Environmental change in the Selenga River—Lake Baikal Basin

Regional Environmental Change -     

Speciation and hydrological transport of metals in non-acidic river systems of the Lake Baikal basin: Field data and model predictions

The speciation of metals in aqueous systems is central to understanding their mobility, bioavailability, toxicity and fate. Although several geochemical speciation models exist for metals, the equilibrium conditions assumed by many of them may not prevail in field-scale hydrological systems with flowing water. Furthermore, the dominant processes and/or process rates in non-acidic systems might differ from well-studied acidic systems. We here aim to increase knowledge on geochemical processes controlling speciation and transport of metals under non-acidic river conditions. Specifically, we evaluate the predictive capacity of a speciation model to novel measurements of multiple metals and their partitioning, under high-pH conditions in mining zones within the Lake Baikal basin. The mining zones are potential hotspots for increasing metal loads to downstream river systems. Metals released from such upstream regions may be transported all the way to Lake Baikal, where increasing metal contamination of sediments and biota has been reported. Our results show clear agreement between speciation predictions and field measurements of Fe, V, Pb and Zn, suggesting that the partitioning of these metals mainly was governed by equilibrium geochemistry under the studied conditions. Systematic over-predictions of dissolved Cr, Cu and Mo by the model were observed, which might be corrected by improving the adsorption database for hydroxyapatite because that mineral likely controls the solubility of these metals. Additionally, metal complexation by dissolved organic matter is a key parameter that needs continued monitoring in the Lake Baikal basin because dependable predictions could not be made without considering its variability. Finally, our investigation indicates that further model development is needed for accurate As speciation predictions under non-acidic conditions, which is crucial for improved health risk assessments on this contaminant.

     

The formation of wood jams in Kamchatka rivers and their role in juvenile fish distribution

In piedmont rivers of the Kamchatka Peninsula, wood jams play a major role in channel formation and largely determine the density distribution of juvenile fish along the river, offering them convenient habitats in areas with rapid current. It has been found that juvenile fish density in wood jams is 1.5–3 times higher than in adjoining open shoals. An analysis of data on the location and morphology of more than 200 wood jams has shown that their occurrence frequency and size depend mainly on river size (flow discharge), the type and morphology of river channel, and the type of tree stand in the floodplain.     

Electro and Baromembrane Methods of Petrochemical Enterprises' Wastewater Treatment

The paper focuses on the development of production methods for new ion‐exchange membranes on the basis of ED‐20 industrial epoxide resin, resorcinol diglycidyl ether (RDGE), vinyl ether of monoethanolamine (VEMEA), and different di‐ and polyamines (polyethylenepolyamine (PEPA), polyethyleneimine (PEI), and hexamethylenediamine (HMDA)) in the presence of polyvinyl chloride (PVC) as a thermoplastic polymer binder. With the purpose to establish optimum conditions for synthesis of interpolymer membranes, the influence of reactants' concentration, of the temperature, of the nature and the quantity of the solvent, and of the process duration, was studied. It was found that when the VEMEA content in the reaction mixture is increased, the static exchange capacity (SEC) of the membrane increases in the presence of: PEI in the range of 1.2 to 4.7 mEq/L; PEPA: 1.0 to 4.0 mEq/L; and, HMDA: 1.4 to 5.2 mEq/L. It was shown that the optimum synthesis conditions are heating the reaction mixture to 60 °C to 70 °C for six to seven hours with constant stirring. For increasing the basicity of membranes, N‐alkylation was carried out using known alkylating agents (methyl iodide, dimethyl sulfate, and epichlorohydrin (ECH)). The primary electrochemical and physic‐mechanic properties of the obtained membranes were studied on pilot electrodialysis cells. The process flow diagram of the electrodialysis plant, as well as the engineering design documentation thereof were developed, and a pilot electrodialysis plant was constructed. The maximum production capacity of the pilot plant was 600 L/hr with a 30 percent desalinization rate. To increase the desalinization rate up to 75 percent, circulation of the solution and a decrease of production capacity was suggested. For meeting the treated water requirements in terms of salt content, a partial recirculation mode was introduced. In the course of the studies conducted, a process flow diagram was developed, and an experimental installation and a pilot reverse osmosis plant were fabricated for phenol and ammonium nitrogen purification. The pilot plant was tested using process condensate from the Pavlodar Petrochemical Plant. It was found that prior oxidation of the condensate with ozone in alkali medium resulted in phenol purification up to 85 percent and ammonium nitrogen up to 93 percent. ©2015 Wiley Periodicals, Inc.     

Patterns of soil contamination,erosion and river loading of metals in a gold mining region of northern Mongolia

Mining has become one of the main causes of increased heavy metal loading of river systems throughout the world. There is however an evident gap between assessments of soil contamination and metal release at the mined sites and estimates of river pollution. The present work focuses on Zaamar Goldfield, which is one of the largest placer gold mines in the world, located along the Tuul River, Mongolia, which ultimately drains into Lake Baikal, Russia. It combines field observations in the river basin with soil erosion modelling and aims at quantifying the contribution from natural erosion of metal-rich soil to observed increases in mass flows of metals along the Tuul River. Results show that the sediment delivery from the mining area to the Tuul River is considerably higher than the possible contribution from natural soil erosion. This is primarily due to excessive mining-related water use creating turbid wastewaters, disturbed filtering functions of deposition areas (natural sediment traps) close to the river and disturbances from infrastructures such as roads. Furthermore, relative to background levels, soils within Zaamar Goldfield contained elevated concentrations of As, Sr, Mn,V, Ni, Cu and Cr. The enhanced soil loss caused by mining-related activities can also explain observed, considerable increases in mass flows of metals in the Tuul River. The present example from Tuul River may provide useful new insights regarding the erosion and geomorphic evolution of mined areas, as well as the associated delivery of metals into stream networks.

     

The Selenga River delta: a geochemical barrier protecting Lake Baikal waters

Regional Environmental Change - The protection of Lake Baikal and the planning of water management measures in the Selenga River Basin require a comprehensive understanding of the current state and...