TRENDS OF AIR POLLUTION AND ITS PRESENT SITUATION IN HIROSHIMA PREFECTURE

摘要

The ambient concentration of SO_2, NOx and O_x in the atmosphere of Hiroshima, Fu-kuyama and Fuchu city which were monitored by the prefectural monitoring stations, are examined to give a picture of the typical air pollution at these sites. Results show that the yearly concentrations of SO_2 in these areas are significantly fall from 20 to 6 ppb during 1978 -1996 when the NOx concentrations having no such significant change which varies from 40 to 30 ppb. The Photochemical Oxidant (Ox) increases annually at the rate of 0.3 ppb to 0.6 ppb in Hiroshima city only. To know the present situation of air pollution the Differential Optical Absorption Spectroscopy (DOAS) system is used in the city of Higashi Hiroshima. The daily average concentrations of SO_2 NO_2, O_3 and HONO measured during the period of August 1999 to March 2000 ranged from 1.4 ppb to 2.8 ppb, 13 ppb to 26.9 ppb, 21 ppb to 53. 6 ppb and 1 ppb to 4.3 ppb respectively. The patterns of concentrations of NO_2 and O_3 measured by DOAS look similar to the seasonal patterns of NOx and Ox by the conventional system.