B13C-0637
Structural and chemical modification of Fe-rich smectite associated with microbial Fe-respiration by psychrophilic bacteria in King George Island, West Antarctica
Monday, 14 December 2015
Poster Hall (Moscone South)
Jaewoo Jung1, Jee-young Kim2, Hyoun Soo Lim3, Yoo Kyung Lee4, Ok-sun Kim4, Kyongryang Park5, Jungbae Lee5, Hoil Yoon6 and Jin-wook Kim1, (1)Yonsei University, Seoul, South Korea, (2)National Institute of Environmental Research, Environmental Infrastructure Research Department, Incheon, South Korea, (3)Pusan University, 3Department of Geological Sciences, Pusan, South Korea, (4)Korea Polar Research Insitute, Incheon, South Korea, (5)Hannam University, Daegeon, South Korea, (6)KOPRI Korea Polar Research Institute, Incheon, South Korea
Abstract:
Biotic/abiotic redox reaction is a ubiquitous process in a mineral alteration and an elemental cycling in the sediments/ocean. The role of psychrophiles in clay mineral alteration was tested in the soil for the seven sites from the coast to the inland at Barton Peninsula. Batch experiments of microbe-mineral interaction under the various temperatures (4 ℃, 15 ℃) that mimics the Antarctic condition were performed to understand the mechanism of biogeochemical alteration of clay minerals. After 12 months incubation of the bulk surface soil samples in the M1 minimal medium, the extent of Fe reduction was reached up to 49 and 42 % at 4 ℃ and 15 ℃. The increase in CEC corresponds to the extent of Fe reduction. Moreover, precipitations of secondary phase mineral such as vivianite were observed only in 12 months enrichment samples at 4 ℃ and 15 ℃. Sulfate reducing bacteria and Fe-reducing bacteria capable of reducing Fe were identified by 16S rRNA pyrosequencing. The Fe reduction coupled to oxidation of organic matter might be enhanced by cooperation of a consortium of Sulfate reducing bacteria and Fe-reducing bacteria. Moreover, Nitrate reducing bacteria which have an ability to oxidize ferrous iron anaerobically with nitrate reduction were identified at 15 ℃. The lower values observed in the extent of Fe reduction at 15 ℃ may be associated with Fe-oxidation induced by nitrate reduction.In order to verify the mechanism of microbial Fe reduction in clay minerals at low temperatures (4 and 15 ℃), Fe-rich Nontronite (NAu-1) and Psychrophilic bacteria were incubated for 4 months in anaerobic condition. Total structural Fe in NAu-1 is 16.4 % and 99.6 % of the total Fe is ferric. The extent of Fe reduction in nontronite was reached up to 11.5 % and 11 % at 4 ℃ and 15 ℃, respectively. The structural modification of biologically Fe-reduced nontronite was observed in the (001) peak shift to the lower 2 theta indicating the layer collapse associated with K-fixation. Vivianite precipitation suggesting the reductive dissolution of nontronite were observed in 4 months enrichment samples at 4 ℃ and 15 ℃. The present study, therefore, indicates the feasibility of biological effects on chemical/structural modification in clay minerals in cold environment suggesting a new pathway of Fe-supply into the Antarctic Ocean.
