Aug 5, 2013 - pollution caused by vehicular or traffic emission, abrasion susceptibility in comparisons to the sub soil and soil of brake lining, discharges from ...
World Applied Sciences Journal 24 (2): 178-187, 2013 ISSN 1818-4952 © IDOSI Publications, 2013 DOI: 10.5829/idosi.wasj.2013.24.02.13173
Measurement of Magnetic Susceptibility of Soils in Jalingo, N-E Nigeria: A Case Study of the Jalingo Mechanic Village M.O. Kanu, 2O.C. Meludu and 2S.A. Oniku Department of Physics, Taraba State University, P.M.B.1167, Jalingo, Nigeria. 2 Department of Physics, Modibbo Adama University of Technology, P.M.B. 2076, Yola, Adamawa State, Nigeria 1
1
Submitted: Jun 22, 2013;
Accepted: Aug 1, 2013;
Published: Aug 5, 2013
Abstract: Measurements of some magnetic properties of soil in the Jalingo Mechanic Village, Jalingo, NE Nigeria were performed on surface and vertical soil profile samples. The purpose was to use the fast, cheap and non destructive magnetic methods to access the level of pollution in the study area. The magnetic parameters (magnetic susceptibility, percentage frequency dependence susceptibility and temperature dependence of susceptibility) were measured using the Bartington MS2 instruments (specifically, MS2B, MS2WF and MS2WFP). Results showed that the magnetic susceptibility obtained varied between 19.8 and 436.8 x 10 8m3kg 1 with an average value of 137.06 x 10 8m3kg 1, indicating high concentration of ferrimagnetic minerals in the soil. The results of the frequency dependence of susceptibility indicates that about 55% of the samples were dominated by multi domain magnetic grains while 37% had a mixture of SD and SP grains, suggesting that pedogenic super paramagnetic grains do not contribute significantly to the overall magnetic susceptibility variation in the area. The vertical distribution of magnetic susceptibility suggests a mixture of lithogenic and anthropogenic contribution to the magnetic susceptibility enhancement. Measurement of the temperature variation of susceptibility showed the cooling curve susceptibility to be higher than the heating curve indicating the formation of new magnetic minerals. Both curves displayed Curie point temperature between 500°C and 535°C representing a titanium- poor magnetite minerals dominate the sample. Key words: Magnetic susceptibility
Frequency dependence
INTRODUCTION
Temperature
Soils
Jalingo
tools for estimating the anthropogenic pollution of industrial areas [2, 7]. Magnetic susceptibility has also been used successfully in soils [8-10] in road side dust [11-13], tree leaves [14], sea sediments [15], river sediments [16]. Magnetic susceptibility has been used to map spatial distribution of pollution and degree of anthropogenic pollution around power plants, cement and metallurgical industries [17, 18]. Two powerful applications of magnetic susceptibility measurements of soils are the identification of polluted areas and the detailed mapping of these areas to reveal the extent of pollution [19]. Studies by [20-22] and others revealed a significant correlation between magnetic susceptibility and heavy metal contents in soils. This allows susceptibility to be used as an indicator for heavy metal contamination and the spatial distribution of the contaminants. The use of magnetic measurements as a proxy for heavy metal
Magnetic susceptibility is defined as the ratio of the total magnetization induced in a sample to the intensity of the magnetic field that produces the magnetization. It is used to measure how magnetisable a material is. The magnetisability tells us about the minerals that are found in soils, rocks, dusts and sediments [1]. Measurement of magnetic properties and in particular magnetic susceptibility have become a generally accepted method to map spatial distribution of pollution, identify polluted sources and provides an alternative to the conventional chemical analysis because its measurements are fast, cost effective, non-destructive, sensitive and informative [2]. Magnetic susceptibility has been used to investigate industrial pollutants, traffic emission and other atmospheric pollutants [3-6]. Magnetic susceptibility mapping of soils is nowadays one of the most important
Corresponding Author: M.O. Kanu, Department of Physics, Taraba State University, P.M.B. 1167, Jalingo, Nigeria.
