Evaporation and sparking during induction heating of metallic drops in relation to utilization of space debris

The paper presents the results of primary experimental studies of intense evaporation of samples made of various metals. The heating is performed with the help of induction currents, being one of the perspective ways of heating in space. Special attention is devoted to the process of intensive small drops (sparks) ejection during heating. The obtained results are supposed to be used for the design of space debris utilization systems directly at the orbit.

Technology for Producing Fine Tungsten Carbide Powders

The article shows the advantage of electric arc synthesis and subsequent centrifugal spraying of tungsten carbide to obtain a high-quality highly dispersed powder. A tungsten electrode (anode) is fed to the surface of a rotating graphite electrode (cathode) until an electric arc occurs between the electrodes, and the cathode is made in the form of a ring. The angular speed of rotation of the annular graphite electrode is set in accordance with the calculated ratio, which provides fine-dispersed centrifugal atomization of the molten product particles. To prevent intense evaporation of tungsten and the formation of an excessive amount of fine particles, the power of the electric arc for melting the anode is limited to a set value.As a result, the uniformity of the powder increases and the dispersion of the particles of the main fraction decreases.

A study on the salinization of coastal water of Sidi Boughaba Lake (Ramsar site 1980) in Morocco using the characteristic reports

The Lake Sidi Boughaba is a Ramsar site (1980) located on the Atlantic coast of north-west Morocco. It is oriented NNE - SSW and located in a secondary interdunal depression formed in a complex of the main wetlands of Morocco. The waters of this lake are deteriorating in quality, with increasing salinization. To identify the processes and chemical reactions that govern salinization, the main major elements as well as the pH, electrical conductivity and salinity were monitored during the winter and summer seasons of the years, 2016-2017 in 6 sites distributed throughout the year. The interpretation of the analysis data is carried out using the correlation of the major elements with the chlorides, the Piper diagram and the variation of the ionic ratios Na/Cl, SO4/Cl, Mg/Ca and the calculation of the saturation index. The saturation index is calculated by the software PHREEQC 2.8, used for modelling the state of saturation of minerals. The results of these analyzes revealed a variety of origins and processes of salinization of the waters. The hydro chemical study shows that the waters are brackish too salty; they are characterized by sodium chloride facies. This remarkable transition is mainly due to the intense evaporation that accentuates the mineralization. The values of the saturation index of the chemical minerals show the under saturation the anhydrite of the gypsum and the halite, on the other hand, the saturation or even supersaturation by the calcite and dolomite. The characteristic ratios of the chemical composition of waters show that salinity has two main origins: ion exchange between rock-water and marine influence by aerosols and sea spray.

Lichens, bryophytes and terrestrial algae of the Lake Untersee Oasis (Wohlthat Massiv, Dronning Maud Land, Antarctica)

Lake Untersee is the largest ice-covered freshwater lake in the interior of East Antarctica. The mountain oasis is situated around it in the Gruber Mts. of the Wohlthat Massif. For approximately 7,000 years the area has been free of ice and the local climate relatively stable. It is very severe, cold, and windy and dominated by intense evaporation and sublimation but with little melt. Relative humidity averages only 37%. Vegetation is sparse in the oasis and previously only poorly investigated. Two lichen species and no bryophytes were known from the area. In November-December 2018, a survey of terrestrial flora and vegetation was made. The list of lichens was completed for the area, bryophytes were found for the first time, and some terrestrial algae were collected. In total, 23 lichen species, 1 lichenicolous fungus, 1 moss, and 18 terrestrial algae were discovered for the locality. The abundance of each species within their habitats was also evaluated. The lichen flora of the Untersee Oasis is typical for continental oases and similar to other previously investigated internal territories of Dronning Maud Land, except for the very rich lichen flora of the Schirmacher Oasis.

Genesis of Pyrite Concretions: Constraints from Mineral and Geochemical Features of Longtan Formation in Anhui Province, Eastern China

The occurrence of pyrite concretions in the Permian Longtan Formation sheds light on the paragenesis, formation conditions and regional paleoenvironment. We analyzed the mineral and geochemical characteristics of pyrite concretions using scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from the Longtan Formation shales in Anhui, Eastern China. These pyrite concretions consist of two types, each with a distinct nucleus and outer layer: The former is mainly made up of quartz, bivalve fragments and minor gypsum, ankerite, siderite and pyrite, the latter consists of pyrite (FeS2) in the voids of quartz. Based on the correlation matrix and geochemical/mineralogical affinity, trace elements in the pyrite concretions fall into three groups, that is, I (Sr, Ba, Rb and K) in calcic minerals from bivalve-bearing nucleus, II (Nb, Ta, Zr and Hf) in certain heavy minerals and III (V, Cr, Co and Ni) in pyrites. Mineral assemblage and paragenetic analysis show that the formation of pyrite concretions can be divided into three stages: (1) deposition of bivalve-bearing nucleus, (2) lithification of diatoms and (3) diagenesis of pyrite. Mineral and geochemical indicators suggest that the formation environment of pyrite concretions has undergone a major shift from lagoon with intense evaporation, to strong reducing marsh.

