Geo-Environmental Evaluation of Shewasoor Soil, Kirkuk/ NE Iraq

The present research aimed to evaluate contamination levels of soil by heavy metals. Eight sites were selected for the collection of soil samples. The soil samples analyzed for eight heavy metals namely As, Pb, Cd, Cr, Co, Cu, Ni, and Zn by using ICP-MS technology. The spatial distribution patterns of environmental assessment factors and indices were drawn using Geographic Information Systems (GIS), which is gives understanding for the geographical distribution of contamination levels in the area. The heavy metals contamination assessed by using several environmental factors and indices: Contamination Factor, Degree of Contamination, Pollution load Index, Enrichment Factor, Geo-accumulation Index, Nemerow Index. The environmental factors and indices showed that the soil was moderate to heavily contaminated by studied heavy metals. The EF values indicated that the metals Pb, Cr, Co, Cu, and Zn were enriched from natural sources, while the metals As, Cd, and Ni were enriched from anthropogenic sources.


Introduction
The Pollution and contamination are substances or metals that introduce into the environment have harmful effects or usually poisonous to human and ecosystem. The soil is natural body comprises of solids, liquid, and gases, it's consists of the land surface and occupies space from earth surface [1]. The pollutants introduced into the soil via several pathways [1,2]. Heavy metals are type of trace elements that are group of metals and semimetals with atomic mass greater than that of sodium and density above (3.5-6) g/ [1,3].
The main sources of heavy metals [1,[4][5][6][7][8][9] are: 1) Natural or geological sources, including weathering, erosion and deposition. 2) Anthropogenic sources, including atmospheric deposition, wood combustion, land application of sewage sludge, animal manure and other organic wastes, agricultural application of fertilizers and pesticides, and fossil fuel combustion. The pollution of soil with heavy metals is one of the most environmental problems, because it is related directly to food chain security and the human health [10,11,12]. Fertilizers play an essential role in increasing food production. Some inorganic fertilizers are containing contaminant metals, metalloids and radionuclides (e.g. Phosphatic, nitrogenous and Potassic fertilizers). Application of these fertilizer in the agricultural lands lead to increase the heavy metals concentration in the soil and in the agricultural crops [3,13]. Heavy metals concentration and distribution in the soil influences by soil type, topography, geology and the erosive processes [14,15]. According to field observations in the Shewasoor area there are many natural and anthropogenic sources that are contributes to pollute the soils of study area by heavy metals are:1) Quarries 2) Large areas of geological outcrops 3) Agricultural lands 4) livestocks breeding (Cattles, Sheeps, and Poultry) 5) discharges of waste water and sewage sludge. This study aimed to: 1) Determine the levels of heavy metals in the soil of study area. 2) Environmental assessment of soil of the study area by using several indices and factors including: Index of geo-accumulation, Nemerow index, Contamination factor, Degree of contamination, Pollution load index, Enrichment factor, Potential ecological risk index, Nemerow pollution index.
southwest sides, and by topographic elevated area from south and southeast sides Fig. 1. Also, the topographic elevations of the study area ranges between (311-1186) m a.s.l.

Fig. 1:
The Location of Study Area and Soil Sampling Sites.

Tectonic and Geological Setting:
The study area lies in the Unstable shelf within Foothill zone in Chamchamal-Arbil subzone according to [16] tectonic division of Iraq. It has stratigraphic sequence extending from oldest (Upper Miocene) up to youngest (Quaternary deposits) [17]. The exposed formations Fig. 2 are: Bai-Hassan Formation: (Pliocene), it consists of thick and coarse conglomerates, thick brown claystone and thin sandstone [17]. Its thickness is more than 2000m in the center of depositional basin within Foothill zone [18].

Environmental Assessment Methods:
The environmental assessment of study area soil was performed by using the following environmental factors and indices, and the spatial distribution patterns of these factors and indices were drawn using ArcGIS software (version 10.2):

Contamination Factor and Degree of Contamination:
The contamination factor is a single-element index used to describe the contamination level of toxic metals in the soil. The contamination factor (CF) value calculated by using the following equation [19], see Table 1: Where: is Measured Concentration of metal in soil sample, is Background (reference) value of metal in earth crust [20].
The degree of contamination was defined as the sum of all determined contamination factors (CF) for each sample Table 1.

Pollution Load Index (PLI):
The pollution load index practice to estimate the sites contamination by heavy metals. The Pollution Load Index (PLI) value was determined using the following equation [21]:

Enrichment Factor (EF):
The enrichment factor suggested by [22] to assess the level of soil contamination, which represents relative abundance of heavy metals in soil. value was calculated by using the following equation [22], see Table 2: Where: is the ratio of concentration of measured heavy metal ( ) to that of iron ( ) in the soil sample, is the ratio of background value of measured heavy metal ( ) to that of reference element ( ), according to [20].

