A characterization of the soils and sediments in contaminated sites and rivers using petroleum biomarker compounds

Abstract

The objective of this study is to reveal the presence of petroleum biomarkers in sediments of contaminated sites and to prove the existence of these compounds in the polluted or unpolluted rivers. Without a thorough investigation, various potentially existing biomarkers might be missed. This study also aims to characterize the distribution of hydrocarbons in the studied sites and to link them to the analyzed biomarker compounds to finally determine their possible anthropogenic sources. Samples from five field sites were analyzed to study the distribution of petroleum biomarkers and to characterize the soils in two closed gas stations and an old refinery product dispatch center. For the comparison, sediment samples from a typical municipal river and a main river with good water quality were also studied. The SIM (selective ion monitoring) mode of GC/MS detected 17 adamantanes, 10 bicyclic sesquiterpanes, 37 terpanes, and 17 steranes, and the analysis protocol was conducted according to our biomarker identification and quantitation technology. Distributions of hydrocarbons demonstrate the occurrence of gasoline/diesel (C10 to C22) and refinery residual oil products (C17 to C25) at the gas stations and dispatch center, respectively. In comparison, the municipal river has a fluctuating carbon distribution of around C10 to C21, which is indicative of pollution, while another main river has a distribution of around C10 to C18 in the estuary zone. Detected concentrations of pristane and phytane were up to 25 and 73 mg kg−1 for the contaminated sites, respectively. Targeted petroleum biomarker compounds were all detected, and the highest terpane concentration was up to 204 mg kg−1 by the developed method. Eleven diagnostic ratios of adamantanes were calculated to distinguish the possible sources of gasoline and diesel products in these studied sites. Distribution of hydrocarbons indicated that studied sites had its pattern and showed the preliminary condition of contamination. Concentrations of pristane, phytane, and the total of the four categories of biomarker compounds highlight the possible sources of different refinery products. This study proves that our developed new method is a practical technology in a chemical forensics investigation, and the calculated normalization and diagnostic ratios helped the identification of the anthropogenic sources of these pollutants.