The seasonal changes in the concentration of polycyclic aromatic hydrocarbons in precipitation and aerosol near Lake Balaton, Hungary.

The concentration of polycyclic aromatic hydrocarbons (PAHs) in atmospheric precipitation and aerosol samples was monitored in a rural site by Lake Balaton, Hungary to examine the seasonal variation. The seasonal mean concentration of individual 3-6-ring PAHs in precipitation varied from 1 to 54 ng l-1 and from 3 to 350 ng l-1 in summer and winter, respectively. In the atmospheric aerosol samples the seasonal mean concentration of PAHs varied from 4 to 880 pg m-3, from 4 to 300 pg m-3, from 11 to 1050 pg m-3 and from 36 to 5000 pg m-3 in spring, summer, autumn and winter, respectively. Wet (412 micrograms m-2 year-1) and aerosol (190-300 micrograms m2 year-1) deposition rates were also estimated indicating that the two processes are of comparable importance in the removal of 3-6-ring PAHs from the atmosphere.

Monitoring of the natural environment by chemical speciation of elements in aerosol and sediment samples.

The development of a monitoring network for chemical speciation of elements of aerosol and sediment samples collected at Lake Balaton has been carried out. Sequential leaching procedures for the determination of the distribution of elements in aerosols (3 steps) and sediments (4 steps) were used. These methods were recently successfully applied to describe environmentally mobile and stable fractions of toxic metals. In aerosol matrices the partition of elements was accomplished by particle size and chemical bonding. In sediments the distribution was performed by chemical bonding. The processes are called fractionation of elements. Particular attention was paid to distinguishing between environmentally mobile and environmentally immobile fractions because these represent the two extreme modes by which the metals are bound to solid matrices. The monitoring objectives were to assess pollution effects on man and his environment and to identify any possible cause and effect relationship between pollutant concentrations and health effects. The results of dry and wet deposition rates showed that most of the toxic metals were dissolved in an aqueous phase and the wet deposition played an important role. It has been found that, while the concentration of Cd and Pb in aerosols is low (0.7 and 29 ng m(-3), respectively), environmentally mobile fractions are considerable. Based upon the data it can be concluded that the effect of the anthropogenic sources on the quality of the lake is minor. This has been the first attempt to correlate speciation results between aerosols and sediments.

Theoretical approach to non-constant uptake rates for tube-type diffusive samplers.

A simple theoretical model was developed for evaluating the validity of the simplified uptake model of diffusive sampling. In the model based on the plate theory diffusion to the adsorbent surface, phase equilibrium of the adsorbate and mass transport in the adsorbent bed were considered. It was found that in the early stage of sampling, the rate of sampling is close to its theoretical value. As sampling progresses, the concentration increases and the mass transfer front gradually moves into the adsorbent layer. Above a certain threshold limit, the mass uptake becomes a steady state process in which the diffusion in the air gap and the mass transport in the adsorbent bed are balanced. As uptake is a cumulative process, sampling should continue long enough to render the effects of these initial changes negligible. That is why constant uptake rates can still be obtained above a critical exposure dose. This critical exposure dose should be exceeded both in the determination of uptake rates and outdoor measurements, to obtain consistent and reliable analytical data. Evaluation of the time and concentration dependence of uptake rate in laboratory experiments and the time dependence of uptake rate in filed test was performed to justify the model results. Since the determination of uptake rates always takes places in the laboratory, where the exposure time is much shorter and the concentration is much higher than in the environment, the uptake rates are thus overestimated by 10-30%. Therefore, the uptake rates should be determined in the field under ambient conditions by means of an independent reference method.

Chemical fractionation of a fly ash sample by a sequential leaching method.

A five-stage sequential leaching procedure was optimized for the analysis of the fly ash sample, CW6, as a candidate reference material. The distribution of particulate elements was achieved for Cd, Cr, Cu, Pb, Zn, and V into different fractions: (1) exchangeable, (2) bound to carbonate, (3) bound to Fe/Mn oxides, (4) bound to sulfide compounds, and (5) acid soluble, residual fraction. The leachability of the metals proved to be different, so various distribution patterns have been achieved. The results of the total elemental analysis and the sequential leaching method were compared and a good agreement was found. The uncertainty of the leaching method is reasonable, even when experimental parameters are strictly fixed and the analysis is quite tedious. The ratio of environmentally mobile fractions was compared to that from the conventional test method and a reasonable conformity has been found. This characterization method can be used to interpret the leaching behavior of element species and mode of binding to the matrix. Using the optimized sequential procedure, a new aspect can be interpreted to understand the behavior of toxic elements released from fly ashes into nature.

