Environmental contamination and exposure to heavy metals is a real growing problem throughout the world. The both natural sources and anthropogenic processes spread heavy metals in to various environmental media. The most important environmental issue which caused by anthropogenic activities such as urban road Construction, agriculture waste, sewage disposal and automobile workshop is the emission of heavy metals  . The presence of heavy metals has been considered as useful indication for contamination in soil of surface, sediment and dust environments  . Atmospheric pollution is the fundamentally sources of heavy metal availability in the environment. These sources include vehicular emissions, industrial discharges and other activities  . Emissions from road traffic have contributed greatly to the level of particulate maters both in developed and developing countries  . Urban soil is an important ingredient of the urban ecosystem  . This can be considered both as a sink of pollutant and source of pollution with the capacity to ground water, into food chain and into the human body   .
In urban city centers, it is common to see high number of industries and vehicles. Thus making urban centers, a major refuge of resource consumption and chemical emissions may create serious environmental problems if not controlled  . Street or urban road side consist of vehicular exhaust particles, household dust, soil dust, construction dust aerosols that are carried clearly by air and water   . Heavy metal may come from abundant different sources to the civilian area such is vehicle emission.
Three main factors known to influence the levels of heavy metal inroad side's samples which have been reported are traffic, industry and particularly house and road dust  . The soil road dust in urban area is indicators of heavy metals pollution from atmospheric precipitation. These metals can accumulate in top soil from atmospheric precipitation by sedimentation, impacting and interception. The assemblage of these metals to stay in urban soils for a long period of time may pose serious environmental and health problems in the urban city centers  . Exposed to weighty metals in road side can occur by means of inspiration, absorption and skinny contact. The pernicious effects of heavy metals in road soil include nervous system retardation, respiratory system disorders, and the risk of cancer in the later life  . For this study Kirkuk city was the chosen area. This city is a rapidly developing area, and is considered a major work place in the north of Iraq. It contains many work place parts such as, north oil company, north gas company, cement factory, construction materials and a lot of the fuel stations.
The aim of this study is to evaluate the distribution of heavy metals (As, Cr and Cd) and to assess the road side samples contamination using indices Single Element Pollution Index (SEPI), Combined Pollution Index (CPI), Geo-Accumulation (GAI), Contamination Factor (CF) and Pollution Load Index (PLI).
2. Material and Methods
2.1. The Area of Study
The study area, Kirkuk city the geographical position being (44˚43'00"N - 44˚32'00"N) and (35˚50'00"E - 35˚38'00"E) is located in Northern Iraq (Figure 1). The altitude above sea level is (367 m), the area of Kirkuk government around (9676 Km2) and represent the ratio about 2.2% of Iraq.
It is situated on the quaternary deposits formed mainly form river sediments. The study area is arid to semi-arid climate. Naturally, it receipts a significant particulate matter from the atmosphere, and it typically influences by gas emitted from industrial state and automobile exhausts. Kirkuk city is one of the rich-oil provinces with a more
Figure 1. Map of Iraq showing the sample location in Kirkuk city.
productive soil. The river was divided Kirkuk city in to tow parts right and left called Khasa. Most of industrial state such as (North oil company, North gas company, industrial quarter, Fuel stations mechanical workshop and heavy traffic etc. were located at right part, while in the left part of studied area only cement factory was found in this part with a little industrial state.
2.2. Sample Collection
Road side sample of 22 samples (11 samples for each location) were collected from the site using polyethylene cylindrical containers in 8th 2013. From within two meter of road side edge these sample ware collected. Using polyethylene brush, dish and containers and were collected in polyethylene containers. The road side soil samples were taken from (0 - 20 cm) depth. The samples were dried at 105˚C to constant mass, and sieved through a <2 mm stainless-steel sieve.
