Molecular weight distribution of humic acids from lake and - terrapub

Geochemical Journal, Vol. 5, pp. 121 to 132, 1971

Molecular weight distribution of humic acids fromlake and marine sediments

RYOSHI ISHIWATARI

Department of Chemistry, Faculty of Science, TokyoMetropolitan University; Setagaya, Tokyo, Japan.

(Received May 20, 1971; in revised form August 9, 1971)

Abstract-Molecular weights of humic acids separated from two lake and three marinesediments were measured by gel filtration through Sephadexes. The results indicate thatmol. wt. of humic acid distributes from less than 700 to over 200,000. On the basis ofmol. wt. the humic acids are divided into three main groups: (1) components with mol.wt. from 100,000 to over 200,000 (43 -70%), (2) components with mol. wt. from 5,000to 10,000 (8 -25%) and (3) components with mol. wt. less than 700 (10 -17%). Thehumic acids gave rise to lower mol. wt. compounds on acid or alkali hydrolysis, but theratio of the hydrolyzable portion to the total varied from sample to sample. A possibleconversion process of sedimentary humic acids is discussed.