Seasonal variations of atmospheric C<sub>2</sub>–C<sub>7</sub> nonmethane hydrocarbons in Tokyo

Shirai, Tomoko; Yokouchi, Yoko; Blake, Donald R.; Kita, K.; Izumi, Katsuyuki; Koike, M.; Komazaki, Yuichi; Miyazaki, Y.; Fukuda, Masato; Kondo, Yutaka

doi:10.1029/2006jd008163

Cited by 34 publications

(35 citation statements)

References 42 publications

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“…The detection limit for PAN, a dominant species of PANs, was 15 pptv with an overall measurement uncertainty of 20%. Online measurements of C 2 –C 7 hydrocarbons were conducted using an automated gas chromatography–flame ionization detector (GC‐FID) system with an interval of 1 h [ Shirai et al , 2007]. The detection limit was approximately 3 pptv to achieve a signal‐to‐noise ratio higher than 2.…”

Section: Observationsmentioning

confidence: 99%

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO₂ radical concentrations during the winter and summer of 2004

Kanaya¹,

Cao²,

Akimoto³

et al. 2007

J. Geophys. Res.

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[1] We used laser-induced fluorescence to measure the concentrations of OH and HO 2 radicals in central Tokyo during two intensive campaigns (IMPACT IVand IMPACT L) in January-February and July-August 2004. The estimated detection limit for the 10-min data was 1.3 Â 10 5 cm À3 for the nighttime and 5.2 Â 10 5 cm À3 for the daytime. The median values of the daytime peak concentrations of HO 2 were 1.1 and 5.7 pptv for the winter and summer periods, respectively, while the values for OH were 1.5 Â 10 6 and 6.3 Â 10 6 cm À3 . High HO 2 mixing ratios (>50 pptv) were observed on a day in summer when O 3 mixing ratios exceeded 100 ppbv. The average nighttime concentrations of HO 2 were 0.7 and 2.6 pptv for the winter and summer periods, respectively, while the values for OH were 1.8 Â 10 5 and 3.7 Â 10 5 cm À3 . A photochemical box model constrained by ancillary observations was able to reproduce daytime OH concentrations reasonably well for both periods, although daytime HO 2 concentrations were underestimated in winter and overestimated in summer. Increasing the wintertime hydrocarbon concentrations in the model led to an increase in daytime HO 2 concentrations, thereby showing better agreement with observations; however, the model continued to underestimate HO 2 concentrations at high NO mixing ratios. This underestimate was most pronounced in the mornings of both periods and during the daytime in winter. We studied processes that are capable of explaining this discrepancy, including unknown reactions of HNO 4 or an unidentified HO x source that is linearly scalable to the NO mixing ratio. The important processes in terms of producing radicals were the olefin + O 3 reactions in the nighttime of both periods and during the daytime in winter, the photolysis of carbonyls in the daytime for both periods, and the photolysis of HONO during the daytime in winter (using measured HONO concentrations) and during mornings in summer (using estimated HONO concentrations).

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Section: Observationsmentioning

confidence: 99%

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO₂ radical concentrations during the winter and summer of 2004

Kanaya¹,

Cao²,

Akimoto³

et al. 2007

J. Geophys. Res.

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227

288

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“…The RONO 2 data were available only for the summer period. The temporal variations of C 2 ‐C 7 VOCs are shown by Shirai et al [2007].…”

Section: Observationsmentioning

confidence: 99%

Formation and transport of oxidized reactive nitrogen, ozone, and secondary organic aerosol in Tokyo

Kondo¹,

Morino²,

Fukuda³

et al. 2008

J. Geophys. Res.

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[1] Measurements of the major reactive nitrogen species (NO y ) i (NO x , peroxyacyl nitrates, HNO 3 , and particulate nitrate (NO 3 À )), total reactive nitrogen (NO y ), volatile organic compounds, OH and HO 2 , and organic aerosol were made near the urban center of Tokyo in different seasons of [2003][2004] to study the processes involving oxidized forms of reactive nitrogen and O 3 . Generally, NO x constituted the dominant fraction of NO y throughout the seasons. The NO x /NO y and HNO 3 /NO y ratios were lowest and highest, respectively, in summer, owing to the seasonally high OH concentration. The fraction of NO y that remained in the atmosphere after emission (R NOy ) decreased with the decrease in the NO x /NO y ratio in summer and fall. It is likely that the median seasonal-diurnal variations of O x = O 3 + NO 2 were controlled by those of the background O 3 levels, photochemical O 3 formation, and vertical transport. O x showed large increases during midday under stagnant conditions in mid-August 2004. Their in situ production rates calculated by a box model were too slow to explain the observed increases. The high O x was likely due to the accumulation of O x from previous days in the upper part of the boundary layer (BL) followed by transport down to near the surface by mixing after sunrise. Considering the tight correlation between O x and secondary organic aerosol (SOA), it is likely that SOA also accumulated during the course of sea-land breeze circulation in the BL.

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“…However, peak amounts ten times as large as the mean values again occur. Further, the concentrations of pollutant trace gases in this region appear to depend largely on local meteorological conditions and transport from the major source regions (Shirai et al, 2007), so the day to day variability in SO 2 could be similar to that for NO 2 . In that case, absorptions by SO 2 could exceed 10% at some wavelengths in the UVB region.…”

Section: Absorptions By Trace Gasesmentioning

confidence: 99%

Effects of urban pollution on UV spectral irradiances

et al. 2008

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Abstract. Spectral measurements of UV irradiances atTokyo are compared with corresponding measurements at a pristine site (Lauder New Zealand) to identify the causes of the reductions in urban UV irradiances, and to quantify their effects. Tropospheric extinctions in Tokyo were found to be up to ∼40% greater than at Lauder. Most of these differences can be explained by differences in cloud and aerosols, but ozone differences are also important in the summer. Examining spectral signatures of tropospheric transmission of both sites shows that reductions due to mean NO 2 and SO 2 amounts are generally small. However, at times the amount of NO 2 can be 10 times higher than the mean amount, and on these days it can decrease the UVA irradiance up to 40%. If SO 2 shows comparable day to day variability, it would contribute to significant reductions in UVB irradiances. The results indicate that at Tokyo, interactions between the larger burden of tropospheric ozone and aerosols also have a significant effect. These results have important implications for our ability to accurately retrieve surface UV irradiances at polluted sites from satellites that use backscattered UV. Supplementary data characterising these boundary layer effects are probably needed.

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Seasonal variations of atmospheric C₂–C₇ nonmethane hydrocarbons in Tokyo

Cited by 34 publications

References 42 publications

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO₂ radical concentrations during the winter and summer of 2004

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO₂ radical concentrations during the winter and summer of 2004

Formation and transport of oxidized reactive nitrogen, ozone, and secondary organic aerosol in Tokyo

Effects of urban pollution on UV spectral irradiances

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Seasonal variations of atmospheric C2–C7 nonmethane hydrocarbons in Tokyo

Cited by 34 publications

References 42 publications

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO2 radical concentrations during the winter and summer of 2004

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO2 radical concentrations during the winter and summer of 2004

Formation and transport of oxidized reactive nitrogen, ozone, and secondary organic aerosol in Tokyo

Effects of urban pollution on UV spectral irradiances

Contact Info

Product

Resources

About

Seasonal variations of atmospheric C₂–C₇ nonmethane hydrocarbons in Tokyo

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO₂ radical concentrations during the winter and summer of 2004

Urban photochemistry in central Tokyo: 1. Observed and modeled OH and HO₂ radical concentrations during the winter and summer of 2004