skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Influence of iron redox cycling on organo-mineral associations in Arctic tundra soil

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1355038
DOE Contract Number:
AC05-00OR22725; AC02-06CH11357; FG02-94ER14466; DBI-1263263
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; Journal Volume: 207
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Herndon, Elizabeth, AlBashaireh, Amineh, Singer, David, Roy Chowdhury, Taniya, Gu, Baohua, and Graham, David. Influence of iron redox cycling on organo-mineral associations in Arctic tundra soil. United States: N. p., 2017. Web. doi:10.1016/j.gca.2017.02.034.
Herndon, Elizabeth, AlBashaireh, Amineh, Singer, David, Roy Chowdhury, Taniya, Gu, Baohua, & Graham, David. Influence of iron redox cycling on organo-mineral associations in Arctic tundra soil. United States. doi:10.1016/j.gca.2017.02.034.
Herndon, Elizabeth, AlBashaireh, Amineh, Singer, David, Roy Chowdhury, Taniya, Gu, Baohua, and Graham, David. 2017. "Influence of iron redox cycling on organo-mineral associations in Arctic tundra soil". United States. doi:10.1016/j.gca.2017.02.034.
@article{osti_1355038,
title = {Influence of iron redox cycling on organo-mineral associations in Arctic tundra soil},
author = {Herndon, Elizabeth and AlBashaireh, Amineh and Singer, David and Roy Chowdhury, Taniya and Gu, Baohua and Graham, David},
abstractNote = {},
doi = {10.1016/j.gca.2017.02.034},
journal = {Geochimica et Cosmochimica Acta},
number = ,
volume = 207,
place = {United States},
year = 2017,
month = 6
}
  • Arctic tundra stores large quantities of soil organic matter under varying redox conditions. As the climate warms, these carbon reservoirs are susceptible to increased rates of decomposition and release to the atmosphere as the greenhouse gases carbon dioxide (CO 2) and methane (CH 4). Geochemical interactions between soil organic matter and minerals influence decomposition in many environments but remain poorly understood in Arctic tundra systems and are not considered in decomposition models. The accumulation of iron (Fe) oxyhydroxides and organo- iron precipitates at redox interfaces may be particularly important for carbon cycling given that ferric iron [Fe(III)] species can enhancemore » decomposition by serving as terminal electron acceptors in anoxic soils or inhibit microbial decomposition by binding organic molecules. Here in this paper, we examine chemical properties of solid-phase Fe and organic matter in organic and mineral horizons within the seasonally thawed active layer of Arctic tundra on the North Slope of Alaska. Spectroscopic techniques, including micro-X-ray fluorescence ( XRF) mapping, micro-X-ray absorption near-edge structure ( XANES) spectroscopy, and Fourier transform infrared spectroscopy (FTIR), were coupled with chemical sequential extractions and physical density fractionations to evaluate the spatial distribution and speciation of Fe-bearing phases and associated organic matter in soils. Organic horizons were enriched in poorly crystalline and crystalline iron oxides, and approximately 60% of total Fe stored in organic horizons was calculated to derive from upward translocation from anoxic mineral horizons. Ferrihydrite and goethite were present as coatings on mineral grains and plant debris, and in aggregates with clays and particulate organic matter. Minor amounts of ferrous iron [Fe(II)] were present in iron sulfides (i.e., pyrite and greigite) in mineral horizon soils and iron phosphates (vivianite) in organic horizons. Concentrations of organic carbon in the organic horizons (28 ± 5% wt. % C) were approximately twice the concentrations in the mineral horizons (14 ± 2 % wt. C), and organic matter was dominated by base-extractable and insoluble organics enriched in aromatic and aliphatic moieties. Conversely, water-soluble organic molecules and organics solubilized through acid-dissolution of iron oxides comprised < 2% of soil organic C and were consistent with a mixture of alcohols, sugars, and small molecular weight organic acids and aromatics released through decomposition of larger molecules. Integrated over the entire depth of the active layer, soils contained 11± 4 kg m -2 low- density, particulate organic C and 19 ± 6 kg m -2 high-density, mineral-associated organic C, indicating that 63 ±19% of organic C in the active layer was associated with the mineral fraction. We conclude that organic horizons were enriched in poorly crystalline and crystalline iron oxide phases derived from upward translocation of dissolved Fe(II) and Fe(III) from mineral horizons. Precipitation of iron oxides at the redox interface has the potential to contribute to mineral protection of organic matter and increase the residence time of organic carbon in arctic soils. Our results suggest that iron oxides may inhibit organic carbon degradation by binding low-molecular-weight organic compounds, stabilizing soil aggregates, and forming thick coatings around particulate organic matter. Organic matter released through acid-dissolution of iron oxides could represent a small pool of readily-degradable organic molecules temporarily stabilized by sorption to iron oxyhydroxide surfaces. The distribution of iron in organic complexes and inorganic phases throughout the soil column constrains Fe(III) availability to anaerobic iron-reducing microorganisms that oxidize organic matter to produce CO 2 and CH 4 in these anoxic environments. Future predictions of carbon storage and respiration in the arctic tundra should consider such influences of mineral stabilization under changing redox conditions.« less
  • Spatial and temporal patterns of CO{sub 2} efflux from arctic tundra soils are examined with three, linked simulation models at a 2.2-km{sup 2} catchment. The model complex runs on a 20*20 m grid and a temporal resolution of 1 h over one growing season. TOPMODEL is used to predict the dynamics of the water balance and spatial pattern of water table. A canopy model (GAS-FLUX) is used to predict moss and vascular plant transpiration rates. Soil respiration is computed form an empirical regression model incorporating the effects of soil temperature and depth to the water table. Soil efflux in themore » riparian zones of 60 g C m{sup {minus}2} compares to 119 g C m{sup {minus}2} in the hillslopes indicating large spatial differences. An increase of air temperature and solar radiation or a decrease of precipitation increase soil respiration. The results indicate a tight connection between water and carbon cycles at the catchment scale. Keeping all other conditions constant, a seasonal increase of transpiration rates by 10% increases soil respiration by 5% or 4.6 g Cm{sup {minus}2}. Data deficiencies and suggestions for future modeling are discussed. 40 refs., 8 figs.« less
  • Temperature rise in the Arctic is causing deepening of active layers and resulting in the mobilization of deep permafrost dissolved organic matter (DOM). However, the mechanisms of DOM mobilization from Arctic soils, especially upper soil horizons which are drained most frequently through a year, are poorly understood. Here, we conducted a short-term leaching experiment on surface and deep organic active layer soils, from the Yukon River basin, to examine the effects of DOM transport on bulk and molecular characteristics. Our data showed a net release of DOM from surface soils equal to an average of 5% of soil carbon. Conversely,more » deep soils percolated with surface leachates retained up to 27% of bulk DOM-while releasing fluorescent components (up to 107%), indicating selective release of aromatic components (e.g. lignin, tannin), while retaining non-chromophoric components, as supported by spectrofluorometric and ultra high resolution mass spectroscopic techniques. Our findings highlight the importance of the lateral flux of DOM on ecosystem carbon balance as well as processing of DOM transport through organic active layer soils en route to rivers and streams. This work also suggests the potential role of leachate export as an important mechanism of C losses from Arctic soils, in comparison with the more traditional pathway from soil to atmosphere in a warming Arctic.« less