Airborne mercury speciation at the western edge of the Houston Ship Channel, TEXAQS 2009 SHARP study

From April 15 to June 3, 2009, gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), and fine (PM2.5) particulate-bound mercury (FPM) were monitored at the City of Houston Clinton Drive (CAMS 304) site as part of the Texas Air Quality Study of Houston Atmospheric Radical Precursors (TEXAQS 2009 SHARP). Instrumentation consisted primarily of Tekran mercury sensor models 2537a, 1130, 1135, for the measurement of GEM, RGM, and FPM, respectively. Overall, the mercury speciation measurements showed large episodic plume enhancements of all mercury species during several periods associated with wind directions from the Houston Ship Channel industrial complex.

The resultant dataset showed GEM concentrations in the range of 1.2 (near normal background) to 8.8 ng m-3 in plumes. Reactive gaseous mercury varied from below detection limit (BDL) to ~90 pg m-3 in plumes. And fine particulate-bound mercury varied from BDL to ~100 pg m-3 in plumes.

During multi-day time periods when the mercury species were not directly enhanced by local plumes, GEM was elevated at night, typically peaking between 0300 and 0700 CST, while RGM and FPM species were enhanced during the day with very broad peaks centered at ~1500 CST. RGM and FPM (both water soluble) dropped to very low values during rain events.