Analysis of ambient measuremements of Formaldehyde, PANs, and CO, at the eastern part of Houston during TexAQS SHARP 2009

For about 6 weeks in the time frame April-June 2009 the University of Houston carried out measurements of formaldehyde (HCHO), peroxyacyl nitrates (PANs) and carbon monoxide (CO) at the TCEQ/City of Houston air quality measurement site Clinton Drive, located in the eastern part of Houston in the close vicinity of the Ship Channel. Additional data for sulfur dioxide (SO₂) nitrogen oxides (NO_x), ozone (O₃) and volatile organic compounds (VOC) as well as meteorological data was provided by the City of Houston and TCEQ. The main objective of this work was to establish correlationships of HCHO with PAN, CO, SO₂, and VOCs to distinguish between potential primary sources of HCHO (e.g. traffic, industrial releases) and secondarily formed HCHO. In addition, this analysis considers dependencies on wind direction to identify potential primary sources for HCHO. For the most period of study diurnal variations of formaldehyde coincide with PANs indicating secondary formation of HCHO. While during major parts of the campaign concentration levels were close to background levels, some enhanced values were found in the late April. Events with significant increase of formaldehyde concentration over 10 ppb as well as PAN amount were observed in early May, last week of May and early June. During this period the patterns of HCHO and PANs appreciably differ on some occasions, in particulary during morning hours, indicating possible primary sources of formaldehyde.