Frequency-dependent Susceptibility Research Articles

Environmental magnetism: Application to cave sediments

Environmental magnetism techniques allow a rapid, low cost and sensitive characterization of sediments and can be applied in a wide range of environments. More specific, magnetic properties can be successfully used to reconstruct paleoenvironmental and paleoclimatic conditions in rockshelter and cave sites. Cave sediments, imprint the environmental conditions at the Earth’s surface at the time of deposition since are well protected both at the interior and at the entrance of the cave systems. In addition, many cultural sequences and archaeological artifacts are well preserved in rockshelter and cave sediment records and can be effectively used for paleoenvironmental interpretations. In this study we present data from two different cave sites from Northern Greece. In the first cave (Maronia Cave) magnetic measurements were performed in two cores 80 and 90 cm, respectively, located inside the cave area. High values of magnetic susceptibility are directly linked with the human activity inside the cave, while lower values show deposition under infiltration and fluvial processes. In the second cave (Mikro Eptamilon Cave), magnetic susceptibility and frequency dependent magnetic susceptibility depicted from a sedimentary sequence with a thickness of 200 cm, located in the entrance of the cave. Results lead to conclusions concerning the velocity of the paleo-flow likely related to the paleoclimatic conditions that dominated the broader area.

Impacts of geology and land use on magnetic susceptibility and selected heavy metals in surface soils of Mashhad plain, northeastern Iran

Magnetic susceptibility is a fast, inexpensive and reliable technique for estimating and monitoring the anthropogenic contamination of soil with heavy metals. However, it is essential to determine the factors affecting magnetic susceptibility before applying this technique to environmental studies. The objectives of this study were to investigate i) the effect of parent materials and land use on the magnetic susceptibility and concentrations of Fe, Ni, Pb and Zn, and ii) capability of magnetic susceptibility as an indicator of anthropogenic heavy metals contamination of soil in Mashhad plain, northeastern Iran. One hundred seventy-eight composite surface soil samples (0–10cm) were taken. The aqua-regia extractable concentrations of Fe, Ni, Zn and Pb were determined by atomic absorption spectroscopy. Magnetic susceptibility at low and high frequency (χlf and χhf) were measured and frequency dependent susceptibility (χfd) was calculated. The average concentrations of Fe, Ni, Pb and Zn were 22,812, 61.4, 74.1 and 31.6mg kg−1, respectively. The highest contents of Pb (69.1mg kg−1) and Zn (149mg kg−1) were observed in urban area. The highest concentration of Ni was 41,538mg kg−1 observed in the soils developed from ultramafic rocks. Magnetic susceptibility varied from 20.3 on marly sediments to 311.8×10−8m3kg−1 on ultramafic rocks. A positive strong correlation (Pvalue<0.01, r=0.88) was obtained between Ni and χlf. There were no significant relationships between Zn and Pb with χlf, therefore it seems that magnetic susceptibility has not been affected significantly by anthropogenic activities which enhanced Pb and Zn concentrations in urban soils. The results indicated that magnetic susceptibility was mainly controlled by Ni containing minerals with lithogenic origin. Therefore, in the soils studied, magnetic susceptibility could not be employed as indicator of anthropogenic contamination of soil with heavy metals.

Effect of magnetic dipolar interactions on temperature dependent magnetic hyperthermia in ferrofluids

