Rock magnetic, chemical and bacterial community analysis of a modern soil from Nebraska

Guyodo, Yohan; LaPara, Timothy M.; Anschutz, Amy J.; Penn, R. Lee; Banerjee, Subir K.; Geiss, C. E.; Zanner, William

doi:10.1016/j.epsl.2006.09.005

Cited by 60 publications

(67 citation statements)

References 29 publications

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“…This fraction would have produced a sextet superposed with the SP doublet at 300 K but it must have been a sufficiently small volume fraction that the sextet cannot be resolved. Furthermore, nanoparticles of antiferromagnetic minerals like goethite may have small uncompensated magnetic moments due to surface or volume defects, enhancing the magnetization over bulk values [e.g., Guyodo et al, 2006]. Therefore, remanent magnetization data may not be directly comparable to Mössbauer data.…”

Section: Mössbauer Spectroscopymentioning

confidence: 87%

“…The offsets were more noticeable for the HM sample group. Large FC-ZFC offsets are typically seen for goethite [Guyodo et al, 2006, Carter-Stiglitz et al, 2006, and much smaller ones in multidomain (> 1 μm), partially oxidized, magnetite [Smirnov and Tarduno, 2000]. Both phases probably contribute to the FC/ZFC behavior, but because of the very large differences in the intrinsic saturation magnetization between magnetite/maghemite and goethite, the former dominates in these series of measurements.…”

Section: Low-temperature Magnetic Properties: Fc Zfc and Rtsirmmentioning

confidence: 99%

“…To evaluate the relative contributions of goethite and hematite to the total remanence, several additional low-temperature cycling runs were measured following procedures in Guyodo et al (2006) and Carter-Stiglitz et al (2006). These additional steps are designed to minimize the contribution from strongly magnetic minerals like magnetite and maghemite, which can dominate the FC, ZFC, and RTSIRM magnetizations, and target weakly magnetic, antiferromagnetic minerals with high coercivities like goethite and hematite.…”

Section: Magnetic Methodsmentioning

confidence: 99%

“…We also determined the type of ferric oxide mineral, whether primarily hematite (-Fe 2 O 3 ) or goethite (-FeOOH), which are the two most common forms in desert soils and surfaces (hereafter collectively referred to as iron oxides or ferric oxides), and which have different optical properties. Reflectance spectroscopy can be used to identify different ferric oxide minerals (e.g., Clark et al, 2007), as can certain magnetic methods (Maher et al, 2004;Guyodo et al, 2006;Carter-Stiglitz et al, 2006;Liu et al, 2006;Maher, 2011). Mössbauer spectroscopy was also employed to identify with high specificity various iron phases, including amounts of hematite and goethite as well as the fraction that occur as nanoparticles, in a sample.…”

Section: Introductionmentioning

confidence: 99%

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Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

et al. 2016

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Atmospheric mineral dust can influence climate and biogeochemical cycles. An important component of mineral dust is ferric oxide minerals (hematite and goethite) which have been shown to influence strongly the optical properties of dust plumes and thus affect the radiative forcing of global dust. Here we report on the iron mineralogy of dust-source samples from the Bodélé Depression (Chad, north-central Africa), which is estimated to be Earth's most prolific dust producer and may be a key contributor to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon Basin. By using a combination of magnetic property measurements, Mössbauer spectroscopy, reflectance spectroscopy, chemical analysis, and scanning electron microscopy, we document the abundance and relative amounts of goethite, hematite, and magnetite in dust-source samples from the Bodélé Depression. The partition between hematite and goethite is important to know to improve models for the radiative effects of ferric oxide minerals in mineral dust aerosols. The combination of methods shows (1) the dominance of goethite over hematite in the source sediments, (2) the abundance and occurrences of their nanosize components, and (3) the ubiquity of magnetite, albeit in small amounts. Dominant goethite and subordinate hematite together compose about 2% of yellowreddish dust-source sediments from the Bodélé Depression and contribute strongly to diminution of reflectance in bulk samples. These observations imply that dust plumes from the Bodélé Depression that are derived from goethite-dominated sediments strongly absorb solar radiation. The presence of ubiquitous magnetite (0.002-0.57 wt. %) is also noteworthy for its potentially higher solubility relative to ferric oxide and for its small sizes, including PM<0.1m. For all examined samples, the average iron apportionment is estimated at about 33% in ferric oxide minerals, 1.4 % in magnetite, and 65% in ferric silicates. Structural iron in clay minerals may account for much of the iron in the ferric silicates. We estimate that the mean ferric oxides flux exported from the Bodélé Depression is 0.9 Tg/yr with greater than 50% exported as ferric oxide nanoparticles (<0.1m). The high surface-to-volume ratios of ferric oxide nanoparticles once entrained into dust plumes may facilitate increased atmospheric chemical and physical processing and affect iron solubility and bioavailability to marine and terrestrial ecosystems.