2.3. Chemical Determinations.
Chemical analyses for the samples of road side soil were performed at the accredited Acme Analytical laboratory of Canada. More specifically, a 0.5 g aliquot of each road side soil was digested with nitric acid (HNO3) and hydrochloric acid (HCl) in a ratio 3:1 at 95C. By coupled plasma, Logistical reasons allowed inductively the geochemical solutions to be analyzed-Mass spectrometry (ICP-MS) type (Elmer Elam perken 6000) Technique, for the road side soils collected from Kirkuk city by (ICP-MS) for the reference soils. The concentrations of As, Cr and Cd were determined in the solution of soil. Compound of replicates, reagent blanks and reference materials introduced by the ACME Analytical laboratories supported the excellent precision and accuracy of analytical results.
3. Results and Discussion
3.1. Effect of pH
The value of pH is equal minus logarithm of hydronium ion concentration, when this value is less than 7 means acidity, higher than 7 basicity and 7 means the solution is natural. The pH play an important role in the transition and movement of heavy metals in soil. The different physic-chemical and biological factors control the movement of metals in soil  . They suggested that a change in pH results in a conversion of element from one phase to another and thus statement the determination of mobility of heavy metals in soil. The results revealed that road side soil pH ranging in a narrow interval (7.1 - 7.8) Table 1, suggests that road side soil is mostly in neutral to sub alkaline condition which referred to the high rate of carbonate, ash and dust of anthropogenic origin  . The neutral to sub-alkaline condition of the road side soil may be concerning to the alkali composition in the atmosphere which can precipitate on the ground and influence the soil pH  . The soil PH to have showed higher effect on the solubility or metal detention in soil; the greater detention and lower solubility of metal happen at high soil pH  .
Table 1. Metal concentration in road side soil of right and left khasa in Kirkuk city in ppm.
3.2. Heavy Metals
The levels of appearance of the metals specified that Cr has germinated as the prevailing metal, while Cd has the lowest concentration in roadside soil. It is observed form the soils right Khasa and left Khasa area that the average values of metals followed the sequence; Cr > As > Cd in both areas, while the mean value in right Khasa is higher concentricity of left Khasa. A comparison of metal average concentration in road side soil indicated that higher concentricity of Cr, As, and Cd (178.1 - 165.8, 10.4 - 8.29, 0.559 - 0.4 ppm respectively) was observed in the right khasa Table 1. This has considerable participation for the metal input from the construction works and other anthropogenic activities like oil refinery fuel station, vehicle agriculture, house hold dust, soil, dust, aerosols, burning of tire and burning of heavy duty oils which released particulates that are subsequently deposited on to the surface soil. This reflects a considerable effect of industrial of the environment of this area  . A brief discussion about single metals follows.
3.2.1. Cadmium (Cd)
The allowable limit of cadmium in soil, recommended by  , is 3 ppm Table 2. In the road side soil concentration of cadmium was recorded low the permissible limit. Concentricity of Cd in road side soil of right and left Khasa ranged between 0.32 ppm to 0.92 ppm with average 0.599 and 0.21 ppm to 0.61 ppm with average 0.4 ppm respectively. Generally, Cd in the environment comes from different a ways of natural and manmade pollution.
The major natural resources of cadmium in the atmosphere are airborne soil particles, volcanogenic aerosols, forest fires and degassing of crustal rocks  . The manmade
Table 2. Average concentration of As, Cd and Cr in studied area and compared with the permissible concentration of heavy metal in soil according to  .
pollution resource of Cd components are combustion process of coal and oil, refuse incineration  , pigments in plastic and consumed batteries. Road side receives different inputs of heavy metals from variety of mobile such as vehicular emission, oil combustion, waste incineration, construction and destruction activities in addition to resuspension of surrounding contaminated soil  .
Cadmium in the road side soil in right Khasa of Kirkuk city was the highest; it ranges between 0.32 - 0.64 ppm with an average of 0.599 ppm Table 1. The lowest value Cd was recorded in the left Khasa in Kirkuk city, it ranges between 0.21 - 0.62 ppm with an average of 0.4 ppm. The high rate of Cd in right Khasa due to anthropogenic and industrial activities. The high concentricity of Cd in road soil in the right Khasa of studied area 0.599 ppm could reflect the effect of human activity. As a result of urban industrial and agricultural practice, human activity can contribute to increased Cd levels  , atmospheric deposition  and phosphate fertilizer use had resulted in the emission of significant amounts of Cd to the environment  .
