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Update on VOC measurements

This report summarizes VOC measurements taken in East St. Louis in August 2013 using Proton Transfer Reaction-Mass Spectrometry (PTR-MS). The study focused on a variety of volatile organic compounds (VOCs), including isoprene, alpha-pinene, and various aromatics, tracked through a specialized sampling method. Findings indicate a significant correlation between CO and aromatics, with notable acid formation observed after sampling events. The analysis highlights the efficiency of sampling and the impacts of environmental conditions on VOC readings.

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Update on VOC measurements

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  1. Update on VOC measurements East St. Louis August 2013

  2. Proton Transfer Reaction - Mass Spectrometer (PTR - MS) • Soft ionization (no fragmentation) • PAR > PAH2O • Udriftis applied to direct to ions Primary ion: H3O+ H3O+ + VOC VOC-H+ + H2O “m/e” M+1 H3O+ + CH3COOH CH3COOHH+ + H2O “m/e” 61 (90%) 1a CH3CO+ + 2 H2O “m/e” 43 (10%) 1b Isomeric compounds: C2H5OH & FA, HO-CH2CHO & AA

  3. VOC’s monitored at the site (~ 20) • Isoprene  MVK & MACR • alpha-pinenenopinone • 3-carene • of biogenic origin • Benzene • p-xylene • Toluene • C9 aromatics (Trimethyl benzene) • Methylethylketone (solvent) • 2-pentanone • 2-hexanone • Anthropogenic • Primary & • Secondary • -biomass • burning • -oxidation • Methanol • HCHO • Acetaldehyde • acetonitrile • Acetone • Formic acid • Acetic acid • Glycolaldehyde Isomeric compounds

  4. “Acid Blaster” trap • GLYAL every two hours • Contains carboblack; treated with KOH • Removes the acids (FA,AA), let go alcohols e.g. methanol,glyal • Disrupts the signal of other masses: raw data is messy Ambient through the trap Trap bkg methanol AA & GLYAL • Findings • GLYAL doesn’t interfere with AA measurements at this site • GLYAL conc ~ < 1ppb • first ambient GLYAL???

  5. A good correlation between CO & aromatics such as benzene & toluene

  6. No monoterpenes or oxidation products; low isoprene alpha-pinene nopinone

  7. PTR & CO to PAM • Can sample before & after PAM • Can switch between PAM & ambient measurements

  8. Optimizing the sampling lines of PAM for VOC measurements lights on • Can see very efficient • acid formation after PAM; lights on lights off Ambient level Before PAM Ambient level

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