Celeste Gomes

Relation between magnetic parameters and nematode abundance in agricultural soils of Portugal--a multidisciplinary study in the scope of environmental magnetism.

Soil is composed of different types of particles which are either natural or of anthropogenic origin. Anthropogenic particles are often related to the presence of heavy metals and thus provide information on soil quality. Magnetic parameters can detect the presence of such particles and may be used as a proxy for environmental pollution. This study explores the relationships between magnetic particles and the nematofauna of agricultural soils. Magnetic, pedological, microscopy and nematological analyses were conducted in soils collected from major regions of potato production in Portugal. The magnetic characterisation of soils identified regions with magnetic particles with possible anthropogenic origin. Microscopy analysis revealed the presence of spherical particles dominantly composed of Fe, O and C. A positive and significant relationship was found between saturation isothermal remanent magnetisation (SIRM) and mass-specific susceptibility (χ), confirming the importance the ferrimagnetic fraction to magnetic properties. The nematode communities were composed of nematodes belonging to four trophic groups (bacterial feeding, plant feeders, fungal feeders and omnivores/predators). The relationships between magnetic parameters and the nematodes showed that (1) S−25 has a linear correlation with number of nematodes per kilogram of soil and with plant feeders’ trophic group and (2) SIRM correlates with the bacterial feeders trophic group. This study reveals that magnetic proxies may provide means for detecting regions with higher levels of pollution, possibly related to heavy metals. Due to the large background variability found in magnetic parameters, the sampling spacial mesh should to be further refined and the input of magnetic minerals needs to be locally calibrated.

Magnetic susceptibility and isothermal remanent magnetization in human tissues: a study case

Abstract This study evaluated the magnetic properties, magnetic susceptibility and isothermal remanent magnetization (IRM) of tissue samples from the brain, liver, spleen, pancreas, heart and lungs, resected from human corpses, with the aim of identifying the magnetic mineral structures and understanding their possible connection to diseases, professional activity, age and gender of the individual, smoking habits and the environment. The heart was the organ with the highest values of magnetic susceptibility and the pancreas showed the lowest values. No relationship was found between magnetic susceptibility, IRM values and ages of the individuals. However the samples obtained in females showed lower values of magnetic susceptibility than those resected from males. The samples collected from the lungs of smokers have higher values of magnetic susceptibility and IRM indicating the presence of magnetic particles with an anthropic origin. Moreover, the complexity of the magnetic behaviour of these tissues may suggest a contribution of both biogenic and anthropogenic magnetic particles also due to some professional activities. In the brain a heterogeneous distribution of the magnetic susceptibility values was found, which might be related mainly to the diamagnetic behaviour of myelin-rich structures. This study suggests that although the diamagnetic and paramagnetic behaviour is common to all structures, magnetite-type structures are always present in the tissues and hematite-type structures may also contribute to the magnetic signal of the sample. IRM values are only dependent on the presence of magnetite or hematite-type magnetic structures and so this technique seems more suitable to achieve the characterization of biomagnetic structures than magnetic susceptibility.

Paleoclimatic Registers from Semi-arid Costal Sediments of Southeastern India: A Multi Proxy Approach

The red sand dunes appear along the south east, -west coast of Tamil Nadu, India between the latitudes and longitudes of 8°07′56″N to 8°22′11″N; 77°19′84″E to 77°53′40″E. The dune sands from this region were studied through magnetic methods such as magnetic susceptibility measurements and acquisition of isothermal remanent magnetization, geochemistry and X-ray diffraction methods. Optically stimulated luminescence (OSL) dating method was used to constrain the chronology of deposits. Three sections were excavated up to 5–9.5 m with one inland deposit (TPV) and two near coastal sections (THOP and MUT). The magnetic parameters show both significant contribution of hematite structures and indicate the presence of multi-domain magnetite or mixed mineral contents of magnetite and anti-ferromagnetic minerals in the sample. The occurrence of magnetite in THOP and TPV sections is possibly due to the marine sediments transported by sturdy onshore winds. In XRD data, correlation analysis indicated TPV and MUT sections have a similar type of deposition and THOP did not show any positive correlation with TPV and MUT and even with its own deposition. In comparison with geochemistry data, χ variation and OSL dates, it was shown that the sample MUT21 (200 cm) with an OSL age of 14 ± 2 ka indicated deposition during the humid interval and at ~17 ± 2 to ~19 ± 2 ka MUT61 (600 cm)depicts the dry period of deposition.

