Viacheslav Gordeev

Development of a Pan‐Arctic Database for River Chemistry

More than 10% of all continental runoff flows into the Arctic Ocean. This runoff is a dominant feature of the Arctic Ocean with respect to water column structure and circulation. Yet understanding of the chemical characteristics of runoff from the pan-Arctic watershed is surprisingly limited. The Pan- Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments ( PARTNERS) project was initiated in 2002 to help remedy this deficit, and an extraordinary data set has emerged over the past few years as a result of the effort. This data set is publicly available through the Cooperative Arctic Data and Information Service (CADIS) of the Arctic Observing Network (AON). Details about data access are provided below.

River flux of dissolved organic carbon (DOC) and particulate organic carbon (POC) to the Arctic Ocean: what are the consequences of the global changes?

An attempt was made to estimate an increase of particulate organic carbon (POC), dissolved organic carbon (DOC) and total organic carbon (TOC) delivery by the Russian Arctic rivers to the Arctic Ocean by 2100. The calculations are based on the previously published estimations of an increase of river water discharge (Peterson et al. 2002) and of suspended matter discharge (Gordeev 2006) to the end of 21st century. The Intergovernmental Panel on Climate Change (IPCC 2007) predicts the global surface air temperature increase in a range between 1.4° and 5.8°C by 2100. The climate warming will result in the thawing of the multiannual permafrost in Siberia. The enriched by organic carbon frozen peatlands will be the very effective source of organics to the rivers and streams. Frey and Smith (2005) predict an increase of DOC concentration in the rivers of West Siberia up to 400% due to this process.

The biogeochemistry of some heavy metals and metalloids in the Ob River estuary-Kara Sea section

The biogeochemical behavior of the group of heavy metals and metalloids in the water (including their dissolved and suspended particulate forms), bottom sediments, and zoobenthos was studied in the Ob River estuary-Kara Sea section on the basis of the data obtained during cruise 54 of the R/V Akademik Mstislav Keldysh in September–October 2007. The changes in the ratios of the dissolved and suspended particulate forms of Fe, Mn, Zn, Cu, Pb, Cd, and As were shown, as well as the growth of the fraction of adsorbed forms in the near-bottom suspended particulate matter under the mixing of the riverine and marine waters. The features of the metals’ accumulation in the typical benthic organisms of the Ob River estuary and the Kara Sea were revealed, and their concentrating factors were calculated based on the specific conditions of the environment. It was shown that the shells of the bivalves possessing a higher biomass compared to the other groups of organisms in the Ob River estuary play an important role in the deposition of heavy metals. The mollusks of the Ob River estuary accumulate Cd and Pb at the background level, whereas the Cu and Zn contents appear to be over the background level.

Forms of some metals in the suspended sediments of the Northern Dvina River and their seasonal variations

The results of the analysis of samples of the Northern Dvina River’s suspended particulate matter obtained by the sedimentation method from large water volumes in the periods of the spring high water and summer low water are presented. By the method of sequential leaching using different reagents, four fractions have been separated: the F1 is the sorbed complex and carbonates, the F2 is the amorphous hydroxides of Fe and Mn, the F3 is the form connected with the organic matter, and the F4 is the residual or silicate-detrital (inert) form. The data have shown that all ten elements determined were grouped with respect to the ratio of the distinguished forms: F4 is the predominant form for Al and Fe (73–88% of all the forms; however, the summer sample contains only 38% of this form of iron, and F2 is the predominant form for this period with 46.6%). As to Mn, the F1, F2, and F4 are nearly equally distributed in the spring high water samples, and only the F3 form is less important (5.4%). In the summer sample, the manganese sorbed complex is predominant (53.5%); for Cu, Ni, Cr, and Co, the inert F4 form is predominant (60–70%) in the sample of the spring suspended matter. The summer low water suspended matter has a lower F4 contribution (25–45%); for Zn, Pb, and Cd, the equal distribution of the forms in the spring samples is typical, while the summer suspended matter differs by the F2 form’s predominance (53–61% for Zn and Pb). The main conclusion from the acquired data is that the geochemical mobility of all the studied elements, except for cadmium, in the summer low water suspended matter is higher than in the spring suspended matter. The more intensive biogeochemical processes in August, the high level of organic matter, and the higher contribution of phytoplankton lead to the intensification of the metals’ geochemical activity in the Northern Dvina suspended matter in the end of the summer compared to the spring high water period when the physical processes are predominant over the biogeochemical ones due to the high speeds of the freshened waters flow.

The geochemistry of deepwater particulate matter over the hydrothermal field at 9°d50′ N (the East Pacific Rise)

The results of geochemical studies of particulate matter in the water mass over the hydrothermal field at 9°50′ N on the East Pacific Rise are presented. The particulate matter was tested in background waters, in the buoyant plume, and in the near-bottom waters. The contents of Si, Al, P, Corg, Fe, Mn, Cu, Zn, Ni, Co, As, Cr, Cd, Pb, Ag, and Hg were determined. No definite correlations were found between the ele-ments in the background waters. Many of the chemical elements correlated with Fe and associated with its oxyhydroxides in the buoyant plume. In the near-bottom waters, microelements are associated with Fe, Zn, and Cu (probably, to their sulfides formed under fluid mixing with seawater). The matter precipitated in a sed-imentation trap was similar to the near-bottom particulate matter in the elemental composition.

The Mixing Zone Between Waters of the Severnaya Dvina River and the White Sea

The geochemical processes in the river-sea mixing zone (the Marginal Filter of the Severnaya Dvina Rivers) are considered in this chapter. The general trend in transformation of the elements and components as a result of physical, chemical, and biogeochemical processes in this zone is the transition from dissolved forms of element existence into particulate suspended forms with the following sedimentation on the bottom. So, the Marginal Filter is a very effective barrier on the way of dissolved and suspended sedimentary materials from the continent to the sea.

Trace Elements in Water and Suspended Matter in the Open Part of the White Sea

The data on trace elements in dissolved and particulate forms (Fe, Mn, Cu, Zn, Ni) in the open waters of the White Sea are presented. The samples of water and suspended particulate matter (SPM) were obtained in the expeditions of R/V “Prof. Shtokman”, R/V “Acad. Mstislav Keldysh”, and R/V “Ecolog” in summer time of 2006, 2007, 2008, and 2010. The concentrations of dissolved forms of these metals have appeared to be higher than in near-bottom waters of the Barents Sea and much higher than in the ocean waters. In surface waters of the sea, the concentrations decrease, as a rule, in direction from coasts to central sea part. No trends were found in the water column: concentrations demonstrated smooth variations in a range of factor 2–3. In general we conclude that the regular interrelations between dissolved trace elements and biogenic elements and basic hydrochemical parameters which are typical for the open ocean are absent in the shallow White Sea with active hydrological regime.

The Geochemical Features of the River Discharge to the White Sea

In the present chapter, the results of detailed investigations of the river discharge into the White Sea are considered. The White Sea is an inland sea of Russian western Arctic territory that appears as the sub-Arctic sea. This sea may serve as a good example for case studies of the Arctic seas. Significant river discharge to this relatively small sea plays very important role in all the processes in it. It’s evident that the detailed knowledge is needed both on the volumes of water and suspended matter fluxes, and also about the chemical composition of water and grain-size, mineralogical, and chemical composition of suspended particulate matter (SPM), that are formed on the extensive area of the basin.