Deep chlorophyll maximum distribution in the central Tyrrhenian Sea described by a towed undulating vehicle

The towed undulating vehicle (TUV), named SARAGO, was used for two fine-scale surveys between the Italian and the Sardinian coasts during the Astraea 2 cruise (6-7 and 26-27 September 1995), studying the deep chlorophyll maximum distribution. SARAGO sections identify a sub-surface doming with higher chlorophyll a and primary production concentrations in the upwelling area of a cyclonic gyre region, detected by sea-surface temperature images. In the first section, the cyclone presents a double doming, in density and salinity, with shallower and concentrated patches of chlorophyll a for about 2 miles. Twenty days later, the second section shows that the gyre changes shape and extension, showing a single doming with higher primary production and chlorophyll a concentrations, distributed over a large area of about 40 nautical miles. SARAGO allows analysis of this high-variability phenomenon (cyclonic gyre) and allows concentrated patches (2 nm) to be identified, thus proving the importance of TUVs in the study of mesoscale processes.     

生物滴滤塔净化多组分废气的研究

通过生物滴滤塔(biotrickling filter,BTF)净化硫化氢(H2S)、四氢呋喃(THF)、二氯甲烷(DCM)混合废气,研究其挂膜启动和稳定运行条件下的降解性能.结果表明,混合废气H2S、THF、DCM浓度分别为200、100和100 mg·m-3,空床停留时间(empty bed retention time,EBRT)50～20 s的条件下,H2S和THF的去除率分别能够维持在99%和60%左右,而DCM的去除率随EBRT的缩短从90%逐渐降低至37%左右.利用Michaelis-Menten动力学模型分析得到,理论降解效果为H2S>THF>DCM.     

Individual stages of bacterial dichloromethane degradation mapped by carbon and chlorine stable isotope analysis

The fractionation of carbon and chlorine stable isotopes of dichloromethane(CH_2Cl_2,DCM)upon dechlorination by cells of the aerobic methylotroph Methylobacterium extorquens DM4 and by purified DCM dehalogenases of the glutathione S-transferase family was analyzed.Isotope effects for individual steps of the multi-stage DCM degradation process,including transfer across the cell wall from the aqueous medium to the cell cytoplasm,dehalogenase binding,and catalytic reaction,were considered.The observed carbon and chlorine isotope fractionation accompanying DCM consumption by cell supensions and enzymes was mainly determined by the breaking of C\Cl bonds,and not by inflow of DCM into cells.Chlorine isotope effects of DCM dehalogenation were initially masked in high density cultures,presumably due to inverse isotope effects of non-specific DCM oxidation under conditions of oxygen excess.Glutathione cofactor supply remarkably affected the correlation of variations of DCM carbon and chlorine stable isotopes(Δδ~(13)C/Δδ~(37)Cl),increasing corresponding ratio from 7.2–8.6 to 9.6–10.5 under conditions of glutathione deficiency.This suggests that enzymatic reaction of DCM with glutathione thiolate may involve stepwise breaking and making of bonds with the carbon atom of DCM,unlike the uncatalyzed reaction,which is a one-stage process,as shown by quantum-chemical modeling.     

Vapor-phase concentrations of PAHs and their derivatives determined in a large city: Correlations with their atmospheric aerosol concentrations

Thirteen PAHs, five nitro-PAHs and two hydroxy-PAHs were determined in 55 vapor-phase samples collected in a suburban area of a large city (Madrid, Spain), from January 2008 to February 2009. The data obtained revealed correlations between the concentrations of these compounds and a series of meteorological factors (e.g., temperature, atmospheric pressure) and physical–chemical factors (e.g., nitrogen and sulfur oxides). As a consequence, seasonal trends were observed in the atmospheric pollutants. A “mean sample” for the 14-month period would contain a total PAH concentration of 13 835 ± 1625 pg m⁻³ and 122 ± 17 pg m⁻³ of nitro-PAHs. When the data were stratified by season, it emerged that a representative sample of the coldest months would contain 18 900 ± 2140 pg m⁻³ of PAHs and 150 ± 97 pg m⁻³ of nitro-PAHs, while in an average sample collected in the warmest months, these values drop to 9293 ± 1178 pg m⁻³ for the PAHs and to 97 ± 13 pg m⁻³ for the nitro-PAHs. Total vapor phase concentrations of PAHs were one order of magnitude higher than concentrations detected in atmospheric aerosol samples collected on the same dates. Total nitro-PAH concentrations were comparable to their aerosol concentrations whereas vapor phase OH-PAHs were below their limits of the detection, indicating these were trapped in airborne particles.     

代谢产物积累对二氯甲烷生物降解的影响

研究了代谢调节产物(NaCl)浓度积累对生物法降解二氯甲烷效率的影响。试验表明,一定浓度的NaCl对二氯甲烷降解菌(GD11)的生长有不同程度的抑制作用。摇瓶试验中NaCl对二氯甲烷降解菌的抑制浓度为35.1g/L;当空塔气速91.7m/h、二氯甲烷进口浓度2.02g/m3、温度28.5℃、循环液流量0.06m3/h、pH值6.5～7.5时,生物滴滤塔中NaCl对二氯甲烷降解菌的抑制浓度为23.4g/L,两者相比有一定差异。NaCl浓度对生物膜的厚度有一定影响,这从侧面反映了NaCl浓度对微生物活性的影响。     

Effect of Ni–V loading on the performance of hollow anatase TiO2 in the catalytic combustion of dichloromethane

A catalyst based on mixed V-Ni oxides supported on TiO_2(Ni-V/TiO_2)was obtained using the sol-gel method.Its catalytic performance relative to dichloromethane(DCM)degradation was investigated.Characterization and analysis were conducted using transmission electron microscopy,H2 temperature-programmed reduction,pyridine-Fourier transform infrared spectroscopy(FTIR)characterization,and X-ray diffraction.Results showed that the original hollow anatase structure of pure Ti02 was well-maintained after Ni-V loading.The loading of NiO-VOx not only significantly improved the stability of pure Ti02 but also inhibited the formation of the by-product monochloromethane(MCM).Among the series of Ni-V/TiO_2 catalysts,4%Ni-V/TiO_2 possessed the highest catalytic activity,with 90%DCM conversion at only 203℃.No by-products and no significant changes in the catalytic activity were observed during combustion of DCM after 100 hr of a continuous stability test.Furthermore,thermogravimetric analysis(O_2-TG)and energy dispersive spectrometer(EDS)characterization of the used 4%Ni-V/TiO_2 catalyst revealed that no coke deposition or chlorine species could be detected on the catalyst surface.     

Deep chlorophyll maximum distribution in the central Tyrrhenian Sea described by a towed undulating vehicle

The towed undulating vehicle (TUV), named SARAGO, was used for two fine-scale surveys between the Italian and the Sardinian coasts during the Astraea 2 cruise (6–7 and 26–27 September 1995), studying the deep chlorophyll maximum distribution. SARAGO sections identify a sub-surface doming with higher chlorophyll a and primary production concentrations in the upwelling area of a cyclonic gyre region, detected by sea-surface temperature images. In the first section, the cyclone presents a double doming, in density and salinity, with shallower and concentrated patches of chlorophyll a for about 2 miles. Twenty days later, the second section shows that the gyre changes shape and extension, showing a single doming with higher primary production and chlorophyll a concentrations, distributed over a large area of about 40 nautical miles. SARAGO allows analysis of this high-variability phenomenon (cyclonic gyre) and allows concentrated patches (2 nm) to be identified, thus proving the importance of TUVs in the study of mesoscale processes.