Concentration Of Heavy Metals and Heavy Metal Pollution Index Used for Groundwater Quality Assessment in Shamamik Basin in Erbil Governorate, Northern Iraq

Thirteen groundwater samples are collected from thirteen groundwater wells at different depths and different locations inside Shamamik basin in Erbil Governorate. The sampling was started in May 2022, then analyzed for heavy constituents such as (As, Cd, Cu, Pb, Va, Ni, Zn, Bo, Cr, Co, Li, Mn, Se, and Ag). The aim of this research is to find the concentrations are within the acceptable limits as prescribed in Iraqi drinking water standards. The average Heavy metal Pollution Index (HPI) concentration is 97.66, which is considerably less than the crucial index value of 100. The percentage of groundwater samples that exceeds 100-index value is 10% indicating that the water is completely unsuitable and unfit for drinking, while 90% are ranging from excellent to very poor quality according to HPI. The Metal Index (MI) concentration is 2.7, and 83.3 percent of groundwater samples found to be very pure water class. The results show that the groundwater in Shamamik basin of wells 27, 28, 29, 30 is highly polluted and unfit for human consumption. Impact of human activity and industrial activity on the study area has played an important role of pollution in groundwater quality in the western part of the Shamamik basin. According to the finding of current study, it can be concluded that the water can be used as safe for drinking without any negatives effect on the human health except some few wells in the western part of the basin.


Introduction
Shamamik Basin, which is located in the most fertile lands in Erbil City, is an unconfined aquifer basin that has seen extreme changes in its properties throughout the years due to agricultural processes and other activities.The largest renewable source of freshwater utilized for drinking, irrigation, and industry is the groundwater.Freshwater is under stress due to rising demands, which is causing water levels to drop and water quality to deteriorate (Krishan et al., 2020).Utilizing an index to evaluate drinking water is a highly useful method concerning the water quality (Naqeeb and Jazza, 2020).Heavy metal pollution in drinking waters is now one of the most serious environmental issues.When their levels in drinking water exceed the allowable limit, some of them can be harmful to human health (Jazza, Najim, and Adnan, 2022); (Prasad, Kumari, Bano, and Kumari, 2014)).Anthropogenic activities are the primary sources of heavy metals in aquatic ecosystems (Bhardwaj, Gupta, and Garg, 2017).Once too much heavy metals enter the water body, they will directly or indirectly impact the human health, and even dangerous to the aquatic ecosystem (Toma and Aziz, 2022).Metals are hazardous to both plants and animals as well as to humans.Heavy metals like zinc and copper are necessary for plant and animal life biota, whereas many others like Pb and Cd, have no known physiological applications (Gautam, Sharma, Mahiya, and Chattopadhyaya, 2014).They are major water pollutants because of their toxicity, persistence, and capacity to accumulation in biota species.They can also have an adverse effect on human body systems even at extremely low concentrations (Hamed, Disli, and Shukur, 2023).The primary sources of anthropogenic in heavy metal pollution are effluents that have been partially treated, waste of mining and untreated disposable heavy metals from different industries such as manufacturing of pharmaceutical as well as the irregular use of heavy metal containing fertilizer and pesticides in agricultural areas (Abdullah, 2013); (Kamel, Al-Zurfi, and Mahmood, 2022).Pollution by heavy metals is understood to be one of the most serious threats to water quality (Elhdad, 2019).Using of HPI and MI as pollution indices provide information about the pollution level of groundwater resources in recent years that have become a popular approach in assessing groundwater quality for heavy metal detection.Indices of pollution regarded a useful technique for water quality management, decision makers, authorities of civil, and environment because they combine all influence of those parameters into a single number (Rezaei et al., 2019).HPI is a method of evaluating and a useful technique for assessing quality of water, particularly for heavy metals (Rezaei et al., 2019).It is mainly used to determine the mobility of pollution in water and to determine the degree of pollution.Metal index is focused on a whole trend evaluation of the current situation that is excessive concentration of metal is present in comparison to each element's maximum allowable concentration (Matta et al., 2020).The Shamamik groundwater and its aquifer is one of the largest aquifers within Erbil Basin, Northern Iraq.The main clean water can be used in Erbil plain is Shamamik basin.Main goals of the current work are to evaluate heavy metal concentration and heavy metal index pollution in Shamamik basin groundwater samples to estimate their suitability for potable uses through using heavy metal pollution index (HPI); moreover, it aims to determine groundwater quality by using and applying heavy metal pollution index and the metal index to assessing the source and existence of heavy metals in groundwater, which are the result of anthropogenic source.