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pollution is based on the fact that the origins of heavy metals and magnetic particles are genetically similar [2]. Urban top soils are sinks to toxic pollutants and this is indicated by magnetic susceptibility enhancement. Magnetic susceptibility enhancements in soils are caused by the presence of ferrimagnetic minerals (commonly iron oxides) in soils and are derived from a number of sources. According to [19], these sources can be grouped into the following key processes:
ultrafine grains is strong but thermal energies quickly counteract induced magnetization after the external field has been removed. The specific magnetic behavior of particles near the ultrafine boundary is dependent on the frequency of the magnetic field: in low frequency fields such grains exhibit SP behavior, in high frequency fields, they behave like SSD grains. Hence the presence of SP materials can be identified by determining the frequency dependence of their magnetic susceptibility [24]. The frequency dependence of coarse grains is small or zero [24]. Samples with low frequency dependence (< 2%) contain virtually no SP grains; while those exhibiting high dependence (> 10%) are dominated by SP grains [1]. This study was conducted in the Jalingo Mechanic Village (JMV). The JMV is an area designated by the Taraba State Government for the repairs and maintenance of vehicles. Hitherto, mechanic workshops were scattered all over the town and this was not a healthy practice for the environment as it leads to environmental pollution with its attendant health threats. The government took the bold step in the right direction to establish the JMV which is about 300 square meters. However, with the increase in population, the land around the mechanic village, is now occupied and used for commercial and residential purposes. This study aims at assessing the level of soil pollution caused by vehicular or traffic emission, abrasion of brake lining, discharges from corrode iron, rusting car parts etc. using the cheap, fast and non destructive magnetic method. The study also attempted to characterize the mineral grain size using frequency dependence of susceptibility and finally, to the type of mineral in the soil samples using temperature dependence of magnetic susceptibility measurements.
Magnetic minerals weather from basic and ultrabasic bedrock and result in the accumulation of primarily coarse grained minerals in overlying soils. These minerals are of primary lithogenic origin and are relatively unaltered by soil processes. A ferromagnetic mechanism which involves the weathering of iron from magnetic and non- magnetic soil parent materials; the weathered product is transformed to magnetic phases via soil forming processes under oxidizing-reducing conditions. These processes tend to form fine-grained secondary magnetite/maghemite with Stable Single Domain (SSD) and Super Paramagnetic/Viscous (SP) properties, referred to as magnetic enhancement, indicating the topsoil has elevated values of magnetic susceptibility and frequency dependent susceptibility in comparisons to the sub soil and soil parent material. Fire transforms non-magnetic iron oxides to magnetic minerals of predominantly fine grained SSD and viscous SP grains. Allochtonous sources which includes atmospheric pollution, soil erosion and pollution. Atmospheric pollution from combustive sources such as coal-fired power plants and steel works tend to form large minerals with varied compositions. Magnetic soil eroded from other areas has the potential to be of mixed composition. Other potential minor causes may include micro meteorites (allochtonous) and SP minerals from magnetic bed rock (in –situ).
MATERIALS AND METHODS Geographical and Geological Setting of the Study Area: The study area is part of Jalingo, the administrative headquarters of Taraba State which is located between latitude 6°30´ and 8°30´ N and between 9°00´ and 12°00´ E (Figure 1). The state has a tropical wet and dry climate, dry season lasts for a minimum of five months (November to March) while the wet season spans from April to October. It has an annual rainfall of about 8000 mm. Jalingo is a city with no major industry and thus less polluted. The major pollution source is the emission from traffic and power generating sets and human activities.
