Assessment of Heavy Metals Pollution in the Tigris River Water within Salah Al-Din Province, and Its Suitability for Irrigation Using the Heavy Metal Pollution Index (HPI) and Metal Index (MI)

• Saad Sami Ahmed Al-Hayali,1 Basim Shakir Obaid Al-Obaidi,2

  Author

Contamination of river water by heavy metals is a major environmental problem because these metals are persistent, toxic and can accumulate in the food chain and the agricultural soil. The present study was designed to explore the extent of heavy metal contamination in the water of Tigris River in Salah Al-Din Province, Iraq and to appraise its suitability for irrigation purposes based on the Heavy Metal Pollution Index (HPI) and Metal Index (MI). Water samples were taken at 15 sampling stations along the river course in December 2024. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used for the determination of the concentrations of the thirteen heavy metals Al, Ba, Cd, Cu, Fe, Pb, Mn, Cr, Ni, Zn, As, Co and Mo.

The results indicated that the order of decreasing mean concentrations of the metals studied was: Fe > Al > Zn > Ba > Pb > Cu ≈ Mn > Cr > As ≈ Cd ≈ Co ≈ Mo ≈ Ni. Concentrations of all the detected heavy metals were below the recommended safe limits by Food and Agriculture Organization (FAO) for irrigation water. Iron had the highest mean concentration (0.33 mg L^-1), followed by the concentration of Aluminium (0.26 mg L^-1) with several others having very low concentrations close to zero such as Cd, As, Co, Mo and Ni.

The values of HPI was ranging from 0.956 to 2.657, with average value of 1.60, which concludes that all the stations had very low level of heavy metal pollution. Likewise, the river water had a range of Metal Index (MI) values from 0.35 to 1.307 with an average value of 0.64 which indicated that the river water is pure to slightly affected and is suitable for irrigation use. The two stations (1 and 5) with the highest relative contamination levels could reflect local geological and anthropogenic sources, such as higher levels of iron, aluminium and barium.

The agreement of the HPI and MI classifications verifies the reliability of the assessment and suggests the absence of major heavy metal pollution from the water of Tigris river in the study area. The results show that the river has good quality with respect to heavy metal content and it can be used for irrigation in agriculture without any restriction due to heavy metal contamination. It is recommended to conduct continuous monitoring in order to protect and sustainably manage this water resource.

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