Assessment of Some Trace Elements in Surface Water and Soil near Al-Ahdab Oil Field, Wasit Governorate, Iraq

The main objective of this munscript is to spot light on the negative consequences of oil emissions from Al-Ahdab oil field on the water and soil surrounding the oil field at Wasit Governorate. To obtain this objective, seven sediment samples were collected from the surfacre soil, in addition to five water samples from the Tigris River near Al-Ahdab oil field within Al-Kut Wasit governorate. The more effective eight trace elements were chosen to detect the limitations of their occurrence in the soil and water of the study area, these are Fe, Cd, Cu, Cr, Ni, Pb, Zn, and Zr. The Zr is used as a background for the specific equations applied. Samples of sediments and water were collected in October 2022. The standardization of the Enrichment Factor (EF), geo-accumulation index (I-geo), and contamination factor (CF) in addition to the pollution load index (PLI) were applied to detect the extent of soil pollution. In contrast, the hydrochemistry of water samples was determined by comparing the results of the analysis with the standards of WHO, 2018, and IQS, 2009. The enrichment factor value (EF) Cadmium value (Cd) in soil samples is 6.6, which reflects a significant impact of air emissions, the cobalt (Co) value is 1.77m this value reflects minimum Enrichment factor while the EF has a rather moderate enrichment factor. By applying the I-geo equation, the oitput results indicate unpolluted soil for Co, and Ni metals, while it is moderately polluted for Cu, Cr, Zn, and Pb metals. According to the PLI index, the soil of the study area is ordered as moderately contaminated for these metals. As for the hydrochemistry of surface water of the Tigris River near the study area, the water samples are classified as not contaminated by (Ni, Cd, Pb, Zn, Cr, and Cu).


Introduction
Numerous environmental changes are occurring on a global scale at different rates that have never been observed in Earth's history.Exposure to environmental pollution is one of the main sources of health concerns worldwide; however, the dangers are typically larger in developing nations where high pollution levels are brought on by a combination of factors like poverty and lax environmental regulations [1].
In addition to existing as individual minerals in the remains of weathering-resistant rocks and as crystal structure constituents of other minerals (such mica, chlorite, and dark minerals), heavy metals can travel great distances in rivers in a variety of ways [2].The over-dependence on fossil fuels and improper utilization of the planet's resources has caused in various environmental problems, such as groundwater, surface water, and soil contamination [3].These issues have become the most significant causes of environmental pollution today.
Dangerous pollutants like lead, cadmium, and others are frequently deposited with natural sediments in the bottoms of river channels; if these metals are deposited on flood plains, they may get ingested by plants, 1300 (2024) 012024 IOP Publishing doi:10.1088/1755-1315/1300/1/012024 2 including food crops, and animals.Heavy metal poisoning may happen after the metal has dissolved in water used for home or agricultural purposes [4].
More contamination is a result of the tremendous industrialization, rapid population growth, and high demand for water, energy, and mineral resources.As a result, numerous aquifers and surface water sources have experienced inorganic and/or organic chemical contamination in various parts of the world.As a result, it is difficult to reverse the effects of environmental degradation in many areas of the world, [3].
Seven production wells had been fully completed by the end of 1985 after Al-Ahdab Oil Field was initially found in 1977.Borehole drilling began in 1978.The concern of pollution in the study region is the Al-Ahdab oil field's expanding oil extraction, which has led to an increase in hazardous gas emissions as well as solid and liquid waste.The study area is plagued by several environmental pollution issues as a result of ongoing oil field activities in Al-Ahdab area, hazardous gas emissions, and contamination of the surrounding area caused by solid and liquid waste from oil extraction [5].
Through adsorption and physical agents, trace elements are collected in sediments [6].According to [7], and [8], a useful way to study ecological pollution by heavy metals is by soil element analysis.The presence of heavy metals in the water's deposits is thought to be a perfect diagnostic of the causes of anthropogenic pollution.[9].According to [10], heavy metals often infiltrate the soil and are mostly produced by human activity through the use of fertilizers, pesticides, and other resources like oil production.
To do this, only a few researchers have incorporated chemical indicators such as pollution load index (PLI), contamination factor (CF), enrichment factor (EF), and accumulation load index (I-geo) [11], [12], and [10].Many researchers have employed conventional analytical methods to detect contamination in sediments [8].Trace elements, which are found in small amounts in natural soil, have become more concentrated as a result of human activity.This means that they now have the potential to build up in aqueous solutions or contaminated water to deadly levels for both people and wildlife.
High concentration of trace elements in soil and water samples represent an indicator for various contamination sources incorporated.Physical weathering typically happens rapidly in arid environments like the study location, whereas chemical change is uncommon since it needs a lot of water [13].

