Mercury contents of samples of sea water and fish from Kagoshima Bay, sediments in rivers, and the surface soil from the area surrounding a waste incinerator in the city of Kagoshima were measured to search for the source of mercury in Kagoshima Bay. The results obtined were as follows:
1) Mercury contents of sea water samples at 26 stations in Kagoshima Bay ranged from 6.3 to 19.7ng/l. When the 26 stations were classified into four areas, the entrance, the middle and the interior of the Bay, and the water around the Sakurajima area, mercury contents of the samples from the last area were significantly higher than either at the entrance or in the interior of the Bay.
2) Mercury contents in the cardinal fish, Apogon notatus, were significantly higher than those in either the dragonet, Callionymus lunatus, or the sillaginoid, Sillago japonica. Merucury contents of fish from the Ushine coast station, the innermost part of the Bay, were significantly higher than those from the other collecting stations. Moreover, significant interactions between the species of fish and the sampling stations were detected, and mercury contents of cardinal fish from Ushine coast station were 6.7-fold higher than those from the sampling station at the mouth of the Shinkawa river.
3) River sediments obtained 1km from the mouth of each river contained from 4 to 96μg/kg of mercury. Mercury contents of the river sediments from the Wada river were higher than those from the other rivers examined.
4) Mercury contents obtained from the surface soils every 0.5km in eight directions, with the waste incinerator as the central point, ranged from 6 to 128μg/kg; however, neither distance nor direction showed significant differences.
Possible sources of mercury in Kagoshima Bay were mainly eruptive products of Mt. Sakurajima and partly man-made products such as mercury-containing pesticides. Mercury levels in the bay remain unchanged with a state of mercury balance between the eruptive products from the increasing activity of Mt. Sakurajima and the reduction of man-made ones by administrative control. Mercury in the environment of Kagoshima Bay should be monitored for the prevention of human disease caused by consuming mercury contaminated fish.
