| PAHs are ubiquitous contaminants in the environment, known for their carcinogenic, teratogenic and mutagenic properties. Because of the toxicity, bioaccumulation, semi-volatility and persistence, PAHs are recognized as Persistent Organic Pollutants (POPs) and received worldwide scientific concerns. In recent years, PAHs have been detected in the atmosphere, water, sediment, soil, food and organism. Different laws have been passed by the People's Republic of China (PRC), the United States of America (USA), the European Union (EU) and the World Health Organization (WHO) to control over PAHs because of their widespread distribution and perniciousness.In view of their widespread distribution in the environment and perniciousness to human health and the ecosystem, the research on the concentrations, distributions and sources identification of PAHs is becoming increasingly important for environmental quality assessment and organic pollution prevention. While PAHs is widely-spread in the environment, their content is very low. At the same time, other POPs would interfere with the analysis. Therefore, the choice of analytical methods has been crucial to the accuracy and precision of the analysis.In this paper, 16 PAHs on the US EPA priority pollutant list were chosen as the target analytes. The analytical procedure for sample collection and storage, sample pretreatment and analysis of PAHs was optimized for the determination of PAHs in soil samples. The idea was to minimize the operation steps and to simplify each step.Ultrasonic extraction was selected as the extraction method, and the extraction efficiencies of two different solvents were compared. Cleanup and evaporation procedures ware also optimized. Based on these studies, an accurate, fast and simple method for pretreatment of soil samples was then established. Under the optimized conditions, the recoveries of PAHs for spiked blanks were 54.82～94.70%, with RSD ranged from 3.02 to 23.22%; the recoveries of PAHs for spiked matrices were 61.20～127.08%, with RSD ranged from 4.01 to 25.13%; the recoveries of PAHs for standard sediment SRM 1941b were 50.79～83.78%, with RSD ranged from 5.24 to 21.28%.The High Performance Liquid Chromatography-Fluorescence Detector (HPLC- FLD), with gradient elution and wavelength programming of the detector, was chosen as the detection method of PAHs in soil samples. The elution procedure and wavelength program were optimized. Under the optimized chromatographic conditions, the RSD (n=5) ranged from 0.048 to 0.140% for retention times and ranged from 1.32 to 4.38% for peak areas, with detection limits of PAHs ranged from 0.75 to 10.99 ng·L-1.Using the established analytical method, we determined the concentrations of 15 PAHs in soils of the Yellow River Delta region. The total concentrations of 15 PAHs varied from 25.53 to 202.78 ng·g-1 (dry weight), which are obviously higher than the value of a typical endogenous soil resulted from plant synthesis and natural fires.According to isomer ratios of PAHs, a mixed source of petrogenic and pyrogenic was identified in the soils of the Yellow River Delta region, mainly from petroleum pollution, industrial waste and emission, as well as sewage discharge.The total PAHs had been compared with the individual PAHs concentrations and the TOC content respectively. The results showed that Pyrere possessed the best linear relationship with the total PAHs, while the correlation between TOC and total PAHs was poor, which might be associated with relatively lower concentrations of PAHs in the soils.The findings of this paper have provided indispensable scientific arguments for related government agencies and environmental protection departments for the prevention and control of PAHs pollution and the implementation of measures for the protection and treatment of soils in the Yellow River Delta region.
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