岐阜県南西部における地下水の臭化物イオン濃度およびBr/Cl比

抄録

Bromide ion concentration and Br/Cl ratio in the ground waters reported in few articles were measured. Water samples were collected from the two areas, confined and unconfined ground water areas, in the southwest region of Gifu Prefecture located in the central Japan. Bromide ion concentrations of 24 confined and 38 unconfined ground water samples ranged from 8 to 229 μg/l (except one hot spring water, 22 mg/l) and from 20 to 625 μg/l, respectively. An extent of Br/Cl ratio of the confined ground water samples including one hot spring water was from 3.1x10^-3 to 4.8x10^-3 (mean value, 4.0x10^-3). This ratio did not vary with chloride ion concentration and was almost equal to that of sea water. On the other hand, Br/Cl ratio of the unconfined ground water showed the wide range from 3.5 × 10^-3 to 35.5 x 10^-3 and, except a few, seemed to be raised with an increase in chloride, nitrate, and sulfate ion concentrations. The unconfined ground water area was considered to be polluted by fertilizer and pesticide. It was considered that bromide ion decomposed from the pesticide containing 1, 2-dibromoethane was mixed into ground water.