Thus, the dominant magnetic sources are bed rock type (lithogenic), pedogenic conditions and anthropogenic contributions. Furthermore, crystal size influences magnetic susceptibility [1] through its effect on the possibility of forming magnetic domains. In crystals smaller than 0.2µm, only SSD forms while in ultrafine (< 0.03µm) grains, SP behavior is exhibited [8]. Magnetic susceptibility in 179
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Fig. 1: Map of study area, Taraba State, Nigeria Sampling and Analysis: A total of 27 topsoil samples (0- 2 cm) were randomly collected using a plastic material to avoid contamination. Soil samples were also taken from two short soil profiles of depth between 20 and 35 cm. The soil profiles samples were collected using a locally sourced plastic rod of 4.5 cm in diameter. The rod was inserted to the soil and samples were taken at 5cm interval after the rod is removed from the soil. The soil profile sample points was labeled JMVP1 (8°56.321´ N and 11°19.909´ E) and JMVP2 (8°56.362´ N and 11°19.922´ E). The samples were enveloped in a plastic bag and taken to the laboratory for further analysis. In the laboratory, the samples were air dried at a temperature of 30°C for some days to avoid any chemical reactions. They were then sieved and stored in a plastic container for further laboratory measurements. The mass specific magnetic susceptibility measurements were then carried out on the sieved samples at laboratory temperature. Measurements of magnetic susceptibility were made at both low (0.47 kHz) and high (4.7 kHz) frequencies using MS2 dual frequency susceptibility meter. All measurements were conducted at the 1.0 sensitivity setting. Each sample was measured
The study area is underlain by the undifferentiated Basement Complex rocks which consist mainly of the migmatites, gneisses and the Older Granites. Tertiary to Recent basalts also occurs in the area. The undifferentiated Basement Complex particularly the migmatites, generally vary from coarsely mixed gneisses to diffused textured rocks of variable grain size and are frequently porphyroblastic [25]. This rock unit constitutes principally the undifferentiated igneous and metamorphic rocks of Precambrian Age [26]. The Pan African Older Granites are equally widespread in the area. They occur either as basic or intermediate intrusives [27]. Different kinds of textures ranging from fine to medium to coarse grains can be noticed on the Older Granites [28]. Other localized occurrences of minor rock types include some doleritic and pegmatitic rocks mostly occurring as intrusive dykes and vein bodies. These occurrences are common to both the undifferentiated Basement Complex and the Older Granite rocks [29, 28]. The Tertiary basalts on the other hand are found in the Mambila Plateau mostly formed by trachytic lavas and extensive basalts which occur around Nguroje [30]. 180
World Appl. Sci. J., 24 (2): 178-187, 2013
three times with an air reading before and after each series for drift correction. The mass specific frequency dependence susceptibility fd was obtained from the relation: fd
=
lf
–
Magnetic minerals present in soils may be inherited from parent material or produced by pedogenic processes or stem from anthropogenic activities [34]. The magnetic signals derived from lithogenic or pedogenic minerals may be too minor to be considered when compared with strong magnetic signal from anthropogenic ferrimagnetic minerals. Though, this is not always true as [35] concluded that soils with volcanic parent materials have high magnetic susceptibility values (> 400 x 10 8m3kg 1) and this does not necessarily implies pollution. High magnetic susceptibility value (1000 x 10 8m3kg 1) was also found for soils derived from Basalt parent material [36]. In order to properly monitor soil pollution with magnetic methods, it is pertinent to discriminate anthropogenic magnetic signals from background signal. Figure 2 compares the magnetic susceptibility measured at low (0.47 kHz) and high (4.7 kHz) frequencies. It can be clearly seen from the