The spatial dynamics of atmospheric pollution in Latvia and the Baltic Republics,as measured in mosses,topsoil and precipitation

Atmospheric pollution in the Baltic countries of Estonia, Latvia, and Lithuania has been mapped using measurements of pollutant concentrations in mosses, topsoil and precipitation. Air masses from western Europe deposit industrial pollutants in the Baltic region and concentrations depend on meteorological conditions. Superimposed on this background is the pattern of deposits from local sources. Large areas receive neutral to basic precipitation due to cement industries and fly ash emissions from fossil fuel combustion. The burning of oil-shale in NE Estonia results in precipitation with pH values over 7.0, and high concentrations of V, Fe, and Cd. Heavy metal concentrations in the topsoil around large cities indicate ecologically unsound city planning and insufficient control of pollutants. The Chernobyl effect in the form of radioactive deposition depended on rainfall events during the accident.     

The behaviour of metals and sulphur during the formation of hydrothermal mercury–antimony–arsenic mineralization, Uzon caldera, Kamchatka, Russia

Uzon caldera, located in the eastern volcanic belt of the Kamchatka peninsula, is a complicated structure of Middle Pleistocene age. The composition of the co-existing solid and fluid phases, temperature and pH were determined with the aim of establishing the distribution of sulphur species, As, Sb and the main ore-forming metals. In the solid samples, the following sulphur-bearing minerals were identified: pyrite, realgar, orpiment, alacranite (As₈S₉), uzonite (As₄S₅), amorphous As-sulphide, stibnite, cinnabar and native sulphur. The following sulphur-bearing species H₂S, H₂S₂+S₅²⁻(aq)(aqueous polysulphanes), S⁰(aq), SO₃²⁻(aq), S₂O₃²⁻, SO₄²⁻ and total concentration of sulphur were determined in solutions. Eh, pH and H₂S concentration were measured potentiometrically in situ. Zero-valent sulphur (S⁰(aq)+H₂S₂+S₅²⁻(aq)) predominates in Uzon solutions. The pair H₂S–S_colloidal is Eh-determining in Uzon solutions up to 75–85°C. A quantitative thermodynamic model of the mineral deposition process at Uzon was constructed using the collected data. It was obtained that the composition of the hydrothermal solution and the precipitation of Sb–As–Hg species can be described using two only main factors: the initial composition of fluid and the temperature variation.     

Aqueous oxidation-reduction kinetics associated with coupled electron-cation transfer from iron-containing silicates at 25°C

Mechanisms and kinetics of aqueous $\text{Fe}{}^{\mathrm{+2}}\text{Fe}{}^{\mathrm{+3}}$ oxidation-reduction and dissolved O₂ interaction in the presence of augite, biotite and hornblende were studied in oxic and anoxic solutions at pH 1–9 at 25°C. Oxidation of surface iron on the minerals coincided with both surface release of Fe⁺² and by reduction of Fe⁺³ in solution. Reaction with iron silicates consumed dissolved oxygen at a rate that increased with decreasing pH. Both Fe⁺³ and O₂ consumption were shown to be controlled by coupled electron-cation transfer reactions of the form;

$\text{[}\text{Fe}{}^{\mathrm{+2}}\text{,}\text{1}\text{zM}{}^{\mathrm{+z}}\text{]}{}_{\mathrm{silicate}}\text{+}\text{Fe}{}^{\mathrm{+3}}\text{→ [}\text{Fe}{}^{\mathrm{+3}}\text{]}{}_{\mathrm{silicate}}\text{+}\text{Fe}{}^{\mathrm{+2}}\text{+}\text{1}\text{zM}{}^{\mathrm{+z}}$

and

$\text{[}\text{Fe}{}^{\mathrm{+2}}\text{,}\text{1}\text{zM}{}^{\mathrm{+z}}\text{]}{}_{\mathrm{silicate}}\text{+}\text{H}{}^{\mathrm{+}}\text{+}\text{1}\text{4}\text{O}{}_2\text{→ [}\text{Fe}{}^{\mathrm{+3}}\text{]}{}_{\mathrm{silicate}}\text{+}\text{1}\text{zM}{}^{\mathrm{+z}}\text{+}\text{1}\text{2}\text{H}{}_2\text{O}$

where M is a cation of charge +z. The spontaneous reduction of aqueous Fe⁺³in the presence of precipitated Fe(OH)₃bracketed the surface oxidation standard half cell between +0.33 and +0.52 volts. Concurrent hydrolysis reactions involving cation release from the iron silicates were suppressed by the above reactions. Calculated oxidation depths in the minerals varied between 12 and 80Å and were apparently controlled by rates of solid-state cation diffusion.     