3.2.2. Chromium (Cr)
The permissible limit of chromium for soil is 100 ppm recommended by  in road soil concentration of chromium was above the permissible limit Table 2. Cr is a low mobility element, especially under moderate oxidizing and reducing conditions and near-neutral pH vales. Cr6+ adsorption decreases with increasing pH, and Cr3+ adsorption increases with increasing pH. On the other hand, Cr is toxic for biotical systems  . Set of few large scale industrial activities such as dyes, ceramic and tanning are mentioned to contribute Cr  . Chromium in the road side soil in studied area was the highest, it ranges between 116 - 273 ppm with an average178.6 ppm Table 1. The lowest value of Cr was recorded in the left Khasa, it was detected to vary from 112 ppm to 242 ppm with an average of 165.8 ppm.
The observed values were the average value from the world literature (84 ppm)  , and also more than the reported world scale of unpolluted soil (83 ppm)  .
However, Cr average value in the all study area road side soil samples to be 10 times higher that chromium content in the rural (control) soil (17.33 ppm) suggesting possible sources of Cr in the urban area.
3.2.3. Arsenic (As)
The permissible limit of Arsenic in soil is 10 ppm recommended by  Table 2. In road side soil sample average concentricity of arsenic was 10.4 and 8.29 ppm in both area respectively and it was concentration approximately equal the permissible limit Table 2.
The anthropogenic sources of arsenic include industrial emission, suspended arsenic rich soil, waste materials, coal burning and use of As-rich phosphate fertilizers  . The highest concentration of As was observed in the right Khasa (10.4 ppm) can indicate the areas with anthropogenic factor such as traffic and urbanization factors. Precipitation from atmospheric sources of arsenic can participate significantly to arsenic concentricity in soils. The ratio of atmospheric natural sources such as volcanic activity, to atmospheric anthropogenic sources like fossil fuel combustion, varies regionally but on average their mutual contributions are about equal  . Other non-atmospheric anthropogenic sources involve agricultural and industrial applications  .
3.3. Performance Evaluation of Soil Pollution
There are many indices that used to estimate the rate of contamination by heavy metal. For this purpose and to subtend the aims of this project. To evaluate the pollution level of As, Cd and Cr in road side soil five indices were selected. These indices are Single Element Pollution Index (SEPT), Combined Pollution Index (CPI), Contamination Factor (CF), Pollution Load Index (PLI) and Geo-Accumulation Load Index (Igeo).
3.3.1. Single Pollution Index
An evaluated index is generally applied to measure environmental quality of soil and one simple and well known index is a single element pollution index (SEPI) which was used as assessment methods and to identify single-element contamination resulting in increased such heavy metal toxicity. The equation used to calculate (SEPI) is as follows:
The acceptable levels for soil suggested by  and  adopted permissible rates and each weighty metal was classified as low contamination (SEPT ≤ 1), moderation contamination (1 < SEPI ≤ 3) or high contamination SEPI > 3  . The SEPI value of As in road side soil of right and left Khasa varied from 0. 7 to 1. 43 ppm and 0. 62 ppm to 1. 13 ppm respectively Table 3, which indicated low or moderate contamination level with an average of 1. 04 ppm to 0. 82 ppm respectively most road soil samples in right Khasa area were heavily polluted by As and classified as moderate contamination level. The SEPI value of Cr ranged from 1.2 ppm to 2.73 ppm and 1.18 ppm to 2.42 ppm respectively in both areas indicating moderate contamination with Cr. The SEPI value for Cd varied from 0.11 ppm to 0.28 ppm and 0.1 ppm to 0.2 ppm respectively in both areas with an average 0.2 ppm to 0.13 ppm respectively suggesting low contamination with Cd. The highest SEPI for Cr and As in the right Khasa area seems therefore to be that industrial soil, human activities, road dust and tire abrasion are polluted in the study area.
