The fingerprint stability of the biomarker hopanes and steranes in soot emissions from in-situ burning of oil

Assessing the chemical composition, potential toxicity and cancer risk of airborne fine particulate matter (PM2.5) near a petrochemical industrial area

In the vicinity of a petrochemical industrial region in São Paulo, Brazil, PM_2.5-bound organic carbon (OC), elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs, oxy-PAHs, hopanes, and inorganic species were evaluated. Oxidative potential (OP), burden (OB), and Alivibrio fischeri bioluminescence inhibition (AFBIA) assays were conducted to determine the potential health effects of exposure to these compounds. The PM_2.5 mean concentration was 32.0±18.2µgm^-3, and benzo (a)pyrene was found to exceed recommended levels by at least four times. Secondary sources and vehicular emissions were indicated by nitro-PAHs, oxy-PAHs, and inorganic species. The OP and OB results revealed that secondary compounds favored antioxidant depletion. The AFBIA results showed that 64% of the samples were toxic. These findings emphasize the need to reduce the exposure risk and take measures to protect human health.

A small-scale neutral alumina column chromatography method for carbon isotope determination of hopanes in crude oils or rock extracts

This paper presents a small-scale column chromatography method for separating hopanes in crude oil or rock extracts using neutral alumina as a solid phase adsorbent and a Pasteur pipette as a separation device. Three oil samples were selected to study the effect of solid phase adsorbent type and column length on the separation of hopanes. The oil samples were eluted with mixed reagents (V _hexane: V _{petroleum ether} = 8:2) and collected at intervals of 0.5 ml. Ten Fractions were collected and tested for the compounds using GC-MS. A quantitative approach was used to reveal distribution characteristics of compounds in each eluted Fraction. Experimental results showed that 100-200 um neutral alumina exhibited significant differences in the adsorptive capacity of biomarkers from oil samples and rock extracts. The elution order of the biomarkers in the chromatographic column (the length is 180 mm) was n-alkanes, steranes and hopanes. The separation of hopanes could be realized by collecting the eluted Fractions 4 and 5. Compared with the urea complexation, the purity of hopanes separated by column chromatography was higher. The concentration of n-alkanes (nC₁₆-nC₃₄) could be reduced from 1.99 to 4.83 mg/ml to 0.79-0.94 mg/ml, and the content of steranes can be reduced from the original 12% to 0.45%. Residual n-alkanes and steranes were not visible in the GC-MS detection. The Total Ion Chromatography (TIC) of hopanes was consistent with the distribution characteristics of the m/z191 mass chromatogram. The isolated hopanes could meet the detection requirements of isotope ratio mass spectrometry. The C₂₉Ts/C₂₉αβ ratio of hopanes decreased gradually from 1.63 to 0.73 as the column length increased. It is speculated that the variation of the C₂₉Ts/C₂₉αβ ratio is not only affected by maturity but also by the oil and gas migration. This method is a new attempt in the field of compound purification and can be widely used in the study of stable carbon isotopes of hopanes monomeric hydrocarbons.

Gas-particle partitioning of polycyclic aromatic hydrocarbons from oil combustion involving condensate, diesel and heavy oil

This study focuses on the gas-particle (G-P) partitioning of 16 polycyclic aromatic hydrocarbons (PAHs) from oil combustion, which is one of the important contributors of anthropogenic PAHs but has been rarely studied. The combustions of different types of oils involving ultra-light to heavy oils were investigated, and the PAH partitioning mechanism was determined by the widely used Junge-Pankow adsorption model, K_oa absorption model, and dual sorption model, respectively. The results show that the source-specific diagnostic ratios of Ant/(Ant+Phe) are between 0.09 and 0.24, the estimated regression slopes of G-P partition coefficients (K_P) of the total PAHs on their sub-cooled liquid vapor pressures (P_L^O) are in the range of - 0.34 to - 0.25, and the predicted fractions of PAHs in the particle phase (φ) by K_oa absorption model are close to the measured values, while the log K_Pvalues of the LMW PAHs from the combustions of diesel and heavy oil are better represented by the dual sorption model. Our findings indicate that PAHs are derived from mixed sources that include the unburned original oil and combustion products, and the PAH partitioning mechanism is governed by the process of absorption into organic matter because of the unburned oil, but both adsorption and absorption exist simultaneously in the lighter PAHs from the combustions of heavier oils (i.e., diesel and heavy oil). Based on these findings, the understanding of the fate and transport of PAH emissions and the optimization of the emergency responses to accidents such as marine oil spills would be potentially improved.