日本地球惑星科学連合2018年大会

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セッション記号 A (大気水圏科学) » A-HW 水文・陸水・地下水学・水環境

[A-HW22] 水循環・水環境

2018年5月24日(木) 09:00 〜 10:30 104 (幕張メッセ国際会議場 1F)

コンビーナ:長尾 誠也(金沢大学環日本海域環境研究センター)、町田 功(産業技術総合研究所地質調査総合センター)、飯田 真一(国立研究開発法人森林研究・整備機構森林総合研究所森林研究部門森林防災研究領域水保全研究室、共同)、林 武司(秋田大学教育文化学部)、座長:林 武司(秋田大学教育文化学部)、飯田 真一(国立研究開発法人森林総合研究所)、町田 功(産業技術総合研究所地質調査総合センター)、長尾 誠也(金沢大学環日本海域環境研究センター)

10:15 〜 10:30

[AHW22-12] Dynamics of particulate organic matter in a small lagoon, Lake Kiba, in Japan

*長尾 誠也1Bui Hong2鈴木 智代2河野 百合子2落合 伸也1福士 圭介1 (1.金沢大学環日本海域環境研究センター、2.金沢大学大学院自然科学研究科)

キーワード:放射性炭素、懸濁粒子、炭素同位体比

Lake Kiba is located at Ishikawa prefecture, Japan, and a shallow, semi-closed lagoon. The lake has been suffering organic pollutant. COD concentration is two times higher than the standard level of class A (< 3 mg/L, Environmental quality standards for conservation of the living environment in Japan) during the last decade. The objectives of this study are to elucidate the characteristics of particulate organic matter (POM) in Lake Kiba using carbon isotopes: δ13C and Δ14C. The carbon isotope composition is basic and useful information to clarify organic pollutants affecting shallow lakes and lagoons.
Water samples were monthly collected at the central lake in the periods of 2014-2016. The percentage and concentration of particulate organic carbon (POC), particulate nitrogen (PN) were measured and calculated from freeze-dried suspended solid which was pretreated from approximately 60 liters of water sample by using continuous flow centrifugation method.
Particulate organic carbon (POC) concentrations of 0.44–5.01 mg/L, δ13C and Δ14C values were, respectively, –32.0 to –22.8 ‰ and –157 to –33 ‰. The organic matter in suspended solid samples consistently showed depleted 14C. The carbon isotopes showed seasonal variation, higher in summer, with positive correlation to POC contents. These results indicate that the POC characteristics are controlled by a mixture of two endmembers, organic matter produced by phytoplankton activity within the lake and the watershed organic matter. However, the relation between Δ14C and δ13C values in 2014 and 2015 is different from that in 2016. The similar difference is observed for the relation between Δ14C and POC content for suspended solids. We will discuss about the variation of carbon isotope signatures based on primary production and climate condition.