Volatilization behavior of lead from molten slag under conditions simulating municipal solid waste melting

To reutilize molten slag derived from an ash melting process, the lead volatilization mechanism under reducing conditions was investigated. Reducing conditions were established by introducing a CO-CO₂-N₂ gas mixture to the reactor or by adding graphite to the molten slag prior to the experiments. As samples, two types of simulated molten slag composed of CaO-SiO₂-Al₂O₃ mixed with PbO were used and the lead volatilization behavior was studied at 1773 K. It was found that the lead volatilization rate increased on increasing the amount of reducing agent for both graphite and the CO-CO₂ gas mixture. For the CO-CO₂ reducing gas mixture, this increase was mainly attributed to PbO conversion to Pb. For the addition of graphite, the increase in lead volatilization ratio was considered to partially result from PbO conversion to Pb and partially from a reaction of graphite with SiO₂ yielding volatile SiO. The volatile SiO gas was then emitted from the furnace, which brought about a reduction in the SiO₂ content of the slag. As a result, the slag viscosity decreased, which led to an enhancement of the lead volatilization ratio.     

Mathematical prediction of imidacloprid persistence in two Croatian soils with different texture,organic matter content and acidity under laboratory conditions

In the present laboratory study, persistence of imidacloprid (IMI) as a function of initial insecticide concentration and soil properties in two Croatian soils (Krk sandy clay and Istria clay soils) was studied and described mathematically. Upon fitting the obtained experimental data for the higher concentration level (5 mg/kg) to mathematical models, statistical parameters (R ², scaled root mean squared error and χ ² error) indicated that the single first-order kinetics model provided the best prediction of IMI degradation in the Krk sandy clay soil, while in the Istria clay soil biphasic degradation was observed. At the lower concentration level (0.5 mg/kg), the biphasic models Gustafson and Holden models as well as the first-order double exponential model fitted the best experimental data in both soils. The disappearance time (DT₅₀) values estimated by the single first-order double exponential model (from 50 to 132 days) proved that IMI can be categorized as a moderately persistent pesticide. In the Krk sandy clay soil, resulting DT₅₀ values tended to increase with an increase of initial IMI concentration, while in the Istria clay soil, IMI persistence did not depend on the concentration. Organic matter of both experimental soils provided an accelerating effect on the degradation rate. The logistic model demonstrated that the effect of microbial activity was not the most important parameter for the biodegradation of IMI in the Istria clay soil, where IMI degradation could be dominated by chemical processes, such as chemical hydrolysis. The results pointed that mathematical modeling could be considered as the most convenient tool for predicting IMI persistence and contributes to the establishment of adequate monitoring of IMI residues in contaminated soil. Furthermore, IMI usage should be strictly controlled, especially in soils with low organic matter content where the risk of soil and groundwater contamination is much higher due to its longer persistence and consequent leaching and/or moving from soil surface prior to its degradation.     

Paramagnetic antibody-modified microparticles coupled with voltammetry as a tool for isolation and detection of metallothionen as a bioindicator of metal pollution

Low-molecular mass proteins rich in cysteines called metallothioneins (MT) can be considered as markers for the pollution of the environment by metals. Here, we report on suggestion for an automated procedure for the isolation of MT followed by voltammetric analysis. Primarily, we optimized the automated detection of MT using an electrochemical analyser. It was found that the most sensitive and repeatable analyses are obtained at a temperature of 4 °C for the supporting electrolyte. Further, we optimized experimental conditions for the isolation of MT by using antibody-linked paramagnetic microparticles. Under the optimal conditions (4 h long interaction between the microparticles and MT), the microparticles were tested on isolation of various amounts of MT. The lowest isolated amount of MT by antibody-linked paramagnetic microparticles was 5 μg ml(-1) of MT (50 ng). The automated procedure of MT isolation was further tested on isolation of MT from guppy fish (Poecilia reticulata) treated with silver(i) ions (50 μM AgNO(3)). The whole process lasted less than five hours and was fully automated. We attempted to correlate these results with the standard method for MT isolation. The correlation coefficient is 0.9901, which confirms that results are in good agreement. Moreover, the concentration of silver ions in tissues of fish treated with Ag(i) ions was determined by high performance liquid chromatography with electrochemical detection.     