Index of geo-accumulation ( ) and Nemerow index ( ):
The geo-accumulation index ( ) was used to determine the extent of metal accumulation in soil or sediments, in current study the level of heavy metals contamination was calculated by using the following [24], see Table 3: Where: is measured concentration of heavy metal (n) in the soil sample, is Geochemical background value for the heavy metal (n), according to [20].
Because of the assessment of geo-accumulation index is only for a single heavy metal pollutant, which it cannot provide a comprehensive description of the contamination status of the study area, the Nemerow index ( ) was developed to give comprehensive description of contamination condition for each site, which was calculated by using the following equation [25], Table 3:

√ ⁄
Where: is Nemerow index of a sample, ( ) is maximum value of each sample, and ( ) is average value of .

Concentrations of Heavy Metals in Soil Samples:
The concentration of selected heavy metals in the studied soil samples were shown in

Correlation Coefficient of Heavy Metals in Soil of the Study Area:
The Pearson's correlation coefficient is a statistical method which describe the strength and direction of the relationship between two variables Table 5 [27], were employed to evaluate the relations among heavy metals Table 6

Contamination Factor and Degree of Contamination:
The results of calculated contamination factor (CF) listed in Table 7, and the spatial variation of CF values for heavy metals shown in Fig. 3. contaminated moderately by Zn, whereas moderate levels of contamination recorded at all sites for Ni, Cd, and Cu, but S1 and S4 are shown low levels of Cu contamination, while all sites contaminated considerably with As. The degree of contamination (Cdeg) for heavy metals Table 7, shown a moderate degree of contamination at all sites, and the spatial distribution of C deg presented in Fig. 4.

Pollution Load Index (PLI):
The Table 7 shows the computed values of PLI, and the spatial distribution of PLI shown in Fig. 4, the results show PLI values higher than 1 (PLI > 1) at all sites, which implies all sites are contaminated with heavy metals to some extent.

Enrichment Factor (EF):
The results of EF for selected heavy metals of eight soil samples are listed in the Table 8, and the spatial variation of EF values for heavy metals shown in Fig. 5

Index of geo-accumulation ( ) and Nemerow index ( ):
The geo-accumulation index (I geo ) results of heavy metals were showed in Table 9, and According to (Müller, 1981) Table 9 showed moderate contamination at all sites, except S2 and S8 classified as uncontaminated to moderately contaminated. The spatial distribution of I N shown in Fig. 7. Table 9: Geo-accumulation Index (I geo ) and Nemerow index (I N ) of Heavy Metals in Soil . Samples.  As Pb Cd Cr Co Cu Ni Zn

Site Name
Geo-environmental assessment of the study area showed that the area is moderate to heavily contaminate by heavy metals, these attributed to: 1) The land use of study area generally is agricultural, the farmers use inorganic fertilizers, pesticides, and manure as organic fertilizers, these materials contribute to increasing the heavy metals concentrations in soil of the study area.
2) The large areas covered by geological outcrops, where the weathering and erosion processes of rock materials contribute to increasing the concentrations of heavy metals in the soil of the study area.
3) livestock breeding, where the animal wastes contribute to pollution the soil too.
4) Because of in the study area there is no wastewater and sewage sludge discharge nets, the populations in the study area discharge these wastes to open areas, which largely pollute the soil also have negative effects on the human health that are residing in this area.

Conclusion
In a current study several environmental indices were used to the assessment of heavy metals contaminations and determine the environmental quality is soil of study area, the results of this study summarized as follows: 1) The abundance trend of average concentrations of heavy metals increasing in order of Ni> Cr> Zn> Cu> Co> Pb> As> Cd. The concentrations of As, Cd, and Ni exceeded the geochemical background values at all sites, whereas concentrations of Pb, Cr, Co, and Zn are lower than the geochemical background values, except Zn at S7 exceeded the same value.
2) Pearson's correlation analysis revealed there is a strong positive correlation among Pb, Co, Cu, Zn, Cr, and Ni indicates these metals have similar origins mostly anthropogenic, while the positive weak correlation was observed between (As-Pb), (Cd-Cu), (Pb-Cd), (Cd-Co), and (Pb-Co) which indicate that these metals are from different origins, also the negative weak correlation noticed for As with Cd, Co, Cu, and Ni.
3) Low levels of contamination were observed for Pb, Cr, Co, and Zn, and moderate contamination for Cd, Cu, and Ni at all sites, except S1 and S4, shows a low level of Cu contamination, while all sites contaminated considerably with As. The C deg showed moderate contamination of heavy metals at all sites, as well as showed PLI > 1 indicate to the soil contaminated with heavy metals.