Abstract
Abstract. We evaluate the rates of secondary production and primary emission of formaldehyde (CH2O) from petrochemical industrial facilities and on-road vehicles in the Houston Texas region. This evaluation is based upon ambient measurements collected during field studies in 2000, 2006 and 2009. The predominant CH2O source (92 ± 4% of total) is secondary production formed during the atmospheric oxidation of highly reactive volatile organic compounds (HRVOCs) emitted from the petrochemical facilities. Smaller contributions are primary emissions from these facilities (4 ± 2%), and secondary production (~3%) and primary emissions (~1%) from vehicles. The primary emissions from both sectors are well quantified by current emission inventories. Since secondary production dominates, control efforts directed at primary CH2O emissions cannot address the large majority of CH2O sources in the Houston area, although there may still be a role for such efforts. Ongoing efforts to control alkene emissions from the petrochemical facilities, as well as volatile organic compound emissions from the motor vehicle fleet, will effectively reduce the CH2O concentrations in the Houston region. We do not address other emission sectors, such as off-road mobile sources or secondary formation from biogenic hydrocarbons. Previous analyses based on correlations between ambient concentrations of CH2O and various marker species have suggested much larger primary emissions of CH2O, but those results neglect confounding effects of dilution and loss processes, and do not demonstrate the causes of the observed correlations. Similar problems must be suspected in any source apportionment analysis of secondary species based upon correlations of ambient concentrations of pollutants.
Highlights
Formaldehyde (CH2O) is an oxygenated volatile organic compound (VOC) that plays an important role in the formation of ozone pollution in urban areas
Based upon the 2000–2009 measurements and the 2005 emission inventory considered here, we have found that secondary production from alkenes emitted by petrochemical facilities and the on-road vehicle fleet is the major source of CH2O (95 ± 3 % of total) in HGB
We have evaluated the rates of secondary production and primary emission of CH2O from petrochemical industrial facilities and on-road vehicles in Houston Texas region based upon ambient measurements made in the 2000–2009 period and a measurement constrained emission inventory based www.atmos-chem-phys.net/12/3273/2012/
Summary
Formaldehyde (CH2O) is an oxygenated volatile organic compound (VOC) that plays an important role in the formation of ozone pollution in urban areas Both primary sources (i.e. direct emissions from anthropogenic sources) and secondary sources (i.e. production in the atmosphere during oxidation of other, directly emitted VOCs) contribute to atmospheric concentrations of CH2O. Houston is home to a very large industrial sector associated with petrochemical and petroleum refining activity, and these industrial activities are associated with the elevated CH2O concentrations Given this industrial activity, the relative contributions from primary and secondary sources may be significantly different from most urban areas. Our primary goal is to provide a quantitative analysis of CH2O emitted by primary sources and formed from secondary sources within the HGB ozone nonattainment area, the approach presented here is applicable to other urban areas and to other photochemical species.
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