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111.
Characteristics of PAHs adsorption on inorganic particles and activated sludge in domestic wastewater treatment 总被引:2,自引:0,他引:2
The occurrence of polycyclic aromatic hydrocarbons (PAHs) in a domestic wastewater treatment plant (WWTP) was investigated in a 1 year period. In order to understand how PAHs were removed at different stages of the treatment process, adsorption experiments were conducted using quartz sand, kaolinite, and natural clay as inorganic adsorbents and activated sludge as organic adsorbent for adsorbing naphthalene, phenanthrene, and pyrene. As a result, the adsorption of PAHs by the inorganic adsorbents well followed the Langmuir isotherm while that by the activated sludge well followed the Freundlich isotherm. By bridging equilibrium partitioning coefficient with the parameters of adsorption isotherm, a set of mathematical models were developed. Under an assumption that in the primary settler PAHs removal was by adsorption onto inorganic particles and in the biological treatment unit it was by adsorption onto activated sludge, the model calculation results fairly reflected the practical condition in the WWTP. 相似文献
112.
Gérard PergentCéline Labbe Céline Lafabrie Roger KantinChristine Pergent-Martini 《Ecological Engineering》2011,37(6):999-1002
In coastal environments, plants are used for phytoremediation of contamination. Organic and inorganic contaminants may be due to natural and/or anthropogenic sources. The aim of this study is to compare inorganic (trace metal) and organic (PAH) contamination in Posidonia oceanica and to analyse the relationship between these types of pollutants indeed very few studies have been interested in their correlations and common sources. P. oceanica leaves were collected in two sites exhibiting different levels of human-induced pressure. Higher values were recorded in the more polluted site (Toulon) for trace metals (Ag, Hg, Pb) as well as for PAHs (Medium Molecular Weight and High Molecular Weight) due to the presence of the city and/or harbour in proximity. For the first time in a coastal environment, correlations were observed between metals and PAHs. 相似文献
113.
Nehring V Evison SE Santorelli LA d'Ettorre P Hughes WO 《Proceedings. Biological sciences / The Royal Society》2011,278(1714):1942-1948
Although social groups are characterized by cooperation, they are also often the scene of conflict. In non-clonal systems, the reproductive interests of group members will differ and individuals may benefit by exploiting the cooperative efforts of other group members. However, such selfish behaviour is thought to be rare in one of the classic examples of cooperation--social insect colonies--because the colony-level costs of individual selfishness select against cues that would allow workers to recognize their closest relatives. In accord with this, previous studies of wasps and ants have found little or no kin information in recognition cues. Here, we test the hypothesis that social insects do not have kin-informative recognition cues by investigating the recognition cues and relatedness of workers from four colonies of the ant Acromyrmex octospinosus. Contrary to the theoretical prediction, we show that the cuticular hydrocarbons of ant workers in all four colonies are informative enough to allow full-sisters to be distinguished from half-sisters with a high accuracy. These results contradict the hypothesis of non-heritable recognition cues and suggest that there is more potential for within-colony conflicts in genetically diverse societies than previously thought. 相似文献
114.
Cuticular hydrocarbons (CHCs) are increasingly recognized as important to insects and are used for constructing taxonomies. However, multiple parameters affect the expression of CHCs besides a genetic component. We propose that selection may act differently on the expression of CHCs, depending on the evolutionary context. To explore the influence of selection, the CHCs of two closely related ant species, Lasius niger and Lasius platythorax, were studied in a multidisciplinary approach. We characterized (i) CHCs and (ii) niches (through baiting, activity observations and foraging analysis). The species were distinct in both measures, although to a varying degree. Although they showed moderate niche partitioning along diet and environmental preferences, chemical differences were unexpectedly pronounced. This may be explained by divergent selection on mate recognition cues or by other influences on CHCs. Such striking chemical differences among closely related species may not be the rule and suggest that taxonomies based on CHCs should be interpreted cautiously; though, they remain useful tools for differentiating among cryptic species. 相似文献
115.
Sulaibikhat Embayment is a severely contaminated coastline in the State of Kuwait. The contaminating pollutants include hydrocarbons, heavy metals, and suspended particles. The objective of this study is to assess the ability of mangroves planted in the Sulaibikhat Embayment to enhance hydrocarbons degradation by the activities of rhizospheric hydrocarbon degrading bacteria (HDB). Accordingly, samples were collected from the rhizosphere of selected mangrove plants and from sediments in the same location but away from mangrove marshes. The samples were analyzed chemically and microbiologically before being enriched with a mixture of hydrocarbon compounds (HC) to isolate HDB.
A number of halophilic HDB were isolated from mangroves rhizosphere and the surrounding sediments such as Pseudomonas balearica, Microbacterium barkeri and Gordonia soli. On the other hand, Bacillus velezensis and Bacillus subtilis subtilis were both isolated only from mangroves rhizosphere. Among the isolated HDB, Bacillus subtilis subtilis was distinguished with its high degradation rates of the tested HC including poly aromatic hydrocarbons. According to our knowledge, this is the first Bacillus subtilis HC-degrading strain that was isolated from Kuwait Bay and from mangroves rhizosphere. 相似文献
116.
Antígona?Segura Rafael?Navarro-GonzálezEmail author 《Origins of life and evolution of the biosphere》2005,35(5):477-487
Methane and other larger hydrocarbons have been proposed as possible greenhouse gases on early Mars. In this work we explore
if volcanic processes may have been a source for such molecules based on theoretical and experimental considerations. Geologic
evidence and numerical simulations indicate that explosive volcanism was widely distributed throughout Mars. Volcanic lightning
is typically produced in such explosive volcanism. Therefore this geologic setting was studied to determine if lightning could
be a source for hydrocarbons in volcanic plumes. Volcanic lightning was simulated by focusing a high-energy infrared laser
beam inside of a Pyrex reactor that contained the proposed volcanic gas mixture composed of 64% CH4, 24% H2, 10% H2O and 2% N2, according to an accretion model and the nitrogen content measured in Martian meteorites. The analysis of products was performed
by gas chromatography coupled to infrared and mass spectroscopy. Eleven hydrocarbons were identified among the products, of
which acetylene (C2H2) was the most abundant. A thermochemical model was used to determine which hydrocarbons could arise only from volcanic heat.
