Abstract
Continuous formaldehyde (HCHO) measurements by the fluorometric (Hantzsch reaction) method have been carried out at a point in the eastern part of the Tokyo Metropolitan Area, which was significantly influenced by many pollution sources from June 2010 to January 2013. In 2012, the average of the daily average concentrations was 3.03 ppbv, the 98 percentile value was 6.90 ppbv and the maximum concentration was 9.99 ppbv (n=318). Based on hourly averages, the median was 2.47 ppbv, the maximum was 29.7ppbv and the geometric average was 2.55 ppbv (n=7776). For the frequency distributions of the hourly averaged HCHO, the peaks decreased in the range of 1 to 2 ppbv. The hourly average concentration showed an approximate log-normal distribution. We presumed source attributions of 76 peak events over 20 ppbv (1-min average) as follows: 8 events correlated with CO indicating their sources were primary emissions from combustion-related stationary sources, 1 event correlated with SO2 indicating its source was the primary emission from ships in Tokyo Bay, 31 events having a low correlation with CO, SO2 and O3 indicating their sources were the primary emission from not-combustion-related stationary sources, 28 events correlated with O3 indicating they were due to the secondary formation by VOC emitted from not-combustion-related stationary sources, and 8 events correlated with both CO and O3 indicating they were due to both the primary emission and the secondary formation. These peak HCHO events were presumed to be highly influenced by the stationary sources in the neighborhood of this area.
