Assessment of Trace and Rare Earth Element Levels in Stream Sediments in Ijero-Ekiti Area, Southwest Nigeria

The study considered the level, sources and extent of trace and rare earth elements (REE) contamination in Agbangudu stream sediments in Ekiti State, Southwestern Nigeria. The samples were analysed with Laser Ablation Inductively Coupled Plasma Spectrometer (LA-ICP-MS). The trace and rare earth elements’ concentration ranged from 0.50 (Mo) to 750 (Ba) and 0.16 (Lu) to 175 (Ce) ppm respectively. The results revealed that the sediments are not that enriched in REEs. The Pollution Load Index (PLI) indicates baseline levels of the metals. The geochemical index (Igeo) of the elements revealed uncontaminated to moderately contaminated, except for Cs and Ta with strongly to extremely contaminated status. The Average Shale Value (AVS) and the Upper Continental Crust (UCC) normalized REE distribution patterns of the sediments. To establish the relationship between the metals, Principal Component Analysis (PCA) and Clusters Analysis (CA) were used as classification techniques. Despite the common occurrences of the elements, their overall patterns were much different as revealed by the cluster analysis.


INTRODUCTION
Sediments are transported and deposited particles or aggregates derived from rocks, soils or biological material (SSSA 2008). Generally, stream sediments are composed of weathering products of basement rocks introduced into streams. Studies of the chemistry of stream sediments have been used in mineral prospecting (Levinson 1974, Rose et al. 1979, Hale & Plant 1994 and environmental studies (Förstner 1983, Howarth & Thornton 1983, Förstner et al. 1991. Most streams in southwestern Nigeria are located on the Basement complex, which lies within the reactivated part of the Pan-African mobile belt between the West African and Congo Cratons (Kennedy 1965). The geochemical compositions of stream sediments reflect the average composition of an entire drainage basin (Halamic et al. 2001, Reimann & Melezhik 2001). According to Grunsky & Sutphin (2009), geochemical studies based on the chemical analysis of active stream sediments are an effective tool with several applications. The expression "rare earth elements" (REEs) does not infer that they are rare in nature; rather, REEs are relatively abundant in the earth. The total contents of REEs exceed 200 ppm in the average crust. Some REEs are even more common than copper or lead in the crust (Castor & James 2006, Chen 2011. REEs are at the lower part of the Periodic Table, which includes 15 lanthanides (from lanthanum to lutetium) and two other elements: scandium and yttrium. These 17 elements form a coherent group with similar chemical properties. Usually, REEs can be divided into three groups by their atomic number and masses -the light rare earth elements (LREE), which comprises of La, Ce, and Pr, the middle rare earth elements (MREE), made up of Nd, Sm, Eu, and Gd, while the heavy rare earth elements (HREE) include those from Tb to Lu (EPA 2012).
Trace and rare earth elements in sediments are derived from both natural (geogenic) and anthropogenic sources. Heavy metals and rare earth elements (REEs) are potentially toxic substances in ecosystems. According to Lin et al. (2008), heavy metals and REEs are added to the hydrological system by natural processes such as rock weathering, volcanic eruption and long-distance atmospheric deposits. In recent times, the chief sources of these elements are due to the human activities: industrialization, agriculture, urban development and waste discharge (Senesi et al. 1999, Ochieng et al. 2007, Chen et al. 2013, Ong et al. 2013, Sofianska & Michailidis 2013, Zhuang et al. 2013. Stream sediments contamination by heavy metals has become a widespread serious problem in many parts of the world (Sofianska & Michailidis 2013). Trace and rare earth element contamination in soils has attracted so much attention because of the hazard it poses to human health (Loska et al. 2004). Rivers, Vol. 19, No. 2, 2020 • Nature Environment and Pollution Technology streams and sediments are contaminated by trace elements such as: As, Fe, Hg, Mn and Pb from artisanal mining activities, and their values have also been found to exceed standard safety levels (Ojo & Oketayo 2006, Nartey et al. 2011. Some metals like Fe, Cu, Co, Mn, Cr and Zn are essential micronutrients, but they can be detrimental to man and other living organisms at higher concentrations (Nurnberg 1982, Kar et al. 2008, Nair et al. 2010). According to Wakida et al. (2008), industrial waste reaching the sea via atmospheric precipitation and dumping of urban and rural waste is mostly responsible for the input of trace elements into the marine and stream environments, which are afterwards incorporated into the sediments. Trace and rare earth elements are serious pollutants because of their toxicity, persistent and non-degradability and thus imparting into the water and debasing its quality in an environment (Tijani et al. 2005). Several studies have shown the harmful effects and health hazards of REEs to human beings, and it has already been proven that longterm exposure of REE dust may cause pneumoconiosis in humans (Hirano & Suzuki 1996).
This work analyses trace and rare earth elements concentration in the Agbangudu stream sediments and pollution indices such as enrichment factor (EF), contamination factor (CF), pollution load index (PLI), degree of contamination (DC) and geochemical index (Igeo).
The migmatite gneiss occurs within the eastern part covering about two-fifth of the area, biotite gneiss predominantly The migmatite gneiss occurs within the eastern part covering about two-fifth of the area, biotite gneiss predominantly covers the northwest (the gneissic rocks are essentially highly foliated and denuded); calc- covers the northwest (the gneissic rocks are essentially highly foliated and denuded); calc-gneiss and quartzite occupy a narrow NE-SW strip around Ijero-Ekiti town (Okunlola & Akinola 2010). Epidiorite occurs as the major ultramafic assemblage while amphibole schist and biotite schist occupy the central, low-lying area that is occasionally pulsed with granites and pegmatite intrusions now exposed due to prolonged weathering activities. The pegmatite occurs as very coarse-grained dykes, dykelets and sometimes of extensive dimension (Okunlola & Akinola 2010). Steeply dipping complex pegmatite around Ijero-Ekiti typically consists of an outer medium-grained microcline-albite-quartz-muscovite zone, an intermediate zone comprising coarse-grained microcline-albite-quartz, blocky microcline-quartz, coarse-grained quartz or lepidolite-quartz and finally, a core of coarsegrained muscovite-quartz and quartz (Okunlola 2005). Several workers have worked on the geology, tectonics, etc., of the Nigerian Precambrian Basement complex (Burke & Dewey 1972, Oyawoye 1972, Rahaman 1976, Rahaman & Ocan 1978, Black et al. 1979, Turner 1983, Ajibade et al. 1987, Rahaman 1988).