Field Classes for Geosciences Education: Teachers’ Concepts and Practices

This study aims to understand the importance of outdoor classes for Portuguese geoscience teachers. From 38 schools, 178 teachers, of different genders, teaching experience and complementary teacher training, answered a questionnaire. For this study, a questionnaire was developed which consists of two parts, one for the characterization of the sample and the other to assess the importance of conducting field classes by geoscience teachers. The second part consisted of 22 items of closed-ended questions and one open-ended question. The questionnaire showed a highly satisfactory internal consistency for investigation issues. The results showed that teachers valued field classes, because they promote motivation, geological skills development and awareness of environmental aspects and geoethics. Although teachers highlighted the importance of fieldwork, they also mentioned difficulties of outdoor classes. It is essential to overcome the difficulties identified for the non-implementation of field classes. This type of practical work stimulates students for geology, allows them to participate actively in their learning process and involves them in relevant tasks. Field classes establish links between students’ learning and reality.

Building up of a nested granite intrusion: magnetic fabric, gravity modelling and fluid inclusion planes studies in Santa Eulália Plutonic Complex (Ossa Morena Zone, Portugal)

The Santa Eulalia Plutonic Complex (SEPC), located in the Ossa Morena Zone (south Portugal), is composed of a medium- to coarse-grained pink granite (G0-type) and a central grey medium-grained biotite granite (G1-type). Available Rb–Sr data indicates an age of 290 Ma. An emplacement model for the SEPC is proposed, taking into account magnetic fabric, 2D gravity modelling and fluid inclusion planes studies. The G0 and G1 types demonstrate different magnetic behaviour: G0 is considered a magnetite-type granite and G1 is an ilmenite-type granite. The formation of G0 required oxidized conditions related to the interaction of mafic rocks with a felsic magma. The 2D gravity modelling and subvertical magnetic lineations show that the feeder zone of the SEPC is located in the eastern part of the pluton, confirming the role of the Assumar and Messejana Variscan faults in the process of ascent and emplacement. The magma emplacement was controlled by ENE–WSW planar anisotropies related to the final brittle stages of the Variscan Orogeny. The emplacement of the two granites was almost synchronous as shown by their gradational contacts in the field. The magnetic fabric however suggests emplacement of the G0-type first, closely followed by emplacement of the G1-type, pushing the G0 laterally which becomes more anisotropic towards the margin. The G1-type became flattened, acquiring a dome-like structure. The SEPC is a nested pluton with G0-type granite assuming a tabular flat shape and G1-type forming a rooted dome-like structure. After emplacement, SEPC recorded increments of the late Variscan stress field documented by fluid inclusion planes in quartz.

Chapter 18 – Mineralogy and Magnetic Parameters of Materials Resulting from the Mining and Consumption of Coal from the Douro Coalfield, Northwest Portugal

The mineralogy and magnetic parameters of materials resulting from coal mining in the Douro Coalfield and its consumption in a thermal power plant were investigated. The coal waste, fly ash disposal, and coal combustion represent a potential source of particulate matter that can be released into the atmosphere and, adversely, affect the environment and human health. The methodologies applied in this work included X-ray powder diffraction for mineralogical characterization, and magnetic susceptibility and isothermal remanent magnetization (IRM) determination for evaluation of magnetic parameters. The results demonstrate that the unburned coal waste material has quartz, illite, mica (mainly muscovite), and in many cases pyrophyllite as the main mineral. Some of the burning/burnt coal waste samples have similar mineralogy to the unburned materials, but some of them also contain mullite, cristobalite, and amorphous material, suggesting that higher temperatures were involved in the in situ combustion process. The fly ash contains amorphous material, mullite, cristobalite, and maghemite, similar to the burnt waste samples. The magnetic parameters show an increase in magnetic susceptibility and IRM in some of the burning/burnt zones, indicating a magnetic enhancement due to the burning process. The fly ash samples exhibit even higher magnetic susceptibility and IRM values, attributed to the industrial combustion in the thermal power plant.