Study area
The basin under study is situated in the Kurdistan region of Iraq (Erbil Governorate),.The study area is located in the Shamamik Basin within the latitudes and longitudes boundaries shown in in figure (1), and it shows the geographical area of the basin.

Sample collection
In the current study, 30 wells are selected inside Shamamik basin to collect 30 groundwater samples for analyses and evaluating the heavy metals concentrations (Table1).Depth of this groundwater aquifer range from 220 m to 450 m.Portable GPS is used to establish the location of each sampling site.The sampling sites are selected so as to ensure that all drinking water wells having potable water are covered.In the study area, groundwater is typically consumed without treatment.Pumping was done for 10 to 15 minutes before sampling to ensure the proper sample is received.The weather is generally stable during the collection period.Before study, the water samples are stored in pre-cleaned acid-washed high-density polyethylene (HDPE) containers after being filtered to remove suspended matter/sediments using 0.45 m nitrocellulose-millipore filters (disposable, not reusable).Next, the water samples are acidified to pH= 2 (0.2 percent v/v) utilizing ultrapure nitric acid (HNO3) (APHA, 2012).

Samples analysis
Groundwater samples are analyzed in the laboratory inside cool-boxes, in accordance with American Public Health Association (APHA, 2012).The analysis of water samples was done in the General Directorate of Water Providing in Erbil Governorate.The total analyzed groundwater heavy metals are 14 (As, Cd, Cu, Pb, V, Ni, Zn, Bo, Cr, Co, Li, Mn, Se, and Ag) (Table 2).All analyzed heavy metals are validated with the IRQ standard for drinking water (IQS, 2001).

Heavy metal pollution index (HPI) and Metal index (MI) Estimation
Heavy metal pollution index (HPI) is a system of rankings and a useful technique for assessing the heavy metal content of water (Abou Zakhem and Hafez, 2015); (Sheykhi and Moore, 2012).This is used to exemplify how metals work together to affect the overall quality of water.(Reza and Singh, 2011).The HPI index has been used extensively by researchers to analyze surface water.The study of HPI in groundwater was presented by the (Yankey, 2013; Kumar, 2012;and Toma, 2022).Metal index (MI) is essentially described by Tamasi and Cini (2004).It is defined as the ratio of each element's concentration in the solution to the maximum allowable concentration for each element.

……………3
Where, MI is index of metal, Ci is the concentration of elements in a given solution.MAC is the maximum permissible concentration for each element, and subscript i represents the i th parameter of samples as shown in equation (3) and table (4).

Heavy metal concentrations
The concentration of heavy metals for cadmium (Cd), copper (Cu), lead (Pb), manganese (Mn), arsenic (As), nickel (Ni) chromium (Cr), and zinc (Zn) are not coming suppressed with IRQ guideline (Table 5) except in wells 30, 29, and28 are higher than IRQ due to effect of hydrocarbon, and refinery industry and activity has existed in last two decades.Silver (Ag), manganese (Mn), cobalt (Co), and selenium (Se) are below detection limits, while another heavy metal are detected but still below IRQ guideline such as chromium (Cr) ranges from 0.0011 -0.52 mg/l, boron (Bo) ranges from 0.02 -0.01mg/l, and lithium (Li) ranges from 0.004-0.019mg/l.The statistical analysis including the maximum value, minimum value, average and the standard deviation are tabulated for respective heavy metals (Table 3).Antimony, aluminum, arsenic, beryllium, cadmium, boron, cobalt, selenium, silver, all groundwater samples are safe and can be used for drinking purpose according to their heavy metal content.Excess nickel and manganese concentrations are due to their presence in earth's crust (Krishan, 2021).The combined impact of industrial pollutants and agricultural fertilizers increase level of heavy metal pollution in groundwater, particularly in the southwest part of Shamamik basin.Even though each and every single parameter of the heavy metals has been analyzed and mapped separately, the study of combined effect for heavy metals is very considerably essential (Fig. 2).