Sample Pre-treatment
Several samples were initially obtained while 10, which were representative of the stream channels, were eventually selected and analysed. Samples were taken at a depth of 20-25cm and bagged and labelled to avoid mix up. The geographical locations of each sample collected were noted and recorded in the field notebook. The samples were air-dried, pulverized, homogenized, packaged and sent to the laboratory in Stellenbosch University, South Africa for geochemical analysis. The trace and rare elemental data for this work were acquired using Laser Ablation inductively coupled plasma spectrometer (LA-ICP-MS) analyses. LA-ICP-MS is a powerful and sensitive analytical technique for multi-elemental analysis. The laser was used to vaporize the surface of the solid sample, while the vapour, and any particles, were then transported by the carrier gas flow to the ICP-MS.
The analytical results were compiled to form a multi-elemental database using Excel and Past. The statistical analyses, including principal component analysis (PCA) and cluster analysis (CA), were performed using Past statistical software.

Distribution of Trace and Rare Earth Elements
The trace and rare elements composition, average values, background values of the Ijero stream sediments sampled,  Table 1. The background or control sample is the normal abundance of uncontaminated background levels in the stream sediments. These data revealed that the mean values of V, Co, Cu, Zr, Nb, Hf, Th, Mo and REEs: La, Ce, Pr, Nd, Sm, Sc, are below the background values, while Cr, Ni, Zn, Rb, Sr, Cs, Ba and the REEs: Eu, Gd, Tb, Dy, Er, Tm, Yb, Lu, Y, exceeded the background values. These elements with higher concentrations than the background values could become a major cause of concern. Figs. 4 and 5 are bivariate plots comparing trace element concentration and REE concentration of the samples studied with the mean of the upper continental crust and the average shale value respectively. Zn, Rb, Zr, and Nb showed significant enrichment compared to UCC and AVS. For the REEs, the concentrations showed the same pattern with the UCC and AVS. Fig. 6 is an AVS and UCC-normalized trace elements patterns for the stream sediments showing high levels of Nb and Ta, and to a lesser extent Rb, Zn, Cs and Hf. The AVS and UCC-normalized REE patterns for the stream sediments show an almost flat pattern, which might suggest the stream sediments are not that enriched in REEs (Fig. 7).