Study's objective
The main objective of conducting this study is to evaluate the water and soil contamination brought on by the release of contaminants from the Al Ahdab Oil Field using a variety of chemical indices, including enrichment factor (EF), pollution load index (PLI), contamination factor (CF), and geo accumulation index (I-geo).Along with contrasting the heavy element pollution of the Tigris River water near the Ahdab oil field with Iraqi and World Health Organization Standards.

Study Area
The research area is located in the Wasit Governorate, 18 km west of Kut City and 180 km southeast of Baghdad.As seen in Fig. 1, it is east of Al-Ahrar District and south of the Al Ahdab oil field.
The study area has a 649.8 km2 coverage.The two main cities in the research area are Al-Ahrar and Al-Kut.They are situated between latitudes 32° 23' and 32° 35' north and longitudes 45° 30' to 45° 46' east.
The study area is located in the stable shelf of the Mesopotamian plain and is covered with a range of Quaternary sediment types, including sand sheets, anthropogenic sediments, floodplain sediments, crevasse splay, shallow depression sediments, and marsh sediments [14].In the vicinity of the Al-Ahdab oil field, seven sediment samples and five water samples have been collected (Figure 1 and Table 1).

Soil Samples Collection
In the vicinity of the Al-Ahdab oil field in the Al-Kut city, Wasit governorate, seven sediment samples were gathered in order to assess the degree of soil contamination by trace elements Fe, Cd, Cu, Cr, Ni, Pb, Zn, and Zr.The background of the Zircon metals is utilized to apply the equations.Sediment samples were gathered in October 2022 and examined at the University of Baghdad's Department of Geology's German-Iraq laboratory.X-ray fluorescence (XRF), a non-destructive analytical method for determining a material's elemental composition, is part of the analysis.XRF analyzers can ascertain a sample's chemistry by observing the fluorescence or secondary X-ray that it releases upon excitation by the primary X-ray source, as shown in Figure 1 and Table 1.

Water-Samples Collection
There are 5 were chosen to collect the water samples from Tigris River, at areas near Al-Ahdab oil field, that affected directly by the output emissions, in order to conduct analyses based on the heavy elements, (Figure 1), and (Table 1).

The Pollution of Water
Using the Atomic Absorption technique (AAS, Shimadzu AA-6300), the following trace elements (Pb, Cd, Cr, Cu, Fe, and Zn) were examined in the water samples from the Tigris River.The Ministry of Science and Technology's laboratories in Iraq are where the analysis of the water samples was carried out.The trace element analysis findings are shown in Table 2.In an acidic, oxidative environment, nickel is accessible, according to the disintegration of rocks containing nickel ore is the main source of nickel in drinking water [15].According to [16], the maximum nickel concentration in drinking water is 0.02 parts per million (mg/l).In river water samples taken from the research region in October 2022, the Ni concentration ranged from 0.003 to 0.008 mg/l with an average of 0.005 mg/l.Nickel concentrations in drinking water must not be more than 0.02 mg/l.In fact, all the samples of river water were within the permissible limits ( With a typical of 0.0394 mg/l, chromium levels fluctuate between 0.034 to 0.043 mg/l.Consequently, water samples don't go above the allowed limits of [17] and [18], (Table 2).

Zinc (Zn)
Water naturally contains zinc, most frequently in mining regions and in industrial waste; the element does not interact with water molecules during metal plating.The temperature and pH of the water affect how soluble Zn is in it.The two most important zinc ores are Smithsonite and Sphalerite.In areas where zinc ore is found, this chemical ends up in the water.zinc-rich industrial wastewater.where the average content is 0.474 mg/l, with a range of 0.023 to 0.86 mg/l.It was found, that hole the examined samples had zinc concentrations within the range allowed by WHO standards (Table 2).

Lead (Pb)
Naturalists believe that lead comes from the minerals galena (Pbs), anglesite (PbSO4), and cerussite (PbCO3).Lead is also associated with the element Rb in the lattice structure of feldspar and mica.The other sources include fertilizers [19].Burning gasoline containing lead releases lead into the atmosphere in large quantities.Due to the ionic exchange between river water and its bottom sediment, which depends on Eh, pH, and temperature, the lead concentration in sediment samples is higher than in water samples [20].Also, lead is released into the environment through mining, plumbing, gasoline, and coal.According to the World Health Organization, the final permitted level for lead concentration in water is 0.01 mg/l, therefore; there is no noticeable lead contamination was recorded (Table 2).

