浜名湖底泥における新生物元素の再生

Abstract

Chemical analyses have been made for chlorinity, sulfate, total carbon dioxide, hydrogen sulfide, ammonia and phosphate in brackish lake waters and sediment pore waters from Lake Hamana. Also dissolved calcium in pore waters and sulfide-sulfur in sediments have been determined. In summer, the bottom water is strongly reducing with hydrogen sulfide due to the stagnation and the development of chemocline. The fact of the decreasing in chlorinity with depth in the pore water column suggests that chloride in the bottom water diffuses from the bottom surface into the deeper layer of the sediment core, where the low salinity lake water has been buried before. The biophile elements are remineralized through microbial sulfate reduction by degradation of utilizable organic matter to release carbon dioxide, ammonia and phosphate into pore waters. A steady state diagenetic model applied to the vertical profiles of total carbon dioxide, ammonia and phosphate in pore waters can be used to estimate the stoichiometric elemental ratio of the metabolized organic matter, and the following ratio is obtained; C : N : P a 106 : 16 : 0.83 which almost agrees with the Redfield ratio.