3.3.2. Combined Pollution Index (CPI)
Generally, extreme of the heavy metal pollution in the surface environment is associated with a mixture of contaminants rather than one metal contaminant  , thus the idea of CPI which was used as another commonly assessment methods of multi-ele-
Table 3. Single element pollution index values.
ment contamination resulting in increased over all metal toxicity  . The CPI is calculated by the average ratio of metal concentration in soil to assumed permissible level and was that classified as low (CPI ≤ 1), middle (1 < CPI ≤ 2) or high (CPI > 2)  . The tolerable levels for soil suggested by  and  were adopted as permissible levels and pollution index was calculated as:
Table 4 shows that the CPI is higher than 1 in most of road side soil samples in right Khasa (with exception of some samples). The range of contamination being more in the samples road side soil in right Khasa than the left road side soil samples in left Khasa area reflecting that road side soil in right Khasa was more polluted by the heavy metal in study area due to anthropogenic sources. Thus, it is very likely that many road side soil in right Khasa of Kirkuk city are moderately polluted with heavy metals. But the CPI of the As, Cd and Cr at left Khasa area was less than 1in most samples which indicates that average levels of metals are below the selected standards but does not necessarily indicate that there are no anthropogenic resources of enrichment over background level, and suggested single metals contamination  . The trend of CPI revealed that the right Khasa area greater than the left Khasa area. This trend indicated that the location along the right road side soil in Kirkuk city received more heavy metals input from anthropogenic induced sources.
3.3.3. Index of Geo Accumulation Index (GAI)
The index of (GIA) means assessment of contamination by contrasting the levels of
Table 4. Combined pollution index values.
heavy metal obtained to a background levels originally used with bottom precipitates (Muller, 1979). It was more used by numerous authors  has applied the index of Igeo, to assess of road soil pollution. Geo accumulation index as proposed by  and cited by  have been widely used to evaluate the degree of heavy metal contamination in wild and aquatic environment as expressed:
where Cm is the mean concentration of metal m in soil and Bm is the background concentration of metal m (crustal abundant)  , while 1.5 is a factor for possible difference in the background concentricity due to lithological differences. GAI is classified into descriptive seven classes as follows: class 0 (GAI < 0) practically uncontaminated; class 1 (GAI 0 - 1) uncontaminated to moderately contaminated; class 2 (GAI 1 -2 ) moderately contaminated; class 3 (GAI 2 - 3) moderately to strongly contaminated; class 4 (GAI 3 - 4) strongly contaminated; clas 5 (GAI 4 - 5) strongly to extreme contaminated and class 6 (GAI > 5) extremely contaminated  .
The overall total (GAI) shows that the Cr in Kirkuk city (right and left Khasa) was found negative in most samples Table 5 and of class 0, but it have positive value 0.04, 0.39, 0.27 in samples 3, 4, 6 in right Khasa respectively and it have positive value 0.23, 0. 27, 0.16 in sample 2, 3, 4 in left Khasa respectively and belong the to the class 1 indicating un-polluted to moderately pollution. Arsenic (As) shows a positive index for all samples (except sample 2 in right Khasa and samples 2 and 5 in left Khasa were negative) indicating unpolluted to moderately polluted. Cd showed a positive geoaccumulation index in six samples of right Khasa are classified as class 2 moderately polluted and 5 sample (R4, R7, R8, R9, R10 and R11) in this area are classified as class 1, while in left
Table 5. Result of Geo Accumulation Index (GAI) compared with the average crustal abundant (background value) in uncontaminated soil, adopted from  .
Khasa the Cd shows a positive index for all sample (except sample 2L) indicating practically un polluted Table 3.
3.3.4. Contamination Factor (CF)
The grade of contamination by metals was determined by applying the contamination factor (CF) that can be calculated as:
where Cm and Bm are defined above where the contamination factor CF < 1 indicates low contamination; 1 ≤ C F< 3 refers to moderate contamination, 3 ≤ CF < 6 means considerable contamination and CF > 6 indicates very high contamination factor. The contamination factor for As, Cr and Cd was calculated in the study areas and the results which have indicated in Table 6.
