsum reduction decomposition ability gradually improving. In addition, SRB and its metabolites can be induced to form good crystallization morphology of calcite and functional carbonate precipitation.SRB reducted decomposition of the carbonate and sulfate minerals has the strong fixation ability with As. In the SRB - sulfate mineral system which contained As, the touch between SRB and sulfate mineral has the minimum amount of fixed As. The fixed ability of As was also reducing with the increase of dialysis bag aperture. This phenomenon showed that dialysis bag influenced sulfate mineral decomposition as well as the iron sulfide formation rate and efficiency of the As fixed at the same time. Sulfide formation rate was also accelerated with the release rate of S2- improved in the reason of the enhance of SRB and metabolic products contacted the mineral, and the fixed quantity of As reduced as the compatible elements of sulfide. The content of As in sulphide combination various conformed to that law after the analysis of As in various forms in solid, but the variation of As in carbonate combination state was on the contrary. The reason is the As for carbonate incompatible elements, therefore carbonate mineral formation rate faster, the weaker the fixed As ability.The study shows that the SRB reduction decomposition in the process of sulfate mineral of sulfide, SRB and metabolic product and the contact between the mineral on sulfur, arsenic, iron and other elements of the cycle has important effect... |
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