Global 3-D Model Analysis of TRACE-P HCN and CH3CN Measurements

Qinbin Li, Daniel J. Jacob, Robert M. Yantosca Harvard Atmospheric Chemistry Modeling Group

Hanwant B. SinghNASA Ames Research Center

Makoto KoikeUniversity of Tokyo

Glen W. SachseNASA-Langley Research Center

Atmospheric Budget of HCN(pre-TRACE-P)

Total atmospheric burden (Tg N) 0.50

Atmospheric lifetime (months) 2.1-4.4

Sources (Tg N yr-1)

Biomass burning 1.4-2.9

Sinks (Tg N yr-1)

Ocean uptake 1.1-2.6

Oxidation by OH 0.3

Photolysis 0.2×10-2

Reaction with O(1D) 0.3×10-3

Li et al. [2000]

Biomass burning emission ratio (relative to CO): 1.1%.

Vertical profiles in marine background atmosphere:Evidence for oceanic uptake of HCN and CH3CN

Background: CO < 120 ppbv, C2Cl4 < 10 pptv

Inferred saturation ratios: 0.84 for HCN, 0.80 for CH3CN

CH3CN-HCN Correlation in TRACE-P

Red: C2Cl4 > 11 pptvBlue: C2Cl4 < 11 pptv

“Shanghai plume” (flight 13)

Biomassburning

Biofuels (?)

Use HCN/CO and CH3CN/CO ratios measured in Chinese pollution plumes to infer biofuel

emission ratios

Assuming fresh fossil fuel+biofuel emissions. CO: biofuel/(fossil fuel+biofuel) ~42% for Shanghai + Jiangsu + Zhejiang [D. Streets, 2001] . Hence HCN/CO biofuel emission ratio ~ 0.40%.

DC-8Flight #13

Correlations: > 2 km Emission ratios relativeto CO (% molar):

biomass burning

Biofuel

HCN 0.14 0.34

CH3CN 0.12 0.22

Asian CO emissions(March 2001):

14 Tg fossil fuel13 Tg biofuel59 Tg biomass burning

Simulated vs. observed vertical profiles

Red: observationBlue: modelGreen: biomass burningPink: biofuelYellow (CO only): fossil fuel

Simulated vs. observed frequency distributions

Red: observationBlue: model

Simulated vs. observed HCN columns

Moshiri (44°N, 142°E)

Rikubetsu (45°N, 144°E)

Tsukuba (36°N, 140°E)

Red: observationBlue: model

Atmospheric Budgets for HCN and CH3CN

HCN CH3CN

Atmospheric burden (Tg N) 0.42 (0.50) 0.20

Atmospheric lifetime (month) 5.0 (2.1-4.4) 3.2

Sources (Tg N yr-1)

Biomass burning 0.51 (1.4-2.9) 0.43

Biofuel 0.48 0.31

Sinks (Tg N yr-1)

Ocean uptake 0.74 (1.1-2.6) 0.52

Oxidation by OH 0.25 (0.3) 0.22

Li et al. [2000] in red