Climate Change Impact on the Evolution of the Saline Lakes of the Soan-Sakaser Valley (Central Salt Range; Pakistan): Evidences from Hydrochemistry and Water (δD, δ18O) and Chlorine (δ37Cl) Stable Isotopes

The surfaces of saline lakes are shrinking at a threatening rate worldwide. Likewise, the Uchhali complex (formed by three saltwater lakes located in the Salt Range, Pakistan) that serves as a major regional source of water for humans and as a habitat for water birds must be monitored. With this objective in mind, we conducted a study coupling hydrochemistry and stable isotope compositions (δ37Cl, δ18O and δD) in order to characterize its hydrochemical properties and the main processes controlling them. Results showed that the Uchhali complex salinity has dramatically increased compared to other similar lakes in the world. While the Uchhali (UL) and Khabbeki (KL) lakes present a sodium-chloride hydrofacies, the Jahlar (JL) is of a sodium-bicarbonate type. Hydrochemistry parameters indicate that the weathering of surrounding rocks is the major vector for the increase of total dissolved solids in the water. On the other hand, the observed enrichment in heavy isotopes of the water stable isotope compositions implies that the different lakes are undergoing a long history of intense evaporation. The study of the corresponding δ37Cl isotope compositions supports the conclusion that evaporation, along with weathering, are the main driving processes. Besides climate effects that result in the decrease of annual precipitation and the increase of evaporation, water consumption for domestic purposes (household and agriculture) aggravates the rise of the lakes’ salinity.

Hydrochemistry and Environmental Isotope Characteristics of Groundwater in the Kashgar Delta Area, Xinjiang, China

The hydrochemistry and isotope characteristics of groundwater of different geomorphological types in the Kashgar Delta in Xinjiang, China were studied using isotopic analyses. Results showed that groundwater in the study area was mainly recharged by precipitation, and that groundwater ions were mainly affected by weathering-leaching of rock salt and evaporite as well as cation exchange and adsorption. The hydrochemical type of phreatic water in the alluvial-proluvial gravel plain on the piedmont slope was mainly SO4·Cl-Na·Ca type, with an average age of 28a. The phreatic water in the fluvial plain had shallow buried depth and intense evaporation. The hydrochemical type of phreatic water varied from SO4·Cl-Na·Mg type to Cl-Na type, with an average age of 99a. Along the groundwater flow path eastward, confined water in the fluvial plain experienced gradually more intense cation exchange and stronger adsorption. The major hydrochemical type of which was the SO4·Cl-Na type, with an average age of 30405a.

THE CHANGE OF OIL QUANTITY AND DYNAMICS OF SOIL PHYTOTOXICITY AT THE OIL POLLUTION

The authors of the article study the regularities of oil quantity change and dynamics of soil phytotoxicity at the oil pollution. The article describes the sequence of study of changes in the amount of pollutant (oil) in the soil. The study was carried out in modeling, laboratory and micro-field experiments. Two types of soils (black soil and turf podzolic soil) were used in the studies. The experiments were carried out in at least three biological and three analytical repetitions. Statistical processing of the results was carried out using Microsoft Office Excel software package. The investigation of evaporation of oil from the soil (when the initial concentration of oil in the soil was 10% and the initial moisture of the soil was 20%) shows that the intense evaporation of the liquid composition (oil+water) occurs within the first 12 days and the intensity of evaporation from black soil is higher than from turf podzolic soil. The phytotoxicity of oil contaminated turf podzolic and black soils, at different humidity, in the process of natural weathering of oil was determined using such plant test objects as L. usitatissimum, H. annuus, F. vulgare. The significant decrease of phytotoxicity, more than twofold compared with the initial one, lasts up to 45 days. After the 45th day further reduction of phytotoxicity is not observed. After the 45th day even the insignificant growth of phytotoxicity is observed. Obviously, this growth happens due to the formation of more toxic derivatives of oil in the process of natural oxidation. It is proved that under natural conditions within the first days there is an intense evaporation of volatile components of oil, which lasts for 45 days in average. At the same time, from 25% to 50% of oil is weathered from the soil depending on its type and the toxicity decreases by 2 approximately. Oil pollution spreads through the profile of the soil and in 6 months, at an initial contamination of 10%, it is observed at a depth of 30-40 cm. The least contaminated is the layer of soil at a depth of 10-20 cm. Therefore, the rehabilitation of soils by phytotherapeutic methods should be carried out 45 days after the pollution, and herbs should be planted at a depth of 10-20 cm.

Режимы с интенсификацией теплообмена при испарении в тонких горизонтальных слоях жидкости при пониженных давлениях

The influence of structures formed during the evaporation and boiling of a liquid (n-dodecane) in thin horizontal layers on heat transfer has been analyzed. Structures shaped with the shapes of funnels and craters are formed at low pressures in liquid layers with thicknesses above the capillary constant under the action of a vapor recoil force. Increasing pressure leads to the onset of bubble boiling. It is established that the formation of these structures in the regime of intense evaporation at low reduced pressures leads to an about 70% increase in the heat-transfer coefficient at analogous layer thicknesses in comparison to the case of bubble boiling.

Surface water leakage, sedimentation and evaporation in arid regions: A case study of the Gargar dam, Algeria

This study was carried out in order to assess the total capacity loss in Gargar dam, third-largest in Algeria, due to the mudding of the reservoir, intense evaporation and water leaks. We analysed the variation in leakage as a function of the reservoir level, and quantify losses due to leaks, sedimentation and evaporation. We relied on site visits and data obtained from the Algerian Agency for Dams and Transfers to assess the leakage volume; reservoir level; sedimentation and evaporation levels for the period 1988–2015. We present an updated report of this problem through the dam. We estimated total average losses of 23 million m3·year−1 for the period 1988–2015, made up of leakage (0.3 million m3·year−1), evaporation (18 million m3·year−1) and dead storage for 4.6 million m3·year−1. However, total losses for 2004 were estimated at 113.9 million m3, which increased to the alarming value of 166.8 million m3 in 2015. We suggest improving the waterproofness by a concrete screen, and reducing mudding and evaporation by reforestation, to increase the storage capacity of the dam.