Material transport between the atmosphere and sediment of the Lake Balaton

A monitoring system was developed to gain information on the present level of pollutants in the Lake Balaton, Hungary. Determination of 13 polycyclic aromatic hydrocarbons (PAHs) and inorganic pollutants (mostly toxic metals) in aerosol, precipitation and sediment samples was carried out. The aim of collecting aerosol and precipitate samples in the same site at the same period was to determine the distribution of elements in two depositions. For the fractionation by particle size, aerosols were sampled by a cascade impactor. A simple three-stage sequential leaching procedure was applied to establish the distribution of metals among environmentally mobile, bound to carbonates and oxides, and environmentally immobile, (bound to silicates) fractions in aerosols. Sediment samples were collected from 17 different sites inside of the lake and 10 sites at harbors at 30–70 cm in depth. Core samples were cut to 10-cm pieces, dried at room temperature, and finally passed through a 63-μm sieve. Total concentrations of elements were determined by atomic absorption spectrometry (AAS) after an acidic digestion. The concentrations of PAHs were determined by HPLC method with fluorescence detection.In aerosol samples collected from September 6, 2002 to January 26, 2003, concentration of Cd was <0.1 μg/m³, and the majority of Cd has been found in the mobile fraction. Cadmium was associated to particles between 0.25 and 2 μm indicating the anthropogenic origin. Similar distribution of Pb was obtained in all seasons, and the highest concentration of Pb was found as 8.6 ng/m³ in particle size of 0.7 and 1.4 μm. Results of total concentration of elements of bottom sediments of the Lake Balaton and harbors were compared to Interim Sediment Quality Guideline (ISQG) values and the Probable Effect Level (PEL) values. Data showed that the average concentrations of elements were usually less than those of ISQGs and other background data for soils and geochemical values. The sediment is not polluted and its disposal is feasible. There is no direct correlation between the concentration of elements deposited onto the surface of the lake from dry and wet deposition and the upper part of the sediment. So, from the budget of the deposition, the concentration of elements in the upper layer of the sediment cannot be predicted.Seasonal changes of the concentration of PAHs in aerosol was observed, samples collected at winter contained the highest values. In December–January 2002/2003, the wet deposition was found as 64 μg/m² period. Among the individual compounds, the wet deposition rate of phenantrane, fluoranthene and pyrene was dominant, while for dry deposition, these compounds were fluoranthene and pyrene. The concentrations of ∑PAHs found for all sites and depth of sediment samples ranged from 11 to 1734 μg/kg dry weight with an average of 132 μg/kg. These values represent a quite low pollution level compared to other sediment with anthropogenic influence. Based on the results, it can be definitely confirmed that the chemical quality of the water and sediment of the Lake Balaton is satisfactory.     

Simplified procedures for the analysis of polycyclic aromatic hydrocarbons in water, sediments and mussels

We describe in this paper simple and robust analytical protocols to determine the 16 polycyclic aromatic hydrocarbons (PAHs) of the US Environmental Protection Agency priority list in water, sediment and mussels. For water samples, eight different solid-phase extraction (SPE) sorbents have been compared and among them, C18 provided highest recoveries and limits of detection of 0.3-15 ng/L. For lyophilized sediments, Soxhlet and ultrasonic extraction were compared, and the last one permitted to recover all analytes with highest repetitivity and was validated by analysing a certified reference material. Finally, the analysis of mussels was undertaken using Soxhlet, ultrasonic and pressurized liquid extraction (PLE) and the performance of several clean-up steps are compared. Whereas for the former two, incomplete recovery or losses of some analytes were evidenced, PLE permitted a more efficient extraction and although alkaline digestion was necessary to remove coextracted compounds, the method gave acceptable recoveries and limits of detection of 0.5-7.7 microg/kg dry mass, as for sediments. In all cases, analysis was performed by gas chromatography coupled to mass spectrometry and internal standard quantification was performed using five deuterated PAHs. Each method performance is discussed for the three matrices analysed and the paper reports advantages and disadvantages of each for their routine application in monitoring programs.     

Multidimensional separation of isomeric species of chlorinated hydrocarbons such as PCB,PCDD, and PCDF

A multidimensional GC-system containing two capillary columns of different polarities, operated within a double oven instrument, was used for the optimized separation of complex isomeric mixtures of various types of chlorinated aromatic compounds such as PCB, PCDD, or PCDF. Electron capture was applied parallel to flame ionization detection to obtain sensitive signals of the PCB or PCDD and the n-alkane standards required for identification by Kovats indices, respectively. Electron capture detection within a valvelessly operated MDGC system forced changes in the usual instrumental set-up, the live-switching coupling piece being located within the second oven of the double oven instrument. This oven is operated isothermally to ensure optimal and interference-free detection, for stable flow conditions within the coupling piece and for the determination of the isothermal retention indices (Kovats), which are much more suitable for identification by retention than the so-called “linear” indices.     

