Sedimentary aliphatic and polycyclic aromatic hydrocarbons (PAHs) in the northwest of Qinling Mountains: Patterns, potential risk and a critical appraisal of PAH ratios to infer source

Surface sediment from the tourism areas of the northwest of the Qinling Mountains was analyzed by GC/MS/MS to determine the concentration, probable sourceand potential risk of aromatic and aliphatic hydrocarbons.... [ view full abstract ]

Surface sediment from the tourism areas of the northwest of the Qinling Mountains was analyzed by GC/MS/MS to determine the concentration, probable sourceand potential risk of aromatic and aliphatic hydrocarbons. Concentrations of aliphatic and aromatic hydrocarbons ranged from ng g‒1 4.18 to 3243.42 ng g‒1and 0.05 ng g‒1 to 101.35 ng g‒1of dry sediment, respectively. The results indicated that the extent of soil contamination by hydrocarbons was generally typified unpolluted to slightly polluted levels. As a result, the incremental life time cancer risks (ILCRs) for exposing to the soil borne PAHs showed a completely safety for tourists. For the origin of hydrocarbons, early diagenesis of natural products, bacteria activities and petroleum were the three main ways of aliphatic hydrocarbons, while the long-range transport of air pollutants from pyrolytic process was the main origin of PAHs. Because the photochemical reaction of PAHs in the atmosphere would produce lower ratios for Ant/(Ant+Phe),BaA/(BaA+Chr) and IcdP/(IcdP+BghiP), but higher ratio for Fla/(Fla+Pyr), the source classification highly depended on the diagnostic ratios chosen and the plot of ΣCOM/Σ14PAHvs. ΣLMW/ΣHMWPAH using more compounds than signal ratio was proposed to distinguish PAHs origins. Additionally, there was a good exponential relationship (r2=0.97) between the Natural n-Alkanes Ratio (NAR)and the carbon preference index for C23‒C35 (CPI23–35) for all the samples. It is of great use for the determination of the aliphatic hydrocarbon origins.