The chemical speciation of Fe(III) in freshwaters

Dialysis and chemical speciation modelling have been used to calculate activities of Fe3+ for a range of UK surface waters of varying chemistry (pH 4.3–8.0; dissolved organic carbon 1.7–40.3 mg l-1) at 283K. The resulting activities were regressed against pH to give the empirical model: log aFe3+ = 2.76(±0.53) – 2.63(±0.08)•pH Predicted Fe3+ activities are consistent with a solid–solution equilibrium with hydrous ferric oxide. However, the apparent solubility of the solid phase decreases as pH decreases, consistent with some previous studies on Fe(III) solubility in the laboratory. The empirical model was used to predict concentrations of Fe in dialysates and ultrafiltrates of globally distributed surface and soil/ground waters. The predictions were improved greatly by the incorporation of a temperature correction for aFe3+, consistent with the temperature–dependence of previously reported hydrous ferric oxide solubility. The empirical model, incorporating temperature effects, may be used to make generic predictions of the ratio of free and complexed Fe(III) to dissolved organic matter in freshwaters. Comparison of such ratios with observed Fe : dissolved organic matter ratios allows an assessment to be made of the amounts of Fe present as Fe(II) or colloidal Fe(III), where no separate measurements have been made

Impacts of CNB Monetary Interventions from 2013 to the Insolvency of the Companies

The diploma thesis is concerned with the intervention of the Czech National Bank in the area of the exchange market and its impact on the insolvency of companies. The majority of the studies dealing with the liquidation of companies focuses primarily on the microeconomic determinants of bankruptcy. Conversely, the empirical study carried out in this project concentrates on the macroeconomic determinants of company bankruptcy. For the purposes of this study were used the quarterly panel data of insolvencies for the 5-year-period between 2010 - 2015. The quantity of insolvencies was established for individual branches. Furthermore, the method Differences-in-Differences was employed in order to compare those branches which were assumed to prove a significant impact of the depreciation of the Czech crown in comparison to those where the exchange rate seems to be rather irrelevant. The results of the regressive analysis have confirmed the initial hypothesis of this work: from the perspective of insolvency, the intervention on the aggregate level has improved the situation of companies. Finally, the impact on individual branches was investigated in this diploma thesis. The results testified that the situation deteriorated in case of the travel agencies (as expected)

Spatial variability of chlorophyll-a and abiotic variables in a river–floodplain system during different hydrological phases

Chlorophyll-a (Chl-a) and abiotic variables were measured in the main channel and floodplain waterbodies of the Middle Paraná River to analyse the system dynamics and to assess their spatial variability during different hydrological phases, including an extreme flood. We wanted to test that the flood does not always have a homogenising effect in a river-floodplain system. An explanatory model for Chl-a was performed according to Akaike?s Information Criterion (AIC), and the relation of water level with the coefficient of variation (CV) among sites for each variable was explored. The model explained 64% of Chl-a variability. Water level, depth:euphotic zone ratio (Zd:Zeu) (inverse correlation) and conductivity (direct correlation) were the significant explicative variables. The CV of Chl-a decreased with flood from the main channel to the floodplain, but for turbidity, Zd:Zeu, pH, dissolved oxygen, soluble reactive phosphorus and Chl-a:pheophytin-a ratio, it increased. However, within the floodplain, CV of turbidity, Zd:Zeu and pH decreased during flood. These suggest that the homogenising effect frequently observed during inundation cannot be generalised and that the floodplain may maintain its identity even during flood. The extreme flood and its overlap with the warm season and sedimentological pulse probably contributed to the heterogenity in the spatial gradient.Fil: Mayora, Gisela Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Devercelli, Melina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Giri, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentin