Isotopic, Chemical Characteristics and Water Quality of Lagoon and River-Water Samples in Niigata Prefecture, Japan(<Special Articles>The First Papers of Prospective Analytical Chemists)

汚染防護の観点から, 環境水中における汚染物質の動態を把握することは重要である.このような背景から, 本研究では新潟県内の河川, 湖沼を対象に, これらの水質評価並びに新たな動態評価法を探索することを目的とした.そこで有機体炭素(TOC), 化学的酸素要求量(COD), 主要イオン濃度, δ^<18>O, pH, 電気伝導度, 溶存酸素を各採水地点について月1回測定し, 結果を解析したところ, 以下のことが明らかになった.(1)TOC対CODとの相関関係は他の水系からの混合の度合いを推定する手掛かりとなる.(2)佐潟における環境水では, 年間を通じて高濃度の硝酸イオン(NO_3^-)が検出された.特に湧き水においては, 30〜60ppmの高濃度を示す試料も見られた.(3)佐潟において, δ^<18>OとTOCとの間に良好な相関関係が見られた.これは甲殻類のプランクトンに起因していると考えられ, δ^<18>Oは有機物汚染に関する指標にもなりうることが示唆される.(4)湖沼水は年間を通して塩基性であったが, 地下水は酸性であった.また, 湖沼は酸素が過飽和状態にあることが多いのに対し, 地下水は不飽和状態にあることが多い.The monitoring and determination of pollutants in environmental water is very significant from the viewpoint of environmental protection. In this study, the objective was to reveal the quality and characteristics of environmental water samples from Niigata Prefecture in recent years, and to establish a new evaluation method for the behavior of environmental water. For the above-mentioned purpose, the total organic carbon (TOC), chemical oxygen demand (COD), the concentration of major ions and oxygen stable isotopic ratios (i.e., δ^<18>O) in some river water, lagoon water and groundwater samples in Niigata Prefecture were measured. Moreover, the water temperature, pH, electric conductivity (EC) and dissolved oxygen (DO) were measured in the field. River water, circumjacent groundwater (located near the river), and lagoon water samples were taken monthly at fixed sampling points from 4 rivers (i.e. Shinano River and its two branch streams, Agano River) and 2 lagoons (i.e. Sakata and Toyanogata) in Niigata Prefecture. Consequently, the following matters have been mainly clarified : (1) The relationship between TOC and COD serve as a useful tool for estimating the effect of mixing from other kinds of river-water systems. (2) The concentration of NO_3^- in water samples from Sakata was larger than those in other environmental water samples. Particularly, those of spring water in Sakata were 30 to 60ppm throughout the year. (3) The relationship between the δ^<18>O values and the TOC was relatively good in the water samples from Sakata. In a lagoon, such as Sakata (not suffering from the inflow of river waters), investigating δ^<18>O values are of interest as one of the indices of organic pollutants (originated from plankton), as well as for characterizing the origin of local water. (4) The pH values of lagoon water samples were 8 to 9, and those of groundwater samples were 5 to 6. It is considered that lagoon water is supersaturated with oxygen, and groundwater is unsaturated