Enrichment Factor
Enrichment Factor (EF) is a useful pointer in assessing the level of contamination in an environment. According to Hernandez et al. (2003), the enrichment factor is the relative abundance of a chemical element in stream sediment compared to the bedrock. EF evaluates the degree of anthropogenic influence on element load in sediments and differentiates between elements of geogenic or anthropogenic origin (Fagbote & Olanipekun 2010). Enrichment factor values of trace and rare earth elements in the Agbangudu stream sediments are presented in Table 2. It was calculated using the formula originally introduced by Buat- Menard & Chesselet (1979): Where, C n is the concentration of the examined element in the examined environment; C ref is the concentration of the reference element in the examined environment; B n is the background value of the examined element, and B ref is the background value of the reference element. The method by Salomons & Forstner (1984) was used, which entails comparing the present-day metal concentrations in sediments with standard earth materials as a normalizer in average shale.
Average shale value (AVS) and control value from Turekian & Wedepohl (1961), UCC: Upper Continental Crust (Taylor & McLennan 1985, 1995 The global average shale is frequently employed to provide background metal levels; the element's concentration

Distribution of Trace and Rare Earth Elements
The trace and rare elements composition, average values, background values of the Ijero stream sediments sampled, upper continental crust values and average shale values are presented in Table 1. The background or control sample is the normal abundance of uncontaminated background levels in the stream sediments. These data revealed that the mean values of V, Co, Cu, Zr, Nb, Hf, Th, Mo and REEs: La, Ce, Pr, Nd, Sm, Sc, are below the background values, while Cr, Ni, Zn, Rb, Sr, Cs, Ba and the REEs: Eu, Gd, Tb, Dy, Er, Tm, Yb, Lu, Y, exceeded the background values. These elements with higher concentrations than the background values could become a major cause of concern. Figs. 4 and 5 are bivariate plots comparing trace element concentration and REE concentration of the samples studied with the mean of the upper continental crust and the average shale value respectively. Zn, Rb, Zr, and Nb showed significant enrichment compared to UCC and AVS. For the REEs, the concentrations showed the in average shale obtained from Turekian & Wedepohl (1961) was used. An element can be considered as a reference element if it is of low occurrence variability and present in the environment in trace amounts (Loska et al. 2003). According to Loska et al. (1997), it is also possible to apply an element of geochemical nature, which occurs in significant amounts in the environment but has no interaction or resistance towards an examined element. A reference element is often a conservative one, unchanged by anthropogenic influences; and the most used reference elements include Sc, Mn, Ti, Al, Fe, Zn, etc. (Loska et al. 1997, Mediolla et al. 2008).  Zn is moderately abundant; its natural abundance and sources surpass its anthropogenic source. In this study, the trace elements were normalized to Zn at global average shale value and Ho for the REE. These elements were chosen as the reference elements because there is no known anthropogenic activity either within the vicinity of the sampling locations or in the long-distance which can be traceable as the source of these elements. Five contaminated categories are recognized on the basis of the Enrichment Factor: EF <2 (deficiency to minimal enrichment); EF = 2 to 5 (moderate enrichments); EF = 5-20 (significant enrichment); EF = 20-40 (very high enrichment) and EF > 40, is extremely high enrichment (Sutherland 2000). According to Zhang & Liu (2002), EF values between 0.5 and 1.5 suggests that the element concerned may be derived entirely from crustal materials or natural weathering processes (geogenic). Values greater than 1.5 suggest a significant portion of the element has been supplied from non-natural (anthropogenic) sources. As the EF values increase, the contributions of the anthropogenic origin also increase (Sutherland 2000).
The results of the enrichment factors of V, Cr, Co, Ni, Cu, Sr, Mo, Ba, Pb, Th, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Mo, Dy, Er, Tm, Yb, Lu Sc, and Y shows that these metals are deficient to minimal enrichment, because EF were < 2. According to Zhang & Liu (2002), they are therefore naturally derived from the stream sediment and geogenic sources resulting from weathering processes in the environment. The average EF values of Rb, Zr, Hf, U and Cs indicated moderate enrichment, because they fall within the range of 2 < EF < 5. Only the EF of Nb has significant enrichment since the EF falls within the range 5 < EF < 20; and Ta has variable EF values from significant enrichment; very high enrichment to extremely high enrichment. Most of the EF values in the sediments were < 2 and 2< EF <5, except the Nb and Ta. According to Sutherland (2000) and Zhang et al. (2007), the metals, therefore, originated from anthropogenic activities.