histogram that lf have higher values than hf. This can be explained as follows: at high frequency, the relaxation time of super paramagnetic grains is shorter than the measurement time and their contribution do not count. At low frequency, the measurement time detects the susceptibility of all grains including those that have a short relaxation time, such as super paramagnetic, which are generally fine. Thus, when the volume of grains in the soil is the same, magnetic susceptibility at low frequency becomes higher than that at high frequency. hf have values ranging from 19.5 – 408.1 x 10 8m3kg 1. Figure 3 is the graph of hf against lf values in the top soils of JMV. The graph shows a linear relationship between the two parameters with very good correlation coefficient (R2 = 0.994). An increase in lf appears to be positively correlated with an increase in mass specific frequency dependence susceptibility fd as show in Figure 4. Such a linear correlation indicates that with increasing magnitude, susceptibility is contributed more by the contribution from the fine pedogenic magnetic fraction [37]. A positive significant correlation between lf and fd (or ) also indicates high homogeneity in the magnetic mineralogy of the soils corresponding with mineral size [38]. The results of percentage frequency dependence of susceptibility ( fd%) may be used to depict the relative concentration of ultrafine Super Paramagnetic (SP) grains. Large grains [coarse Multi Domain (MD) grains] are practically insensitive to change in the frequency dependence of the applied magnetic field used and hence
hf
where lf and hf are the low frequency and high frequency susceptibility respectively. This parameter is sensitive only to a very narrow grain size region crossing the super paramagnetic/single domain threshold; ~ 20-25 nm for maghemite [31]. For natural samples which generally exhibit a continuous and nearly constant grain size distribution, fd can be used as a proxy for relative changes in concentration in pedogenic fined- grained magnetic particles [32]. The relative fd also called Percentage Frequency Dependent Susceptibility ( fd %) was then calculated following [1] as: if − hf = × 100 fd (%) if High temperature dependence of susceptibility was measured on two selected samples using MS2WF furnace connected to MS2WP power supply. The samples were heated from 50°C to 600°C at a ramp rate of 10°C per minute.
RESULTS AND DISCUSSION The results of the magnetic measurement of the JMV are displayed in Table 1. The low frequency magnetic susceptibility values ( lf) for the JMV varied between 19.8 and 436.8 x 10 8m3kg 1 with an average of 137.06 x 10 8m3kg 1. Most of the samples had lf values below 100 x 10 8m3kg 1. In comparison to the magnetic susceptibility value of 128 x 10 8m3kg 1 obtained in Hanzhou, China [10], the average value of lf obtained from the JMV was a little higher. [33] classified soils into three broad categories as follows: normal ( lf < 10 x 10 8m3kg 1), moderately magnetic ( lf 10 – 100 x 10 8m3kg 1) and highly magnetic ( lf > 100 x 10 8m3kg 1). From the above classification, about 55% of the samples were moderately magnetic while others were highly magnetic. This result indicated high concentration of ferrimagnetic minerals in the soil. The differences in the values of lf obtained showed that the relatively high lf values could not be due to the local geology. Thus, high magnetic susceptibility values in the top soils might be attributed to anthropogenic input of various origins and other human activities. 181
World Appl. Sci. J., 24 (2): 178-187, 2013 Table 1: Table showing magnetic measurements from JMV soil samples Sample
Mass (g)
Latitude
Longitude
JMV1 JMV2 JMV3 JMV4 JMV5 JMV6 JMV7 JMV8 JMV9 JMV10 JMV11 JMV12 JMV13 JMV14 JMV15 JMV16 JMV17 JMV18 JMV19 JMV20 JMV21 JMV22 JMV23 JMV24 JMV25 JMV26 JMV27
14.70 15.46 13.58 16.13 13.64 16.24 14.69 16.04 15.23 15.38 15.28 12.90 15.48 12.33 14.99 13.09 12.27 12.28 14.82 14.80 14.97 17.01 14.20 14.71 14.37 12.36 15.71
