Browsing by Author "Rappengluck, B"

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    An urban photochemistry study in Santiago de Chile
    (PERGAMON-ELSEVIER SCIENCE LTD, 2005) Rappengluck, B; Schmitz, R; Bauerfeind, M; Cereceda Balic, F; von Baer, D; Jorquera, H; Silva, Y; Oyola, P
    During spring time 2002 a field experiment was carried out in the Metropolitan Area of Santiago de Chile at three monitoring sites located along a SW-NE transect that represents upwind, downtown and downwind conditions, respectively. Three consecutive days (30 October-01 November 2002) reflecting different photochemical and meteorological conditions were selected. These days included two workdays and one holiday and thus the effect of different primary emissions could be investigated. A variety of trace gas measurements (O-3, NOx, CO, volatile organic compounds (VOC)) were obtained at these sites. Alkanes represent the largest VOC fraction at all sites, followed by aromatics and alkenes, the smallest fractions are represented by the alkynes or isoprene. Regarding reactivity ranking propene equivalent values show that during morning hours, alkenes are the most reactive compounds, at noon, aromatics are dominant, and in the afternoon isoprene becomes important. Alkanes do not contribute more than 20% to the total air mass reactivity despite being present at the higher concentration levels. Regarding liquefied petroleum gas (LPG) impacts, we find a threefold decrease of concentrations at the eastern side of the city-and no significant trend at Downtown Santiago-which we ascribe to a switch to natural gas in the higher income eastern side of town. The generation of ozone impacts above 50 ppbv is mainly due to anthropogenic traffic-related hydrocarbons. In addition, traffic emissions are contributing most to the formation of secondary organic aerosols (SOA). A model study was carried out, applying a Lagrange trajectory model coupled with photochemical and aerosol modules. The model results are in good agreement with the observations. Additionally, the relative contribution of the respective hydrocarbons to the ozone production in an air parcel along the trajectory was computed. The model also indicates SOA formation by means of oxidation of higher alkanes, alkenes, and aromatics, the latter being the major contributors to those secondary pollutants. (c) 2005 Elsevier Ltd. All rights reserved.
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    Receptor modeling of ambient VOC at Santiago, Chile
    (PERGAMON-ELSEVIER SCIENCE LTD, 2004) Jorquera, H; Rappengluck, B
    Ambient VOC measured at a 1996 spring campaign at Santiago, Chile, have been analyzed using the receptor models UNMIX and Positive Matrix Factorization (PMF). The ambient campaign took place at two sites: a downtown site, close to major traffic emissions, and a residential site, downwind of major industrial sources and highways. At the downtown site the following source apportionments estimates were obtained: fuel evaporation, 29.1 +/- 1.1%; gasoline exhaust, 22.0 +/- 3.4%; diesel exhaust, 18.1 +/- 2.9%; biogenic, LPG and evaporative emissions, 18.0 +/- 3.4%, unexplained: 12%. At the residential site, the following source apportionment was obtained: transported gasoline exhaust, 31.2 +/- 4.1%; local gasoline exhaust, 25.5 +/- 4.0%; evaporative losses, 11.7 +/- 2.8%; LPG losses, 11.0 +/- 2.5%; biogenic emissions, 7.7 +/- 1.7%; diesel exhaust, 6.2 +/- 1.5%; unexplained, 7.7%. Thus, near 70% of ambient VOC impacts at both sites are due to mobile sources. The receptor analyses produced source profiles that had distinctive, dominant compounds; in addition, source contributions exhibited diurnal profiles that were consistent with ambient temperature and wind speed data, and the expected activity patterns within the city. Typical errors in the source contributions vary between 15% for the larger sources-like gasoline exhaust-and 25% for the smaller sources-like biogenic emissions. It was found that the number of factors given by the UNMIX model was a good starting point to refine the solution using PMF. Both models showed good performance at discriminating between source profiles that had similar compositions in subsets of common species, but PMF was able to find better, cleaner source profiles that did UNMIX. At both monitoring sites LPG losses appear mixed in with other source profiles, and this feature could not be solved by adding more source profiles in the analyses; this was likely due to a lack of C-3 measurements needed to better resolve an LPG source profile. (C) 2004 Elsevier Ltd. All rights reserved.