Magnetic hyperthermia (MHT), where localized heating is generated when magnetic nanoparticles (MNPs) are subjected to a radiofrequency magnetic field, has a great potential as a non-invasive cancer therapy treatment. The efficiency of heat generation depends on the magnetic properties of MNPs, such as saturation magnetization (Ms) and magnetic anisotropy (K), as well as the particle size distribution and magnetic dipolar interactions. We have investigated MHT in two Fe3O4 ferrofluids prepared by co-precipitation (CP) and hydrothermal (HT) synthesis methods showing similar physical particle size distribution (14 ± 4 nm) and saturation magnetization (70 ± 2 emu/g of Fe3O4) but very different specific absorption rates (SAR) of ∼110 W/g and ∼40 W/g at room temperature (measured with an ac magnetic field amplitude of 240 Oe and a frequency of 375 kHz). This observed reduction in SAR has been explained by taking into account the dipolar interactions and the distribution of the magnetic core size of MNPs in ferrofluids. The HT ferrofluid shows a higher effective dipolar interaction and a wider distribution of the magnetic core size of MNPs compared to those of the CP ferrofluid. We have fitted the temperature dependent SAR data using the linear response theory, incorporating an effective dipolar interaction, to determine the magnetic anisotropy constant of MNPs prepared by CP (22 ± 2 kJ/m3) and HT (26 ± 2 kJ/m3) synthesis methods. These values are in good agreement with the magnetic anisotropy constant determined using frequency and temperature dependent magnetic susceptibility data obtained on powder samples.

Sizing and Eddy currents in magnetic core nanoparticles: an optical extinction approach.

Optical extinction is a handy and ubiquitous technique that allows us to study colloidal nanoparticles in their native state. The typical analysis of the extinction spectrum can be extended in order to obtain structural information of the sample such as the size distribution of the cores and the thickness of the coating layers. In this work the extinction spectra of Fe3O4, Fe3O4@Au, and Fe3O4@SiO2@Au single and multilayer nanoparticles are obtained by solving full Mie theory with a frequency dependent susceptibility derived from the Gilbert equation and considering the effect of Eddy currents. The results are compared with non-magnetic Mie theory, magnetic dipolar approximation and magnetic Mie theory without Eddy currents. The particle size-wavelength ranges of validity of these different approaches are explored and novel results are obtained for Eddy current effects in optical extinction. These results are used to obtain particle size and shell thickness information from the experimental extinction spectra of Fe3O4 and Fe3O4@Au nanoparticles in good agreement with TEM results, and to predict the plasmon peak parameters for Fe3O4@SiO2@Au three layer nanoparticles.

Millennial scale climate oscillations recorded in the Lower Danube loess over the last glacial period

In this study we provide a correlative age model for last glacial loess at the Rasova-Valea cu Pietre site in the Lower Danube region, based on the correlation of palaeoenvironmental proxies to independently dated palaeoclimate archives, luminescence dating and independent age control provided by the geochemically confirmed presence of the Campanian Ignimbrite (CI) tephra. The CI tephra, originating in the Phlegrean fields of southern Italy, has been dated elsewhere by 40Ar/39Ar to 39–40ka BP, and is frequently found in the Lower Danube loess. As such, the CI tephra represents a valuable temporal and stratigraphic maker across loess deposits in the region. Our age model facilitates high-resolution correlation of palaeoenvironmental features observed at Rasova to palaeoclimate archives in Greenland and the Black Sea – Mediterranean area. We observe semi-cyclic behaviour of the frequency dependent magnetic susceptibility throughout the profile, which we ascribe to millennial-scale climate variability also observed elsewhere in the Black Sea region. This is the first study to clearly identify millennial-scale climate variability over the Holocene and last glacial in the Lower Danube loess. Proxy variability in the Holocene indicates continuous aeolian sedimentation through this epoch.

New insights into the palaeoclimatic interpretation of the temperature dependence of the magnetic susceptibility and magnetization of Mid-Late Pleistocene loess/palaeosols in Central Asia and the Chinese Loess Plateau