Development of a monitoring network for the analysis of elements in aerosol samples collected at Lake Balaton.

Determination of different toxic elements in aerosol and precipitation samples collected at Lake Balaton were carried out. A simple sequential leaching procedure was applied for the determination of the distribution of elements. The distribution of elements was determined among environmentally mobile, bound to carbonates and oxides, and bound to silicates and organic matters (environmentally immobile) fractions. Particular attention was paid to distinguish between environmentally mobile and environmentally immobile fractions because these represent the two extreme modes by which the metals are bound to the solid matrices. Aerosol samples were weekly collected in Tihany, Siófok and Keszthely on 5 cm diameter Teflon filters with a membrane pump. While Cd-compounds have been found enormously in the environmentally mobile fractions, As-compounds accumulated almost evenly among portions. The results of sequential leaching give an indication of the mobility of the elements once the aerosol is mixed directly into natural waters on during scavenging of the aerosol by wet deposition. Based upon the data it can be concluded that the effect of anthropogenic sources is minor in this area.

Electrokinetic injection in capillary electrophoresis and its application to the analysis of inorganic compounds.

In capillary electrophoresis, electrokinetic injection is a highly controversial sampling technique. It is a simple mode of sample introduction which is suitable for on-line preconcentration of the analytes, but its precision and accuracy are more strongly affected by experimental conditions compared to hydrodynamic injection. In the first part of this paper the features of electrokinetic and hydrodynamic injections are compared, followed by a detailed discussion on the different biases of electrokinetic injection and on how to reduce them. Finally, applications of the electrokinetic injection are reviewed with special emphasis on the analysis of inorganic compounds.

Sample preparation of atmospheric aerosol for the determination of carbonyl compounds.

Sample preparation including sonication and solid phase extraction has been developed for the determination of carbonyl compounds in atmospheric aerosol. Aerosol samples were sonicated in acidified acetonitrile containing 2,4-dinitrophenylhydrazine (DNPH) to form hydrazone derivatives of aldehydes and ketones. Water was added to the extract to increase its polarity. Then the solution was passed through an octadecyl or phenyl solid phase extraction cartridge. The concentrated hydrazone derivatives were eluted with tetrahydrofuran, the eluate was evaporated to dryness then dissolved in acetonitrile/water mixture and finally analysed by RP-HPLC with UV detection at 360 nm. The absolute detection limits of the individual carbonyl compounds range from 0.4 to 5.8 ng.

Application of an artificial neural network (ANN) and piezoelectric chemical sensor array for identification of volatile organic compounds.

A piezoelectric chemical sensor array was developed using four quartz crystals. Gas chromatographic stationary phases were used as sensing materials and the array was connected to an artificial neural network (ANN). The application of the ANN method proved to be particularly advantageous if the measured property (mass, concentration, etc.) should not be connected exactly to the signal of the transducers of the piezoelectric sensor. The optimum structure of neural network was determined by a trial and error method. Different structures were tried with several neurons in the hidden layer and the total error was calculated. The optimum values of primary weight factors, learning rate (eta=0.15), momentum term (mu=0.9), and the sigmoid parameter (beta=1) were determined. Finally, three hidden neurons and 900 training cycles were applied. After the teaching process the network was used for identification of taught analytes (acetone, benzene, chloroform, pentane). Mixtures of organic compounds were also analysed and the ANN method proved to be a reliable way of differentiating the sensing materials and identifying the volatile compounds.

Comparison of calibration methods in quantitative diffuse reflectance infrared spectroscopy.

Four different calibration methods were used for quantitative analysis of quartz and calcite in atmospheric aerosols by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS): (A) conventional calibration with one measurement on each standard (single calibration); (B) calibration with an internal standard; (C) calibration with parallel (n = 4) measurements on each standard (multiple calibration); (D) multiple calibration followed by reference reflectance correction. The accuracy and the precision of the methods were compared and it was found that by using method D the reliability of the conventional pellet preparation transmission technique can be achieved.

Application of pattern recognition and piezoelectric sensor array for the detection of organic compounds.

Organic vapours were measured by an array of piezoelectric crystal detectors. Quartz crystals were coated by different GC stationary phases. Four coated crystals were placed in an array and pattern recognition was used for identification of the compounds including acetone, benzene, chloroform and pentane. A computer program was developed for the measurement of the frequency changes and data processing. Pattern recognition method using feature extraction was applied for identification of analytes.

The evaluation of a tenax GR diffusive sampler for the determination of benzene and other volatile aromatics in outdoor air.

The applicability of a tube-type diffusive sampler as an environmental monitor for benzene, toluene, ethylbenzene and xylene (BTEX) is reported. Uptake rates have been experimentally determined for a novel type adsorbent, Tenax GR, and compared to theoretical values. It is shown, that the uptake rates are virtually independent of environmental parameters within the experimental conditions studied. The response of the sampler to transient changes in concentrations has been determined in the laboratory. It is found that the sampler is capable of following an extreme concentration profile. Field comparisons with pumped samplers have been performed and good agreement is observed between the results of the two independent methods. The samplers have also been applied as environmental monitors at different locations.

Effect of sample packing on the scattering properties of the reference material in diffuse reflectance infrared spectrometry.

Effect of the sample packing on the scattering properties of KBr, one of the most conventional matrix used in diffuse reflectance Fourier transform infrared (IR) spectrometry (DRIFTS), has been studied. The particle size of KBr ranged between 2 and 15 mum with a mean of 9.9 mum. The average particle size of quartz and calcite used as analytes were 2 mum and 6 mum, respectively. The scattering coefficient of KBr has been found to increase with increasing pressure applied during sample packing. 1 MPa pressure was necessary for reproducible scattering properties and quantitative results. The scattering coefficient of KBr using 1 MPa pressure for 1 min during sample packing has been determined from calibration curves and found to be as s = 107 +/- 11 cm(-1). It has been experimentally demonstrated that using 2 mm deep sample cups, the criteria of infinite sample thickness is practically fulfilled. It has been also shown that band intensities of reflectance spectra were strongly influenced by the change of the reflectance of the reference material and the less the sample concentration (c) the greater the effect. If c < 0.1 w/w%, that often occurs in practice, the RSD of band intensities can vary upto +/- 10-60%. Therefore, in quantitative analysis all spectra should be measured against one and same sample of reference material.

Determination of chemical species of selected trace elements in fly ash.

Complex analytical methods have been developed for determining the chemical composition of fly ashes. Samples were collected at coal-fired power plants and municipal waste incinerators. Morphological investigations and single particle analysis were performed by SEM/EDAX method. A survey of mineralogical phases was made by X-ray powder diffraction and infrared spectrometry. Solvent-leaching experiments were carried out for the information on the mobility of metal pollutants under real environmental conditions. Copper, Ni, Co, Cr, Pb and Cd have been studied, and of the toxic metals, Cd has been found in exchangeable forms in a great amount. Mobile species of toxic metals may have an impact on the quality of receiving waters or on organisms in soils.

Determination of the total dissolved sulphide in the pH range 3-11.4 with sulphide selective ISE and Ag/A92S electrodes.

An electrochemical method for the determination of the total sulphide concentration of sewage water samples has been studied using a potentiometric cell containing either a sulphide ion selective ISE-glass electrode pair or a Ag/Ag(2)S electrode-glass electrode system. The performance of the two sulphide ion sensors was investigated and compared in both acidic and basic pH ranges. It was proved that the cell potential can be made directly proportional to the logarithm of the total sulphide concentration when both the pH < lg K(2) - 1.5 condition (acidic range) and also when the lg K(2) + 1.5 < pH < lg K(1) - 1.5 condition prevails in the system (alkaline range); where K(1) and K(2) are the first and second protonation constants of the sulphide ion, respectively. A suitable calibration method for a wide range of sulphide concentration is also presented for both ranges of the pH scale. The overall performance of the measuring system was tested using model solutions and real waste water samples.

Fibre-optic biosensor for hypoxanthine and xanthine based on a chemiluminescence reaction.

Fibre-optic biosensors were constructed for determination of hypoxanthine and xanthine. Xanthine oxidase and peroxidase were immobilized on different preactivated membranes which were subsequently mounted onto the tip of a fibre-optic bundle. The H2O2 generated by the reaction of hypoxanthine and xanthine oxidase was measured by chemiluminescence (CL) detection using luminol and peroxidase. A linear calibration curve of the sensors in the range of 1-316 microM hypoxanthine and 3.1-316 microM xanthine, respectively, with a detection limit of 0.55 microM hypoxanthine was obtained. Recovery of hypoxanthine ranged between 91 and 102%.