Contamination Factor (CF) and Degree of Contamination (C d )
According to Demie (2015), the degree of contamination is aimed at providing a measure of the degree of overall contamination in surface layers of a particular sampling site. CF is calculated for individual elements using the formula proposed by Hakanson (1980): CF = C Element / C Background , where C Element is the concentration of elements at the con-According to Sutherland (2000) and Zhang et al. (2007), the metals, therefore, originated from anthropogenic activities.  The results of the enrichment factors of V, Cr, Co, Ni, Cu, Sr, Mo, Ba, Pb, Th, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Mo, Dy, Er, Tm, Yb, Lu Sc, and Y shows that these metals are deficient to minimal enrichment, because EF were < 2. According to Zhang & Liu (2002), they are therefore naturally derived from the stream sediment and geogenic sources resulting from weathering processes in the environment. The average EF values of Rb, Zr, Hf, U and Cs indicated moderate enrichment, because they fall within the range of 2 < EF < 5. Only the EF of Nb has significant enrichment since the EF falls within the range 5 < EF < 20; and Ta has variable EF values from significant enrichment; very high enrichment to extremely high enrichment. Most of the EF values in the sediments were < 2 and 2< EF <5, except the Nb and Ta.
According to Sutherland (2000) and Zhang et al. (2007), the metals, therefore, originated from anthropogenic activities.  Contamination Factor values of trace and rare earth elements in the Agbangudu stream sediments are presented in Table 3. Hakanson (1980) Where, Cf is the contamination factor of each element; n is the number of elements under investigation. A modified form of the Hakanson (1980)   Where, mC d is modified degree of contamination, n is the number of analysed element and Cf i is the contamination factor; the mC d data for the work are presented in Table 4.
concentration of elements at the contaminated site and C background is the background value of the same element.  Contamination Factor values of trace and rare earth elements in the Agbangudu stream sediments are presented in Table 3. Hakanson (1980)

Contamination Factor (CF) and Degree of Contamination (C d )
According to Demie (2015), the degree of contamination is aimed at providing a measure of the degree of overall contamination in surface layers of a particular sampling site. CF is calculated for individual elements using the formula proposed by Hakanson (1980): CF = C Element / C Background , where C Element is the concentration of elements at the contaminated site and C background is the background value of the same element. Contamination Factor values of trace and rare earth elements in the Agbangudu stream sediments are presented in Table 3. Hakanson (1980) applied the CF under four categories: CF<1 indicates low Abrahim & Parker (2008) proposed the following classes for the modified degree of contamination: mCd<1.5, nil to very low degree of contamination; 1.5£mCd<2, low degree of contamination; 2£mCd<4, moderate degree of contamination; 4£mCd<8, high degree of contamination; 8£mCd<16, a very high degree of contamination; 16 £ mCd< 32, an extremely high degree of contamination and mCd³32 means the ultra-high degree of contamination. Results from this study classified the level of the metal as non-contaminated to very low contamination, while Ta and Nb showed a high degree of contamination.

Pollution Load Index (PLI)
The Pollution Load Index (PLI) was developed by Tomlin-  (1980) to compare pollution levels between sites and propose a necessary line of action. According to Priju & Narayana (2006), PLI represents the number of times by which the element concentrations in the sediments exceeds the background concentration, and gives a summative indication of the overall level of element toxicity at a particular sample site. The PLI was computed based on the method proposed by Tomlinson et al. (1980). The PLI of the area was evaluated by obtaining the n-root from the n-CFs that were obtained for all the elements. This parameter is expressed as: Where, n is the number of elements and CF is the contamination factor, the PLI values are shown in Table  4. According to Tomlinson et al. (1980), a Pollution Load Index (PLI) <1 denote perfection; PLI = 1 present that only baseline levels of pollutants are present and PLI > 1 would indicate deterioration of site quality. The results obtained put the PLI values at approximately 1, which indicates only baseline levels of metals. However, PLI data without Ta and Cs denotes perfection. Likuku et al. (2013) proposed that a PLI value of ³1 indicates an immediate intervention to ameliorate pollution; 0.5£PLI<1 suggests that more detailed study is needed to monitor the site, whilst a value of <0.5 indicates that there is no need for drastic rectification measures to be taken.