The temperature dependence of magnetic susceptibility (chi-T curves) and magnetization (M-T curves) has been used as a routine rock magnetic tool to characterize the magnetic mineralogy and magnetic granulometry of Chinese loess/palaeosols. However, palaeoclimatic interpretation of these thermomagnetic analyses remains controversial. In the present study, total organic carbon (TOC), thermomagnetic and low-temperature magnetic experiments on Mid-Late Pleistocene loess/palaeosols in Central Asia and the Chinese Loess Plateau (CLP) have been conducted. We found that the M (T) cooling curves at room temperature were mostly lower than the corresponding heating curves, whereas for the chi(T) analyses the cooling curves at room temperature were always much higher than the heating curves. Low-temperature magnetic measurements demonstrated that a large amount of superparamagnetic ferrimagnetic particles were produced during the thermal treatment and resulted in the aforementioned differences. This finding further indicated that the use of the M-T curves to estimate the relative content of maghemite in the loess/palaeosols from the CLP was problematic. In addition, a positive correlation exists between the TOC and the frequency-dependent susceptibility (chi(FD)) in the CLP, suggesting that stronger pedogenesis would result in the simultaneous increase in the content of both maghemite and organic matter. Consequently, the parameters Delta chi(1) (representing the relative content of pedogenic maghemite), Delta chi(2) (inverted left perpendicular chi(ph) - chi- inverted right perpendicular] + Delta chi(1)) and chi(ph) (related to the organic matter concentration), which can be calculated from the chi-T analyses, can potentially be used as new indicators of pedogenesis and palaeoclimate in Central Asia and the CLP.

The Nature of the Bridging Anion Controls the Single-Molecule Magnetic Properties of DyX4M 12-Metallacrown-4 Complexes.

A family of DyX4M(12-MCMnIII(N)shi-4) compounds were synthesized and magnetically characterized (X = salicylate, acetate, benzoate, trimethylacetate, M = NaI or KI). The bridging ligands were systematically varied while keeping the remainder of the MC-geometry constant. The type of monovalent cation, necessary for charge balance, was also altered. The dc magnetization and susceptibility of all compounds were similar across the series. Regardless of the identity of the countercation, the Dy(Hsal)4M 12-MC-4 compounds were the only compounds to show frequency-dependent ac magnetic susceptibility, a hallmark of single-molecule magnetism. This indicates that the nature of the bridging ligand in the 12-MCMnIII(N)shi-4 compounds strongly affects the out-of-phase magnetic properties. The SMM behavior appears to correlate with the pKa of the bridging ligand.

The influence of interparticle correlations and self-assembly on the dynamic initial magnetic susceptibility spectra of ferrofluids

Using computer simulations and a mean-field theoretical approach, we study how the growth in dipolar interparticle correlations manifests itself in the frequency-dependent initial magnetic susceptibility of a ferrofluid. Our recently developed theory gives the correct single-particle Debye-theory results in the low-concentration, non-interacting regime; and it yields the exact leading-order contributions from interparticle correlations. The susceptibility spectra are analysed in terms of the low-frequency behaviours of the real and imaginary parts, and the position of the peak in the imaginary part. By comparing the theoretical predictions to the results from Brownian dynamics simulations, it is possible to identify the conditions where correlations are important, but where self-assembly has not developed. We also provide a qualitative explanation for the behaviour of spectra beyond the mean-field limit.

Microwave synthesis of high-quality and uniform 4 nm ZnFe2O4 nanocrystals for application in energy storage and nanomagnetics.

Magnetic nanocrystals with a narrow size distribution hold promise for many applications in different areas ranging from biomedicine to electronics and energy storage. Herein, the microwave-assisted sol–gel synthesis and thorough characterization of size-monodisperse zinc ferrite nanoparticles of spherical shape is reported. X-ray diffraction, 57Fe Mössbauer spectroscopy and X-ray photoelectron spectroscopy all show that the material is both chemically and phase-pure and adopts a partially inverted spinel structure with Fe3+ ions residing on tetrahedral and octahedral sites according to (Zn0.32Fe0.68)tet[Zn0.68Fe1.32]octO4±δ. Electron microscopy and direct-current magnetometry confirm the size uniformity of the nanocrystals, while frequency-dependent alternating-current magnetic susceptibility measurements indicate the presence of a superspin glass state with a freezing temperature of about 22 K. Furthermore, as demonstrated by galvanostatic charge–discharge tests and ex situ X-ray absorption near edge structure spectroscopy, the as-prepared zinc ferrite nanocrystals can be used as a high-capacity anode material for Li-ion batteries, showing little capacity fade – after activation – over hundreds of cycles. Overall, in addition to the good material characteristics, it is remarkable that the microwave-based synthetic route is simple, easily reproducible and scalable.

