日本地球惑星科学連合2018年大会

講演情報

[EE] ポスター発表

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-HW20] 流域の物質輸送と栄養塩循環-人間活動および気候変動の影響-

2018年5月21日(月) 15:30 〜 17:00 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:齋藤 光代(岡山大学大学院環境生命科学研究科)、小野寺 真一(広島大学大学院総合科学研究科)、細野 高啓(熊本大学大学院先導機構、共同)、Adina Paytan(University of California Santa Cruz)

[AHW20-P17] Nitrate Dual-Stable Isotope Analysis Identifies Sources of Groundwater Nitrogen Pollution in the Silang-Sta. Rosa Subwatershed of Laguna de Bay

*Osbert Leo Alcantara Privaldos1,2Ken'ichi Osaka3Yoshitoshi Uehara4Asano Satoshi5Lei Fujiyoshi4Chikage Yoshimizu4Ichiro Tayasu4Adelina C. Santos-Borja1Maria Pythias B. Espino2Noboru Okuda4 (1.Laguna Lake Development Authority、2.Institute of Chemistry, University of the Philippines-Diliman、3.The University of Shiga Prefecture、4.Research Institute for Humanity and Nature、5.Lake Biwa Environmental Research Institute)

キーワード:nitrate stable isotopes, denitrified method, Silang-Sta. Rosa subwatershed

Excess nitrogen in freshwater systems contributes to water quality degradation and eutrophication. Nitrates (NO3-) in river and ground waters are constantly turned over by internal biogeochemical processes. Dual-stable isotope measurement provides conclusive information in tracing NO3- sources and forms. Signatures of nitrate stable isotopes (d15N, d18O) in the river and ground waters of Silang-Sta. Rosa subwatershed – measured using denitrifier method. Nitrate sources in the study site were ammonia (NH4+) from fertilizer and precipitation, soil NH4+ in the upstream and midstream, and manure and septic waste in the downstream area both in river and ground waters. The concentrations of nutrients and metals were also analyzed to determine the anthropogenic activities, industrialization, and urbanization effects in the subwatershed. The movement of water between river and ground waters provides a pathway for chemical transfer such as nutrients between terrestrial and aquatic systems. Principal component analysis of these concentrations shows that the movement of ions in ground waters is from upstream to downstream. This suggests chemical contamination caused by nitrate fertilizers used in farming lands in the upstream affecting the characteristics of aquatic systems by altering biogeochemical processes, especially in the downstream area.