Preprints
https://doi.org/10.5194/acp-2021-565
https://doi.org/10.5194/acp-2021-565

  26 Jul 2021

26 Jul 2021

Review status: this preprint is currently under review for the journal ACP.

Measurement report: Summertime and wintertime VOCs in Houston: Source apportionment and spatial distribution of source origins

Bavand Sadeghi, Arman Pouyaei, Yunsoo Choi, and Bernhard Rappenglueck Bavand Sadeghi et al.
  • Department of Earth and Atmospheric Science, University of Houston, 77054, USA

Abstract. The seasonal variations of volatile organic compounds (VOCs) was studied in the Houston metropolitan area in the summertime and wintertime of 2018. The analysis of hourly measurements obtained from the automated gas chromatograph (auto-GC) network showed the total VOC average concentrations of 28.68 ppbC in the summertime and 33.92 ppbC in the wintertime. The largest contributions came from alkane compounds, which accounted for 61 % and 82 % of VOCs in the summer and winter, respectively. We performed principal component analysis (PCA) and Positive Matrix Factorization (PMF) and identified seven factors in the summertime and six factors in the wintertime, among which alkane species formed three factors according to their rate of reactions in both seasons: (1) the emissions of long-lived tracers from oil and natural gas (ONG long-lived species), (2) fuel evaporation, and (3) the emissions of short-lived tracers from oil and natural gas (ONG short-lived species). Two other similar factors were (4) emissions of aromatic compounds and (5) alkene tracers of ethylene and propylene. Summertime factor 6 was associated with acetylene, and one extra summertime factor 7 was influenced by the biogenic emissions. The factor 6 of wintertime was affected by vehicle exhaust. Higher nighttime and lower daytime values of the ethylene/acetylene ratios during the summertime indicated the stronger impacts of ethylene photochemical degradation. Also, the exploration of the photochemical processes of the VOCs showed that the ethylene and propylene had the highest contributions to the summertime and wintertime ozone formation as well as the emissions of the isoprene, which showed a high impact on summertime ozone. Our results acknowledged that ethylene and propylene continue to be significant emissions of VOCs, and their emissions control would help the mitigation of the ozone of Ship Channel. Based on trajectory analysis, we identified main VOC emission sources in Houston Ship Channel (HSC) local industrial areas and regions south of the HSC. Ambient VOC concentrations measured at the HSC were influenced by the emissions from the petrochemical sectors and industrial complexes, especially from the Baytown refinery and Bayport industrial district next to the HSC and Galveston Bay refineries at the south of the study area.

Bavand Sadeghi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-565', Anonymous Referee #1, 29 Aug 2021
  • RC2: 'Comment on acp-2021-565', Anonymous Referee #2, 03 Sep 2021

Bavand Sadeghi et al.

Bavand Sadeghi et al.

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Short summary
The most significant contributions of VOCs over the Houston Ship Channel came from alkanes. Light alkanes were dominant sources in both seasons. We explored the photochemical reaction of organic compounds and studied their contributions to ozone formation. Ethylene and propylene have the highest. Through weighted trajectory, VOCs at Lynchburg Ferry site was influenced by petrochemical sectors of Baytown and Galveston Bay refineries and industrial facilities of the Bayport industrial district.
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