Atmospheric peroxyacyl nitrates in urban/remote sites and the lower troposphere around Japan

The methods of sampling, carrying and keeping, and the instruments for measuring atmospheric peroxyacetyl nitrate (PAN) and peroxypropionyl nitrate (PPN), were developed for field studies and had been used for the surveys on four remote islands and in the troposphere since 1991. PAN and PPN were detected in most of over 500 samples. Mean concentrations of PAN and PPN in the islands and in the lower troposphere (altitude; 400-4500 m) from the Yellow Sea to the Japan Sea are 0.1-0.4 ppb (10(-9), v/v) and 0.01-0.03 ppb, respectively. Good correlation between PAN and PPN at each point was observed, and PPN was found to be 5-9% of PAN. In addition, PAN in the urban area had been monitored continuously at Ichihara close to metropolitan Tokyo since 1985. The yearly means of PAN there were constantly around 0.4 ppb for ten years. The ratios of PANs to NO(x)* or NO(x)(+) (which were detected by chemiluminescence type or Griess-Saltzman type of NO(x) analyzers) were found to be mostly, 1% in the urban air, 15-20% on the remote islands, and 15-60% in the lower troposphere (occasionally exceed 80% in the upper 2500 m altitude). PANs in the remote area were confirmed to be relatively more important, compared with in the urban area. The higher ratios in aircraft surveys were partly related to the atmospheric temperature in the sampling area.