DEVELOPMENT OF ECONOMICAL DESIGN AND PREDICTION CONCEPT SOFT FOR DECONTAMINATION PROJECTS OF ENVIRONMENTAL CONTAMINANTS.

在过去的25年里，在八代海的24个固定采样站收集了表层沉积物，深度为4.0cm。研究人员发现，样本中的汞含量并不令人担忧，海湾外的浓度低于急性毒性水平。与此同时，研究人员在633平方公里的海域中发现了汞行为的趋势。在1975年至1984年期间，汞浓度逐渐增加，靠近水俣湾的采样站显示出最大的上升，从1975年的0.62ppm上升到1984年的10.3ppm。在另一个更偏远的监测站，浓度略有上升。这种模式在1982年中断，这是一个特殊的年份，三小时内降雨量达到400毫米，这是200年一遇的事件。数百万吨的干净土壤从周围的山坡上被冲下来，覆盖在八代海的沉积物上。风暴发生三年后，政府启动了一项去污工程。1985年至1990年，海湾附近一个采样站的汞浓度从10.5 ppm下降到1.56 ppm，1997年进一步下降到0.3 ppm的背景水平。日本政府最终对海湾的汞污染采取了负责任的行动，但行动太慢。这项耗资5亿美元的净化工程是世界上第一次这样的努力，它不仅将在未来许多年内清理海湾，保护八代海周围的人们。

During the last 25 years, surface sediments have been collected from 24 fixed sampling stations to a depth of 4.0cm in the Yatsusiro Sea. Researchers have found that the mercury content of the samples was not a cause for concern and that the concentrations outside the bay were below the acutely toxic level. At the same time the investigators spotted a trend in mercury behavior in the sea of 633km^2. Between 1975 and 1984 mercury concentrations gradually increased, with sampling stations close to Minamata Bay showing the greatest rise, from 0.62ppm in 1975, to 10.3ppm in 1984. At another, more remote station, concentrations rose slightly. The pattern was interrupted in 1982, an exceptional year when 400 mm of rain fell in three hours, a 200-year event. Millions of tons of clean soils were washed from surrounding mountain slopes to cover the sediments in the Yatsushiro Sea. Three years after this storm, the government initiated a decontamination project. Mercury concentrations at one sampling station near the bay dropped from 10.5 to 1.56ppm from 1985 to 1990 and decreased further to a background level of 0.3ppm in 1997. The Japanese government eventually took responsible action against mercury pollution in the bay, but it was too slow to act. The decontamination project costing US$500 million and the first such effort in the world, will not only clean up the bay and protect the people around the Yatsushiro Sea for many years to come.