[Effects of nitrate on organic removal and microbial community structure in the sediments].

The strategy promoted pollutant degradation and transformation under the anaerobic circumstance by adding nitrate as an electron acceptor has been widely used in sediment bioremediation. However, few literature reports on organic removal characteristics and microbial community responses in the contaminated river sediment under the nitrate reduction condition. Methods including the polar and non-polar chemical fractionation, relative abundance detection of organic matters by GC-MS were combined and applied to investigate organic removals and PCR-DGGE analysis was used for microbial community structures in sediment incubation systems with or without calcium nitrate addition. The results indicated that the addition of calcium nitrate could significantly enhance removal efficiencies of organic pollutants. The removal efficiency of total organic carbon (TOC) and the total peak area of organic matters in GC-MS were 47.25% and 29.55% which were higher than those of the control. The effect descending order of organic pollutants was: silicon materials > alkanes > polycyclic aromatic hydrocarbons > heterocyclic compounds > olefins > benzene homologues > polar compounds > phthalates > aldehydes and ketones > alkyl esters. And removal rates of silicon materials, the persistent organic pollutants, benzene homologues and heterocyclic compounds were 46.73%, 36.25%, 23.19% and 35.92% which were higher than those of the control. The PCR-DGGE profile of bacterial 16S rDNA V3 fragments showed obviously different microbial community structures between the treatment and the control systems. Blastn analysis revealed that sequences of 10 predominant bands from DGGE profile were closely related to Proteobacteria, Actinobacteria, Clostridia, Chloroflexi, Caldiserica and uncultured bacterium. The research findings provide some helpful scientific information for promoting organic pollutant removal of river sediment by nitrate reduction.

[Characteristics of organic pollutants in the sediments from a typical electronics industrial zone].

In order to investigate the contamination status of organic pollutants in a river of a typical electrical equipment industrial area, Ronggui, Foshan, the sediments were sampled for the composition, concentration and occurrence analysis of organic pollutants. The polar and non-polar fractionation methods were employed for the fingerprint establishment of organic pollutants. One hundred and seventy-one of organic chemicals including ten categories of alkanes, alkenes, polycyclic aromatic hydrocarbons, benzene, heterocyclic compounds, phthalate esters, aldehydes, ketones, polar compounds, silicon-containing material as well as alkyl esters were examined. The number of different categories of the detected organic pollutants in a descending order was: alkanes > polar compounds > polycyclic aromatic hydrocarbons > aldehydes and ketones > heterocyclic compounds > benzene homologues, phthalate ester > alkyl esters > silicon material > olefins. The abundance of detected organic pollutants in a descending order was: alkanes > polar compounds > alkyl esters > olefins > polycyclic aromatic hydrocarbons > phthalates > silicon material > aldehydes and ketones > heterocyclic compounds > benzene homologues. Among the 51 kinds of alkanes detected, nonadecane accounted for 14.83%, and the persistent organic pollutants accounted for 2.33% of the total organic matter. Compared to similar studies, there were 51 kinds of alkanes and they accounted for 55.5% of the total organic chemicals, showing high diversity and abundance. In addition, some electronics industry-related organic pollutants such as silicone materials were also detected in high frequency.

[Distribution and potential ecological risk of polycyclic aromatic hydrocarbons in the sediments from typical electronics industrial zone].

In order to investigate the polycyclic aromatic hydrocarbons (PAHs) contamination status in a river of a typical electrical equipment industrial area, Ronggui, Foshan, 8 sediments simples were collected. The results showed that 12 components of PAHs were detected in all sediment samples, and the other 4 components were also detected in different degree. The total 16 EPA priority PAHs contents in surface sediments varied from 343.5 microg x kg(-1) to 2 099 microg x kg(-1) (dry wt), with an average of 1215.9 microg x kg(-1), and no significant variation was found in vertical distribution. The 2 to 3 aromatic rings were the dominant PAHs, and they accounted for 50.69% to 82.5% of the total PAHs. Diagnostic ratios were used to identify the possible sources of PAHs, and the results indicated that PAHs were mainly pyrogenic origin. Sediments were polluted by PAHs heavily according to Maliszewska-Kordybach's standard, the very high risk level was also confirmed by the contamination factors assessment which was investigated by comparison with the background area (SO). The assessment by the method of sediment quality guidelines (SQGs) and relative contamination factor (RCF) demonstrated that adverse biological toxicity effect might occasionally happen in a few sampling sites, and the ecological risk components included acenaphthene (Ace), fluorine (Flu), and phenanthrene (Phe).

[Horizontal and vertical distribution of polybrominated diphenyl ethers (PBDEs) in river sediment from a typical electrical equipment industrial area].

Polybrominated diphenyl ethers (PBDEs) were determined in sediment collected from a river in a typical electrical equipment industrial area, Ronggui, Foshan. Eight samples were collected from river sediment. The results indicated that PBDEs were presented in all samples. Spatial trends showed that the concentrations of PBDEs in all sediment samples were ranged from 62 ng x g(-1) to 349 ng x g(-1), with an average of 178 ng x g(-1). The predominant congener was BDE-209 (90% - 99%), which ranged from 56-337 ng x g(-1), with an average of 171 ng x g(-1). Some of congeners such as BDE-196, 197 and 203 may be were the degradation product of BDE-209. Vertically, the concentrations of PBDEs were increased with the depth, whereas the concentrations were 147 ng x g(-1) in layer 0-10 cm and 260 ng x g(-1) in layer 30-40 cm, respectively. Distribution profile of PBDEs in vertical direction was similar in different depths. The commercial deca-BDE (94%), which contained BDE-209, 208, 207 and 206, was the dominate pollutant with minor contributions from penta-and octa-BDEs. The results suggested that this area was polluted by PBDEs and BDE-209 was the most dominate congener, which is related with the manufacturing activities for electrical equipment.