Geoaccumulation Index (Igeo)
Geoaccumulation index (Igeo) was first introduced by Muller (1969) to compare the present-day heavy metal concentration with the pre-civilized background values. According to Singh et al. (1997), Igeo can be used to quantify the degree of contamination in stream sediments. Afkhami et al. (2013) affirmed that Igeo values can be used effectively and more meaningfully in explicating sediment quality. The Igeo of the elements was calculated by computing the base 2 log of the measured total concentration of the element over its background concentration using this equation: Where, Cn is the measured concentration of the stream sample for the element (n), and Bn is the background value of the element (n). The correction factor; 1.5 was used to account for possible variations in background data due to lithogenic effects. Muller (1969) proposed seven descriptive classes for increasing Igeo values: Igeo>5 indicates extremely contaminated; 4<Igeo<5 indicates strongly to extremely contaminated; 3<Igeo<4 indicates strongly contaminated; 2<Igeo<3 indicates moderately to strongly contaminated; 1<Igeo<2 indicates moderately contaminated; 0<Igeo<1 indicates uncontaminated to moderately contaminated; and Igeo = 0 indicates uncontaminated. The geoaccumulation index (Igeo) of the elements in the stream sediments is shown in Table 5. All the elements showed uncontaminated to moderately contaminated, except for Cs and Ta with strongly to extremely contaminated status.

Rare Earth Element
The chondrite normalisation curves (Fig. 8)   commonly observed from river sediments is due to the average upper crustal surface composition and source rocks (Sholkovitz 1993). Also, according to Sholkovitz (1993), the mixing and homogenizing effects of sedimentary processes will produce uniform REE pattern which signifies the abundance in the upper continental crust. Enrichment of LREE reflects the intense silicate weathering of crustal materials and a subsequent increase in LREEs in detrital. The LREE/ HREE ratios for the stream sediments range from 6.7 to 12.9 with an average of 9.13 (Table 5), which is slightly more than the upper crustal ratio and is equal to average shale ratio. (La/Yb)n ratios range between 7.89 to 28.93 with a mean ratio of 13.22 and that indicates very high erosional rates, which suggests that La was removed from the crustal According to McLennan (1988), generally, the La/Yb ratio is found to be very low in sediments rich in coarse size fractions and felsic minerals. Ramesh et al. (2000) opined that physical weathering is predominant in fine-grained sediments, which suggests that REEs fractionation took place in the stream. Y exhibits a moderate positive correlation with the LREEs (0.50), suggesting a partial association with detrital. Variation in Ce anomalies is indicative of terrigenous input, depositional environment and diagenetic conditions (Toyoda et al. 1990). Ce/Ce*>1 and <1 indicates positive (reducing environment) and negative (toxic environment) anomalies, respectively (Toyoda et al. 1990). Ce/Ce* ratio range of 3.14 to 3.70 with a mean ratio of 3.47 suggests minimal terrigenous input in a reducing environment.
All the Eu/Eu* ratios for the stream sediments are <1 (Table 6), implying that the origin of this element (Eu) is rich in feldspar source, contributing to a positive anomaly in the stream. According to Burg et al. (1984) and Gansser et al. (1983), this may also be due to the weathering of granite and granitic gneiss in the source region.

Cluster Analysis
For a more detailed comparison of the analysed metals and oxides in the stream sediments, cluster analysis by Ward (1963) method was performed and a dendrogram illustrating the results were presented in Figs. 10 to 12. This was employed in the study to see a possible association of the elements and to determine the similarities as regards the levels of the analysed metals and oxides. The distance cluster represents the degree of association between the elements and oxides. The lower the values on the distance cluster the more significant the association. Despite the common occurrence of these elements and oxides, their overall patterns were much different as revealed by the (1984) and Gansser et al. (1983), this may also be due to the weathering of granite and granitic gneiss in the source region.   (1984) and Gansser et al. (1983), this may also be due to the weathering of granite and granitic gneiss in the source region.    cluster analysis. In Fig. 10, three distinct clusters can be identified; Cluster 1 contained Y, La, Nd, SiO2 and Ce; indicating a close relationship between La and Nd, while a possible relationship was also exhibited between SiO2 and Ce. This was similar to the enrichment factor of the metals, where the results revealed that the metals were naturally derived and geogenic sources resulting from weathering processes in the sediments. Clusters 2 showed possible interaction between most rare-earth elements and oxides such as CrO 2 , MnO, P 2 O 5 , CaO, TiO 2 , Fe 2 O 3 , K 2 O, Na 2 O and MgO, while Cluster 3 reflected the strong relationship of Al 2 O 3 with Sc, Gd, Dy, Pr and Sm at a particular level. These elements may probably be affected by a similar factor or originate from the same natural parents of the sediments. In Fig. 11, three clusters were also formed. Cluster 1 showed a close relationship between Zr, Rb and Ba. Cluster 2 showed that majority of the trace elements and oxides were found to be closely associated with other elements in natural materials, especially with those that formed a distinct cluster at a distance cluster of below 200, while Cluster 3 showed a close association between Zn, Nb, Cr, Sr, Ta, V and SiO 2 . The association may reflect possible Fig.10: Dendrogram derived from the hierarchical cluster analysis of rare-earth elements and major oxides in the analysed stream sediments.   A distance cluster of about 160 was used for trace elements and rare-earth metals analysis (Fig. 12). Cluster 1 showed a close association between Cr, Sr and Ce. Cluster 2 is in three groups, with Ta, La, Ni and Nd in group 1, while the second group contained Cu, Pb, Y and Th and combines with the other group which contain most elements. This suggested that the association between these elements is very significant and further indicates that the elements probably originated from natural materials or natural geochemical system and/or possibly associated with inputs from anthropogenic activities.
The clustering of the metals also reaffirms the confirmation of EF results, which shows that the metals are majorly from natural and geogenic sources. A distinct relationship was observed between Zn and Nb, while Rb, Ba and Zr also formed a distinct cluster at about 720 Euclidean distance. Rb and Zr indicated moderate enrichment from the EF, this was also affirmed from the close association of the metals.

