Estimation Accuracy of Annual Average Value of Atmospheric Concentration by Measurement Cycle and Frequency

Abstract

In this study, we analyzed the estimation accuracy of the annual average value of 16 volatile organic compounds (VOCs) in the atmosphere according to the measurement frequency. As the analysis data, VOCs continuous monitoring data that has been observed hourly for 3 years at 6 points in Tokyo was used. In the case of 24 -hours sampling, the coefficient of variation (CV) of the annual average value in the 30 -days cycle to accurate annual average was 0 . 25 on average 16 substances. On the other hand, when the measuring day of the week is fixed, as in the case of the 7 -days cycle, there were substances that had a significantly higher CV. Especially for trichloroethylene and dichloromethane, it was higher than that in the 30 -days cycle. It was considered that this is influenced by the concentration fluctuation due to industrial and / or traffic activities, and it was speculated that if the measuring day of the week was fixed even once a month, the accuracy of the annual average value would decrease. In the monthly monitoring, the CV of the annual average value for one-week sampling was smaller than for the 24 -hours sampling. It was estimated that the monitoring 4 times per year with one-week sampling was the same level or less than the CV of the monitoring 12 times per year with the 24 -hours sampling. The annual average value by 1 -week sampling of 4 times per year was as accurate as the value obtained by 24 -hours sampling of 12 times per year that was commonly performed in Japan.