Large magnetic cooling power involving frustrated antiferromagnetic spin-glass state inR2NiSi3(R=Gd,Er)

The ternary intermetallic compounds ${\mathrm{Gd}}_{2}{\mathrm{NiSi}}_{3}$ and ${\mathrm{Er}}_{2}{\mathrm{NiSi}}_{3}$ are synthesized in chemically single phase, which are characterized using dc magnetization, ac magnetic susceptibility, heat capacity, and neutron diffraction studies. Neutron diffraction and heat capacity studies confirm that long-range magnetic ordering coexists with the frustrated glassy magnetic components for both compounds. The static and dynamical features of dc magnetization and frequency-dependent ac susceptibility data reveal that ${\mathrm{Gd}}_{2}{\mathrm{NiSi}}_{3}$ is a canonical spin-glass system, while ${\mathrm{Er}}_{2}{\mathrm{NiSi}}_{3}$ is a reentrant spin cluster-glass system. The spin freezing temperature merges with the long-range antiferromagnetic ordering temperature at 16.4 K for ${\mathrm{Gd}}_{2}{\mathrm{NiSi}}_{3}$. ${\mathrm{Er}}_{2}{\mathrm{NiSi}}_{3}$ undergoes antiferromagnetic ordering at 5.4 K, which is slightly above the spin freezing temperature at 3 K. The detailed studies of nonequilibrium dynamical behavior, viz., the memory effect and relaxation behavior using different protocols, suggest that both compounds favor the hierarchical model over the droplet model. A large magnetocaloric effect is observed for both compounds. Maximum values of isothermal entropy change $(\ensuremath{-}\mathrm{\ensuremath{\Delta}}{S}_{M})$ and relative cooling power (RCP) are found to be 18.4 J/kg K and 525 J/kg for ${\mathrm{Gd}}_{2}{\mathrm{NiSi}}_{3}$ and 22.6 J/kg K and 540 J/kg for ${\mathrm{Er}}_{2}{\mathrm{NiSi}}_{3}$, respectively, for a change in field from 0 to 70 kOe. The values of RCP are comparable to those of the promising refrigerant materials. A correlation between large RCP and magnetic frustration is discussed for developing new magnetic refrigerant materials.

Nonequilibrium simulations of model ionomers in an oscillating electric field.

We perform molecular dynamics simulations of a coarse-grained model of ionomer melts in an applied oscillating electric field. The frequency-dependent conductivity and susceptibility are calculated directly from the current density and polarization density, respectively. At high frequencies, we find a peak in the real part of the conductivity due to plasma oscillations of the ions. At lower frequencies, the dynamic response of the ionomers depends on the ionic aggregate morphology in the system, which consists of either percolated or isolated aggregates. We show that the dynamic response of the model ionomers to the applied oscillating field can be understood by comparison with relevant time scales in the systems, obtained from independent calculations.

Quantifying paleoprecipitation of the Luochuan and Sanmenxia Loess on the Chinese Loess Plateau

