抄録
In conventional monitoring of dioxins (PCDDs, PCDFs, and dioxin-like PCBs) in ambient air in Japan, the average of TEQ concentration in four samples obtained by one solid week sampling in each season (TEQ-S) is regarded as the annual average. The TEQ in the ambient air depends on meteorological conditions and human activities. Due to assess the annual average of TEQ concentration based on four data points, it is necessary to know the accuracy of TEQ-S comparing with the actual annual average from over 50 weeks. In this study, we continuously measured dioxins in the ambient air in Kazo-city (the northeastern part of Saitama prefecture) from December 2006 to March 2010 (3 years and 3 months) collected by one solid week sampling. The TEQs in the ambient air ranged from 0.030 to 0.51 pg-TEQ/m3, which is below the environmental standard value of 0.6 pg-TEQ/m3. The TEQs showed seasonal changes, which tend to be higher in winter and lower in summer. Ninety five % (2.5-97.5 percentile) of TEQ-S ranged in 0.5-2.0 times of the actual annual average. Moreover, we found the concentration of TEQ-S was lower than the actual annual average in many cases. This indicates that the ambient air dioxins should be assessed with considering of which there is a possibility that TEQ-S might be a half of the actual annual average in variation. The actual annual average during the sampling period showed the tendency to decline slightly.
