气候变化领域集成服务门户(CCPortal): Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin

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DOI	10.1016/j.epsl.2020.116288
	Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin
	Luo M.; Torres M.E.; Hong W.-L.; Pape T.; Fronzek J.; Kutterolf S.; Mountjoy J.J.; Orpin A.; Henkel S.; Huhn K.; Chen D.; Kasten S.
发表日期	2020
ISSN	0012821X
卷号	541
英文摘要	We present geochemical data collected from volcanic ash-bearing sediments on the upper slope of the northern Hikurangi margin during the RV SONNE SO247 expedition in 2016. Gravity coring and seafloor drilling with the MARUM-MeBo200 allowed for collection of sediments down to 105 meters below seafloor (mbsf). Release of dissolved Sr2+ with isotopic composition enriched in 86Sr (87Sr/86Sr minimum = 0.708461 at 83.5 mbsf) is indicative of ash alteration. This reaction releases other cations in the 30-70 mbsf depth interval as reflected by maxima in pore-water Ca2+ and Ba2+ concentrations. In addition, we posit that Fe(III) in volcanogenic glass serves as an electron acceptor for methane oxidation, a reaction that releases Fe2+ measured in the pore fluids to a maximum concentration of 184 μM. Several lines of evidence support our proposed coupling of ash alteration with Fe-mediated anaerobic oxidation of methane (Fe-AOM) beneath the sulfate-methane transition (SMT), which lies at ∼7 mbsf at this site. In the ∼30-70 mbsf interval, we observe a concurrent increase in Fe2+ and a depletion of CH4 with a well-defined decrease in δ13C-CH4 values indicative of microbial fractionation of carbon. The negative excursions in δ13C values of both DIC and CH4 are similar to that observed by sulfate-driven AOM at low SO4 2− concentrations, and can only be explained by the microbially-mediated carbon isotope equilibration between CH4 and DIC. Mass balance considerations reveal that the iron cycled through the coupled ash alteration and AOM reactions is consumed as authigenic Fe-bearing minerals. This iron sink term derived from the mass balance is consistent with the amount of iron present as carbonate minerals, as estimated from sequential extraction analyses. Using a numerical modeling approach we estimate the rate of Fe-AOM to be on the order of 0.4 μmol cm−2 yr−1, which accounts for ∼12% of total CH4 removal in the sediments. Although not without uncertainties, the results presented reveal that Fe-AOM in ash-bearing sediments is significantly lower than the sulfate-driven CH4 consumption, which at this site is 3.0 μmol cm−2 yr−1. We highlight that Fe(III) in ash can potentially serve as an electron acceptor for methane oxidation in sulfate-depleted settings. This is relevant to our understanding of C-Fe cycling in the methanic zone that typically underlies the SMT and could be important in supporting the deep biosphere. © 2020 Elsevier B.V.
关键词	deep biosphere diagenesis Fe-AOM Hikurangi margin volcanic ash
英文关键词	Carbon; Isotopes; Methane; Oxidation; Positive ions; Sediments; Sulfur compounds; Underwater mineral resources; Volcanoes; Anaerobic oxidation of methanes; Isotopic composition; Mass balance considerations; Maximum concentrations; Numerical modeling approach; Seafloor drilling; Sequential extraction; Sulfate-methane transitions; Iron compounds; carbon cycle; chemical alteration; concentration (composition); iron; marine sediment; methane; porewater; volcanic ash; Hikurangi Margin; Pacific Ocean
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202765
作者单位	Shanghai Engineering Research Center of Hadal Science and Technology, College of Marine Sciences, Shanghai Ocean University, Shanghai, 201306, China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266061, China; College of Earth, Ocean and Atmospheric Science, Oregon State University, Corvallis, OR 97331, United States; Geological Survey of Norway, Trondheim (NGU), Norway; MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany; Faculty of Geosciences, University of Bremen, Bremen, Germany; GEOMAR Helmholtz Centre for Ocean Research, Kiel, 24148, Germany; National Institute of Water and Atmospheric Research, Wellington, New Zealand; Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
推荐引用方式 GB/T 7714	Luo M.,Torres M.E.,Hong W.-L.,et al. Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin[J],2020,541.
APA	Luo M..,Torres M.E..,Hong W.-L..,Pape T..,Fronzek J..,...&Kasten S..(2020).Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin.Earth and Planetary Science Letters,541.
MLA	Luo M.,et al."Impact of iron release by volcanic ash alteration on carbon cycling in sediments of the northern Hikurangi margin".Earth and Planetary Science Letters 541(2020).