Exposure to source-specific VOCs around the Houston Ship Channel

Area of Science:

• Environmental Chemistry
• Atmospheric Science
• Air Quality Monitoring

Background:

• Atmospheric volatile organic compounds (VOCs) originate from human and natural sources, contributing to secondary pollutants like ozone and secondary organic aerosol.
• Understanding VOC sources is crucial for assessing human and ecosystem health impacts in urban environments.
• The Houston Ship Channel is an area with significant industrial activity and associated VOC emissions.

Purpose of the Study:

• To investigate and compare the sources of VOCs in the Houston Ship Channel area between 2012 and 2023.
• To assess spatial and temporal variations in ambient VOC levels and their contributing sources.
• To understand the relationship between source emissions and population exposures.

Main Methods:

• Utilized hourly VOC measurements from 8 Pollution Assessment Monitoring Stations (PAMS) sites.
• Analyzed spatial and temporal variations using coefficients of divergence (CoD) and squared Pearson correlation coefficients (r²).
• Resolved seven distinct VOC source types across the two study years.

Main Results:

• A shift in VOC source contributions was observed between 2012 and 2023, with petrochemical industries decreasing significantly.
• In 2023, a polymer production-related source emerged, and a distinct biogenic isoprene source from 2012 was no longer resolvable.
• Substantial spatial heterogeneity in VOC concentrations was noted, with most sites showing no dominant source type, suggesting localized exposures.

Conclusions:

• The industrial landscape and VOC emission profile in the Houston Ship Channel have evolved over the decade.
• Changes in industrial processes, particularly in polymer production, have altered the VOC source mix.
• The findings support the assessment that VOC exposures in the area are primarily driven by local sources.