Principal Component Analysis
The results of principal component analysis (PCA) of the metals and oxides concentrations in the stream sediments are shown in Tables 7-9. Five principal components were em-   ployed, PC1 accounted for 64.5 to 95.9% of the total variance in three interactions. Table 7 showed the factor loadings for major oxides and trace elements. PC1, PC2, PC3, PC4 and PC5 accounted for 65.8%, 18%, 7.32%, 5.6% and 2.10% respectively. Interpretation of PCA patterns factor loadings greater than 0.71 is typically considered excellent, while those less than 0.32 are regarded as very poor (Nowak 1998     elements and major oxides were less than 0.32 in the five rotated factors. Factor 2 accounted for 18%, where Zn and Zr were closely associated. Vanadium was found to be associated with Ni and Zr in PC3, while Rb was associated with Sr and Nb in PC4; making up 5.86% of the total variance. The results indicated that the metals are associated with some rock-forming elements, which may have originated from parental materials of the sediments. Factors 2 and 3 association revealed low to moderate contamination of the metals involved as revealed by the contamination factor result. Table 8 is the factor loadings for the metal oxides and rare-earth elements interactions from PCA. The first component explains 95.9% of the total variance and loads heavily on La, Ce and Nd. The loading pattern of these metals possibly reflects scarcely low contamination level. The second and third component, loaded on Y and (Al 2 O 3, La , Dy and Sc), accounting for 1.95% and 1.68% of the total variance. The factors loading for trace and rare-earth elements interaction are shown in Table 9. The principal components that have eigenvalues higher than one were also employed for their interactions. The first component (PC1) explains 64.5% of the total variance and loads heavily on Sr and Ba. The PC2 loads heavily by Zr, Nb and Ba and accounted for 18.9% of the total variance. The third and fourth component PC3 and PC4 account for 7.09% and 5.83% respectively, and loaded by Cr, Rb, Sr and Nb, while the PC5 accounted for 2.3% and loaded by Zr and Ba. The PCA analysis results suggest that the metals that load positively on the same component are likely associated and possibly showed similar sources, distribution pattern and/or possibly affected by the same factors in the stream sediments.

CONCLUSIONS
This study revealed that the mean values of V, Co, Cu, Zr, Nb, Hf, Th, Mo and REEs: La, Ce, Pr, Nd, Sm, Sc, are be-low the background values, while Cr, Ni, Zn, Rb, Sr, Cs, Ba and the REEs: Eu, Gd, Tb, Dy, Er, Tm, Yb, Lu, Y, exceeded the background values. The average EF values of Rb, Zr, Hf, U and Cs indicate moderate enrichment, while Nb has significant enrichment. The study also classified the metals as non-contaminated to very low contamination, while Ta and Nb showed a high degree of contamination. The results showed the PLI values of approximately 1, which indicates only baseline levels of metals. The geoaccumulation index (Igeo) of the elements revealed uncontaminated to moderately contaminated, except for Cs and Ta with strongly to extremely contaminated status. The LREE/HREE ratios for the stream sediments range from 6.7 to 12.9 with an average of 9.13. The (La/Yb)n ratios indicate very high erosional rates, which suggests that La was removed from the crustal source through the weathering process, which was later transported and deposited by the streams.