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71.
In a surfactant assisted biodegradation process, the choice of surfactant(s) is of crucial importance. The question is: does the type of surfactant(i, e. chemical family) affect the biodegradation process at fixed hidrophillic-lypofillic balance(H/B) values? Microcosm assessments were developed using contaminated soil, with around of 5000 mg/kg of hydrocarbons as TPH-diesel. Mixtures of three nonionic surfactants were employed to get a wide range of specific HLB values. Tween20 and Span20 were mixed in the appropriate proportions to get HLB values between 8.6 and 16.7. Tween/Span60 mixtures reached HLB values between 4.7 and 14.9. Finally,Tween/Span80 combinations yielded HLB values between 4.3 and 1.5. TPH-diesel biodegradation was measured at the beginning, and after 8 weeks, as well as the FCU/grsod, as a measure of microorganisms‘ development during the biodegradation period. A second aim of this work was to assess the use of guar gum as a biodegradation enhancer instead of synthetic products. The conclusions of this work are that surfactant chemical family, and not only the HLB value clearly affects the assisted biodegradation rate. Surfactant‘s synergism was clearly observed. Regarding the use of guar gum, no biodegradation enhancement was observed for the three assessed concentrations,i.e., 2, 20, and 200 mg/kg, respectively. On the contrary, TPH-diesel removal was lower as the gum concentration increased. It is quite possible that guar gum was used as a microbial substrate. 相似文献
72.
Voluminously epidemiological studies show that the relationships exist between the air pollution and human health and cancer. Aromatic hydrocarbons(AHs)in air form a large class of organic pollutants,which are widely in environment and many of them are known to be carcinogenic and/or mutagenic and contribute to ambient air pollution.In the past decades,bioassays mainly have been used to evaluate the toxicity of chemical mixtures in atmospheric particulates or aqueous environment.However,it is well known that the covalent complexes formed by carcinogens with DNA may be exert negative results in bioassay.So the main aim of this paper is to develop an evaluation method of toxicity effects of chemical mixtures in atmospheric particulates from chemical standpoint.In this study,the in vitro interaction of the AHs with DNA was investigated by absorption,fluorescence and resonance light scattering (RLS)spectroscopic techniques.The results showed that the AHs in the atmospheric particulates could combine with calf thymus DNA(ctDNA)and herring sperm DNA(hsDNA)without being activated or metabolized by organism,respectively.Intercalation may be present in the mechanism of interaction.The binding constants of the AHs with ctDNA and hsDNA were 2.5×10~2 and 2.0×10~3, respectively,which indicated that the interaction of the AHs with hsDNA is stronger than that with ctDNA.In addition,the relationships of dose-effect between the total mole concentration of chemical components and the ability of binding ctDNA and hsDNA were confirmed.This research made it possible to study the toxicity effects of chemical mixtures in atmospheric particulates by chemical method.It is believed that the composition and contents of unknown AHs and the interaction of DNA with AHs in atmospheric particulates of Xigu District of Lanzhou City,China are first reported in the past twenty years. 相似文献
73.
天然气是从地下采集出的一种碳氢化合物，其主要成分是甲烷（CH4）。液化天然气（LNG）是天然气在常压下冷却至-162℃后形成，为无色透明液体，外观如普通自来水。液化后其体积缩小600倍，使之便于运输及贮存。液化天然气升温气化后即为普通天然气，为无色无味气体，比空气轻。 相似文献
74.
75.
A halotolerant bacterial strain VA1 isolated from marine environment was studied for its ability to utilize polycylic aromatichydrocarbons (PAHs) under saline condition. Anthracene and pyrene were used as representatives for the utilization of PAH by thebacterial strain. Glucose and sodium citrate were used as additional carbon sources to enhance the PAH utilization. The strain VA1was able to utilize anthracene (73%) and pyrene (66%) without any additional substrate. In the presence of additional carbon sources(glucose/sodium citrate) the utilization of PAH was faster. PAH was utilized faster by VA1 in the presence of glucose than sodium citrate.The stain utilized 87% and 83% of anthracene and pyrene with glucose as carbon source and with sodium citrate the strain utilized 81%and 76% respectively in 4 days. Urea as an alternative source of nitrogen also enhanced the utilization of PAHs (anthracene and pyrene)by the bacterial strain up to 88% and 84% in 4 days. Sodium nitrate as nitrogen source was not able to enhance the PAH utilization rate.Phenotypic and phlyogenetic analysis proved that the PAHs utilizing halotolerant strain VA1 belongs to Ochrobactrum sp. 相似文献
76.
