Diurnal variations in H2O2, O3, PAN, HNO3 and aldehyde concentrations and NO/NO2 ratios at Rishiri Island, Japan: potential influence from iodine chemistry

The presence of iodine chemistry, hypothesized due to the overprediction of HO(2) levels by a photochemical box model at Rishiri Island in June 2000, was quantitatively tested against the observed NO/NO(2) ratios and the net production rates of ozone. The observed NO/NO(2) ratios were reproduced reasonably well by considering the conversion of NO to NO(2) by IO, whose amount was calculated so as to reproduce the observed HO(2) levels. However, the net production rates of ozone were calculated to be negative when such high mixing ratios of IO were considered, which was inconsistent with the observed buildup of ozone during daytime. These results suggest that iodine chemistry may not be the sole mechanism for the reduced mixing ratios of HO(2), or that "hot spots" for iodine chemistry were present. Diurnal variations in the mixing ratios of HCHO, CH(3)CHO, peroxy acetyl nitrate (PAN) and HNO(3) observed during the study are presented along with the simulated ones. The box model simulations suggest that the effect of iodine chemistry on these concentrations is small and that important sources of CH(3)CHO and sinks of PAN are probably missing from our current understanding of the tropospheric chemistry mechanism.

Measurement of Gas-Phase Hydroperoxides by Chemical Ionization Mass Spectrometry

A new method for the detection of gas-phase hydroperoxides is described. The clustering chemistry of CF3O- is exploited to produce speciated measurements of several hydroperoxides with high sensitivity and fast time response. Correspondence of airborne observations made with this technique and the established HPLC method is illustrated. CF3O- appears to be a highly versatile reagent ion for measurements of both weak and strong acids in the atmosphere.

Development of ion drift-chemical ionization mass spectrometry

An ion drift-chemical ionization mass spectrometry (ID-CIMS) technique has been developed to detect and quantify trace gases, including volatile organic compounds and inorganic species. The trace species are chemically ionized into positive or negative product ions with a well-controlled ion-molecule reaction time. The ID-CIMS method allows for quantification of the trace gases without the necessity of performing calibrations with authentic standards for the trace gases. Demonstrations of the ability of ID-CIMS to accurately quantify isoprene and HNO3 in a laboratory setting are presented. The results illustrate that the ID-CIMS technique facilitates detection and quantification of organic and inorganic species in laboratory kinetic investigations and field measurements.