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Abstract

The main objective of the study was to evaluate if macrophytes structure and trophic status of dam reservoir Kraśnik on a small lowland river Wyżnica are determined by phosphorous loadings. Studies were conducted seasonally in May, July and October during the years 2008-2009. Samples were taken at four sites: Site 1 - inflow of the Wyżnica River to pre-dam, Site 2 − pre-dam, Site 3 − dam reservoir and Site 4 - outflow of the Wyżnica River from dam reservoir. Physical and chemical parameters (temperature, Secchi disc depth, dissolved oxygen, pH, conductivity, total suspension, chlorophyll-a, TP and P-PO4) were measured in water samples. Together with water parameters there were estimated biomass of phytoplankton and species composition and biomass of emergent, floating-leaved and submerged macrophytes. Concentrations of TP, chlorophyll-a and Secchi disc depth were used to calculate trophic state index of Carlsson for dam reservoir and its pre-dam. Based on mean water current, mean residence time of water in dam reservoir and concentrations of TP and P-PO4 loadings (g m-2) flowing into dam reservoir with the Wyżnica River were calculated. The results showed visible negative effect of phosphorous loadings on both macrophytes composition and trophic state of the reservoir. The marked changes concerned soft vegetation. High P loadings (7.74 g m-2 of TP and 6.03 g m-2 P-PO4) during the spring of 2008 caused the disappearance of characeans meadows. In 2009, the presence of rigid hornwort (Ceratophyllum demersum L.), the species typical for eutrophic lakes was noted. This unrooted submerged plant uptakes dissolved orthophosphates directly from the water column.

Values of Carlsson index (51.4 ≤ TSI ≤ 68.2) indicate the eutrophic state of dam reservoir Kraśnik. During summer season in dam reservoir there were observed algal blooms (biomass of phytoplankton exceed 10 mg WW dm-3) and low water transparency (Secchi disc depth ranged from 0.4 to 0.65 m). During the two-year studies in dam reservoir Kraśnik a high reduction of P loadings, mostly dissolved orthophosphates was observed. Dependently on season, reduction of P-PO4 loadings ranged from 52% (July 2008) up to 91% (May 2009). The reduction of TP was lower and reached values from 15% (May 2008) to 48% (July 2009).

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Authors and Affiliations

Monika Tarkowska-Kukuryk
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Abstract

Worldwide commercial interest in the production of cerium doped yttrium aluminium garnet (YAG:Ce) phosphors is reflected in the widespread use of white light emitting devices. Despite of the fact that YAG:Ce is considered a “cool phosphor” it is the most important in white LED technology. This article reviews the developed techniques for producing phosphors with superior photoluminescence efficiency, including solid-state reaction, sol-gel and (co)precipitation methods. Also, by co-doping with rare earth elements, a red/blue shift is reached in the spectrum. The characteristics of YAG:Ce phosphors are investigated because the properties of the phosphors are strongly influenced by the synthesis routes and the sintering temperature treatment. After the phase analysis, morphology and emission studies of the phosphors there may be seen the conditions when the transition from the amorphous phase to the crystalline phase appears, when luminescent properties are influenced by the crystalline form, purity, average size of the particles, co-doping and so on.

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Authors and Affiliations

V. Tucureanu
A. Matei
A.M. Avram
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Abstract

In zinc electrowinning, small amounts of manganese ions additives are needed in the electrolyte to reduce the corrosion of anodes and minimize the contamination of cathodic zinc by dissolved lead. However, excess manganese oxide could cover the dimensionally stable anodes (DSA) surface and decrease their service life. Additives of phosphoric acid are put in the electrolyte to complex the manganic Mn3+ ion and hence reduce its disproportionation to MnO2. In the investigation, phosphoric acid was added to sulfuric acid or zinc electrolytes, and conventional and recent electrochemical measurements were carried out to examine electrochemical behaviour of DSA (Ti/IrO2-Ta2O5) anode during zinc electrolysis at 48 mA/cm2 and 39°C. It was observed that the anodic potentials of DSA anodes were lower by 27 mV after 5 h polarization in the zinc electrolyte containing 35 g/L phosphoric acid at 39°C. Electrochemical impedance measurements show that the addition of 35 ml/L H3PO4 to the zinc electrolyte can increase impedance resistances of the DSA mesh anodes. Cyclic voltammogram studies (CV) at a scan rate of 5 mV/s without agitation show that the oxidation peak in the solution with 35 ml/L phosphoric acid addition is highest, followed by that with 17 ml/L phosphoric acid addition and that without addition of phosphoric acid.
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Authors and Affiliations

Wei Zhang
1 2
ORCID: ORCID
Georges Houlachi
3
ORCID: ORCID
Sanae Haskouri
2
ORCID: ORCID
Edward Ghali
2
ORCID: ORCID

  1. Hunan University of Technology, School of Metallurgical, ZhuZhou, China, 412002
  2. Laval University, Department of Mining, Metallurgical and Materials Engineering, Quebec, QC, Canada, G1K 7P4
  3. Hydro-Québec research institute, Shawinigan, QC, Canada, G9N 7N5

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