Cs-137 and Pb-210 in lacustrine sediments of Stepnoi Altai as indicators of the dynamics of anthropogene changes in geochemical background throughoutthe 20th century
Vm. Gavshin et al., Cs-137 and Pb-210 in lacustrine sediments of Stepnoi Altai as indicators of the dynamics of anthropogene changes in geochemical background throughoutthe 20th century, GEOL GEOFIZ, 40(9), 1999, pp. 1331-1341
Three of tens of small lakes in Stepnoi Altai were studied in detail. In on
e of them, located in the center of the region, far from the sources of tec
hnogenic components, bottom sediments from a 25 cm deep column were sampled
, with a sampling step of 1.5 cm. For all samples, a gamma spectrometric an
alysis of the activities of Cs-137 and Pb-210 and atomic-absorption analysi
s for heavy metals (Cu, Zn, Ni, Co, Pb, Cd, Hg), As, and Be were performed.
It has been established that the wind erosion of soils of the surrounding
watersheds affected the chemical composition of forming lacustrine sediment
s. The activities of Cs-137 and Pb-210 in the sediments are two or three ti
mes higher than those in atmospheric precipitation, which also evidences th
at soils are "intermediate collectors" of technogenic radionuclides. The la
tter were probably transported mainly by sand storms, which are typical of
Stepnoi Altai. From the Pb-210 distribution throughout the column, we have
estimated the dynamics of changes in concentrations of Al, Fe, organic matt
er, heavy metals, As, and Be in the sediments. The greatest compositional c
hanges of the sediments were caused by the disruption of the natural soil c
over during the exploration of virgin and long-fallow lands, which provoked
intense sand storms. Despite the slight increase in concentrations of heav
y metals for the last 100 years, they virtually do not exceed their clarkes
for sedimentary rocks. Therefore, the central part of Stepnoi Altai may be
considered unpolluted by technogenic components.