Distribution and source apportionment of polycyclic aromatic hydrocarbons in the surface soil of Baise, China.

To estimate the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in the soils of Baise, in southwest China, soil sampling sites were selected from industry, traffic, rubbish, gas station, residential, and suburban areas for analysis of PAHs. The average concentrations of ∑16PAHs in the present study varied significantly, depending on the sampling location, and ranged from 16.8 to 6,437.0 µg/kg (dry weight basis), with a mean value of 565.8 µg/kg. PAH concentrations decreased significantly along the industry-traffic-rubbish-gas station-residential-suburban transect. The PAH profiles in the surface soil of the different areas imply that either source proximity to the sampling sites, or transport and deposition effects influenced PAH distributions. Two diagnostic ratios were selected and used to apportion PAH sources in the surface soil, and bivariate plots show general trends of covariation. Principal component analysis and multivariate linear regression were used to determine the primary sources and their contributions of PAHs to the soils. The model showed that factors 1 (coal and wood combustion) and 2 (petroleum combustion) contributed over 52.1 and 32.5% of the total source of soil PAHs, respectively. The remaining 15.4% came from evaporative and uncombusted petroleum.

Complete mitochondrial genome of Tubulipora flabellaris (Bryozoa: Stenolaemata): the first representative from the class Stenolaemata with unique gene order.

Mitochondrial genomes play a significant role in the reconstruction of phylogenetic relationships within metazoans. There are still many controversies concerning the phylogenetic position of the phylum Bryozoa. In this research, we have finished the complete mitochondrial genome of one bryozoan (Tubulipora flabellaris), which is the first representative from the class Stenolaemata. The complete mitochondrial genome of T. flabellaris is 13,763bp in length and contains 36 genes, which lacks the atp8 gene in contrast to the typical metazoan mitochondrial genomes. Gene arrangement comparisons indicate that the mitochondrial genome of T. flabellaris has unique gene order when compared with other metazoans. The four known bryozoans complete mitochondrial genomes also have very different gene arrangements, indicates that bryozoan mitochondrial genomes have experienced drastic rearrangements. To investigate the phylogenetic relationship of Bryozoa, phylogenetic analyses based on amino acid sequences of 11 protein coding genes (excluding atp6 and atp8) from 26 metazoan complete mitochondrial genomes were made utilizing Maximum Likelihood (ML) and Bayesian methods, respectively. The results indicate the monopoly of Lophotrochozoa and a close relationship between Chaetognatha and Bryozoa. However, more evidences are needed to clarify the relationship between two groups. Lophophorate appeared to be polyphyletic according to our analyses. Meanwhile, neither analysis supports close relationship between Branchiopod and Phoronida. Four bryozoans form a clade and the relationship among them is T. flabellaris+(F. hispida+(B. neritina+W. subtorquata)), which is in coincidence with traditional classification system.

The complete mitochondrial genome of Watersipora subtorquata (Bryozoa, Gymnolaemata, Ctenostomata) with phylogenetic consideration of Bryozoa.

The phylogenetic position of the Bryozoa has long been controversial. In this paper, we have determined the complete mitochondrial genome of the Watersipora subtorquata (Bryozoa, Gymnolaemata, Ctenostomata). It is a circular molecule of 14,144 bp, relatively small compared with most other metazoan mitochondrial genomes, and bears some unusual features. All genes in the W. subtorquata mtDNA, unlike those in two bryozoan mtDNAs and most other metazoan mtDNAs published previously, are transcribed from the same strand. It has a unique gene order which differs radically from that of other metazoans. Drastic gene rearrangements were also found among bryozoan mtDNAs. To investigate the phylogenetic position of Bryozoa, analyses based on amino acid sequences of 11 protein-coding genes (excluding atp6 and atp8) from 25 metazoan mtDNAs were made utilizing ML and Bayesian methods. Lophotrochozoa was recovered as monophyletic with strong support in our analyses. Lophophorate was undoubted within Lophotrochozoa, but appears as polyphyletic, which indicates that the lophophores of this group may be of different origin. The existence of Phoronozoa was rejected. Our analyses indicated that Phoronida is more closely related to Annelid instead of Brachiopod. Chaetognatha appeared as the sister group of Bryozoa and they formed a clade together with strong support. More evidence is needed to clarify the relationship of these two phyla.