Studies on the Freshly Precipitated Deposits in Lake Takasukanuma. Part I.

Abstract

1) Two sets of bottles were suspended in Lake Takasukanuma, one at the depth of 1 m above the bottom and the other 2.5 m. At in tervals of some 20-30 days the contents of the bottles were examined. The results reported here cover June 23rd, 1935- Jan. 19th, 1936, and their full description in English will be published after the completion of these studies.
2) The deposits increase in weight from early summer (some 4.2 mg dry weight per cm² per day) towards the end of autumn. They attain their maximum (some 10.5 mg) during the period Nov. 11th-Dec. 15th, while they decrease suddenly to their minimum (0.79mg) during the period Dec. 26th-Jan. 19th.
3) From the vartical veriation in the chemical composition of the deposits reported in my previous paper (1), and from the data of the chemical analysis of the freshly precipitated deposits (tables 1 and 2), it is concluded that more than 45% of the deposited nitrogen dissolves again into the main body of water after its precipitaion, and more than 34% of carboneous deposits, represented as the loss of ignition, disap pears through fermentation.
4) The comparison of the ratios of Mn₂O₃ to Fe₂O₃, respectively in the mud, in the freshly precipitated deposits and in the supernatant water in the bottle for collection of deposits, confirms the author's conviction that the deposited manganese tends to dissolve more easily than iron due to the higher oxido-reduction-potential of the former.