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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.
Express Letter

Apparent increase in Mn and As accumulation in the surface of sediments in Lake Biwa, Japan, from 1977 to 2009

TAKAAKI ITAI, MICHIO KUMAGAI, YUIKA HYOBU, DAISUKE HAYASE, SAWAKO HORAI, MICHINOBU KUWAE, SHINSUKE TANABE
Geochemical Journal, Vol. 46, No. , P. e47-e52, 2012

ABSTRACT

An apparent temporal increase in Mn and As in a thin surface layer (ca. 2 cm) of sediments in Lake Biwa, Japan, was observed by comparing depth profile data from 1977 and 2009. By our estimation, several thousand tonnes of Mn and a few hundred tonnes of As newly accumulated during the 32 years to 2009. Given various methodological concerns and geochemical factors associated with Mn and As dynamics, this phenomenon is believed to have been caused by increased Mn and As influxes to the lake rather than by redistribution induced by the intra-annual decrease in the level of dissolved oxygen. Mass balance calculations indicated that it is unlikely that the recently accumulated quantities of Mn and As were supplied via rivers as dissolved phases; rather, ground-water is the more likely source of these quantities. Further monitoring surveys will be important for assessing the environmental impact of this temporal change.

KEYWORDS

Lake Biwa, manganese, arsenic, temporal variation, environmental change

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