Measurements of Magnetic Susceptibility and Its Application in Pollution Detection- A Case Study in the Tigris River in Baghdad City, Iraq

Abstract

The Tigris River is considered the largest river that crosses Baghdad City, the capital of Iraq. It is regarded as one of the main water suppliers to the city.

River sediments can be used to detect the pollution in rivers; thirty sediment samples were collected one to two meters away from the riverside to assess the level pollution in sediments. The area is situated not so far from an industrial area, the Dura oil refinery, factories, and other facilities.

A series of magnetic measurements has been performed, including magnetic susceptibility (χ), anhysteretic remanent magnetisation (ARM), saturation isothermal remanent magnetisation (SIRM) and thermomagnetic analyses (κ-T).

Very high values of χ, χ_ARM and SIRM were detected; the mean values were 2962×10^-8 (m³/kg), 569×10^-8 (m³/kg) and 2721×10^-5 (Am²/kg), respectively.  The high correlations between χ and χ_ARM, χ and SIRM are (R²=0.78) and (R²=0.82), respectively.

Thermomagnetic analyses at high and low temperatures show that the curves of high temperatures (0 to 700 ºC) decrease around 580 ºC, which is the Curie temperature of magnetite; the low-temperature curve (0 to -200ºC) shows a typical curve of magnetite, and the Verwey transition is clearly detected. These results indicate the presence of Single-Domain (SD) to Multi-Domain (MD) grains of magnetite (Fe₃O₄) in high concentrations and the absence of superparamagnetic (SP) grains in the sediments. The results indicate that the river sediments are highly polluted, which could be due to anthropogenic activities, including oil refineries, industrial activities, and atmospheric particle pollution.