8°56.322´ N 8°56.323´N 8°56.329´N 8°56.342´N 8°56.361´N 8°56.382´N 8°56.401´N 8°56.402´N 8°56.413´N 8°56.423´N 8°56.425´N 8°56.424´N 8°56.400´N 8° 56.374´N 8° 56.378´N 8° 56.391´N 8° 56.411´N 8° 56.429´N 8° 56.438´N 8° 56.453´N 8° 56.461´N 8° 56.467´N 8° 56.452´N 8° 56.441´N 8° 56.429´N 8° 56.430´N 8° 56.481´N
11°19.909´E 11°19.923´E 11°19.932´E 11°19.924´E 11°19.922´E 11°19.910´E 11°19.907´E 11°19.879´E 11°19.883´E 11°19.897´E 11°19.911´E 11°19.930´E 11°19.945´E 11° 19.952´E 11° 19.967´E 11° 19.962´E 11° 19.957´E 11° 19.956´E 11° 19.958´E 11° 19.948´E 11° 19.957´E 11° 19.972´E 11° 19.984´E 11° 19.994´E 11° 19.997´E 11° 19.990´E 11° 19.965´E
lf
x10
8
m3kg
44.6 19.8 91.8 91.5 48.2 216.3 248.3 74.2 33.5 69.1 436.8 212.2 159.5 375.2 208.9 298.6 151.8 246.5 92.9 52.6 48.2 67.6 49.4 63.7 35.2 173.9 100.2
Fig. 2: The magnetic susceptibility values (x 10 8m3kg 1) at both low and high frequency ( lf and hf)
1
×hf x 10
8
m3kg
44.0 19.5 88.6 89.5 47.5 215.3 248.3 72.7 32.7 58.9 408.1 208.2 156.3 324.8 207.8 298.2 148.9 228.1 90.7 52.5 47.3 67.2 48.6 62.8 31.9 172.8 95.8
1
fd
x 10
8
m3kg
0.6 0.3 3.2 2.0 0.7 1.3 0.0 1.5 0.8 0.2 28.7 4.0 3.2 50.4 1.1 0.4 2.9 18.4 2.2 0.1 0.9 0.4 0.8 0.9 3.3 1.1 4.4
1
fd
(%)
1.35 1.52 3.49 2.19 1.45 0.55 0.00 2.02 2.39 0.34 6.57 1.89 2.01 13.43 0.53 0.13 1.91 7.46 2.37 0.19 1.87 0.59 1.62 1.41 9.38 0.63 4.39
Fig. 4: The frequency dependent magnetic susceptibility against low frequency magnetic susceptibility for JMV samples
Fig. 3: Relationship between the low and high frequency (x 10 8m3kg 1)
Fig. 5: fd% profiles of JMV samples 182
World Appl. Sci. J., 24 (2): 178-187, 2013
contribute significantly to depression of high frequency susceptibility. Therefore the closer fd% is to zero (usually < 2%), the more MD assemblages are expected to dominate the sample. Generally, for MD grains, fd% is < 2%, for SP grains fd % lies in the range 10 – 12 % while fd% values between 2 – 10 % indicates mixture of SD and SP grains [1]. Most of the samples (about 55%) in JMV had low fd% values between 0 – 2%, indicating an assemblage of MD magnetic grain. This implied that SP particles from pedogenic process were completely excluded from these samples. About 37% of the samples had fd% values ranging between 2 – 10%, indicating an assemblage of a mixture of SP and MD grains. Only one sample had a value greater than 10 % (13.43%), meaning that the dominant magnetic component on the sample was SP ferrimagnetic grains. These results are displayed in Figure 5. In summary, the mean value of fd% in the JMV was found to be 2.66%, suggesting that pedogenic SP grains did not contribute to the total magnetic susceptibility variation in the studied area. Unpolluted soils are usually characterized by the presence of an important super paramagnetic fraction produced by pedogenesis [2]. The low fd% value indicated that the soils did not contribute much magnetic material to the formation of magnetic susceptibility in the studied top soils. Figure 6 is fd% - lf scattergram showing typical positions of samples. Samples dominated by MD ferrimagnets from anthropogenic sources showed low fd% values. The fd% and lf were poorly, but positively correlated. Positive correlation of both parameter is typical of sedimentary rocks [10]. The increase of fd% and lf indicated that the magnetic susceptibility enhancement was due to pedogenic SP ferrimagnetic grains. Similar result was obtained by [35] for the Chinese loess. Many authors [e.g. 2, 10] reported a negative correlation for polluted urban soils, which indicated that the magnetic enhancements in urban soils were contributed by coarse MD magnetic grains from industrial and anthropogenic sources. The graph of fd% versus fd showed a good positive correlation with correlation coefficient R2 of 0.705 (Figure 7). ×fd gave a semi quantitative amount of MD, SSD or SP grains present in a sample. A plot of fd% against fd may help to discriminate between grain size and domain state and may give a first order classification of magnetic properties and even sources [1]. The graph indicated that most of the samples were concentrated within the MD grains range.
