Mercury content in sediments obtained from Razdol'naya River, Vtoraya Rechka and Amur Bay

Estuaries are transitional zones between continents and oceans. In terms of geochemistry, they comprise an extremely important geochemical barrier, which separates areas with different conditions of the sedimentation environment (hydrodynamic, physicochemical, biogeochemical, etc.). This results in a sharp change in the intensity of migration of a certain group of chemical elements, their concentrations, and migration forms. The migration forms of an element are controlled, not only by its occurrence in either dissolved or suspended states, but also its affinity for a particular suspended fraction and sorption properties. Fine suspended fractions may serve as an active form of migration and control the migration capacity of an element. The sedimentary material of rivers experiences a fundamental transformation at the river-sea boundary, and its major portion is eliminated from the carrier flow in the marginal filter area. Owing to the accumulation of a metal during early diagenesis, its natural concentration can be distinguished from the anthropogenic component, which provides an opportunity to estimate the degree of pollution in the area studied and the contribution of different components. This study focuses on the problems of mercury accumulation in the fine fraction of bottom sediments from various segments of the marginal filter of the Razdol'naya River, its accumulation during sedimentation, and determination of the background and anthropogenic concentrations of mercury in bottom sediments affected to a varying extent by anthropogenic impacts. This paper is a continuation of our research of the late 1980s

Late Holocene diatom abundaces in sediment core HC-11

The study of diatoms in core HC11 collected from the southwestern part of Chukchi Sea, allowed to distinguish 3 diatoms ecological zones, reflecting paleoenvironmental changes during the last 2300 years. The sediment age was based on the sedimentation rates, determined by 210Pb and radiocarbon dating of mollusk shells. The environmental changes of Chukchi Sea revealed by examination of diatoms correlates with global climate changes - the warming of the early and middle Subatlantic and cooling of the late Subatlantic (Little Ice Age). Warming early and middle Subatlantic in the Chukchi Sea was probably stronger than the warming of the late 20th century and was not accompanied by significant changes in sea level