Volatile chemical products (VCPs), such as pesticides, coatings, cleaning products, and personal care products, significantly contribute to anthropogenic VOC emissions in urban areas. VCPs are shown to contribute to over half of the VOC emissions, OH reactivity, and secondary organic aerosol (SOA) formation in major metropolitan areas of North America and Europe. However, the emission, spatial and temporal distribution, and impacts of VCPs often show inhomogeneity among urban areas and climate zones, creating uncertainties. Houston, Texas has no prior reported VCP emissions despite being the fourth-largest city in the United States. In this study, we establish the first spatial and temporal measurements of selected VCPs in Houston, TX using a Vocus 2R Chemical Ionization Mass Spectrometer (Vocus 2R CIMS) on a mobile platform. Ambient measurements of 5 major VCP tracers, including D5-siloxane, monoterpenes, para-dichlorobenzene, para-chlorobenzotrifluoride (PCBTF), and Texanol, were obtained in two seasons during January 2023 and August 2023. Most measured compounds showed significantly higher concentrations in the summer compared with winter, apart from D5-siloxane and PCBTF. Using a customized 0-D box model, the emissions in winter for D5-siloxane, monoterpenes, para-dichlorobenzene, PCBTF, and Texanol in the Greater Houston Metropolitan Area are estimated to be 382, 376, 15, 12, and 101 mg/person/day in winter and 631, 1771, 210, 58, and 313 mg/person/day in summer, respectively. The study provides unique spatial and temporal quantification of VCPs in a major metropolitan city in the subtropical climate zone, further improving understanding of urban VCP emissions and their atmospheric implications on ozone and SOA formation.

Timothy Onasch

Appearances