Magnetometry in Environmental Sciences

The goal of the paper is to describe the degree of applicability of magnetic susceptibility measurements for determination of lateral and vertical extension of soil pollution in the neighborhood of selected sections of roads in Poland. Magnetic susceptibility measurements were supported by petromagnetic, geochemical and SEM analyses. In the case of subordinate roads, increased magnetic susceptibility values appears only at the shoulder of the road, i.e., within 3 m from the edge of the road, while in the case of main roads an anomalous band usually reaches about 15 m. Increased values of magnetic susceptibility were observed up to a depth of 30 cm. Main magnetic carriers are Fe and Ti oxides and metallic iron, appearing as irregular grains and spherules. At some grains containing Fe and Ti, fragments of crystal walls were observed. Other grains appeared as elongated slivers. Fe and Ti oxides with remains of crystal walls are of natural, i.e., geogenic nature. Their concentration in the vicinity of the road results from degradation (elution, erosion) of gravel and sand foundation of the road. Irregular grains and metallic iron are coming from traffic (shards of car bodies, combustion products). Magnetic susceptibility carriers of soil samples taken from anomalous areas are associated with elements such as zinc, lead, sulfur and (to a less extent) nickel. Increase of magnetic susceptibility at the topsoil level is accompanied by increasing content of these elements. The zone up to 15 m away, and somewhere even up to 40 m away from the road edges should be excluded from cultivation.

The aim of the study was to identify magnetic particles in the sediments of Warsaw part of the Vistula river (Poland) and the impact of anthropogenic factors on the magnetic susceptibility. One of the most important parts of this study was to determine the procedure for sediment sampling and preparation of material for magnetic measurements. The paper presents results of the preliminary study on the test collection of sediment samples from the Vistula river bank within Warsaw. The main magnetic study was carried out on the collection of sediments taken from six areas with different impact of anthropogenic sources of pollution using the procedure developed for test collection. For samples of sediments, several magnetic parameters, such as magnetic susceptibility χ, temperature dependent magnetic susceptibility, and hysteresis loop parameters, were determined. The study showed that the magnetic susceptibility of sediments reflects the anthropogenic impact. In the city center, the magnetic susceptibility reached maximum values which reflect the highest anthropogenic factor. The lowest magnetic susceptibility values were recorded in sediments taken from out of the city center areas which shows relatively low impact of anthropogenic factor. The fine-grained fractions of sediments contain most of the magnetic particles in which multidomain magnetite is the main magnetic phase. It was found that the spherical-shaped particles represent a significant part of magnetic fraction of sediment. The results bring us to the conclusion that the application of magnetic methods for study of river sediments is very important for understanding and tracing the anthropogenic input in the river sediments.

Heavy metal contents in sediments from the vicinity of small shipwrecks (Munin and Abille) in the Gulf of Gdańsk and their relationship with mass magnetic susceptibility (χ) were investigated. The values of χ are not very high, however they reveal significant differences between investigated sites. Magnetic susceptibility values vary from 5.33 to 8.02 × 10⁻⁸ m³/kg for Abille and from 3.07 × 10⁻⁸ m³/kg to 12.92 × 10⁻⁸ m³/kg for Munin. It is mainly carried by fraction <0.1 mm in the case of Abille, whereas for Munin χ for <0.1 mm shows different distribution of values. Organic matter content is in the range of 1.60–18.86%, which is characteristic for this area. The concentration of heavy metals is relatively small, as in the case of χ. The relationship amongst analysed heavy metals is strong, but between PLI, LOI and χ is weak. Generally sediments around Munin wreck demonstrate the strong correlation of mass magnetic susceptibility with toxic elements. This is the result of the shipwrecks location and hydrodynamic conditions of this area. The low heavy metal concentration and χ values indicate low level of contamination around both wrecks.

Central Asia is a vast area extending from the Caspian Sea to the western borders of China, with highly differentiated geography (high mountains, excessive deserts, grassy steppes), geology and anthropological history. As such it poses a perfect site for various studies, including paleoenvironmental and paleoclimatic research. Up to now, we performed two distinct studies in Central Asia: (1) a preliminary study on the Holocene loess-soil succession in the Karasu Valley, at the Tien Shan foothills in Uzbekistan; (2) and a study on development of high mountain lakes in the Pamir, based on lake sediments of the Rangkul Lake in the Eastern Pamir, Tajikistan (initial results presented here). In both studies we used magnetic properties of studied sediments and soils as one of parameters in multiproxy analyses. Paleosols from the Karasu Valley developed into continuous and uninterrupted sedimentary sequences interbedded with loess horizons. These sequences are characterized by diversified magnetic susceptibility values that reflect changes in their formation. Sediments form the Rangkul Lake show 5 significant shifts in deposition processes, caused by changes in water level. These shifts are clearly reflected both in sediment composition and in magnetic susceptibility of deposited material.

