抄録
Dissolved organic matter (DOM) comprises major part of aquatic organic matter, but is poorly understood, because of the difficulty in isolating a sufficient amount of DOM for the detailed chemical analyses. It is known that more than half of DOM is composed of a large molecular weight material, water humus. This study aimed to concentrate and isolate the high molecular weight DOM (HMW-DOM: MW>1000) using a tangential flow ultrafiltration (TFF), and to characterize the isolated solid organic matter. The water samples (80L〜100L) were collected from five lakes (Lakes Nakatsuna, Kizaki, Suwa, Misuma-ike and Shirakoma-ike) in Nagano Prefecture, Japan. DOM was concentrated from 100L to 1L by TFF, and then from 1L to 200mL by a conventional agitational ultrafiltration, equipped with filters of nominal molecular cut-off (MCO), 1000 dalton. The concentrated water was finally lyophilized to give DOM as a solid material. HMW-DOM thus obtained accounted for about 30〜40% of DOM in each lake water. Elemental and stable isotopic analyses gave the atomic C/N ratios: 10〜28, the δ13C: -28〜-25‰ and δ15N: 0.4〜8.6‰, respectively. Together with the lipid composition, these analytical data supported the assumption that the limnological properties reflect on the chemical nature of DOM.
