Abstract:[1] We report the first in situ measurements of hydrogen cyanide (HCN) and methyl cyanide (CH 3 CN, acetonitrile) from the Pacific troposphere (0-12 km) obtained during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) airborne mission (February-April 2001). Mean HCN and CH 3 CN mixing ratios of 243 ± 118 (median 218) ppt and 149 ± 56 (median 138) ppt, respectively, were measured. These in situ observations correspond to a mean tropospheric HCN column of 4.2 Â 10 15 molecules cm À2 and a CH … Show more
“…A third distinct plume was observed above northern Africa in boreal spring. Possibly due to ocean uptake (Li et al, 2000Singh et al, 2003), the tropospheric HCN amounts exhibit minima above the tropical and subtropical oceans, which are most pronounced during boreal winter and spring. There is generally good agreement with the HCN climatology obtained from spaceborne ACE-FTS measurements and with airborne in situ data from the INTEX-B campaign.…”
Section: Discussionmentioning
confidence: 99%
“…This minimum is probably caused by ocean uptake (cf. Li et al, 2000Li et al, , 2003Singh et al, 2003) during a long period without southern hemispheric biomass burning. Because of its long middle atmospheric lifetime of 2.5 years (Cicerone and Zellner, 1983), stratospheric HCN is able to map seasonal cycles.…”
Section: Seasonal Climatologymentioning
confidence: 99%
“…In recent years ocean uptake has been assumed to be the additional, major sink of HCN. Inclusion of this process in model calculations constrained by aircraft observations leads to a tropospheric lifetime of 5-6 months (Li et al, 2000Singh et al, 2003).…”
Section: Introductionmentioning
confidence: 99%
“…These observations led to the conclusion that biomass burning is a major source of atmospheric HCN and that there must be an additional sink of tropospheric HCN. Today, HCN is considered as an almost unambiguous tracer of biomass burning Singh et al, 2003;Yokelson et al, 2007;Lupu et al, 2009). HCN has been used as tracer of biomass burning by, for example, Glatthor et al (2009) and Tereszchuk et al (2013).…”
“…A third distinct plume was observed above northern Africa in boreal spring. Possibly due to ocean uptake (Li et al, 2000Singh et al, 2003), the tropospheric HCN amounts exhibit minima above the tropical and subtropical oceans, which are most pronounced during boreal winter and spring. There is generally good agreement with the HCN climatology obtained from spaceborne ACE-FTS measurements and with airborne in situ data from the INTEX-B campaign.…”
Section: Discussionmentioning
confidence: 99%
“…This minimum is probably caused by ocean uptake (cf. Li et al, 2000Li et al, , 2003Singh et al, 2003) during a long period without southern hemispheric biomass burning. Because of its long middle atmospheric lifetime of 2.5 years (Cicerone and Zellner, 1983), stratospheric HCN is able to map seasonal cycles.…”
Section: Seasonal Climatologymentioning
confidence: 99%
“…In recent years ocean uptake has been assumed to be the additional, major sink of HCN. Inclusion of this process in model calculations constrained by aircraft observations leads to a tropospheric lifetime of 5-6 months (Li et al, 2000Singh et al, 2003).…”
Section: Introductionmentioning
confidence: 99%
“…These observations led to the conclusion that biomass burning is a major source of atmospheric HCN and that there must be an additional sink of tropospheric HCN. Today, HCN is considered as an almost unambiguous tracer of biomass burning Singh et al, 2003;Yokelson et al, 2007;Lupu et al, 2009). HCN has been used as tracer of biomass burning by, for example, Glatthor et al (2009) and Tereszchuk et al (2013).…”
“…Benzene is predominantly emitted during fossil fuel combustion and biomass burning and it has a lifetime of 10 days against oxidation by OH. It is believed that biomass burning is the main source of acetonitrile to the atmosphere (de Gouw et al, 2003c), while estimates of its atmospheric lifetime range from ∼1 year against oxidation by OH, to months if ocean uptake is assumed to be significant (de Gouw et al, 2003c;Sanhueza et al, 2004;Singh et al, 2003). The global atmospheric budget of acetone, reviewed in Jacob et al (2002), includes primary sources from anthropogenic and biogenic emissions and a photochemical ocean source, in addition to secondary production from oxidation of anthropogenic and biogenic VOC.…”
Abstract. In this paper we describe measurements of volatile organic compounds (VOC) made using a Proton Transfer Reaction Mass Spectrometer (PTR-MS) aboard the UK Facility for Atmospheric Airborne Measurements during the African Monsoon Multidisciplinary Analyses (AMMA) campaign. Observations were made during approximately 85 h of flying time between 17 July and 17 August 2006, above an area between 4 • N and 18 • N and 3 • W and 4 • E, encompassing ocean, mosaic forest, and the Sahel desert. High time resolution observations of counts at mass to charge (m/z) ratios of 42, 59, 69, 71, and 79 were used to calculate mixing ratios of acetonitrile, acetone, isoprene, the sum of methyl vinyl ketone and methacrolein, and benzene respectively using laboratory-derived humidity-dependent calibration factors. Strong spatial associations between vegetation and isoprene and its oxidation products were observed in the boundary layer, consistent with biogenic emissions followed by rapid atmospheric oxidation. Acetonitrile, benzene, and acetone were all enhanced in airmasses which had been heavily influenced by biomass burning. Benzene and acetone were also elevated in airmasses with urban influence from cities such as Lagos, Cotonou, and Niamey. The observations provide evidence that both deep convection and mixing associated with fair-weather cumulus were responsible for vertical redistribution of VOC emitted from the surface. Profiles over the ocean showed a depletion of acetone in the marine boundary layer, but no significant decrease for acetonitrile.
Isocyanic acid (HNCO) has only recently been measured in the ambient atmosphere, and many aspects of its atmospheric chemistry are still uncertain. HNCO was measured during three diverse field campaigns: California Nexus-Research at the Nexus of Air Quality and Climate Change (CalNex 2010) at the Pasadena ground site, Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT 2011) at the Boulder Atmospheric Observatory (BAO) in Weld County, CO, and Biofuel Crops emission of Ozone precursors intensive (BioCORN 2011), in a cornfield NW of Fort Collins, CO. Mixing ratios varied from below detection limit (~0.003 ppbv) to over 1.2 ppbv during a period when agricultural burning impacted the BAO Tower site. Urban areas, such as the CalNex 2010 Pasadena site, appear to have both primary (combustion) and secondary (photochemical) sources of HNCO, 50 ± 9%, and 33 ± 12%, respectively, while primary sources were responsible for the large mixing ratios of HNCO observed during the wintertime NACHTT study in suburban Colorado. Isocyanic acid during the BioCORN study in rural NE Colorado was closely correlated to ozone and therefore likely photochemically produced as a secondary product from amines or formamide. The removal of HNCO from the lower atmosphere is thought to be due to deposition, as common gas phase loss processes of photolysis and reactions with hydroxyl radicals, are slow. These ambient measurements are consistent with some HNCO deposition, which was evident at night at these surface sites.
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