Cadmium (Cd)
The Clay minerals, and weathering of Cademoselite (CdSe) are two natural sources of Cd [21].Small amounts of cadmium are also found in phosphate fertilizers.However, the majority of cadmium in the environment is found as dissolved Cd +2 ions or insoluble cadmium complexes.Due to runoff erosion of natural deposits, the cadmium is getting into drinking water.The maximum allowable limit for cadmium according to [16], is 0.005, and 0.003 mg/l according to [18].The concentration of Cd in the water samples ranged between 0.001 to 0.02 mg/l, with a mean value of 0.004 mg/l.Accordingly, the water samples at the study area did not record a notable contamination in cadmium trace element (Table 2).

Copper (Cu)
Copper also occurs as copper sulfate and carbonate in the forms of azurite and malachite.The crust of the earth has an average of 50 mg/l [21].Fertilizers are another source of copper because they contain a significant amount of it [19].Cu concentration in the water samples ranged between 0.02-0.11mg/l, with an average concentration of 0.062 mg/l.Therefore, the water samples of the area are free from Cu contamination (Table 2).

Soil Pollution
Naturally occurring metals that have an atomic weight higher than that of water are known as heavy metals [22].Since heavy metal concentrations are assumed to be the main factor contributing to pollution issues in the examined area, this study focuses on these concentrations.
Because heavy metals have so many uses in industry, agriculture, medicine, and technology, they are widely distributed in the environment.Concerns over its potential effects on both human health and the environment have been raised by its pervasive influence on the environment.Priority metals of concern for human health include arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and mercury (Hg) due to their extreme toxicity [23].The most widely used methods for figuring out how enriched sediment is with trace elements are the enrichment factor (EF), geo-accumulation index (I-geo), contamination factor (CF), and pollution loadindex (PLI) (Table 3).The I-geo has been widely used as a pollution indicator in freshwater sediment, and Franco-Uria et al. claim that the Enrichment Factor (EF) is a helpful tool for determining the concentration of heavy metals in sediment [24].Background concentrations for Cd, Cu, Cr, Ni, Pb, Co, Zn, and Zr were gathered for this investigation [25].

Equations of Soil Pollution Indicators
The amount of heavy metal pollution in the soil surrounding the Al-Ahdab oil field was assessed using the EF, I-geo, CF, and PLI indices:

Enrichment Factor, or EF
The amount of anthropogenic pollutants that have been deposited and their presence in river sediments are measured using an enrichment factor.This pollution indicator is made by comparing the concentration of one element in the soil to the concentration of the background element.Background metal (Zr) was used for all sediment sample tests to calculate EF.
Since zircon is less expensive than relative enrichment, it has been utilized extensively in scientific research [26], (Equ.1)

.EF = (M/Zircon) for the Earth's crust / (M/Zircon) for sediment ….(Equ.1)
where M is the milligrams per liter (mg/l) concentration of heavy metals.Zircon concentration (mg/l) in (earth's crust/sediment sample).as mentioned in [27].The (EF) level is divided into five categories (Table 4).Moderate enrichment level.The following metals had the highest mean EF values in the research area: Cd > Pb > Cu > Zn > Ni > Cr > Co.The EF values of metals in the soil of the research area (Table 5).

(Cn / 1.5 * Bn) log 2 is I-geo ….(Equ.2)
where Bn is the geochemical background, and Cn is the element's concentration as determined by the sediment.
The constant 1.5 was utilized as a factor to accommodate for variations in background caused by lithological factors.Table 6 lists the finalized results of I. geo in the sites under study.
In Al-Ahdab Oil Field sediments, the typical (I-geo) accumulation index values of heavy metals were as follows: Cd > Pb > Cu > Zn > Ni > Cr > Co (Figure 2), and (Table 7).

