Determination of the Concentration of Linear Alkylbenzene Compounds in Surface Sediments of Rivers in the East of Mazandaran

Linear alkylbenzenes is one of the most important surfactants in the industry. Due to their source specificity, degradation resistance and long-term survival in marine sediments, these compounds are unique molecular markers for studying organic matter input derivatives and their effects on aquatic environments. Due to the presence of multiple sources of these compounds in the study areas, this study was conducted to determine the linear alkyl benzene concentrations in the 5 rivers of Nekaroud, Tajan, Talaroud, Babolroud and Sorkhroud that lead to the Caspian Sea. In this study, 15 river samples were collected from the bottom of rivers (near estuaries) from 0-5 cm depth by Grab van veen device. After preparation, the extracted samples were injected into a gas chromatography-mass spectrometer (GC-MS). Finally, the concentration of linear alkyl benzene compounds in surface sediments of 5 rivers leading to the Caspian Sea was determined. The average concentration of linear alkylbenzene compounds in rivers was determined in the range of 56730/28-91288/58 ng/g dry weight. Based on the results, stations in the densely populated and urban areas showed higher concentrations of these compounds. There was also a positive correlation between these compounds and total organic carbon (TOC) (p< 0.05). Therefore, the concentration changes of these compounds are a function of the TOC concentration changes in the sediments. The ratio of internal to external isomers (I/E) in the studied rivers ranged from 0.25 to 0.44. High concentrations of alkyl benzene with a low I/E ratio showed that the streams of Mazandaran province were heavily influenced by human activities. According to cluster analysis, Nekaroud and Tajan rivers have lower concentration than other rivers and are more desirable for release of fish than other rivers.