Investigation of Cd, Pb, and Ni contamination in soil and wheat plant in alluvial lands of Tigris River in southern Baghdad, Iraq

Accurate information on the concentration of heavy metals in the soil is essential to manage soil contamination. The objective of this study was to investigate the contamination of soil and wheat plants with Ni, Cd, and Pb in the alluvial plain of Tigris River in southern Baghdad. A total of hundred surface soil samples (0-30 cm) and aerial parts of the wheat plant were taken in an area of ~100 km2 at an interval distance of 1000 meters. Heavy metals in air-dried soil samples and plant were extracted by the aqua regia solution and wet digestion method, respectively. The mean concentration of Cd in soil and wheat plant was 0.4 and 1.1 mg kg-1, respectively. The amount of plant-Cd was higher than the allowable standards of FAO and WHO. Mean Pb concentration in the soil of the study area was 14.5 mg kg-1. The concentration of Pb in the plant was less than the detection limit of the device. The mean concentration of Ni in the soil and plant was 214 and 17 mg kg-1, respectively, which was more than the allowable standards of FAO and WHO. The source of Ni is fine sediments transferred from eroded ultramafic rocks in the upper part of the river. A positive correlation between Pb and Cd in the soil indicates a similar origin. They were added to the soil by agricultural activities and vehicles. The results showed that the studied soils are at the beginning of the contamination with Cd and Pb, which needs to be considered to prevent more contamination.