Aerobic dechlorination of cis- and trans-dichloroethenes by some indigenous bacteria isolated from contaminated sites in Africa

The innate toxicity of dichloroethenes(DCEs) and their tendency to be reduced to vinyl chloride(VC)(a known human carcinogen) is a cause for environmental concern. Aerobic bacteria capable of growth on cis- and trans-DCEs as sole carbon and energy sources were isolated by enrichment culture technique and identified to belong to the genera; Bacillus, Pseudomonas and Acinetobacter. Axenic and mixed cultures of the bacterial isolates utilized DCEs at concentrations above the maximum contaminant level allowable in drinking water by the Environmental Protection Agency. Their specific growth rate constant ranged significantly(P<0.05) between 0.346—0.552 and 0.461—0.667 d -1; while the maximum specific substrate utilization rate ranged significantly(P<0.05) between 20.01—29.79 and 31.40—42.83 nmol h -1 (mg of protein) -1 in cis- and trans-DCE, respectively. The optimum growth was observed at 30℃ and at a pH of 7.0 with up to 96% of the stoichiometric-expected chloride released. Serial adaptation positively affected the growth yields and dehalogenase activities of the organisms with multiple antibiotic patterns also demonstrated by the isolates. These findings therefore indicated the important roles that these organisms may play in the bioremediation of sites polluted with chlorinated ethene compounds in Africa.

Spatial Model of Sky Brightness Magnitude in Langkawi Island, Malaysia

Sky brightness is an essential topic in the field of astronomy, especially for optical astronom- ical observations that need very clear and dark sky conditions. This study presents the spatial model of sky brightness magnitude in Langkawi Island, Malaysia. Two types of Sky Quality Meter （SQM） manu- factured by Unihedron are used to measure the sky brightness on a moonless night （or when the Moon is below the horizon）, when the sky is cloudless and the locations are at least 100 m from the nearest light source. The selected locations are marked by their GPS coordinates. The sky brightness data obtained in this study were interpolated and analyzed using a Geographic Information System （GIS）, thus producing a spatial model of sky brightness that clearly shows the dark and bright sky areas in Langkawi Island. Surprisingly, our results show the existence of a few dark sites nearby areas of high human activity. The sky brightness of 21.45 mag arcsec-2 in the Johnson-Cousins V-band, as the average of sky brightness equivalent to 2.8 × 10-4cd m-2 over the entire island, is an indication that the island is, overall, still relatively dark. However, the amount of development taking place might reduce the number in the near future as the island is famous as a holiday destination.

Investigation and Evaluation of Site Contaminated Soil

The investigation and evaluation of site contaminated soil were mainly conducted.Firstly,investigation measures of site contaminated soil were proposed,including increasing attention to the production process of the original enterprise,investigating the types of pollutants on the site,clarifying the key points of different environmental investigations,and refining the initial record of site pollution investigation.Secondly,the key points of the risk assessment of site pollution were discussed.Finally,a specific case analysis was conducted,mainly covering the introduction of a contaminated site,investigation and evaluation methods,etc.,aiming to promote the smooth progress of the investigation and evaluation of site contaminated soil,and solve the problem of site pollution smoothly based on the in-depth perspective.