Fig. 6: fd% vs
lf
showing sample positions
Fig. 7: fd% against fd x 10 8m3kg
Fig. 8:
1
lf (x 10 8m3kg 1) and fd% vs depth for profile 1 of JMV samples
Vertical susceptibility distribution in soil profiles were measured in order to distinguish between lithogenic (natural) and anthropogenic contributions to the overall susceptibility of the area under consideration. In the first profile JMVP1, the measured magnetic susceptibility varied from 18 – 63.8 x 10 8m3kg 1 (Table 2). From Figure 8, two sources of magnetic enhancement were 183
World Appl. Sci. J., 24 (2): 178-187, 2013 Table 2: JMV profile 1 Data Sample JMVP1 1 JMVP1 2 JMVP1 3 JMVP1 4 JMVP1 5 JMVP1 6 JMVP1 7 JMVP1 8
Depth (cm)
Mass (g)
0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0
14.70 15.35 15.62 15.99 15.95 13.13 13.31 12.58
lf
x10
8
m3kg
1
44.6 33.2 18.0 24.5 25.7 45.6 48.5 63.8
×hf x 10
8
m3kg
1
44.0 33.2 17.3 23.7 25.5 44.9 47.8 63.2
fd
(%)
1.35 0 3.89 3.27 0.78 1.54 1.44 0.94
Table 3: JMV profile 2 Data Sample JMVP2 1 JMVP2 2 JMVP2 3 JMVP2 4 JMVP2 5 JMVP2 6
Depth (cm)
Mass (g)
0.0 5.0 10.0 15.0 20.0 25.0
13.64 15.32 15.72 14.95 16.10 15.42
lf
x10
8
m3kg
10.2 9.7 3.4 2.8 5.7 3.8
noticed: anthropgenic sources on the topsoil and lithogenic sources in the subsurface soil. The magnetic susceptibility values decreased with depth up to 15 cm (Figure 8), indicating anthropogenic contribution to the magnetic susceptibility of the top soils. Below 15 cm, an increase in the magnetic susceptibility with depth was observed. This indicated lithogenic contribution to magnetic susceptibility. The frequency dependence of magnetic susceptibility ranged from 0 to 3.89% in the profile JMVP1. From the table, only two samples (between 10 to 15 cm) exhibited a mixture of SP and MD grains, while the other samples showed that the profile was dominated by multi domain grains, supporting the presence of anthropogenic sources of the magnetic enhancement in the soils. The fd% vs depth plot did not show a clear pattern, but an initial increase in fd% with depth up to 15 cm was observed followed by a decrease downward. In contrast to JMVP1, magnetic susceptibility decreased with depth (Figure 9) in the second profile (JMVP2) although with minor fluctuations. This trend indicated anthropogenic contribution to the magnetic susceptibility. The low values of lf in JMVP2 which ranged from 2.8 – 10.2 x 10 8m3kg 1 (Table 3) portrayed the soil to be normal. However, the frequency dependence susceptibility values indicated that the soils within the profile were made up of multi domain grains which is a characteristics of soils with anthropogenic loadings as confirmed also by the trend of the lf vs depth plot. The values of xfd% ranged from 0 to 1.96% (Table 3). The graph of fd% vs depth was similar in trend with that of lf vs depth and showed decrease of fd% with depth.
