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In this study, we introduce a novel index called the modified inverse sum indeg (MISI) energy as an extension of the traditional inverse sum indeg (ISI) energy and neighbor degree sum energy. We devised an algorithm that employs the simplified molecular input line entry system (SMILES) formula of compounds to compute the MISI energy of polycyclic aromatic hydrocarbon (PAH). Additionally, we established the bounds of the MISI energy for certain classes of graphs with fixed number of vertices. A strong correlation between the MISI energy and the total $\pi$-electron energy of PAHs is observed through regression analysis. Remarkably, this correlation outperforms that achieved by the classical ISI energy. These findings highlight the enhanced effectiveness of the MISI energy as a descriptor for capturing significant molecular properties. Moreover, our study establishes a foundation for further theoretical extensions and practical applications in the field of chemical graph theory.

Quantitative structure–property relationship (QSPR) modeling is a powerful approach for predicting environmental behavior of organic pollutants with their structure descriptors. This study reports an optimal QSPR model for estimating logarithmic soil sorption coefficients (log K_OC) of polycyclic aromatic hydrocarbons (PAHs). Quantum chemical descriptors computed using density functional theory at the B3LYP/6-31G(d) level and partial least squares (PLS) analysis with an optimizing procedure were used to generate QSPR models for log K_OC of PAHs. The correlation coefficient of the optimal model was 0.993, and the results of a cross-validation test () showed this optimal model had high fitting precision and good predicting ability. The log K_OC values predicted by the optimal model are very close to those observed. The PLS analysis indicated that PAHs with larger electronic spatial extent tend to more easily adsorb and accumulate in soils and sediments, whereas those with higher molecular total energy and larger energy gap between the lowest unoccupied and the highest occupied molecular orbital adsorb and accumulate in soils and sediments less readily.

Occurrence of electron transfer was studied for different combinations of polycyclic aromatic hydrocarbons (PAHs) and DNA bases as electron donors or acceptors and free radicals only as electron acceptors. Geometries of all the molecules and radicals were optimized in aqueous medium employing the polarizable continuum model. Single electron transfer (SET) and sequential proton loss electron transfer mechanisms were investigated employing Gibbs free energies of the appropriate neutral, anionic and cationic species. Barrier energies involved in these phenomena were calculated using the Marcus theory. The SET barrier energies were found to be linearly correlated with $\mathrm{\Delta }E=$ (Electron affinities of acceptors – Ionization potentials of donors). SET barrier energies from the DNA bases to the PAHs follow the order Cy $>$ Th $\approx$ Ad $>$ Gu, whereas SET barrier energies from the PAHs to the DNA bases follow the order Gu $>$ Ad $>$ Th $\approx$ Cy. Thus, guanine, among the DNA bases, is the best electron donor to the PAHs and worst electron acceptor from the same.

Hydrophobic Fe₃O₄@SiO₂@C₁₈ magnetic nanoparticles (MNPs) composites were synthesized. Then it was characterized by TEM, SEM and FT-IR. In combination with HPLC-FLD/VWD, it was applied to extract extract 8 typical PAHs in water. The impact of extraction and analytical conditions on the extraction efficiency were studied in detail. The result shows that Fe₃O₄@SiO₂@C₁₈ MNPs has good extraction effect on the target PAHs. On optimum conditions, the limits of detection, linearity range and relative standard deviation for polycyclic aromatic hydrocarbons were satisfactory.

With the acceleration of urbanization process, the PAHs pollution in the urban soil is increasingly serious. The research summarize three main factors which influence PAHs pollution condition in the urban soil, including source pollution factor, biological factor and environmental factor. Besides, the research summarizes qualitative and quantitative techniques of source analysis methods of PAHs in the soil comprehensively. The research is believed to provide technical support for the study on pollution condition and source apportionment of PAHs in the soil of our country cities in future.

The pollution issue of PAHs in the soil of cities and outskirts gets more and more attention. The research is based on the sixteen kind of target compounds of PAHs controlled preferentially by EPA in the ten soil sampling points of fields in five towns of Yong Qing area in Lang Fang city, Hebei province. It applys PCA to recognize main sources of PAHs in the soil. The results show that the region has four primary sources, civilian combustion and traffic pollution sources, industrial coal and oil pollution sources, gasoline engine pollution sources and coking of oil pollution sources. The pollution of Langfang area mainly stems from the compound PAHs pollution of oil sources and coal tar. The levels of pollution of PAHs in the soil is: Bie Guzhuang town > Hou Yi town > Yong Qing town > Han Cun town > Li Lancheng town.