ISSN:
1573-0662
Keywords:
nonmethane hydrocarbons
;
troposphere
;
ambient hydrocarbon measurements
;
seasonal variation
;
biogenic emissions of light olefins
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Geosciences
Notes:
Abstract Long-term measurements of light hydrocarbons(C2–C5 HC‘s) were performed in the courseof the EUROTRAC sub-project TOR (Tropospheric Ozone Research) in thesouthern part of the Black Forest in southwest Germany. The measurementscover a time period of five years (January 1989–January 1994) and theair samples were analyzed onsite by an automated GC-system. Pronouncedannual cycles with maxima in late winter and minima in late summer wereobserved in the case of the slowly reacting hydrocarbons ethane, propane andacetylene, reflecting the fact that the seasonal variation of these speciesis photochemically driven. For the shorter lived compounds the seasonalvariations are considerably weaker, connected with a stronger scatter of theindividual measurements, which is caused by different distances to theirmain sources for different wind vectors as well as by varying sourcestrengths. From a detailed characterization of the hydrocarbon patterns theinfluence of two different sources could be distinguished. An extrapolationto photochemical age of zero and completion of our data with those from aspeciated VOC inventory yields an estimated [VOC]/NOx sourceratio for Schauinsland of ≈5 [ppbC/ppb]. Comparable[VOC]/NOx ratios are observed in automobile exhaust gasesunder low speed conditions, which points to the important role of trafficunder conditions, when freshly polluted air masses from a near-by city areadvected to the site. From an investigation of the photochemical age of theadvected air masses it becomes clear that there must exist biogenic sourcesof light olefins in the vicinity of the observatory during the vegetationperiod. For propene and the butenes we are able to estimate a lower limit oftheir contributions in terms of reactivity to the total reactivity(∑ [HC](i)⋅ k_OH(i),i=C2-C5) of the measured hydrocarbons. Forlowest pollution levels in summer (acetylene 〈300 ppt, about 40%of the summer values) this source is found to be responsible for15–20% of the total C2–C5reactivity observed at Schauinsland. On the average, this source accountsfor 5–10% of the total C2–C5reactivity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1005878018619
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