Fig. 9:
1
×hf x 10
8
m3kg
10.0 9.7 3.0 2.6 5.3 3.5
1
fd
(%)
1.96 0 0.4 0.2 0.4 0.3
(x 10 8m3kg 1) and fd% vs depth for JMVP2 samples lf
Temperature- dependent susceptibility measurements were conducted on two selected samples (JMV11 and JMV 4) from a temperature of 50 °C to 600 °C and then back. The samples were selected based on the value of their magnetic susceptibility. JMV11 had the highest top soil lf value of 436.8 x 10 8m3kg 1 and JMV4 had a lower value of 91.5 x 10 8m3kg 1. Thermal treatment of magnetic minerals often leads to the destruction and formation of new mineral phases. The thermal alteration of magnetic minerals can correspond to the appearance of a new ferrimagnetic mineral from paramagnetic phases, the transformation of ferrimagnetic phases into other ferrimagnetic minerals or to grain size and structural changes of ferrimagnetic carriers [39]. The most widely used method for detecting these thermal alterations is temperature dependent susceptibility. This method measures the bulk magnetic 184
World Appl. Sci. J., 24 (2): 178-187, 2013
Figure 10 displayed the results of heating and cooling curves for sample JMV11. There is no major alteration in both curves which is a characteristic of coarse grained magnetite. The heating curve rapidly decreased after 500°C and displayed a Curie point temperature at 530°C. This value indicates that titanium poor magnetite is the dominant magnetic mineral in the sample [41]. The temperature –dependence of susceptibility measured for the JMV4 sample is shown in Figure 11. The curves showed higher susceptibilities values on cooling, implying that new magnetic minerals were created from weakly magnetic phases due to heating. The heating curve decreased to zero susceptibility at temperature of 500 °C. The observed peak in the cooling curve around the 150 – 200 °C may be due to the creation of new minerals. The lack of smooth curve as seen in the figure is an indication of complex mineral alterations during the heating and cooling runs.
Fig. 10: Ttemperature variation with low field magnetic susceptibility for JMV 11 sample
CONCLUSIONS The Major Conclusions Reached in Include:
Fig. 11: Temperature variation with low field magnetic susceptibility for JMV 4 sample
this Study
Environmental magnetism parameters measurement showed a significant enhancement of magnetic susceptibility in the Jalingo Mechanic Village, indicating increased pollution and this could be attributed to anthropogenic sources and other human activities within the study area. The percentage frequency dependence susceptibility showed that the dominant magnetic grains in the area is in the multi domain range and that pedogenic super paramagnetic mineral grains contributes little to the susceptibility enhancement in the area. A poor but positive correlation was found between magnetic susceptibility and frequency dependence susceptibility in the area. Vertical plots of magnetic susceptibility against depth showed both lithogenic and anthropogenic contributions to the magnetic susceptibility enhancement. Thermal analysis confirmed a formation of new magnetic minerals on heating as cooling curves rises above heating curve in JMV4 samples. However, the Curie point temperature obtained from both curves indicated that titanium- poor magnetite dominates the sample.
susceptibility at room temperature after successful thermal steps. Acquisition of temperature dependent susceptibility cooling and heating curves helps identify the magnetic minerals in a sample [40]. Diamagnetic minerals exhibit no temperature variation of susceptibility. Paramagnetic minerals behave in accordance to the Curie-Weiss law: k = C/T, where C is a constant and proportional to the concentration of paramagnetic ions and T is absolute temperature. Therefore, the paramagnetic susceptibility is inversely proportional to the absolute temperature. Ferrimagnetic minerals carry a remanent magnetization below a critical temperature called the Curie temperature. Above the Curie temperature, thermal activation energies disrupt the ordering of the magnetic moments and ferrimagnetism is lost resulting in paramagnetic behavior. Curie temperature occurs at a critical point that is specific for each mineral. However, the degree of purity and/or lattice substitutions within a mineral may affect the temperature at which the Curie temperature is reached, resulting in slightly higher or lower temperatures. Temperature –dependent susceptibility are effective in identifying mineralogy, however, the measured values reflect only the result of all the simultaneous changes in a complex mineral system. 185
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