Studies on magnetic properties of soils have been recently applied in the soil environment quality monitoring in relation to basic physical and chemical properties. However, the issue of distribution of ferrimagnetic materials in particular genetic soil horizons, especially in altered soils, has not yet been considered in environmental studies. The main subject of the research was to evaluate a potential of magnetic susceptibility measurements as implements for supporting the soil classification through indication of particular distinctive genetic horizons in the soil profile. The study objects were soils whose formation was strictly conditioned by hydrotechnical regulations in the area of the Vistula River Cross-Cut (northern Poland). It has been demonstrated that the magnetic susceptibility test is an accurate supporting tool in recognition and classification of genetic horizons in a soil profile. The obtained results properly reflected the soil morphological variability and also were good indicators of the presence of lithologic discontinuities of technogenic origin.

This paper presents the results of measurements of the magnetic susceptibility of samples taken in the profiles of Holocene sediments. Locations from which samples were analyzed were previously investigated with various methods (such as geological, geomorphological, sedimentological, geochemical and pollen). Most of the examined sites have a well-known geological structure, the origin and age of existing forms. The sediments recognized with the drillings represent differentiated sedimentary environments (e.g., slopes, fluvial), differentiated facies (mineral and mineral-organic deposits, peat, carbonaceous tufa) and come from different types of the landscape: from Polish loess plateaus and associated valleys bottoms of Ponidzie to Middle Poland plains with dunes and alluvial fans occurring on the terrace in the Vistula River valley. Analysis of changes in magnetic susceptibility in selected well-recognized (i.e. of known age, origin and sedimentological features) vertical profiles makes it possible to determine the relationship between the measured value of magnetic susceptibility and environmental changes that have taken place in the past. Knowledge of these relationships allows to read the events in the development of the natural environment of the studied areas and in the case of possession of radiocarbon dating in the reference profiles it allows to make a vertical correlation with the neighboring sediment profiles of unknown age.

The article presents the results of an analysis of the surface layer of bottom sediments in the naval harbour in Hel. During field work conducted in June 2013, 54 sediment samples were collected. The aim of the study was to examine magnetic susceptibility of harbour sediment as a parameter determining the degree of anthropopressure. As part of laboratory tests, grain size analysis was performed in order to determine organic matter content and magnetic susceptibility of the sediment. The study also measured the impact of environmental factors on fluctuations in the other studied parameters. The results demonstrate increased dynamics of sedimentary environment in the open part of the naval harbour, better sediment sorting and reduced percentage share of <0.063 mm grain size fraction. Variability in magnetic susceptibility values measured in isolated parts of the harbour correlates with increased percentage share of the fine fraction and LOI%. A significant impact on the accumulation of pollutants in surface sediments is exerted by the harbour’s closed hydrodynamic conditions.

This work reports the study of depth differentiation of magnetic properties of four soil types: Kastanozem, Cambisol, Luvisol and Chernozem. The aim of the study is to find the way of magnetic minerals formation and transformation. The three profiles: Cambisol, Luvisol and Chernozem were taken from moderate temperature and moisture region from Slovak Republic and one profile, Kastanozem, was taken from semi-dry region of Southern Ukraine. Thermal behavior of saturation remanence revealed that magnetic composition of studied soils is a mixture of two components. Upper layers contain significant contribution of maghemite. This is demonstrated by unblocking temperature T_ub lower than 670 °C and higher than 600 °C and low values of coercivity B_c and B_cr. Variable amounts of hematite demonstrated by T_ub ~ 670 °C are seen for samples from parent rock horizons. Cumulative log Gaussian (CLG) analysis of the IRM acquisition curve revealed the presence of at least two components of coercivity along each profile. The variation of hematite content along profile was evaluated by depth variation of hard component of saturation remanence HIRM. The domain state of magnetic minerals derived from the Day’s plot modified by Dunlop showed that all samples are grouped in the area between the mixing curve for single-domain SD and multi-domain MD grains and the mixing curve for SD and superparamagnetic SP grain. The depth variation of susceptibility χ, frequency dependence of susceptibility χ_fd, hysteresis parameters, anhysteretic remanence ARM, hard component of isothermal remanence HIRM, and relations between these magnetic parameters were used as indicators of development of pedogenesis. The results allow us to conclude that formation of iron oxides occurred by a transient intermediate phase—hydromaghemite which was transformed to hematite and/or to goethite depending on soil environment. The ratio χ_fd/HIRM allows to evaluate approximately similar precipitation for Kastanozem, Cambisol and Luvisol and much lower for Chernozem. As Chernozem should be formed in the same conditions as Cambisol and Luvisol, we probably observed the effect of higher permeability of parent rock in Chernozem profile sediments than in the case of Cambisol (granite) and Luvisol and Kastanozem (loess). Relation of loss on ignition LOI to magnetic parameters indicates that organic matter promotes pedogenesis progress. It is possible to relate vertical magnetic structure of soil to pedogenic differentiation into genetic horizons.