The Contamination Factor (CF) and the Pollution Load Index (PLI)
In the (PLI), the Contamination Factors (CF) had significant importance.For a single site, PLI is the root of the product of n (CF) factors [29].CF is used to classify the amount of polluted sediments in Al-Ahdab Oil Field samples.Subtracting the (n-root) from the (n-CF) obtained for all metals yields the PLI of a given location [30].(Table 8).The (PLI) as the following equation was developed by Tomlinson et al. in 1982, (Equ.3, and 4), (Table 9) Where CF: is the contamination factor and n is the number of metals.C = Sedimentary metal concentration.C = Background value calculated using the clay percent ratio.According to the mean pollution load index (1.29)above the baseline threshold, it is obvious that all sediment samples were polluted with heavy metals and that the negative influence of the Al -Ahdab oil field on the sediment of the research region was evaluated.
A natural resources of trace elements contamination include dust storms, erosion or weathering by air or water, and biota decay in water, whereas man-made agents include sewage wastes, automotive effluent, petroleum, fertilizer, and industrial effluent.The Iraqi Quality Standards [18], and the World Health Organization Standard [17] were depended to comparison (Table 10).Accordingly, all water samples in the study sites were not record a significant contamination by these elements (Ni, Cd, Pb, Zn, Cr, and Cu).The river water samples are all within permitted standards.The water in the Tigris River was not contaminated by (Cadimum, lead, Zinc, Cromium, and Copper).
The standard grade of these metals must be established in order to calculate the amount of heavy metals present in the soil of Kut City.From man-made agents like the sewage and solid waste sectors, as well as by products of the Al-Ahdab oil production, heavy metals may enter the hydrous system.Using the chemical indices EF, CF, PLI, and I-geo to determine the usual grades of these metals is one of the most successful approaches for evaluating the heavy metal presence in sediment.Heavy metal levels are 1300 (2024) 012024 IOP Publishing doi:10.1088/1755-1315/1300/1/01202410 always paired with the hydrous system, grain size analyses, and in addition to anthropogenic activities such as sewage, agriculture, and solid waste industries, high levels of heavy metals are always associated with the hydrous system, grain size analysis.One helpful technique for assessing the level of metal pollution in soil is the Enrichment Factor (EF), which is now the subject of research [31].The mean enrichment factor (EF) of Cd in the sediment samples was 6.6, showing a significant human influence from irrigation effects, phosphate fertilizers, and sewage sludge, according to the enrichment factor (EF) data in (Table 8).Compared to other metals, cobalt has a low enrichment factor (mean EF value of 1.77), whereas other metals have a moderate enrichment factor (Table 11).The sediments were classified as moderately contaminated by Cu, Cr, Zn, and Pb but uncontaminated by Co and Ni metals based on the geo-accumulation Index.The soil of the Al-Ahdab oil field is typically moderately contaminated by these elements (Table 12).Later, an estimate of the Pollution Load Index (PLI) was made.using the contamination factor (CF), which was first used to identify soil pollution.Mean contamination factor values of o.8, 0.75, and 0.44 for the heavy metals Co, Cr, and Zr are regarded as low contamination levels.With CF values of 3, 2.1, 1.7, 1.66, and 1.63 for Cd, Cu, Zn, Pb, and Ni, respectively, these metals are considerably contaminated and above background levels due to human inputs and external discrete sources such industrial operations and agricultural runoff (Table 13).PLI was higher than 1 on every site.

Conclusion
Air pollution, soil contamination, and contamination of surface and groundwater are only two of the many environmental problems caused by the careless use of the planet's resources and excessive reliance on fossil fuels.Numerous sources of environmental contamination caused by natural activities and different factories' failure to utilize flawless environmental measures and haphazard dumping of municipal garbage.In many impoverished countries, wastewater is untreated and discharged directly into water sources.
Overexposure to levels of pollution that exceed the guidelines set by international organizations, including the World Health Organization, can have detrimental effects on all living organisms and even endanger their survival.For the heavy metals Co, Cr, Zn, Cu, Ni, Pb, and Cd, the enrichment factor, I-geo index, contamination factors (CF), and pollution load index (PLI) were used to determine chemical indices in the soil near the Al-Ahdab oil field in Al-Kut city.These indicators demonstrate how the adjacent soil was negatively impacted by air pollutants from the Al-Ahdab oil field.
The Cd in sediment samples had enrichment factor ratios of 6.6, indicating a significant human influence from sewage sludge, phosphate fertilizers, and irrigation effects.While other metals have a modest enrichment factor, Co has a low enrichment factor with a typical EF value of 1.77.
According to the I-geo, the sediment in the research region was deemed to be uncontaminated by the metals Co and Ni, but highly contaminated by Cu, Cr, Zn, and Pb.In general, these metals have moderately contaminated the soil of the Al-Ahdab oil field.
By applying heavy metal comparing the results analyses of the soil samples near the oil field, it was found higher concentration than those located far of the source of pollution.Likewise, the soil samples taken near the oil field were affected by deposits of gaseous emissions, especially in areas where It is located in the direction of the wind, where it carries gases and emissions, making both soil and water vulnerable to contamination by these elements.

Figure 1 .
Figure 1.Location map of the study area

Figure 3 .
Figure 3.The value of mean CF values, with the threshold of the heavy metals.

Table 1 .
The location of soil and water samples in study area

Table 2 .
Trace elements concentration in water samples (μgm/l)

Table 3 .
Trace element concentrations in the soil of the study area

Table 4 .
EF categories

Table 5 .
The EF values of heavy metals in soil samples

Table 7 .
I-geo values of Heavy meta

Table 9 .
CF, and PLI value in the sediment of Al-Ahdal oil field area

Table 10 .
Standards specification for trace element in natural water

Table 11 .
The mean values of EF and the categories of EF

Table 12 :
The Mean of I-geo values and Grades

Table 13 :
The mean CF values and CF Categories in soil of the study area