Study of the extent of pollution of river island sediments with some heavy metals in the Tigris River within Wasit Province

Abstract

A study was aimed to determine the pollution levels of certain heavy metals on river islands in the Tigris River within Wasit Governorate. Five sites were identified for the study distributed across the districts and sub-districts through which the river flows within Wasit Province. The samples were collected from Al-Suwaira, Al-Aziziyah, Al-Zubaidiyah, and Al-Numaniyah and south of Kut Districts. Two islands were selected at each site (district or sub-district): one located north of the city before the river enters it, and the other located below the city after the river enters it. Two sampling points were selected on each island: one at the island's head and the other in the middle, at depths of 0 to 30 cm and 30 to 60 cm, respectively. Sediment samples were collected on October 20, 2025. The material was placed in special bags, and the heavy metal pollution levels (Fe, Cd, Zn, Ni, and Pb) were assessed. The heavy metal pollution results showed that the Al-Zubaidiya and Al-Suwaira areas recorded the highest levels. Nickel concentration was approximately 82 mg/kg⁻¹ before the city of Al-Kut and 48.5 mg/kg⁻¹ after Al-Aziziyah. These values are considered high, placing the area within the categories of high to moderate pollution. Iron concentrations were 17624 and 24102 mg.kg⁻¹, indicating moderate contamination, as concentrations were higher in surface layers compared to subsurface layers, with spatial variation between study sites. Al-Suwaira came in second, recording the highest lead level 62.5 mg kg⁻¹ at the beginning of the island, at the surface depth after Al-Suwaira. This value is high when compared to the limits set by the US Environmental Protection Agency (US.EPA). Overall, for all the studied pollutants, the results indicate that location between districts was the most influential and consistent factor in explaining the variation in heavy metal concentrations. This indicates that spatial differences between the study sites are a crucial factor in the distribution of these metals.