Paleoprecipitation is one of the most important paleoclimatic factors for monsoon studies. Magnetic properties of the Chinese loess/paleosol sequences have been demonstrated to be controlled strongly by the mean annual precipitation (MAP). In this study, temporal variations of MAPs were systematically investigated for the Luochuan (LC) and Sanmenxia (SMX) sequences from the loess unit L1 (~10ka) to the paleosol unit S5 (~620kyr) by applying the new climofunction MAP=8.06×χFD/HIRM+254 (where χFD and HIRM are frequency-dependent magnetic susceptibility and “hard” isothermal remanent magnetization, respectively). For both the LC and SMX sequences, our climofunction indicates paleosols have higher MAPs than loess units and the maximum MAP value occurs in S5, indicating that the East Asian summer monsoon was the strongest during the formation of S5. In agreement with previous studies, overall, MAPs of SMX are higher than those of LC, as SMX is in the southeast of LC and receives more precipitation. The positive correlation between the reconstructed MAPs and χFD and ARM suggests that precipitation is a key factor controlling degree of pedogenesis. MAPs of paleosols from SMX display a negative correlation with synchronous insolation maxima and a positive correlation with corresponding insolation minima. However at LC, MAPs have a less significant relationship with insolation. This may be because the summer monsoon signals are relatively weak in LC and covered by local climate and environmental alterations. In interglacials, the summer monsoon, associated with precipitation, is controlled by the corresponding insolation maxima and minima. In addition, the MAP gradient between LC and SMX is also modulated by the insolation amplitude.

Influence of dipolar interactions on the magnetic susceptibility spectra of ferrofluids.

The frequency-dependent magnetic susceptibility of a ferrofluid is calculated under the assumption that the constituent particles undergo Brownian relaxation only. Brownian-dynamics simulations are carried out in order to test the predictions of a recent theory [A. O. Ivanov, V. S. Zverev, and S. S. Kantorovich, Soft Matter 12, 3507 (2016)1744-683X10.1039/C5SM02679B] that includes the effects of interparticle dipole-dipole interactions. The theory is based on the so-called modified mean-field approach and possesses the following important characteristics: in the low-concentration, noninteracting regime, it gives the correct single-particle Debye-theory results; it yields the exact leading-order results in the zero-frequency limit; it includes particle polydispersity correctly from the outset; and it is based on firm theoretical foundations allowing, in principle, systematic extensions to treat stronger interactions and/or higher concentrations. The theory and simulations are compared in the case of a model monodisperse ferrofluid, where the effects of interactions are predicted to be more pronounced than in a polydisperse ferrofluid. The susceptibility spectra are analyzed in detail in terms of the low-frequency behavior, the position of the peak in the imaginary (out-of-phase) part, and the characteristic decay time of the magnetization autocorrelation function. It is demonstrated that the theory correctly predicts the trends in all of these properties with increasing concentration and dipolar coupling constant, the product of which is proportional to the Langevin susceptibility χ_{L}. The theory is in quantitative agreement with the simulation results as long as χ_{L}≲1.

Nonlinear electronic polarization and optical response in borophosphateBPO4

The electronic structure, nonlinear electronic polarization induced by a static external electric field, and frequency dependent second-harmonic susceptibility tensor of the borophosphate ${\mathrm{BPO}}_{4}$ are studied by a first-principles calculation based on density-functional theory. Our calculated results show that the borophosphate ${\mathrm{BPO}}_{4}$ has a large band gap $\ensuremath{\sim}10.4$ eV, which is larger than the band gap of the widely used nonlinear optical crystal ${\mathrm{KBe}}_{2}{\mathrm{BO}}_{3}{\mathrm{F}}_{2}$. However, ${\mathrm{BPO}}_{4}$ also has a nonlinear coefficient ${d}_{36}=0.92$ pm/V at static limit, which also is larger than the nonlinear coefficient ${d}_{11}=0.47$ pm/V of ${\mathrm{KBe}}_{2}{\mathrm{BO}}_{3}{\mathrm{F}}_{2}$. The unexpected larger nonlinear coefficient of ${\mathrm{BPO}}_{4}$ can be interpreted by the relatively strong $s\text{\ensuremath{-}}p$ hybridization in ${\mathrm{BPO}}_{4}$, which can enhance the inter-band Berry connections, while the O $2p$ orbitals dominating valence bands in ${\mathrm{KBe}}_{2}{\mathrm{BO}}_{3}{\mathrm{F}}_{2}$ are very flat, resulting from weak $s\text{\ensuremath{-}}p$ hybridization.