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Section: Mössbauer Spectroscopymentioning

confidence: 87%

Section: Low-temperature Magnetic Properties: Fc Zfc and Rtsirmmentioning

confidence: 99%

Section: Magnetic Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

et al. 2016

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“…We used the goethite-pretreatment low-temperature measure sequence designed by Guyodo et al (51) to target weak magnetic minerals such as goethite and hematite. Detailed protocols are provided in Fig.…”

Section: Methodsmentioning

confidence: 99%

Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China

Zhu

Feinberg

Xie

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

166

137

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Extreme hydrologic events such as storms and floods have the potential to severely impact modern human society. However, the frequency of storms and their underlying mechanisms are limited by a paucity of suitable proxies, especially in inland areas. Here we present a record of speleothem magnetic minerals to reconstruct paleoprecipitation, including storms, in the eastern Asian monsoon area over the last 8.6 ky. The geophysical parameter IRMsoft-fluxrepresents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRMsoft-fluxexhibits relatively higher values before 6.7 ky and after 3.4 ky and lower values in the intervening period, consistent with regional hydrological changes observed in independent records. Abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial El Niño−Southern Oscillation (ENSO) patterns, documenting the occurrence of ENSO-related storms in the Holocene. Spectral power analyses reveal that the storms occur on a significant 500-y cycle, coincident with periodic solar activity and ENSO variance, showing that reinforced (subdued) storms in central China correspond to reduced (increased) solar activity and amplified (damped) ENSO. Thus, the magnetic minerals in speleothem HS4 preserve a record of the cyclic storms controlled by the coupled atmosphere−oceanic circulation driven by solar activity.

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Magnetism of Al‐substituted magnetite reduced from Al‐hematite

et al. 2016

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Aluminum‐substituted magnetite (Al‐magnetite) reduced from Al‐substituted hematite or goethite (Al‐hematite or Al‐goethite) is an environmentally important constituent of magnetically enhanced soils. In order to characterize the magnetic properties of Al‐magnetite, two series of Al‐magnetite samples were synthesized through reduction of Al‐hematite by a mixed gas (80% CO2 and 20% CO) at 395°C for 72 h in a quartz tube furnace. Al‐magnetite samples inherited the morphology of their parent Al‐hematite samples, but only those transformed from Al‐hematite synthesized at low temperature possessed surficial micropores, which originated from the release of structural water during heating. Surface micropores could thus serve as a practical fingerprint of fire or other high‐temperature mineralogical alteration processes in natural environments, e.g., shear friction in seismic zones. In addition, Al substitution greatly affects the magnetic properties of Al‐magnetite. For example, coercivity (Bc) increases with increasing Al content and then decreases slightly, while the saturation magnetization (Ms), Curie temperature (Tc), and Verwey transition temperature (Tv) all decrease with increasing Al content due to crystal defect formation and dilution of magnetic ions caused by Al incorporation. Moreover, different trends in the correlation between Tc and Bc can be used to discriminate titanomagnetite from Al‐magnetite, which is likely to be important in environmental and paleomagnetic studies, particularly in soil.

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Rock magnetic, chemical and bacterial community analysis of a modern soil from Nebraska

Cited by 60 publications

References 29 publications

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China

Magnetism of Al‐substituted magnetite reduced from Al‐hematite

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