Abstract
To obtain basic information on the natural abundance of deuterium water, water samples in Hokkaido were collected and analyzed. The average and range of δ_D values of rain (snow) water samples in the suburbs of Sapporo were -60.6 and -140~1.5‰, and the daily fluctuation seemed to be significant. The values of coastal sea waters around Hokkaido were slightly lower than those of the standard sea water (-20~-10‰) ; especially in Ishikari Bay, the natural abundance of deuterium water was lower than that of other coastal regions. This may be attributable to the isotope dilution by big-river water. The δ_D values of big-river waters, e.g. Ishikari River, were in the range from -95~-75‰, and their variation was not remarkable. The low, consistent δ_D values of big-river waters would be due to the dilution by discharges form inland tributaries. The natural abundance of deuterium water in lake waters and related river waters, e.g. Lake Shikotu and Chitose River, were higher compared with those of the big-river waters. This is probably caused by the sampling strategy of the present study. Small tributaries and lakes in inland areas should be included to obtain limnologically unbiased results. The natural abundance of deuterium water in the greater numbers of soil samples was -116.3‰ in average and its variation was in the range of -150~-60‰. In general, both the average and the range of the natural abundance were greater in surface soils than those in subsurface soils and the values of subsurface soils were around -120‰. The influence of D supply by preceding rains was usually held in the profiles of δ_D values in soils and the behavior of water in soils could be studied by tracing their change with time. Some correction on the amount of deuterium water that is supplied by rains in the duration of the experiments is indispensable, especially in the long-term field experiments. This means that the determination of D/H has to be performed in a low D/H range near the natural abundance. Precise analysis managements, therefore, are required to perform this by using TCD-gas chromatography. Frequent calibrations together with the reduction of background by using low D/H hydrogen carrier gas are recommended to maintain high accuracy and good reproducibility of the laboratory analysis as described previously.
