M.Y. Lychagin

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.

INTEGRATING MULTI-SCALE DATA FOR THE ASSESSMENT OF WATER AVAILABILITY AND QUALITY IN THE KHARAA—ORKHON—SELENGA RIVER SYSTEM

The environmental and socio-enonomic impacts of water pollution are particularly severe in regions with relatively limited water resources [WWAP, 2012]. Water quantity and quality are closely interlinked aspects which are relevant for surface water ecology, water use, and integrated management approaches. However, an intensive monitoring of both is usually prohibitive for very large areas, particularly if it includes the investigation of underlying processes and causes. For the Kharaa - Orkhon - Selenga River system, this paper combines results from the micro (experimental plots, individual point data), meso (Kharaa River Basin) and macro (Selenge River Basin) scales. On the one hand, this integration allows an interpretation of existing data on surface water quantity and quality in a wider context. On the other hand, it empirically underpins the complimentary character of intensive monitoring in selected model regions with more extensive monitoring in larger areas.

Heavy Metals in the Water, Plants, and Bottom Sediments of the Volga River Mouth Area

ABSTRACT Lychagin, M.Yu.; Tkachenko, A.N.; Kasimov, N.S., and Kroonenberg, S.B., 2015. Heavy metals in the water, plants, and bottom sediments of the Volga River mouth area. Deltaic landscapes occupy a special place in environmental geochemical studies of water bodies. Their ecotone position at the land–sea boundary determines the biological richness of the deltaic ecosystems and creates a unique variety of landscape–geochemical conditions. The Volga River delta is one of the largest in the world. It serves as a geochemical “focus” that reflects the character of fluxes of substances of natural and anthropogenic origin in the entire system of the Volga basin. This paper presents the results of long-term environmental geochemical research of aquatic landscapes in the mouth area of the Volga River. The study has shown the high spatial and temporal variability of the chemical element migration in the area due to the influence of hydrodynamic conditions, variations in water and sediment discharge, and local features of the aquatic systems that determine their geochemical identity. The environmental geochemical conditions of the Volga delta are still relatively safe, especially compared with many other estuaries of the major rivers. Contamination of aquatic systems is manifested mainly in excess of heavy metals (Cu, Pb, and Cd) in suspended matter over the global background values, most notably in the flood period. The content of heavy metals in the water and sediments during the most recent decades remains low; pollution of the bottom sediments is largely insignificant and local.