Methanol measurements in the lower troposphere near Innsbruck (047°16′N; 011°24′E), Austria

Diurnal variations on a time scale of minutes of the mixing ratios of methanol were measured using proton transfer reaction mass spectrometry (PTR-MS) technique during 67 days throughout the time span from November 1996 to July 1998 together with benzene and other volatile organic compounds at the western outskirts of Innsbruck, Austria. Comparison with the course of the mixing ratio of benzene, which served as marker for traffic emissions, as well as the observation of a seasonal variation allowed to distinguish between different sources for methanol release into the troposphere. Strong evidence for methanol removal via deposition on dew-wetted surfaces is obtained from the comparison of meteorological data with methanol mixing ratios. The mean volume mixing ratio of total methanol was 7.5 nmol mol⁻¹. Mixing ratios ranged from 0.03 up to 45 nmol mol⁻¹.     

Aromatic hydrocarbons at urban,sub-urban,rural (8°52′N; 67°19′W) and remote sites in Venezuela

Using the novel on-line proton transfer reaction mass spectrometry (PTR-MS) technique, atmospheric concentrations of benzene, toluene, xylenes, and C₉-benzenes were measured in Caracas (urban), Altos de Pipe (sub-urban), Calabozo (rural) and Parupa (remote), during various campaigns in 1999 and 2000.Average daytime mixing ratios measured in Caracas are 1.1, 3.2, 3.7, and 2.7 nmol/mol for benzene, toluene, xylenes, and C₉-benzenes. At the sub-urban site, located only few km from Caracas, relatively low levels (∼20% of the levels measured in Caracas) of these aromatic hydrocarbons were observed.At the rural site during the dry season, higher concentrations of benzene (0.15 nmol/mol) were recorded, whereas those of toluene (0.08 nmol/mol) were lower during that time. The aromatic hydrocarbon ratios in the wet season (benzene: 0.08 nmol/mol; toluene: 0.09 nmol/mol) are consistent with an aged urban plume, whereas biomass burning emissions dominate during the dry season. From rural and urban [benzene]/[toluene] ratios a mean HO concentration of 2.6×10⁶ molecules/cm³ was estimated during the wet season. This value must be considered an overestimate because it does not account for background concentrations which are likely for benzene and toluene.At the remote “La Gran Sabana” region (Parupa) very low mixing ratios (0.031 and 0.015 nmol/mol for benzene and toluene) are showing the pristine region to be unaffected by local sources. From the [benzene]/[toluene] ratio we deduced, that “urban” air arriving from the coastline (350 km) is likely mixed with air containing some background of benzene and toluene.Urban emissions (automobiles) should be the major source of aromatic compounds, however, during the dry season biomass burning seems to make an important contribution.     

′93首届中国国际环境标志产品博览会将在京举办

“环境标志”是一种印在商品或其包装上的图形,用来表明该产品从生产、使用及回收处置的过程中均符合环境保护要求。实行环境标志是人类认识和解决环境问题的一大进步,也是国际贸易中出现的新趋势。为进一步推动我国环保事业的发展,促进我国对外贸易,中国未来研究会和国家环保局将于10月20日     

超声协同TiO2光催化降解4,4′-二溴联苯

以纳米TiO2膜为光催化剂,对4,4′-二溴联苯水溶液进行了超声光催化（US＋UV）、光催化（UV）和超声（US）降解,探讨了初始浓度、超声的声强和频率等对降解4,4′-二溴联苯的影响。结果表明,4,4′-二溴联苯的超声光催化降解存在协同效应,降解率随4,4′-二溴联苯初始浓度的增大而下降,随声强和频率的增大而增大。超声光催化过程符合一级动力学方程,反应数率常数为0.011 min^-1。超声光催化与光催化的降解产物不同。     

超声协同TiO_2光催化降解4,4′-二溴联苯

以纳米TiO2膜为光催化剂,对4,4′-二溴联苯水溶液进行了超声光催化(US+UV)、光催化(UV)和超声(US)降解,探讨了初始浓度、超声的声强和频率等对降解4,4′-二溴联苯的影响。结果表明,4,4′-二溴联苯的超声光催化降解存在协同效应,降解率随4,4′-二溴联苯初始浓度的增大而下降,随声强和频率的增大而增大。超声光催化过程符合一级动力学方程,反应数率常数为0.011 min-1。超声光催化与光催化的降解产物不同。     

Simultaneous measurements of ammonia and nitric acid in ambient air at Agra (27°10′N and 78°05′E) (India)