Heavy metal pollution index (HPI) and Metal pollution (MI)
The primary goal of this work is to evaluate two major heavy metal pollution indices, heavy metal pollution index (HPI), and metal index (MI).Table (3) demonstrates the HPI and MI calculations in Shamamik basin (sample 2).Table (4) demonstrates the HPI and MI values in selected wells for study area, while figure (3) depicts variation of HPI and MI.Depending on the HPI value greater than100 (HPI > 100), the water is polluted, while less than 100 (HPI < 100) is non-polluted.HPI value of current study for all wells in total sum are 97.66 (Table 4) which is (HPI < 100) indicating that no pollution according to HPI is detected but regarded to critical limits of pollution (Anitha, 2021) and table (4).Based on table (5), Caeriro (2005) classification of HPI 26.6% water sample is excellent, 6.6 percent of samples is good, 46.6 percent of samples is poor, 10percent of samples is very poor, and10 percent of samples is unsuitable.The water samples 1 to 27 vary from excellent to very poor, while samples 28,29, and 30 are unsuitable (Fig. 4).Excessive HPI values in the samples 28,29, and 30 are attributed to the presence of oil and gas production and industries such as refineries, EWT, and power plants close to wells 27, 28, 29, and 30.The increased HPI value is due to higher levels of total cadmium, copper, lead, nickel, zinc, and vanadium in groundwater samples.The MI values have been calculated for each and every sampling well location by substituting the analysis results in the above-mentioned equation (2) to calculate Qi which have been substituted in the equation (1) to calculate metal index (MI).The results along with the geographic coordinates have been interpolated using ArcGIS to obtain the spatial distribution of whole basin.Heavy metal pollution index values are then mapped according to their results as shown in table (4) and figure (5).The MI values above 0.03 is considered as threat for the groundwater and below MI value considered pure water (Kumar, 2012).Mean value of metal index concentration is 2.7 with 83.3 % of samples are classified as very pure (class I), which are suitable for drinking, with the remaining 16.6 percent of samples are as classified pure (class II) (Table 4).Table ( 5) demonstrates the distribution of groundwater quality in Shamamik basin based on metal index concentration.Figure ( 5) depicts the groundwater quality distribution of MI in the study area.From the MI spatial distribution maps (Fig. 5), it is clear that the main hazardous zones have been found in the village Minara (sample 29) and Hellawa (sample 30) in the western part of study area.The less hazardous threat zones (MI from <0.3) have been found in the eastern part of study area.

Conclusion
The primary objective of the present research is to assess the levels of heavy metal concentration in the groundwater within the Shamamik basin.The methods of Heavy metal pollution index (HPI) and metal index (MI) are emerged as the most influential and effective approaches in gauging both the concentration of heavy metals and the impact of human activities on this concentration.Based on the current investigation, the main findings are as follows: The mean value of HPI is 97.66.Extreme HPI values represent approximately 10% of the samples.The average MI concentration is 2.7, with 83.3 percent of groundwater samples classified as very pure.The conclusion emphasizes the effect of oil and gas production industry activity and poor management of influent in study area.A high concentration of heavy metals appears to be the source of groundwater pollution.As a result of which the water quality is extremely low and unsafe to drink.Pollutants from oil and gas industries should be treated separately before discharged to the natural (heavy crude oil, and waste water).The heavy metal pollution index model, which is used here as a technique for evaluating all pollution level of groundwater in terms of heavy metals, is more beneficial and promising than metal index, which is used to assess heavy metals in a given groundwater samples.According to findings, HPI is the best technique that can be used for determining the quality of groundwater.The HPI model could be applied to other suspect areas in the future.Only wells 27, 28, 29, and30 in the western part of the basin are polluted by heavy metals.These findings indicate that the water can be used for drinking purpose and safe water for human consumption with no negative effects on human health.According to the results of analyzing heavy metal concentration in groundwater of Shamamik basin, they are found to be less than guideline limits recommended by Iraqi drinking water standard except in sites 27, 28, 29, and 30 for Pb, Cd, and as depending on single constituent heavy metal.Heavy metal pollution index (HPI) values show that the groundwater of Shamamik basin is free of heavy metal pollution and can be used for human consumption.

Recommendation
Continuous monitoring of Shamamik groundwater wells is highly recommended particularly in the western polluted part.

Fig. 1 .
Fig.1.Location map of Shamamik Subbasin located in the southern part of Erbil Governorate Wi and Qi represent the unit weightage and sub-index of i parameter.As shown in the equation (1), n is the total number of parameters to be considered.The Qi (sub-index) is calculated by, …………………..2 Where, Mi and Li depict the monitored and ideal values of the i th parameter respectively, Si represents the standard value of the i th "parameter in parts per million (ppm): as shown in equation (2) and table (3).

Fig. 2 .
Fig.2.Spatial distribution of heavy metals in the studied basin.

Fig. 3 .
Fig.3.HPI and MI fluctuation in groundwater samples in Shamamik basin