Determining the spread of aromatic oil compounds caused by gasoline leakage in the Shazand well No. ۷ and the role of the cone of depression around the well in developing contamination

Abstract

Today, one of the most critical problems and challenges in the world and Iran is the pollution of groundwater resources. Groundwater accounts for only 4% of the world's water reserves, and like surface water, they are exposed to various pollutants. Among the most critical pollutants that threaten the health of water resources are oil pollutants, a clear example of which is the oil pollution crisis in industrial areas and around refineries and petrochemicals (Mirzaii et al., 2012). the most important part of petroleum pollutants is soluble substances such as gasoline and diesel, which include BTEX and additives such as MTBE. The family of four BTEX is one of the most common aromatic hydrocarbons in refinery wastes and can contaminate aquifers (Firmino et al., 2015). Also, MTBE is an additive added to gasoline to increase the octane number (Fels, 1999). These hydrocarbons dissolve quickly in water and form plumes after entering the underground water. These compounds have high toxicity and carcinogenic effects on human health and the environment (Chiu et al., 2017). Of course, these compounds can be removed or converted into less harmful compounds using chemical reactions (Liang et al., 2017; Gholami et al., 2018). In this study, in the northern parts of Shazand Plain, a part of Arak city, due to the leakage of the 12-inch Malayer-Hamedan pipeline, oil pollution was seen in well No. 7, which is located upstream of the plain. In the study area, after drilling 13 Piezometers, the type of pollution and the extent of the plume were determined through sampling. The gasoline pollutant contaminated almost 10 ha of the area during the spill and is considered a severe danger to the agricultural lands downstream because this groundwater is not suitable for drinking and agriculture. In this research, 13 wells drilled in the study area were sampled in two stages (March 2021 and August 2020) and sent to the laboratory for analysis. The test related to BTEX and MTBE compounds was performed based on the gas chromatography method. In order to investigate the pollution of the region, the results of the laboratory measurements of BTEX and MTBE compounds were compared with the 1053 Iranian drinking water standard and the irrigation water standard The results of laboratory tests show that five wells located around Shazand Well No. 7 are contaminated with BTEX and MTBE compounds. This pollution is caused due to leakage from 12 inches MalayerHamedan pipeline. Considering the nature and spread of pollution, it is suggested to calculate the speed of pollutant movement in the groundwater before any action to clean it, and in this way to start the digging of cleanup wells and related operations.