大气中空气动力学直径在2.5um以下的粒子对人体健康和生态环境的危害性极大，而燃烧过程中产生的烟炱是空气中可吸入颗粒物的主要来源之一。阐述了烟炱生成与排放方面研究的新进展；通过对碳氢燃料在空气中燃烧时烟炱的生成和氧化进行分析，讨论了火焰温度，流场结构等因素对烟炱的生成和排放的影响，为减少高温空气燃烧过程中的烟炱排放量提供了研究基础。 相似文献
77.
Effects of bioremediation on microbial communities jn soils contaminated with petroleum hydrocarbons are a scientific problem to be solved. Changes in dominate microbial species and the total amount of microorganisms including bacteria and fungi in rhizospheric soils after bioremediation were thus evaluated using field bioremediation experiments. The results showed that there were changed dominant microorganisms including ] ] bacterial strains which are mostly Gram positive bacteria and 6 fungal species which were identified. The total amount of microorganisms including bacteria and fungi increased after bioremediation of microbial agents combined with planting maize. On the contrary, fungi in rhizospheric soils were inhibited by adding microbial agents combined with planting soybean. 相似文献
78.
Four pure cultures were isolated from soil samples potentially contaminated with gasoline compounds either at a construction sitenear a gas station in Fai Chi Kei, Macau SAR or in the northern parts of China (Beijing, and Hebei and Shandong). The e ectsof di erent concentrations of benzene, toluene, ethylbenzene, and three isomers (ortho-, meta-, and para-) of xylene (BTEX), totalpetroleum hydrocarbons (TPH), and trichloroethylene (TCE), when they were present in mixtures, on the bio-removal e ciencies ofmicrobial isolates were investigated, together with their interactions during the bio-removal process. When the isolates were tested forthe BTEX (50–350 mg/L)/TPH (2000 mg/L) mixture, BTEoX in BTEoX/TPH mixture was shown with higher bio-removal e ciencies,while BTEmX in BTEmX/TPH mixture was shown with the lowest, regardless of isolates. The TPH in BTEmX/TPH mixture, on theother hand, were generally shown with higher bio-removal e ciencies compared to when TPH mixed with BTEoX and BTEpX. Whenthese BTEX mixtures (at 350 mg/L) were present with TCE (5–50 mg/L), the stimulatory e ect of TCE toward BTEoX bio-removalwas observed for BTEoX/TCE mixture, while the inhibitory e ect of TCE toward BTEmX for BTEmX/TCE mixture. The bio-removale ciency for TPH was shown lower in TPH (2000 mg/L)/TCE (5–50 mg/L) mixtures compared to TPH present alone, implying theinhibitory e ect of TCE toward TPH bio-removal. For the mixture of BTEX (417 mg/L), TPH (2000 mg/L) along with TCE (5–50 mg/L), TCE was shown co-metabolically removed more e ciently at 15 mg/L, probably utilizing BTEX and/or TPH as primarysubstrates. 相似文献
79.
上海市大气中非甲烷烃行为研究 总被引：4，自引：3，他引：4
经1993年7月～1994年4月对上海市区大气中非甲烷烃(NMHC)的测定,探讨了上海市大气中NMHC的浓度水平、浓度时间变化、浓度分布等状况。实验结果表明,上海市大气中NMHC的浓度日变化有比较明显的双峰形规律,即8:00～10:00和15:00～17:00各出现一次浓度高峰。上海市区大气中NMHC浓度,春季平均值为1.31×10~(-3)mg/m~3,夏季为2.00×10~(-3)mg/m~3,秋季为1.31×10~(-3)mg/m~3,冬季为1.29×10~(-3)mg/m~3,全年平均值为1.49×10~(-3)mg/m~3。根据对数正态分布检验的结果可以看出,上海市大气中NMHC并非来自单一类型的污染,而是多种类型的总体污染。 相似文献
80.