Elise-Andrée Guérette

Development of a Particle-Trap Preconcentration-Soft Ionization Mass Spectrometric Technique for the Quantification of Mercury Halides in Air

Measurement of oxidized mercury, Hg(II), in the atmosphere poses a significant analytical challenge as Hg(II) is present at ultra-trace concentrations (picograms per cubic meter air). Current technologies are sufficiently sensitive to measure the total Hg present as Hg(II) but cannot determine the chemical speciation of Hg(II). We detail here the development of a soft ionization mass spectrometric technique coupled with preconcentration onto nano- or microparticle-based traps prior to analysis for the measurement of mercury halides in air. The current methodology has comparable detection limits (4-11 pg m(-3)) to previously developed techniques for the measurement of total inorganic mercury in air while allowing for the identification of HgX2 in collected samples. Both mercury chloride and mercury bromide have been sporadically detected in Montreal urban and indoor air using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). We discuss limitations and advantages of the current technique and discuss potential avenues for future research including quantitative trace measurements of a larger range of mercury compounds.

Fine particle emissions from tropical peat fires decrease rapidly with time since ignition

Abstract Southeast Asia experiences frequent fires in fuel‐rich tropical peatlands, leading to extreme episodes of regional haze with high concentrations of fine particulate matter (PM2.5) impacting human health. In a study published recently, the first field measurements of PM2.5 emission factors for tropical peat fires showed larger emissions than from other fuel types. Here we report even higher PM2.5 emission factors, measured at newly ignited peat fires in Malaysia, suggesting that current estimates of fine particulate emissions from peat fires may be underestimated by a factor of 3 or more. In addition, we use both field and laboratory measurements of burning peat to provide the first mechanistic explanation for the high variability in PM2.5 emission factors, demonstrating that buildup of a surface ash layer causes the emissions of PM2.5 to decrease as the peat fire progresses. This finding implies that peat fires are more hazardous (in terms of aerosol emissions) when first ignited than when still burning many days later. Varying emission factors for PM2.5 also have implications for our ability to correctly model the climate and air quality impacts downwind of the peat fires. For modelers able to implement a time‐varying emission factor, we recommend an emission factor for PM2.5 from newly ignited tropical peat fires of 58 g of PM2.5 per kilogram of dry fuel consumed (g/kg), reducing exponentially at a rate of 9%/day. If the age of the fire is unknown or only a single value may be used, we recommend an average value of 24 g/kg.