ALBERT

Description: Airborne measurements of a large number of oxygenated organics were carried out in the Pacific troposphere (to 12 km) in the Spring of 2001 (Feb. 24-April 10). Specifically these measurements included acetaldehyde, propanaldehyde, acetone, methylethyl ketone, methanol, ethanol, PAM and organic nitrates. Independent measurements of formaldehyde, peroxides, and tracers were also available. Highly polluted as well as pristine air masses were sampled. Oxygenated organics were abundant in the clean In troposphere and were greatly enhanced in the outflow regions from Asia. Extremely high concentrations of aldehydes could be measured in the troposphere. It is not possible to explain the large abundances of aldehydes in the background troposphere without invoking significant oceanic sources. A strong correlation between the observed mixing ratios of formaldehyde and acetaldehyde is present. We infer that higher aldehydes (such as acetaldehyde and propanaldehyde) may provide a large source of formaldehyde and sequester Cox throughout the troposphere. The atmospheric behavior of acetone, methylethyl ketone, and methanol is generally indicative of their common terrestrial sources with a Image contribution from biomass/biofuel burning. A vast body of data has been collected and it is being analyzed both statistically and with the help of models to better understand the role that oxygenated organics play in the atmosphere and to unravel their sources and sinks. These results will be presented.

Description: We report the first in-situ measurements of hydrogen cyanide (HCN) and acetonitrile (CH3CN) from the Pacific troposphere (0-12 km) obtained during the NASA/Trace-P mission (Feb.-April, 2001). Mean HCN and CH3CN mixing ratios of 243 (+/-118) ppt and 149 (+/-56) ppt respectively, were measured. The in-situ observations correspond to a total HCN column of 4.4-4.9 x 10(exp 15) molec. cm(exp -2) and a CH3CN column of 2.8-3.0 x 10(exp 15) molec. cm(exp -2). This HCN column is in good agreement with available spectroscopic observations. The atmospheric concentrations of HCN and CH3CN were greatly influenced by outflow of pollution from Asia. There is a linear relationship between the mixing ratios of HCN and CH3CN, and in turn these are well correlated with tracers of biomass combustion (e.g. CH3Cl, CO). Relative enhancements with respect to known tracers of biomass combustion within selected plumes in the free troposphere, and pollution episodes in the boundary layer allow an estimation of a global biomass burning source of 0.8+/-0.4 Tg (N)/y for HCN and 0.4+/-0.1 Tg (N)/y for CH3CN. In comparison, emissions from automobiles and industry are quite small (〈0.05 Tg (N)/y). The vertical structure of HCN and CH3CN indicated reduced mixing ratios in the MBL (Marine Boundary Layer). Using, a simple box model, the observed gradients across the top of the MBL are used to derive an oceanic flux of 6.7 x 10(exp -15) g (N) cm(exp -2)/s for HCN and 4.8 x 10(exp -15) g (N) cm(exp -2)/s for CH3CN. An air-sea exchange model is used to conclude that this flux can be maintained if the oceans are under-saturated in HCN and CH3CN by 23% and 17%, respectively. It is inferred that oceanic loss is a dominant sink for these nitrites, and they deposit some 1.3 Tg (N) of nitrogen annually to the oceans. Assuming reaction with OH radicals and loss to the oceans as the major removal processes, a mean atmospheric residence time of 4.7 months for HCN and 5.1 months for CH3CN is calculated. A global budget analysis shows that the sources and sinks of HCN and CH3CN are roughly in balance. There are indications that biogenic sources may also be present. Mechanisms involved in nitrate formation during combustion and removal in the oceans are poorly understood.

Description: A new capillary gas chromatographic method using a Reduction Gas Detector was developed to measure HCN and CH3CN in the remote troposphere. This instrumental configuration was deployed for the very first time in the Trace-P field mission performed during the spring of 2001. The NASA DC-8 aircraft afforded an opportunity to measure HCN and CH3CN in polluted and pristine environments over the Pacific to a maximum altitude of 12 km. These are some of the first in situ measurements of the distribution of HCN and CH3CN over the Pacific. Large background concentrations of both nitriles were found to be present and significant variability was observed. The abundance of HCN and CH3CN was strongly impacted by outflow of pollution from Asia. In general there appeared to be a direct but nonlinear relationship between the mixing ratios of HCN and CH3CN. The vertical structure of these chemicals shows direct evidence of the presence of a significant oceanic sink. These observations will be compared with the column content HCN data from satellites and other available measurements. A large body of data have been collected and are being analyzed, both statistically and with the help of models, to better understand the sources and sinks of these nitriles. These results will be presented.