Insights into the chemical partitioning of trace metals in roadside and off-road agricultural soils along two major highways in Attica’s region, Greece

We report in this study the magnetic properties and partitioning patterns of selected trace metals (Pb, Zn, Cu, Cd, Ni) in roadside and off-road (>200m distance from the road edge) agricultural soils collected along two major highways in Greece. Sequential extractions revealed that the examined trace metals for the entire data set were predominantly found in the residual fraction, averaging 37% for Cd up to 80% for Cu. Due to the strong influence of lithogenic factors, trace metal pseudototal contents of the roadside soils did not differ significantly to those of the off-road soils. Magnetic susceptibility and frequency dependent magnetic susceptibility determinations showed a magnetic enhancement of soils; however, it was primarily related to geogenic factors and not to traffic-derived magnetic particles. These results highlight that in areas characterized by strong geogenic backgrounds, neither pseudototal trace metal contents nor magnetic properties determinations effectively capture traffic-related contamination of topsoils. The vehicular emission signal was traced by the increased acid-soluble and reducible trace metal contents of the roadside soils compared to their off-road counterparts. In the case of Cu and Zn, changes in the partitioning patterns were also observed between the roadside and off-road soils. Environmental risks associated with agricultural lands extending at the margins of the studied highways may arise from the elevated Ni contents (both pseudototal and potentially mobile), and future studies should investigate Ni levels in the edible parts of plants grown on these agricultural soils.

A new family of interdimer [MnII2LnIII2]2 clusters: Syntheses, structures, and magnetic properties

A new family of isostructural Mn/Ln clusters: [MnII2LnIII2(hmp)6(NO3)4(CH3OH)2][MnII2LnIII2(hmp)6(NO3)4(H2O)2] ([Ln=Gd (1), Tb(2), Dy(3), hmpH=2-(hydroxymethyl)pyridine]) have been synthesized by the reaction of Mn(NO3)2 and Ln(NO3)3·6H2O with hmpH as ligand under solvothermal conditions. Compounds 1–3 are isostructural and possess butterfly core. That the antiferromagnetic interactions within compounds 1–3 were suggested by soild-state dc magnetic susceptibility analyses. Compound 1 displays a magnetic-caloric effect (MCE) with 21.91JKg−1K−1 of the entropy change at 5K for ΔH=8T. Compounds 2 and 3 exhibit frequency-dependent ac susceptibility signals suggestive of slow magnetic relaxation.

Spatial variability of soil magnetic susceptibility, organic carbon and total nitrogen from farmland in northern China

Spatial variability of magnetic susceptibility (χ), soil organic carbon (SOC) and total nitrogen (TN) concentrations were analyzed using geostatistics method in different soil horizons from farmland in the North China. Results showed that a significant difference in SOC and TN contents, while no significant difference in χ was observed at two soil horizons using the t-test. The average values of χ 93.0×10−8m3kg−1, SOC 11.25gkg−1 and TN 1.03gkg−1 were higher at the 0–20cm than those measured at the 20–40cm depth, respectively. The value of frequency dependent susceptibility (χfd) was greater than 6% indicated the formation of superparamagnetic particles through pedogenesis and/or human activities. The isotropic semivariogram models of χ, SOC and TN were fitted to spherical model. A clear variogram of soil properties with a medium spatial dependent was observed. The range of spatial correlations was determined to be approximately12km, which seemed to be characteristic for a regional scale. The kriging interpolated maps provided information for soil monitoring and management. Geometric and small spherical magnetic particles were identified by microscopy. Vertical distributions of soil properties proved that soil magnetic signature mainly originated from lithogenic and anthropogenic contribution.

Magnetoelectric Coupling, Ferroelectricity, and Magnetic Memory Effect in Double Perovskite La3Ni2NbO9.