Cadmium in Kirkuk city especially in right Khasa classified as class 3 in most samples and representing a considerable contamination except samples no. 2R, 3R and 6R represents a moderate contamination (class 2) (Table 6). Samples collected from left Khasa displayed contamination factor value not exceed 3 indicating a contamination rate of low to moderate contamination except sample no 4L, 7L, 8L, 9L, 10L and 11L represents a moderate contamination. The resource of contaminated materials might be attributed to the automobile emission, industrial activity and agriculture which used phosphate fertilizers, these activities which abundant in right Khasa rather than the left Khasa had been received of significant amounts of Cd to the environment of the area of
Table 6. Results of As, Cd, Cr and their Contamination Factor (CF) and Pollution Load Index (PLI) compared with the average crustal abundance (background value) in un contaminated soil adopted from  .
study especially in the right Khasa. The heavy metals have been added in to urban soil through urban wastes  and most importantly through vehicle emission  . Contamination factor for As and Cr in the studied area are classified as class 2 and represent moderate contamination in all samples (Table 6). As, for examples is known to come from the utilize of industrial emission, coal burning and phosphate fertilizers  , whereas Cd from tire abrasion, industrial and incinerator emission  . The source of Cr in road soil is known to come from the use of paints manufacture, leather tanning industries, metal plating, ceramic manufacture are reported to contribute Cr in the environment  .
3.3.5. Pollution Load Index (PLI)
Pollution Load Index (PLI) has been suggested by  for evaluating particular site. This index expressed as:
where n is the number of metals. The PLI provides sample but comparative means for assessing a site quality, where a value of PLI < 1 denote perfection; PLI = 1 present that only base line levels of pollutant are present and PLI > 1 could indicate deterioration if site quality  . Pollution load index are showed in (Table 6). PLI in the right Khasa ranges from 1.76 ppm to 2.77 ppm with an average 2.29 ppm, while in the left Khasa ranges from 1.43 ppm to 2.1 ppm with an average 1.81 ppm. All samples in studied areas have PLI more than 1 indicates a deterioration of site quality. All samples in Kirkuk city (Right and left Khasa) are more that base line level (1.0).
The results of the present study revealed significant presence of As, Cr, and Cd in the road side soil in Kirkuk city. The results appeared the following trend in road side soil: Cr > As > Cd, but the average concentrations of this metal in Khasa area of Kirkuk city showed abundant in right area more than the left area. The main concentration of As 10.4 ppm and 8.29 ppm respectively, Cr was 178.9 ppm and 165.8 ppm, while Cd was 0.59 ppm and 0.4 ppm respectively. It is clear that the pollutant affected the right Khasa more that the left Khasa road side because of the predominant industrial activities such as (oil and gas company) and in an increasing the pollutants. The result of SEPI values indicated moderate contamination with As and Cr, while SEPI values of Cd suggesting low contamination with this element in right Khasa. The CPI values indicated moderate contamination with As, Cr and Cd in most of the samples in right Khasa and this specified that the right area received more heavy metals input from anthropogencally stimulated sources. The contamination factor in study area was moderately to considerable contamination with Cd in most samples especially in the right Khasa, slightly contamination with As and presently moderate contaminated with Crin both studied area. The result of Igeo in the most samples in right Khasa showed unpolluted to moderately polluted with cadmium.
It was recommended from the present study that:
1) Increasing green areas and implantation more trees because trees help in cleaning soil, protecting its fertility and in reducing the level of pollutants.
2) Continuous monitoring of concentrations of heavy metals, especially Cd and As to avoid being beat permissible limit.
3) The severe laws should be activated to prevent hazardous pollutants to the environment and increase environmental knowing among the people.
The author wish to thank Mr. Marwan Al-Jobory and Qayssar M. Ajaj, the maps designer of the search and, Mr. Ali Al-Saleh, the linguist. Thanks must also go to the ACME laboratory in Canada for helping me with the analyses of heavy metals.
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