Metal pollution in Tokyo as recorded in sediments of the Palace Moat.

概要

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A record of metal pollution in the Tokyo atmosphere is developed for the past 30 years in sediments from the Palace Moat. Zinc, copper, chromium, silver, lead, cadmium, cobalt and nickel are identified as pollutants on the basis of higher contents in recently deposited strata. On the other hand, aluminum, vanadium and iron were essentially uniform in concentration throughout the sedimentary record. Manganese showed an increasing concentration with depth in the deposit. Apparently it diffuses to the overlying waters following reduction of higher valence state species to the more soluble divalent state. Elemental carbon, most probably arising from the combustion of wood, varied between 0.30 and 0.78% by weight. Opalline tests contributed between 21 and 31% of the weight of the dried sediment. The ages of the strata were determined by Pb-210, Pu-239+240 and Cs-137 geochronologies. The amounts of the pollutants do not bear a direct relationship to their atmospheric levels inasmuch as there is an enhancement in the sediment concentrations through the entry of soil debris containing anthropogenic metals. This magnification of direct fallout appears to be between four and five-fold.
日本地球化学会の論文