We observe ferroelectricity in an almost unexplored double perovskite La3Ni2NbO9. Ferroelectricity appears below ∼60 K, which is found to be correlated with the significant magnetostriction. A reasonably large value of spontaneous electric polarization is recorded to be ∼260 μC/m(2) at 10 K for E = 5 kV/cm, which decreases signifi- cantly upon application of a magnetic field (H), suggesting considerable magnetoelectric coupling. The dielectric permittivity is also influenced by H below the ferroelectric transition. The magnetodielectric response scales linearly to the squared magnetization, as described by the Ginzburg-Landau theory. Meticulous studies of static and dynamic features of dc magnetization and frequency dependent ac susceptibility results suggest spin-glass state below 29 K. Intrinsic magnetic memory effect is observed from zero-field cooled magnetization and isothermal remanent magnetization studies, also pointing spin-glass state below 29 K. Appearance of ferroelectricity together with a significant magnetoelectric coupling in absence of conventional long-range magnetic order is promising for searching new magnetoelectric materials.

Sensitivity of Sediment Magnetic Records to Climate Change during Holocene for the Northern South China Sea

Magnetic property has been proved to be a sensitive proxy to climate change for both terrestrial and marine sediments. Based on the schedule frame established by AMS 14C dating of foraminifera, detail magnetic analyses were performed for core PC24 sediments at sampling intervals of 2 cm to discuss magnetic sensitivity of marine sediment to climate during Holocene for the northern South China Sea. The results indicated that: 1) Concentration dependent magnetic parameters are positive corresponding to variation of temperature. The frequency dependent susceptibility coefficient basically reflected the variation in humidity; 2) XARM/SIRM was more sensitive to detrital magnetite particles and SIRM/X was more effective to biogenic magnetite particles. Variations of XARM/SIRM and SIRM/X are corresponding to precipitation and temperature, respectively; 3) the Holocene Megathermal in the study area was identified as 7.5-3.4 cal. ka BP. The warmest stage of Holocene for the study area should be during 6.1 to 3.9 cal. ka BP; 4) The 8 ka cold event was characterized as cold and dry during 8.55 to 8.25 cal. ka BP; 5) During early and middle Holocene, the climate combinations were warm dry and cold wet. It turned to warm and wet after 2.7 cal. ka BP.

Combination of geo- pedo- and technogenic magnetic and geochemical signals in soil profiles – Diversification and its interpretation: A new approach

Magnetic and geochemical parameters of soils are determined with respect to geology, pedogenesis and anthropopression. Depending on local conditions these factors affect magnetic and geochemical signals simultaneously or in various configurations. We examined four type of soils (Entic Podzol, Eutric Cambisol, Humic Cambisol and Dystric Cambisol) developed on various bedrock (the Tumlin Sandstone, basaltoid, amphibolite and serpentinite, respectively). Our primary aim was to characterize the origin and diversification of the magnetic and geochemical signal in soils in order to distinguish the most reliable methods for correct interpretation of measured parameters. Presented data include selected parameters, both magnetic (mass magnetic susceptibility – χ, frequency-dependent magnetic susceptibility – χfd and thermomagnetic susceptibility measurement – TSM), and geochemical (selected heavy metal contents: Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn). Additionally, the enrichment factor (EF) and index of geoaccumulation (Igeo) were calculated. Our results suggest the following: (1) the χ/Fe ratio may be a reliable indicator for determining changes of magnetic signal origin in soil profiles; (2) magnetic and geochemical signals are simultaneously higher (the increment of χ and lead and zinc was noted) in topsoil horizons because of the deposition of technogenic magnetic particles (TMPs); (3) EF and Igeo evaluated for lead and zinc unambiguously showed anthropogenic influence in terms of increasing heavy metal contents in topsoil regardless of bedrock or soil type; (4) magnetic susceptibility measurements supported by TSM curves for soil samples of different genetic horizons are a helpful tool for interpreting the origin and nature of the mineral phases responsible for the changes of magnetic susceptibility values.