Isotopic Analysis and Cycling of Dissolved Inorganic Carbon at Lake Biwa, Central Japan

Abstract

This paper reports on concentrations and carbon isotopic results of dissolved inorganic carbon (DIC) in water samples collected at four locations and from several depths in Lake Biwa, central Japan, covering every season of the year, starting in the spring of 1995. Depth profiles of DIC concentration and DIC delta-13C showed a strong seasonal pattern, as a result of vertical mixing of the lake water in winter and early spring, or lack of mixing in the other seasons. No seasonal change in DIC Delta-14C depth profiles was recognizable, mainly owing to the wide scatter of DIC Delta-14C. Values typically ranged from 0.47 to 0.65 mmol kg-1 for DIC concentration, and from -4 to -8 per mil from +10 to +80 per mil for DIC delta-13C and DIC Delta-14C, respectively, for the Lake Biwa water.