Evaluation of the Industrial Point Source Emission Inventory for the Houston Ship Channel Area Using Ship-Based, High-Time-Resolution Measurements of Volatile Organic Compounds

Proton Transfer Reaction Ion Trap Mass Spectrometry (PIT-MS) was used to characterize several large (>100 ppbv) industrial volatile organic compound (VOC) plumes in the Houston, Texas Ship Channel observed from the NOAA R/V Ronald H. Brown during the 2006 Texas Air Quality Study (TexAQS) field campaign. Because the ship was sampling close to numerous large emission sources, many of the observed plumes were highly transient making the PIT-MS, with its high time resolution and continuous full mass scan capability, a very useful tool for VOC characterization of the plumes. Plume compositions are compared to the TexAQS2K6 Houston-Galveston-Brazoria Point Source Emission Inventory for individual aromatic compounds; oxygenated VOCs and other selected industrial VOCs observed by PIT-MS. In many cases, we do not find good agreement between the measured plume composition and the VOC speciation in the emissions inventory. These observations are not surprising, as previous research has shown that emission fluxes of individual VOCs may be underestimated by as much as 1-2 orders of magnitude in inventories for the Houston area. In many cases, PIT-MS measurements show clear evidence of industrial emissions not previously identified by the Proton Transfer Reaction (PTR) method. The frequent lack of correlation between large VOC enhancements and enhancements in SO2, NOx and CO suggests large, non-combustion sources of VOCs.