Pathway of total petroleum hydrocarbon in a lotic ecosystem: water and sediment of Tigris River, Iraq

Abstract The monitoring of lotic ecosystems is an important issue. This study investigated the total petroleum hydrocarbons (THP) in the Tigris River within Baghdad City, Iraq, which is considered the ultimate water supply source of the city. The study included measurement of THP concentrations, distribution, and origins of total petroleum hydrocarbons (TPHs) in various matrices (water, sediment, and macrophyte) in Tigris River within Baghdad City, in addition to some environmental factors during two seasons (dry and wet) for October 2020 to April 2021. The sampling was collected from three sites along the river. Thirteen compounds were identified in the current investigation from total petroleum hydrocarbons (TPHs), including hexatriacontane, tetracontane, tetratetracontane, undecane, dodecane, hexane, nonane, tetradecane, hexadecane, eicosane, dortiacontane, decane, and octadecane. TPHs concentrations were arranged in the following order macrophyte > sediment > water, and the oil refinery (site 2) was the most hydrocarbon contamination due to its anthropogenic activity. The highest results varied: 54.8 mg/L for hexatriacontane in water, 258.8 mg/g for hexadecane and nonane in sediment, while macrophyte was 393 mg/g for hexadecane. The origin of TPHs in different matrices in the current investigation was pyrogenic (Anthropogenic) according to the portion of low molecular weight/high molecular weight (LMW/HMW). The oil refinery site is considered a risk site by the increasing concentration of TPHs. The THPs pollution is beside other environmental problems in Iraq need to find a quick solution to save the river.