Simultaneous measurements of ammonia and nitric acid in ambient air were conducted at Dayalbagh, Agra using the mist chamber technique. The sampling site is located near a cattle shed. A total of 120 samples were collected during the period July–September and November–February (1997–1998). Sampling was performed during six different times a day. Gas-phase HNO₃ was estimated as NO₃⁻ using ion chromatographic technique while ammonia was determined colorimetrically as NH₄⁺ using indophenol blue method. The mean levels of NH₃ and HNO₃ for the entire data set were 16.3±2.8 and 1.6±1.4 ppbv, respectively. In the monsoon, mean values for NH₃ and HNO₃ averaged to 16.4±3.5 and 0.9±0.7 ppbv while the winter means were 11.8±4.4 and 2.1±1.2 ppbv, respectively. Concentration of both the species (NH₃ and HNO₃) did not show any significant diurnal behaviour in both the seasons. However, concentration of both NH₃ and HNO₃ were lower at dawn than the previous night's value. This has been ascribed to their removal through dew. Concentrations of HNO₃ are observed to increase during the daytime, consistent with its formation by photochemical reactions. Nitric acid and ammonia concentrations show a significant seasonal variation. Levels of HNO₃ are higher in winter but lower in monsoon, while ammonia shows a reverse trend with higher monsoon and lower winter values. Observed trends in nitric acid and ammonia concentration are due to seasonal variation in emission sources, chemistry and meteorology. Gaseous ammonia and nitric acid are in equilibrium with NH₄NO₃ (solid or aqueous) in the atmosphere. The existence of this equilibrium was examined from simultaneous measurements of NH₃ and HNO₃ in the ambient air. It is found that for the monsoon data, measured concentrations are qualitatively below the predicted equilibrium value, while in the winter, concentration product ([NH₃] [HNO₃]) lies consistently above the predicted values. These deviations may be explained due to local sources of both [NH₃] and [HNO₃], presence of coarse nitrate particles and low-temperature and high-humidity conditions.     

氢氧化铝胶体对2,2′,4,4′-四溴联苯醚的吸附

溴代阻燃剂多溴联苯醚(polybrominated diphenyl ethers,PBDEs)是一种被广泛使用的阻燃剂,其对神经、甲状腺、肝脏等具有潜在毒性。其中,2,2′,4,4′-四溴联苯醚(BDE-47)作为一种重要单体,在环境介质中被广泛检出。胶体是环境中污染物迁移过程中的重要载体,它对有机污染物在土壤-地下水系统中的迁移有不可忽略的影响。开展典型无机胶体氢氧化铝胶体对BDE-47的吸附动力学和吸附热力学研究,以期为BDE-47在土壤-地下水中的迁移提供理论依据。结果表明:Sips等温吸附方程对该吸附过程拟合效果最佳(R_(adj)~2=0.943 94),计算得出氢氧化铝胶体对BDE-47的饱和吸附量为609.37 mg·g~(-1);吸附动力学实验结果显示,准二级反应动力学方程拟合氢氧化铝胶体对BDE-47吸附反应过程最佳(R_(adj)~20.95),同时该吸附反应速率随BDE-47浓度的升高逐渐减小;Van't Hoff方程拟合表明,吸附热力学参数标准反应焓变△H~0=40.506 kJ·mol~(-1)、标准反应熵变△S~0=0.075 7 kJ·(mol·K)~(-1),标准反应吉布斯自由能△G~0(298 K)=17.98 kJ·mol~(-1)。此外,反应体系的pH和阳离子种类及浓度均会影响氢氧化铝胶体对BDE-47的吸附过程。     

Eddy flux measurements of methane over the fen “Murnauer Moos”, 11°11′E, 47°39′N,using a fast tunable diode laser spectrometer

Eddy covariance measurements of methane were carried out over the fen “Murnauer Moos” in the south of Germany in order to evaluate the performance of a newly developed eddy covariance measurement system, based on a frequency-modulated tunable diode laser spectrometer as a fast chemical sensor. During a six-day period, an average daytime methane emission of (5.4±1.8) mg CH₄ m⁻² h⁻¹ was measured. We find this value moderate, considering the favorable meteorological and soil conditions for methane emission. Diurnal cycles of the fluxes of methane and carbon dioxide as well as of sensible and latent heat are presented. Results are discussed in terms of relevant micrometeorological quantities, and quality control procedures based on Allan variance and spectral analysis are discussed.