Concentrations of suspended particulate matter (SPM) at many air monitoring stations do not satisfy the environmental quality standard (EQS).High concentrations of SPM are suggested to be caused by particular meteorological conditions as well as through the increase of SPM-releasing sources.
Data collected in Fukuoka Prefecture in 1989 and 199 showed wide variation in the achievement of the EQS. So an investigation for these two years was carried out to determine what meteorological conditions contributed to high levels of SPM.
The relationship between atmospheric pressure patterns and average SPM concentrations in this area was examined. Results indicate that SPM concentration increased with the passing of travelling anticyclones and also during the summer monsoon.
Days during which SPM concentrations exceeded the EQS were classified into the three types according to the meteorological conditions at the time, 1) yellow sand type, 2) summer type and 3) travelling anticyclone type. Of these, the travelling anticyclone type mainly contributed to the high SPM concentrations. Yellow sand, while rare in occurrence, also significantly decreased the achievement of the EQS.
Samples of particulate matter were collected with high volume air samples. The compositions of samples taken during high concentration type conditions were compared with those in the usual low concentration days. Samples from the summer type showed increases in SO
42- rather than T-C, while those from the travelling anticyclone type showed an increase in both SO
42- and T-C. These results suggest that high concentrations of SPM found with the summer type conditions are caused by photochemical reaction, while those of the travelling anticyclone type are caused by the influence of an inversion layer associated with this type.
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