Comparison of Recoveries by Lead Fire Assay and Nickel Sulfide Fire Assay in the Determination of Gold/ Platinum/ Palladium and Rhenium in Sulfide Ore Samples

We compared the recovery of gold, palladium and platinum by two fire assaying procedures, using nickel sulfide and lead as collectors. The presence of appreciable amounts of sulfide minerals in the sample caused interferences in both procedures. An in-house reference sample, a reference sample of high-grade sulfide ore and samples of high sulfide content from the Recsk porphyry copper ore in Hungary were analysed by both methods. The elements were determined by inductively coupled plasma-atomic emission (ICP-AES) and/or inductively coupled plasma-mass spectrometry (ICP-MS). It was found that for the sulfide ore samples, the recoveries of Au and Pd are sometimes lower by nickel sulfide fire assay than by lead fire assay. Recovery of Re by nickel sulfide fire assay was found to be low: the average recovery of five repeated analyses of the reference sample NIST SRM 330 was 9% with a relative standard deviation of 48%. Increasing the amount of S in the fusion flux gave better recovery.     

Observations of noctilucent clouds from Lithuania

We present an analysis of systematic visual and photographic observations of noctilucent clouds seen from Lithuania in the years 1973–2009. The main trends in the noctilucent cloud occurrence frequency and the mean brightness are derived from statistical and correlation analysis. A clear signature of the solar activity cycle is imprinted on the noctilucent cloud occurrence frequency and mean brightness, both showing distinct anti-correlation with the sunspot numbers; however, no statistically significant increase of either noctilucent cloud occurrence frequency or brightness has been detected at least over past 19 yr (1991–2009). The only statistically significant positive trend is established for the numbers of very bright noctilucent cloud displays in the years 1973–2009. The most recent noctilucent cloud observations are linked to variations of local mesospheric temperatures, measured by the Aura satellite.     

Acoustic gravity waves and the atmospheric electric field perturbations accompanying them

Data on observations of acoustic gravity waves and variations in the electric field strength in the surface layer of the atmosphere are presented. Analysis of the obtained data shows that synchronous variations in the pressure and electric field strength appear with the passage of a weather front, solar terminator, and in some other cases. It is seen that the amplitude of electric field perturbations is approximately proportional to the amplitude of variation in the pressure. A possible mechanism of generating electric field perturbations during the passage of microbaroms has been considered.     

The ecological fallacy in a time series context: evidence from Spanish regional unemployment rates

The ecological fallacy (EF) is a common problem regional scientists have to deal with when using aggregated data in their analyses. Although there is a wide number of studies considering different aspects of this problem, little attention has been paid to the potential negative effects of the EF in a time series context. Using Spanish regional unemployment data, this paper shows that EF effects are not only observed at the cross-section level, but also in a time series framework. The empirical evidence obtained shows that analytical regional configurations are the least susceptible to time effects relative to both normative and random regional configurations, while normative configurations are an improvement over random ones.

A spectrophotometric study of neodymium(III) complexation in sulfate solutions at elevated temperatures

The formation constants of neodymium complexes in sulfate solutions have been determined spectrophotometrically at temperatures of 30-250 °C and a pressure of 100 bars. The dominant species in the solution are NdSO₄⁺ and Nd(SO₄)₂⁻, with the latter complex being more important at higher temperature. Equilibrium constants were calculated for the following reactions:

     

Impact of physico-geographical factors and climate variability on flow intermittency in the rivers of water surplus zone

Climate change is inevitably altering the hydrological regime of water bodies. The interest in changing behaviour of intermittent rivers is increasing in many countries. This research was focused on intermittent rivers (rivers which naturally, periodically cease to flow) in Lithuania. The purpose of this research was to provide an overview of flow intermittency phenomena according to available data in a historical period and to evaluate the impact of catchment geographical features and climate variability on zero-flow events. The calculated indices of flow intermittency showed that the selected rivers had very different flow regimes. The threshold for the separation of typically intermittent rivers from only occasionally intermittent ones was suggested. Multiple linear regression analysis defined the crucial role of catchment size and watercourse slope on the river cessation process in Lithuania. The applied non-parametric Wilcoxon–Mann–Whitney test revealed the significance of the relationship between precipitation (in June–September) and zero-flow duration. Flow intermittency phenomena in Lithuanian rivers were linked to a low-frequency teleconnection pattern (SCAND index). A methodology of estimating the relation between river intermittency and large-scale atmospheric circulation pattern (based on SCAND index) was created. The generated regression equations between flow intermittency indices and catchment characteristics might be useful for the estimation of zero-flows in ungauged river catchments. The main aspect of future investigations might be related to forecasting flow intermittency using modern hydrological models and climate scenarios as well as the defined relationships between zero-flow indices and physico-geographical features of river catchments.