Abstract
Around 10 o'clock, July 2nd, 1997, a large-sized tanker stranded on the center of Tokyo bay and a great deal of crude oils flowed out from the ship. Because the oil was volatile, the about 30 percent of the outflow oil evaporated immediately and was released in the atmosphere as a great deal of petroleum gas. The purpose of this study is to investigate an atmospheric environmental impact by this oil outflow accident by means of the analysis of the monitoring station data and the numerical simulation by chemical transport model.
The result of analyzing observation data shows as follows. A puff with the high concentration NMHC which evaporated from outflow oil on Tokyo bay was transported to the southern part of Ibaraki prefecture passing the northeast part of Tokyo bay in the about 10 m/s southwest wind. Its maximum concentration reached 6 ppmC in the northern coastal area of Tokyo bay. When the high concentration NMHC puff pass, the increases of the NMHC and photochemical oxidant concentrations were detected.
In order to evaluate the atmospheric environmental impact by the accident quantitatively, a numerical simulation was conducted. First, by the computation of the base case, it confirmed that the model could reproduce the basic characteristic of the atmospheric environmental impact caused by the oil outflow. We assumed that the concentration difference between the accident case and the non-accident case was equal to the environmental impact by the accident. As a result of numerical simulations, the 03 and NO2 were produced by the photochemical reactions in the high concentration NMHC puff, and the maximum concentration of O3 and NO2 is 18 ppb and 2 ppb, respectively.