In this case, acetylene and ethylene are formed at magmatic temperatures. Our results indicate that explosive volcanism may
have injected into the atmosphere of early Mars ∼6×1012 g yr−1 of acetylene, and ∼2×1012 g yr−1 of 1,3-butadiyne, both produced by volcanic lightning, ∼5×1011 g yr−1 of ethylene produced by volcanic heat, and 1013 g yr−1 of methane. 相似文献
117.
AIMS: To study the effect of zinc on the biodegradation of phenanthrene by the microbial biomass in soil. METHODS AND RESULTS: Uncontaminated soil was amended with zinc and phenanthrene as single or co-contaminants, and microbial metabolic activity was measured using an intracellular dehydrogenase enzyme bioassay over 37 days. Contaminants were amended at optimum, action and double the action level specified in 'The New Dutch List' (Ministry of Housing, Spatial Planning and Environment, the Netherlands, 2000). Microbial activity in soils with zinc or phenanthrene alone indicated the presence of tolerant, albeit inhibited soil micro-organisms. A zinc concentration at the optimum level of 140 mg kg(-1) in the co-contaminated soil (phenanthrene at 40 mg kg(-1)) resulted in marginal stimulation of the rate of phenanthrene biodegradation. However, Zn2+ concentrations at the action and double the action level of zinc (720 and 1440 mg kg(-1)) inhibited phenanthrene degradation. CONCLUSIONS: Biodegradation of phenanthrene in soils co-contaminated with zinc at concentrations above the action value is impeded. SIGNIFICANCE AND IMPACT OF THE STUDY: Bioremediation efforts to remove polycyclic aromatic hydrocarbon in zinc co-contaminated soils are likely to be constrained. 相似文献
118.
Euphorbia tirucalli L., known as the petroleum plant, produces a large amount of triterpenes, such as beta-amyrin. Degenerate RT-PCR based on the sequences conserved among known beta-amyrin synthases led to cloning of a putative triterpene synthase cDNA, EtAS, from leaves of E. tirucalli. The deduced amino acid sequence of the EtAS cDNA showed the highest identity of 82% to the Panax ginseng beta-amyrin synthase. Heterologous expression of the EtAS ORF in the methylotrophic yeast, Pichia pastoris, resulted in production of beta-amyrin, revealing that the EtAS cDNA codes for a beta-amyrin synthase. This is the first report of a gene involved in the triterpene synthetic pathway from Euphorbiaceae plants. 相似文献
119.
Cuticular hydrocarbons (CHCs) are valuable characters for the analysis of cryptic insect species with few discernible morphological characters. Yet, their use in insect systematics, specifically in subterranean termites in the genus Reticulitermes (Isoptera: Rhinotermitidae), remains controversial. In this paper, we show that taxonomic designations in Reticulitermes from California (USA) suggested in light of differences among CHC phenotypes are corroborated by phylogenetic analyses using mtDNA sequences. Analyses based on CHC phenotypes and supported, in part, by behavioral and ecological differences have suggested the presence of more species than the two currently recognized: R. hesperus Banks and R. tibialis Banks. We analyze a 680 base pair fragment of the mitochondrial DNA cytochrome oxidase (COII) gene from 45 new (21 collection localities) and two previously recorded samples of Reticulitermes from California using parsimony and maximum likelihood methods. Both methods result in trees with highly similar topologies. Bootstrapping indicates support for six clades of Reticulitermes, and corroborates groupings based on cuticular hydrocarbons. One of the clades, R. hesperus, is already recognized in California, while four clades appear to be previously undescribed taxa. Although identification of the final clade is inconclusive, it includes a sample putatively identified as R. tibialis. Therefore, using phylogenetic analyses we corroborate chemical characters used to identify taxa, associate a chemical phenotype with a previously described species, and provide additional support for undescribed taxa of Reticulitermes. 相似文献
120.
AIMS: To characterize the bioemulsifier produced by a nonfluorescent strain of Pseudomonas putida isolated from a polluted sediment and to determine the influence of pH, temperature, media composition, and carbon and nitrogen source on growth and emulsifying activity. METHODS AND RESULTS: Different indexes were employed to determine the emulsifying properties of culture supernatants of P. putida ML2 in defined and complex media. Surface tension of cell-free supernatants was measured. Purification and chemical analysis of the emulsifier was performed. Confirmed results indicate that a polysaccharide with hexasaccharide repeating units is responsible for the emulsifying activity in a mineral medium with glucose as sole carbon source. Moreover, an emulsifier is produced when growing on naphthalene. CONCLUSIONS: Culture media composition influences the amount and the properties of the emulsifier produced by this P. putida strain. Under nitrogen limiting conditions, a polysaccharide is responsible for the emulsifying activity in defined mineral media. In complex nitrogen rich medium, a different kind of emulsifier is produced. The exopolymer may contribute to hydrocarbons solubilization. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first exopolysaccharide with emulsifying properties produced by a Pseudomonas strain reported to the present. Also chemical composition is significantly different from previous reports. This strain has potential use in bioremediation and the purified polysaccharide may be used in food and cosmetic industry. Moreover, the production of the exopolymer may play a role on biofilm formation. 相似文献