Concentration and Isotopic and Elemental Composition of Organic Matter in Subsea Thawed and Permafrost Deposits of Buor-Khaya Bay

Oceanology - A comparative analysis of the content and composition of organic matter (OM) in samples of bottom sediments and subaqueous permafrost rocks by the concentration of organic carbon (OC),...     

Characteristic of quaternary sedimentation on a shelf of the Laptev Sea according to the molecular composition of n-alkanes

The molecular composition and distribution of the concentration of n-alkanes are considered for sediments of boreholes drilled in the shallow part of the Laptev Sea, in the area of Buor Khaya Gulf. The diverse molecular composition of n-alkanes is dominated by long-chain odd homologs, which indicate terrigenous organic matter (OM). Heterogeneous distribution and burial of OM are shown under conditions of pulsating contribution of river and thermoabrasive material and multiple changes in them up to hiatuses in sedimentation.     

Grain Size Properties of the Bottom Sediments from Buor-Khaya Bay

Oceanology - The paper presents the results of grain size analysis of bottom sediments and subsea permafrost from three cores drilled in Buor-Khaya Bay. A pronounced lithologic differentiation of...     

Subsea Permafrost Thawing as a Factor of Changes in the Elemental Composition

Doklady Earth Sciences - The differences in the concentration of elements between thawed and frozen sediments were shown in the samples from two boreholes from the coastal zone of the Laptev Sea...     

Humic acids in brown coals from the southern Russian Far East: General characteristics and interactions with precious metals

Brown coals with high Au and PGE concentrations from six deposits in the southern Russian Far East were analyzed for elemental composition, acid-base properties, and the molecular-size distribution of humic acids (HA). The ash contents of the coals were determined to be negatively correlated with their Au concentrations, and the content of “organic Au” (which is chemically bound to humic substances, HS) reaches 95%. The most probable mode of Au occurrence in the brown coals is submicrometer-sized particles of elemental gold stabilized by HA. Quantum-mechanical calculations of interactions between Au(0) clusters with model HS fragments confirm that HS could be originally strongly chemically adsorbed on the surface of elemental gold particles. Different stability of colloids during centrifuging of alkali extracts of the gold-bearing brown coals was proved to be likely responsible for the selective separation of free HA and those bound with gold particles, and this can be used to develop a technology for gold recovery from coals without decomposing their organic matrix.     

Organic and carbonate carbon in permafrost and thawed deposits from Buor-Khaya Bay (Laptev Sea)

Doklady Earth Sciences - The distribution of organic and carbonate carbon in core samples from holes drilled in the shallow part of the Laptev Sea, in the region of Buor-Khaya Bay and Bykovskii...     

Particle size composition of Holocene–Pleistocene deposits of the Laptev Sea (Buor-Khaya Bay)

New data on the particle size composition of the Laptev Sea shelf deposits were obtained on the basis of results of low-angle laser light-scattering of core samples from the columns studied. It was revealed that the sand fraction dominates. The results of comparative analysis of the particle size composition of deposits show that the Laptev Sea shelf zone was characterized by highly variable spatial–temporal conditions and settings of sedimentation in the Quaternary, a polygenic character of deposits, and a pulsating influence of fluvial and slope processes on the conditions of sedimentation. A tendency of coarsening in the vertical sequence that contributes to thawing of the permafrost was revealed in the Ivashkina lagoon.     

Germanium speciation in lignite from a germanium-bearing deposit in Primorye

We studied a number of chemical characteristics in the coals of the Spetsugli germanium-bearing area of the Pavlovskoe coalfield in southern Primorye. It was found that the coals show variable contents of ash, extractable organic matter (OM), and germanium. No less than 60% germanium in the coals are bound to mobile OM, including 25–60% in complex compounds of humic acids and 8–39% in the low-molecular-weight fraction of OM not precipitated by acids. It was shown that germanium can be partly accumulated in coals as organic compounds owing to the dissolution of the mineral forms of germanium by humic acids.     

Alkanes in Quaternary deposits of the Laptev Sea

The distribution and genesis of n-alkanes in sediments from the 38-m sequence obtained during core boring in the Ivashkina lagoon were studied. Sediments were formed in the Holocene as a result of thermokarst and penetration of seawater. The sequence mostly includes permafrost rocks partially molten in the upper horizons and covered by Quaternary deposits, which are mostly the products of thermoabrasion.     

A new approach to precious metals recovery from brown coals: Correlation of recovery efficacy with the mechanism of metal-humic interactions

The presence of gold and platinum group elements (PGE) in low-rank brown coals around the world has promoted interest in the industrial exploitation of this alternative source of precious metals. However, due to low efficacy of the methods traditionally used for the processing of mineral ores, there exists a high demand for new strategies of precious metal recovery from refractory carbonaceous materials that could significantly increase the economic potential of gold- and PGE-bearing organic resources. Here we discuss the possibility of gold and PGE recovery from alkaline extracts of brown coals using the difference in colloidal stability of bulk organic matter and its fractions enriched with precious metals. This approach enables one to avoid complete oxidation or combustion of brown coals prior to gold recovery, to minimize organic content in gold concentrate, and to obtain a valuable by-product - humic extracts. Using gold-bearing brown coals from several deposits located in the South Far East of Russia, we show that up to 95% of gold can be transferred to alkaline extracts of humic acids (HA) and up to 85% of this gold can be recovered by centrifugation at pH 4.0-6.0, when only 5-15% of HA precipitated simultaneously. We have shown that the high efficacy of gold recovery can be attributed to the occurrence of fine-dispersed elemental gold particles stabilized by HA, which differ significantly in colloidal stability from the bulk organic matter and, thus, can be separated by centrifugation.