Nonmethane hydrocarbons and halocarbons were measured during two Lagrangian experiments conducted in the lower troposphere of the North Atlantic as part of the June 1992, Atlantic Stratosphere Transition Experiment/Marine Aerosol and Gas Exchange (ASTEX/MAGE) expedition. The first experiment was performed in very clean marine air. Meteorological observations indicate that the height of the marine boundary layer rose rapidly, entraining free tropospheric air. However, the free tropospheric and marine boundary layer halocarbon concentrations were too similar to allow this entrainment to be quantified by these measurements. The second Lagrangian experiment took place along the concentration gradient of an aged continental air mass advecting from Europe. The trace gas measurements confirm that the National Center for Atmospheric Research (NCAR) Electra aircraft successfully intercepted the same air mass on consecutive days. Two layers, a surface layer and a mixed layer with chemically distinct compositions, were present within the marine boundary layer. The composition of the free troposphere was very different from that of the mixed layer, making entrainment from the free troposphere evident. Concentrations of the nonmethane hydrocarbons in the Lagrangian surface layer were observed to become depleted relative to the longer‐lived tetrachloroethene. A best fit to the observations was calculated using various combinations of the three parameters, loss by reaction with hydroxyl, loss by reaction with chlorine, and/or dilution from the mixed layer. These calculations provided estimated average concentrations in the surface layer for a 5‐hour period from dawn to 11 UT of 0.3 ± 0.5 × 106 molecules cm−3 for HO, and 3.3 ± 1.1 × 104 molecules cm−3 for Cl. Noontime concentration estimates were 2.6 ± 0.7 × 106 molecules cm−3 for HO and 6.5 ± 1.4 × 104 molecules cm−3 for Cl.

A total of 1667 whole air samples were collected onboard the NASA DC-8 aircraft during the 6-week Pacific Exploratory Mission over the western Pacific (PEM-West A) in September and October 1991. The samples were assayed for 15 C2-C7 hydrocarbons and six halocarbons. Latitudinal (0.5øS to 59.5øN) and longitudinal (114øE to 122øW) profiles were obtained from samples collected between ground level and 12.7 km. Thirteen of the 18 missions exhibited at least one vertical profile where the hydrocarbon mixing ratios increased with altitude. Longitude-latitude color patch plots at three altitude levels and three-dimensional color latitudealtitude and longitude-altitude contour plots exhibit a significant number of middle-upper tropospheric pollution events. These and several lower tropospheric pollution plumes were characterized by comparison with urban data from Tokyo and Hong Kong, as well as with natural gas and the products from incomplete combustion. Elevated levels of nonmethane hydrocarbons (NMHC) and other trace gases in the upper-middle free troposphere were attributed to deep convection over the Asian continent and to typhoon-driven convection near the western Pacific coast of Asia. In addition, NMHCs and CH3CC13 were found to be useful tracers with which to distinguish hydrocarbon and halocarbon augmented plumes emiued from coastal Asian cities into the northwestern Pacific.

Approximately 900 whole air samples were collected and assayed for selected C2‐C10 hydrocarbons and seven halocarbons during the 5‐week Arctic Boundary Layer Expedition (ABLE) 3B conducted in eastern Canadian wetland areas. In more than half of the 46 vertical profiles flown, enhanced nonmethane hydrocarbon (NMHC) concentrations attributable to plumes from Canadian forest fires were observed. Urban plumes, also enhanced in many NMHCs, were separately identified by their high correlation with elevated levels of perchloroethene. Emission factors relative to ethane were determined for 21 hydrocarbons released from Canadian biomass burning. Using these data for ethane, ethyne, propane, n‐butane, and carbon monoxide enhancements from the literature, global emissions of these four NMHCs were estimated. Because of its very short atmospheric lifetime and its below detection limit background mixing ratio, 1,3‐butadiene is an excellent indicator of recent combustion. No statistically significant emissions of nitrous oxide, isoprene, or CFC 12 were observed in the biomass‐burning plumes encountered during ABLE 3B. The presence of the short‐lived biogenically emitted isoprene at altitudes as high as 3000 m implies that mixing within the planetary boundary layer (PBL) was rapid. Although background levels of the longer‐lived NMHCs in this Canadian region increase during the fire season, isoprene still dominated local hydroxyl radical photochemistry within the PBL except in the immediate vicinity of active fires. The average biomass‐burning emission ratios for hydrocarbons from an active fire sampled within minutes of combustion were, relative to ethane, ethene, 2.45; ethyne 0.57; propane, 0.25; propene, 0.73; propyne, 0.06; n‐butane, 0.09; i;‐butane, 0.01; 1‐butene, 0.14; cis‐2‐butene, 0.02; trans‐2‐butene, 0.03; i‐butylene, 0.07; 1,3‐butadiene, 0.12; n‐pentane, 0.05; i‐pentane, 0.03; 1‐pentene, 0.06; n‐hexane, 0.05; 1‐hexene, 0.07; benzene, 0.37; toluene, 0.16.

Abstract. Vertical profiles of volatile organic compounds (VOCs) within the convective boundary layer (CBL) were measured at a tropical forest site in the Peruvian Amazon during July 1996 from a tethered balloon sampling platform. A profiling technique based on the collection of VOCs onto solid adsorbent cartridges was used to take samples at altitudes up to 1600 m above ground. VOC analysis was performed by thermal desorption with gas chromatographic separation and mass spectrometric and flame ionization detection. A total of 26 VOCs were stmcturally identified. VOCs were dominated by biogenic compounds. Highest concentrations were observed for isoprene, followed by c•-pinene, p-cymene, and [3-pinene. Combined, all monoterpenes accounted for approximately 15-20% of the total carbon from biogenic VOCs (BVOCs). The isoprene oxidation products methacrolein (MAC), methylvinylketone (MVK), and 3-methylfuran were observed throughout the CBL. Besides the ubiquitous chlorofluorocarbons, anthropogenic VOC concentrations were at the lower end of concentration ranges observed in rural air. From the vertical profiles, BVOC surface flux estimates were derived. Emission rates were estimated from five vertical profiles using the mixed-layer gradient and CBL budget methods. Emission estimates

Abstract.We simulate accumulation of AleO3 particles in the atmosphere produced by solid-fueled rocket motors by using the Goddard Institute for Space