Study of partitioning and dynamics of metals in contaminated soil using modified four-step BCR sequential extraction procedure

The modified four-step BCR sequential extraction procedure (exchangeable and weak acid available species, reducible, oxidisable and residual fractions) was used to examine the distribution of As, Cd, Cr, Cu, Pb, and Zn with soil depth in an area (Baia Mare — Bozanta, Romania) with both high natural level of elements considered as toxic and historical pollution resulting from nonferrous metallurgy. The BCR approach proved a high metal input of anthropogenic origin down to 40 cm, while at lower depths the naturally elevated metal content must be considered. Results of the partitioning study and XRD analysis of solid matrix showed the greatest potential for chemical remobilisation of Cd, Zn, and Cu in weak acidic medium as well as their affinity for the oxidisable fraction (organic matter/sulphide). The tendency of Cr, Pb, and As to be immobilised as residual or reducible species on Fe-Mn oxides was evident. Although the partitioning of As in chemically inactive forms such as scorodite (FeAsO₄ · 2H₂O) soluble under reducible conditions and beudantite (PbFe₃(AsO₄)(SO₄)(OH)₂)), a residual species soluble in acid media, chemical mobilisation from soil in groundwater was confirmed. Dynamic processes of metal retention in soil under different conditions, namely acidic, reducing or oxidisable, were predicted from the Pearsonșs correlation analysis of element species with soil characteristics and components such as Fe, Mn, organic matter content, pH, and total element content, respectively. At the moment of the study, soil and groundwater in the area were found to be polluted with As, Cd, Cu, Pb and Zn. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Photovoltaic properties of sputtered silicon films

The photovoltaic properties of several 1 μm thick films of rf-sputtered amorphous Si (a-Si) sandwiched between lower Al electrodes and upper semitransparent Mo or Al electrodes have been investigated. After fabrication, the Al–Si–Al samples were annealed in vacuum at temperatures between 100 and 450°C. The spectral variation of the photoresponse in the wavelength region between 300 nm and 2 μm was measured. The results indicate that the optical gap of a-Si is 1.5 eV and the Schottky barrier height at the Al–a-Si interface is 0.75 eV. the current-voltage characteristics of these Schottky-type devices were investigated under illumination. Photovoltaic energy conversion efficiencies of up to 0.03% were observed for the 100 mW/cm² white light of a tungsten-halogen lamp.     

Disorientated optical polarization devices

By using a pure operatorial (nonmatrix) approach to some of the variable composite polarization devices, we show that for some values of the variable internal parameters, these devices lose their anisotropy. Their principal axes, or more generally their eigenvectors, become undetermined, i.e., in this sense, the anisotropic devices get "disorientated."     

Experimental investigation on the sound pressure level for a high thermal capacity burner during a running cycle

In many research or technical expertise studies the maximum noise level of a boiler is associated with the maximum thermal load of the burner. However, this type of air injected burners presents a complex running cycle with different functioning periods, where different parts (engine, fan, flame) of the burner are running separately or in the same time. In this study we are focused on the analysis, by experimental measurements, of the entire functioning cycle of a boiler by pointing out the noise differences and their importance when doing an experimental acoustical investigation. The entire 1/3 octave spectrum of the sound pressure level (SPL) was recorded during a complete running cycle by means of logging software associated to the sound meter. The sound equivalent level was calculated for each period of the running cycle and compared to the norms and with two theoretical prediction models that take into account the heating power and the boiler room volume. It was found that the most accurate data are obtained when the measurements are done in one-third octave. The maximum noise level was established to be not for the maximum thermal load period, but for the ventilation period of the boiler (before gas injection) with 82.1 dB at 125 Hz. A shut down delay was detected at the end of the cycle with 13 s for higher frequencies, due to the vibration of the boiler parts. Two 3D graphical representations point out the most important frequencies characterizing each running state of the burner. Compared to the noise curve (NC85) the minimum differences between the admissible values and the ones produced by the burner were found to be around 5.5 dB and therefore no acoustical treatment was needed. The results of the SPL prediction models matched the experimental data only for some of the boiler cycle periods and for only some of the frequencies. This type of detailed experiment investigation of the burner noise highlights the periods of the running cycle and the frequencies where the noise level requires acoustical treatment.     

Quasi-Schreier Domains II

We study a class of integral domains characterized by the property that every nonzero finite intersection of principal ideals is a directed union of invertible ideals.     

LCM-splitting sets in some ring extensions

Let be a saturated multiplicative set of an integral domain . Call an lcm splitting set if and are principal ideals for every and . We show that if is an -stable overring of (that is, if whenever and is principal, it follows that and if is an lcm splitting set of , then the saturation of in is an lcm splitting set in . Consequently, if is Noetherian and is a (nonzero) prime element, then is also a prime element of the integral closure of . Also, if is Noetherian, is generated by prime elements of and if the integral closure of is a UFD, then so is the integral closure of .

     

Theoretical analysis of output statistics of Er3+:Ti:LiNbO3 M-mode straight waveguide amplifiers

In this paper we present a theoretical analysis of some statistical parameters which characterize the Er³⁺-doped Ti:LiNbO₃ M-mode straight waveguides. The derivation and the evaluation of the spectral optical gain, the spectral noise figure, the Fano factor, the statistical fluctuation and the spontaneous emission factor are performed under the small gain approximation. The simulations show the evolution of these parameters under various pump regimes and waveguide lengths. The obtained results can be used for the design of complex rare earth doped integrated circuits.     

Some remarks concerning unique continuation for the Dirac operator

We show that the strong unique continuation property for the Dirac operator holds if the potential belongs toL ^p withp = max(d,(3d – 4)/2).     

Mercury speciation in fish tissue by eco-scale thermal decomposition atomic absorption spectrometry: method validation and risk exposure to methylmercury

A non-chromatographic method for Hg speciation in fish muscle using eco-scale thermal desorption atomic absorption spectrometry was validated according to the demands of the Decisions 2007/333/EC, 2011/836/EC and 2002/657/EC. The method is based on the determination of total Hg in solid sample and MeHg⁺, respectively, after double liquid–liquid extraction (47% HBr, toluene, 1% l-cysteine) according to a procedure recommended by the European Commission. The method was applied for the speciation of Hg in fish muscle to asses the weekly intake and health risk exposure to MeHg⁺. The method provided calibration coefficients better than 0.999, limits of detection of 0.2 µg kg^?1 total Hg and 3.0 µg kg^?1 MeHg⁺. The accuracy of the method assessed by the analysis of CRMs was 100 ± 9% for total Hg and 101 ± 13% for MeHg⁺ for a coverage factor k = 2. The figures of merit of the method comply with the requirements in the European legislation. Total Hg in the analyzed fish species was in the range 12–108 µg kg^?1 wet mass, of which 83–97% as MeHg⁺. Although significant variation in total Hg was observed among fish species, no differences in terms of distribution of organic and inorganic Hg species were identified. No risk exposure to MeHg⁺ was ascertained from muscle fish consumption from reliable sources, since weekly intake was below 30% of provisional tolerable weekly intake of 1.6 µg kg^?1 body weight. Speciation is recommended as MeHg⁺ is much more helpful than total Hg to evaluate the dietary risk exposure.