宮古島における窒素負荷発生量と地下水窒素濃度の長期的推移

抄録

Groundwater pollution by nitrogen is a common environmental problem in the islands covered with coral limestone. Total annual emission of nitrogen from fertilizers, livestock wastes, and domestic wastes at Miyako Island, Okinawa was examined from 1977 to 1998, and compared with the concentration of nitrogen in groundwater. The trend of nitrogen emission was reflected on the groundwater concentration with the delay of seven years. This suggests that the velocity of nitrogen permeating down to the groundwater is 3 m per year. The amount of nitrogen leaching into the groundwater was 39% of the total nitrogen emission on the ground. These results emphasize the importance of data collection on nitrogen emission in order to predict the future nitrogen concentration of groundwater in coral islands.