Christopher M. Kiley

Eastern Asian emissions of anthropogenic halocarbons deduced from aircraft concentration data

Asian carbon tetrachloride (CCl4) source of 21.5 Gg yr � 1 , several-fold larger than previous estimates and amounting to ’30% of the global budget for this gas. Our emission estimate for CFC-11 from eastern Asia is 50% higher than inventories derived from manufacturing records. Our emission estimates for methyl chloroform (CH3CCl3) and CFC-12 are in agreement with existing inventories. For halon 1211 we find only a strong local source originating from the Shanghai area. Our emission estimates for the above gases result in a ’40% increase in the ozone depletion potential (ODP) of Asian emissions relative to previous estimates, corresponding to a ’10% global increase in ODP. INDEX TERMS: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; KEYWORDS: anthropogenic, halocarbon emissions, troposphere, TRACE-P

Photochemical production and evolution of selected C2–C5 alkyl nitrates in tropospheric air influenced by Asian outflow

Author(s): Simpson, IJ; Blake, NJ; Blake, DR; Atlas, E; Flocke, F; Crawford, JH; Fuelberg, HE; Kiley, CM; Meinardi, S; Rowland, FS | Abstract: The photochemical production and evolution of six C2-C5 alkyl nitrates (ethyl-, 1-propyl-, 2-propyl-, 2-butyl-, 2-pentyl-, and 3-pentyl nitrate) was investigated using selected data from 5500 whole air samples collected downwind of Asia during the airborne Transport and Chemical Evolution over the Pacific (TRACE-P) field campaign (February-April 2001). Air mass age was important for selecting appropriate field data to compare with laboratory predictions of C5 alkyl nitrate production rates. In young, highly polluted air masses, the ratio between the production rates of 3-pentyl nitrate and 2-pentyl nitrate from n-pentane was 0.60-0.65. These measured ratios show excellent agreement with results from a field study in Germany (0.63 ± 0.06), and they agree better with predicted ratios from older laboratory kinetic studies (0.63-0.66) than with newer laboratory results (0.73 ± 0.08). TRACE-P samples that did not show influence from marine alkyl nitrate sources were used to investigate photochemical alkyl nitrate evolution. Relative to 2-butyl nitrate/n-butane, the measured ratios of ethyl nitrate/ethane and 2-propyl nitrate/propane showed notable deviations from modeled values based on laboratory kinetic data, suggesting additional Asian sources of their alkyl peroxy radical precursors. By contrast, the measured ratios of 1-propyl-, 2-pentyl-, and 3-pentyl nitrate to their respective parent hydrocarbons were fairly close to modeled values. The 1-propyl nitrate findings contrast with field studies in North America, and suggest that air downwind of Asia was not significantly impacted by additional 1-propyl nitrate precursors. The sensitivity of modeled photochemical processing times to hydroxyl radical concentration, altitude, city ventilation times, and dilution is discussed.

Airborne measurements of cirrus‐activated C2Cl4 depletion in the upper troposphere with evidence against Cl reactions

[1] Airborne whole air samples collected over the western Pacific in spring, 2001 showed depletion of tetrachloroethene (C2Cl4) in every upper tropospheric (UT) air parcel that had interacted with large areas of cirrus less than three days upwind. The amount of C2Cl4 depletion showed a negative correlation with time since the interaction, consistent with the C2Cl4-depleted air parcels mixing with the ambient air as they moved downwind of the cirrus. Ethane and C2Cl4 both react relatively quickly with atomic chlorine (Cl) but ethane was not significantly depleted in these same air parcels, indicating that the C2Cl4 depletion cannot be attributed to Cl chemistry alone. Based on the minimum ethane depletion that can be detected by our measurements, a daytime upper limit of roughly 3 10 4 atom Cl cm 3 is indirectly estimated for heterogeneous chlorine activation by cirrus clouds in the UT in tropical- and mid-latitudes during spring. INDEX TERMS: 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0365 Atmospheric Composition and Structure: Troposphere— composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry;