Low field frequency dependent magnetic susceptibility inversion

Ustra, Andréa Teixeira; Mendonça, Carlos Alberto; Leite, Aruã; Jaqueto, Plinio; Novello, Valdir F.

doi:10.1016/j.cageo.2019.104326

Cited by 4 publications

(3 citation statements)

References 18 publications

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“…In this work, we carried out MS frequency-dependent measurements with MFK1 (Agico, Inc.) at three frequencies (976 Hz, 3904 Hz, and 15.616 Hz). To quantify the SP response contribution to magnetic susceptibility, the limiting frequency effect (LFE) was estimated using the procedure proposed by Ustra et al 25 . In this procedure, a Debye relaxation model is used to fit the in-phase MS frequency measured at the MFK frequencies, yielding estimations of the low and high-frequency asymptotes, which are used to determine the LFE parameter.…”

Section: Methodsmentioning

confidence: 99%

Magnetic signatures of a creosote oil contaminated site: case study in São Paulo, Brazil

Moraes

Ustra

Barbosa

et al. 2022

Sci Rep

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Soils and groundwater contamination modifies the physical–chemical conditions of the environment, altering natural biogeochemical processes of the ground. As a result, several mineral transformations occur, in which iron plays a decisive role. The presence of iron enables the study of magnetic properties, improving the understanding of the geophysical signatures of highly dynamic environments (e.g., biogeochemical hotspots and contamination plumes). In this work, we seek to identify creosote biodegradation related to the precipitation of magnetic minerals on sediments at a contaminated site in São Paulo, Brazil. Several rock magnetism analyses were carried out to provide the magnetic mineralogy of the samples in terms of their composition, size, and abundance. We conducted high-temperature thermomagnetic curves, frequency-dependent magnetic susceptibility, anesthetic remanent magnetization (ARM) and isothermal remanent magnetization (IRM) data, superparamagnetic concentration and dipole moment (SPCDM), and scanning electron microscopy (SEM) analyses. The magnetic signatures of the contaminated samples suggest an increase of superparamagnetic grains in the water table fluctuation zone if compared to the magnetic signatures of the uncontaminated samples. Thermomagnetic curves of contaminated samples showed a lower heterogeneity of the magnetic mineral phases than the uncontaminated ones. This work contributes to the advancement of the understanding of how natural biogeochemical processes are impacted by human actions, such as soil contamination, and even by climate change, which should affect soil redox conditions in periods of drought and flooding.

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Section: Methodsmentioning

confidence: 99%

Magnetic signatures of a creosote oil contaminated site: case study in São Paulo, Brazil

Moraes

Ustra

Barbosa

et al. 2022

Sci Rep

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“…For measurements with a set of at least three frequencies f , (e.g. 976, 3,904 and 15,616 Hz as for the MFK1-FA Kappabridge susceptibility meter) the FDS data allow solving for unknown parameters (χ h , Δχ, τ) according to a constrained, non-linear data-fitting procedure (Ustra et al, 2019). Once estimated, such model parameters are used to determine the transition parameter F t χ l /χ h v/v c , that relates the mean volume v for the particle assemblage with respect to a characteristic volume v c…”

Section: Frequency Dependent Susceptibility (Fds)mentioning

confidence: 99%

“…Characteristic time τ 0 is a time-factor varying from 10 -12 to 10 -8 s (Dormann et al, 1996;Worm 1999). We use the MATLAB program FDS_inv.m (Ustra et al, 2019) to invert the three-frequency dataset acquired with Kappabridge MK1 at LabCore (University of São Paulo).…”

Section: Frequency Dependent Susceptibility (Fds)mentioning

confidence: 99%

Ultrafine Magnetic Particles: A DIET-Proxy in Organic Rich Sediments?

et al. 2021

Self Cite

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In this work we present results of the magnetic properties characterization of sediment samples from a brownfield site that is generating methane biogas in São Paulo–Brazil. We applied interpretation procedures (frequency dependent susceptibility and time-dependent Isothermal Remanent Magnetization) appropriate to study the ultrafine magnetic fraction response of the samples. The higher content of superparamagnetic (SP) particles correlates well with the detected biogas pockets, suggesting that the methanogens activity produces these ultrafine particles, different from the magnetic particles at other depth levels. We propose the use of two simple measurement and interpretation techniques to identify such magnetic particles fingerprints. The results presented here support the use of environmental magnetism techniques to investigate biogeochemical processes of anaerobic microbial activity.

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Comparative study on the applicability of regularization method in ship’s magnetic signature modeling based on monopole array

Liu

Zong

2022

AIP Advances

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In this paper, we first study the applicability and stability of the Tikhonov regularization method (TRM) and the truncated singular value decomposition method in ship’s magnetic signature inversion modeling. To further improve the noise immunity and robustness of the model, we apply an iterative regularization algorithm based on the conjugate gradient least squares (CGLS) method. Numerical simulation shows that the proposed algorithm is more applicable and can obtain better results of ship’s magnetic field extrapolation under different noise backgrounds. In the ship model experiment, the errors of the TRM and CGLS method for magnetic signature extrapolation are, respectively, 4.77% and 3.67%, showing that the proposed algorithm can improve the inversion effect of the ship model magnetic field.

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Low field frequency dependent magnetic susceptibility inversion

Cited by 4 publications

References 18 publications

Magnetic signatures of a creosote oil contaminated site: case study in São Paulo, Brazil

Magnetic signatures of a creosote oil contaminated site: case study in São Paulo, Brazil

Ultrafine Magnetic Particles: A DIET-Proxy in Organic Rich Sediments?

Comparative study on the applicability of regularization method in ship’s magnetic signature modeling based on monopole array

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