Fluorescence optosensor using an artificial neural network for screening of polycyclic aromatic hydrocarbons

This paper presents an optosensor for screening of four polycyclic aromatic hydrocarbons: anthracene (ANT), benzo[a]pyrene (BaP), fluoranthene (FLT), and benzo[b]fluoranthene (Bbf) using a photomultiplier device with an artificial neural network as transducer. The optosensor is based on the on-line immobilization on a non-ionic resin (Amberlite XAD-4) solid support in a continuous flow. The determination was performed in 15 mM H₂PO₄⁻/HPO₄²⁻ buffer solution at pH 7 and 25% of 1,4-dioxane. Feed forward neural networks (multiplayer perceptron) have been trained to quantify the considered Polycyclic aromatic hydrocarbons (PAHs) in mixtures under optimal conditions. The optosensor proposed was also applied satisfactorily to the determination of the considered PAHs in water samples in presence of the other 12 EPA–PAHs.     

Gas chromatographic-mass spectrometric determination of polycyclic aromatic hydrocarbons formed during the pyrolysis of phenylalanine

The formation of polycyclic aromatic hydrocarbons (PAHs) during pyrolysis process of phenylalanine had been studied. Ten PAHs, including fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[k]fluoranthene, benzo[e]pyrene, and benzo[a]pyrene were analyzed by gas chromatography-mass spectrometry using selective ion monitoring mode. This technique offers the capability to analyze trace amounts of PAHs in phenylalanine pyrolyzates. The pyrolysis was carried out in a micro-furnace with quartz furnace liner. The injection was conducted with glass pelletizer syringe to avoid metal contamination. Qualitative results were obtained at 900 degrees C and quantitative analysis of 10 PAHs was done for 700 and 900 degrees C.     

A Large Volume Injection Procedure for GC-MS Determination of PAHs and PCBs

A simple on-column injection system for large volume of liquid samples for the GC-MS determination of traces of PAHs and PCBs has been investigated. A deactivated fused silica capillary 20 m × 0.53 mm I.D. and 2 meters of an HP5 column (0.53 mm,1 m film thickness) were used as retention gaps. Injection volumes of 80 L for PAHs and 90 L for PCBs, allow determination of 5–50 ng L^–1 PAHs and 11–44 ng L^–1 PCBs in hexane solution with an RSD of < 10%. The method has been used for the determination of PCBs and PAHs in soil sample.     

大气压旋转螺旋状电极辉光放电等离子体催化甲烷偶联

采用新研制的具有旋转螺旋状电极的大气压辉光放电等离子体反应器催化甲烷偶联制碳二烃. 实验采用铜电极和不锈钢电极分别考察了输入电场峰值电压和甲烷、氢气进料流量等参数对甲烷转化率和碳二烃收率、选择性的影响. 在长时间连续反应无明显积碳的情况下, 最佳试验结果是电极材料为金属铜, 进料流量为60 mL•min^-1, V(CH₄ )/V(H₂)=1的条件下, 输入电场峰值电压为2.3 kV时, 甲烷转化率为70.64%, 碳二烃单程收率及其选择性分别为69.85%和 99.14%.     

吹扫-捕集气相色谱法测定水中挥发性卤代烃

研究建立了吹扫 捕集法富集样品 ,利用HP 1大口径厚液膜通用型熔融石英毛细管柱 (30m× 0 .5 3mm×2 .6 5 μm) ,ECD检测器 ,测定水中 10种挥发性卤代烃的方法 ,确定了最佳吹扫 捕集条件 .结果表明 :水样体积为 5mL时 ,标准偏差在 0 .0 2～ 0 .0 7μg L之间 ,变异系数在 1.0 9%～ 3.2 8%之间 ,加标回收率为 94.0 %～ 10 7%之间 ,10种物质的检出限在 0 .0 7～ 0 .19μg L之间     

C4/C5烃催化裂解制低碳烯烃的研究进展

从催化剂类型、裂解工艺、催化裂解的影响因素和裂解机理4个方面对国内外C4／C5烃催化裂解制低碳烯烃的研究进行了综述。催化裂解制低碳烯烃催化剂主要采用ZSM-5分子筛系列催化剂，在此基础上发展了酸改性或水热改性高硅ZSM系列分子筛及介孔MCM41分子筛。总结了国内外C4／C5烃的裂解工艺，认为影响催化裂解的主要因素是裂解原料、催化剂类型及工艺条件。目前，裂解机理主要是自由基与碳正离子机理相结合的机理。并简述了本课题组目前有关C4烷烃催化裂解的主要研究进展。