Polycyclic aromatic hydrocarbons in soils in the vicinity of Nanjing, China.

The occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) in vegetable soils from five vegetable fields (including: Liuhe, Xixia, Pukou, Jianye and Yuhua districts) in Nanjing outskirt were investigated with high performance liquid chromatography (HPLC) equipped with fluorescence detector. The total concentrations of 15 priority PAHs in 126 soil samples ranged from 21.91 to 533.84ng g(-1) dry weight, and the sum of seven carcinogenic PAHs concentrations varied from 1.48 to 236.19ng g(-1) dry weight. Statistical analysis of the PAHs concentrations showed that the highest PAHs concentration was observed in Liuhe, and the lowest PAHs concentrations were found in Xixia among the five districts. The ratios of fluoranthene to sum of fluoranthene and pyrene concentrations (Flt/(Flt+Pyr)) were more than 0.5 in 99% of vegetable soil samples, showing that the PAHs in soils were generally derived from straw and coal combustion sources. The results from principal component analysis (PCA) further indicated that extensive combustion activities affected the PAHs distribution in Nanjing vegetable soils.

[Study on degradation of polycyclic aromatic hydrocarbons (PAHs) with different additional carbon sources in aged contaminated soil].

This study was conducted with different additional carbon sources (such as: glucose, DL-malic acid, citrate, urea and ammonium acetate) to elucidate the degradation of polycyclic aromatic hydrocarbons (PAHs) in aged contaminated soil under an indoor simulation experiment. The results showed that the quantity of CO2 emission in different additional carbon sources treatments was obviously much more than that of check treatment in the first week, and the quantity of CO2 emission in DL-malic acid treatment was the largest. The average CO2 production decreased in an order urea > glucose approximately citrate approximately DL-malic acid approximately ammonium acetate > check. Meanwhile, the amount of volatized PAHs in applied carbon sources treatments was significantly less than that in check treatment. The amount of three volatized PAHs decreased in an order phenanthrene > fluoranthene > benzo(b)fluoranthene. Compared with the check treatment, the average degradation rates of the three PAHs were significantly augmented in the supplied carbon sources treatments, in which rates of the three PAHs were much higher in DL-malic acid and urea treatments than those in other treatments. The largest proportion of residual was benzo(b)fluoranthene (from 72% to 81%) among three PAHs compounds, followed by fluoranthene (from 53% to 70% ) and phenanthrene (from 27% to 44%).

[Effects of different fertilizations on the extractable concentrations of polycyclic aromatic hydrocarbons (PAHs) in aged contaminated soil].

This study was conducted with amaranth as a representative leafy vegetable to elucidate the effects of application of different fertilizers such as inorganic nitrogen and organic fertilizers, which were widely used in agricultural production, on the extractable concentrations of polycyclic aromatic hydrocarbons (PAHs) in aged contaminated soil under a greenhouse incubation experiment. The results show that the extractable concentrations of phenanthrene (Phe), fluoranthene (Flt) and benzo (b) fluoranthene (BbF) decrease significantly in organic fertilizer treatments than those in inorganic nitrogen fertilizer treatments (p < 0.05). In the same sampling time and treatment, the ratios of extractable concentrations to primary concentrations in aged contaminated soil of three PAHs increase in an order, BbF < Flt < Phe (p < 0.05), showing that the adsorption of PAHs among soil components varies clearly with their physicochemical properties. The extractable concentrations of three PAHs are significantly higher in unvegetated soil than those in rhizosphere soil (p < 0.05).

[Characters of soil-vegetable transfer and accumulation of polycyclic aromatic hydrocarbons].

The transfer and accumulation of polycyclic aromatic hydrocarbons (PAHs) from aged contaminated agricultural soil to vegetable was studied. The results show that the positive correlation between the PAHs concentrations in tested vegetables and those in the corresponding soils is present. The PAHs concentrations in contaminated soils are significantly (p < 0.05) higher than that in roots, stems and leaves of vegetables, and the PAHs concentrations in roots are also significantly (p < 0.05) higher than that in stems and leaves. The ratio of sum of low molecular weight PAHs to total PAHs concentrations (Sigma LMW-PAHs/Sigma PAHs) in polluted vegetable roots is higher than that in corresponding soils (p < 0.05), and LMW-PAHs are more easily accumulated in vegetable roots than HMW-PAHs (high molecular weitht PAHs). The distinction of PAHs concentrations among the four selected leafy vegetables in the same tested soils does not achieve the significant level.