Reductive decomposition of waste gypsum with SiO<Subscript>2</Subscript>, Al<Subscript>2</Subscript>O<Subscript>3</Subscript>, and Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> additives

From the point of view of a sustainable and environment-friendly society based on the recycling of material resources, it is preferable to utilize waste gypsum as a substitute for lime, which is currently produced by the calcination of limestone. In the present work, the reductive decomposition of CaSO₄ was investigated under an atmosphere of CO: 2 vol%, CO₂: 30 vol%, with N₂ as a carrier gas without and with the addition of SiO₂, Al₂O₃, or Fe₂O₃. It was found that the decomposition temperature of CaSO₄ was significantly reduced from 1673 K to 1223 K when only 5 wt% Fe₂O₃ was added to CaSO₄. In the case of the addition of SiO₂ or Al₂O₃ to CaSO₄, the decomposition temperature was reduced from 1673 K to 1623 K. This was due to the formation of composite oxides (calcium ferrite, calcium silicate, or calcium aluminate) during the reaction of CaSO₄ with the additives at a lower temperature. In addition, the formation of unfavorable product CaS was inhibited in the presence of 5 wt% Fe₂O₃, and this inhibition effect further increased as the addition of Fe₂O₃ was increased. In contrast, no significant effect on the inhibition of CaS formation was observed on the addition of SiO₂ or Al₂O₃.     

Ozone flux over a Norway spruce forest and correlation with net ecosystem production

Daily ozone deposition flux to a Norway spruce forest in Czech Republic was measured using the gradient method in July and August 2008. Results were in good agreement with a deposition flux model. The mean daily stomatal uptake of ozone was around 47% of total deposition. Average deposition velocity was 0.39 cm s⁻¹ and 0.36 cm s⁻¹ by the gradient method and the deposition model, respectively. Measured and modelled non-stomatal uptake was around 0.2 cm s⁻¹. In addition, net ecosystem production (NEP) was measured by using Eddy Covariance and correlations with O₃ concentrations at 15 m a.g.l., total deposition and stomatal uptake were tested. Total deposition and stomatal uptake of ozone significantly decreased NEP, especially by high intensities of solar radiation.     

Lead,cadmium and mercury contents and bioaccumulation potential of wild edible saprophytic and ectomycorrhizal mushrooms,Croatia

ABSTRACT

Lead (Pb), cadmium (Cd), and mercury (Hg) contents in ten species of edible mushrooms in Trako??an, Croatia were determined. In addition, the similarity between the studied species was determined by cluster analysis. The caps and stipes of the fruiting bodies were analysed separately. The analyses were carried out by inductively coupled plasma - optical emission spectrometry (ICP-OES). The greatest mean lead concentrations of 1.91 and 1.60 mg kg ^?1 were determined in caps and stipes of Macrolepiota procera. The greatest mean concentrations of cadmium (3.23 and 2.24 mg kg^?1) were determined in caps and stipes of Agaricus campestris and of mercury (2.56 and 2.35 mg kg^?1) in Boletus edulis. In terms of the anatomical parts of the fruiting body (cap-stipe), a considerably greater concentration of the analysed elements was found in the cap for all mushroom species. According to calculated bio-concentration factors, all the examined species were found to be bio-accumulators of Cd and Hg. On the basis of the accumulation of the studied metals, great similarity of mushroom species belonging to the same genus and partial similarity of species of the same ecological affiliation was obtained by cluster analysis.     

Effects of temperature on sorption-desorption processes of imidacloprid in soils of Croatian coastal regions

Sorption-desorption behavior of imidacloprid in six soils collected from five coastal regions in Croatia at 20, 30 and 40°C was investigated using batch equilibrium technique. Isothermal data were applied to Freundlich, Langmuir and Temkin equations, and the thermodynamic parameters ΔH°, ΔG°, ΔS° were calculated. The sorption isotherm curves were non-linear and may be classified as L-type, suggesting a relatively high sorption capacity for imidacloprid. Our results showed that the K ^sor _F values decreased for all the tested soils as the temperature increased, indicating that the temperature strongly influences the sorption. Values of ΔG° were negative (?4.65 to ?2.00 kJ/mol) indicating that at all experimental temperatures the interactions of imidacloprid with soils were spontaneous processes. The negative and small ΔH° values (?19.79 to ?8.89 kJ/mol) were in the range of weak forces, such as H-bonds, consistent with interactions and partitioning of the imidacloprid molecules into soil organic matter. The ΔS° values followed the range of ?57.12 to ?14.51 J/molK, suggesting that imidacloprid molecules lose entropy during transition from the solution phase to soil surface. It was found that imidacloprid desorption from soil was concentration and temperature-dependent, i.e. at lower imidacloprid concentrations and temperature, lower desorption percentage occurred. Desorption studies revealed that hysteretic behavior under different temperature treatments existed, and it was more pronounced at 20°C in the soils with higher OC content. The study results emphasize the importance of thermodynamic parameters in controlling soil pesticide mobility in different geographical locations, seasons and greenhouse conditions.