31-16 Evaluation of Large-Particle Breakthrough Past PM2.5 Inlets During Personal Filter Sampling in Ghana

Session: Environmental Geochemistry and Health (Posters)

Poster Booth No.: 42

Presenting Author:

Isabella Placantonakis

Authors:

Placantonakis, Isabella¹, Mutjaba, Mohammed², Ross, James³, Karaba, Charles⁴, Ebert, Yael⁵, Kaali, Seyrem⁶, Lee, Alison ⁷, Jack, Darby⁸, Chillrud, Steven⁹, Poku Asante, Kwaku¹⁰

(1) Environmental Science Department, Barnard College, NYC, NY, USA, (2) Kintampo Health Research Center, Kintampo, Ghana, (3) Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA, (4) Kintampo Health Research Centre, Kintampo, Ghana, (5) Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA, (6) Kintampo Health Research Centre, Kintampo, Ghana, (7) Icahn School of Medicine at Mt. Sinai, NYC, NY, USA, (8) Mailman School of Public Health at Columbia University, NYC, NY, USA, (9) Lamont-Doherty Earht Observatory of Columbia University, Palisades, NY, USA, (10) Kintampo Health Research Centre, Kintampo, Ghana,

Abstract:

Accurate measurement of personal PM2.5 exposure is essential for understanding the health impacts of household air pollution. The GRAPHS (Ghana Randomized Air Pollution and Health Study) team uses personal air monitors to measure PM2.5 exposures among mothers and children. However, GRAPHS identified large particles (>> 2.5 µm) sporadically bypassing the size-selective cyclone inlet of UPAS v2+ monitors (Access Sensor Technologies) and accumulating on filters, biasing gravimetric PM2.5 measurements by median factors of 2-3. Field evaluations were conducted in Ghana to assess the effectiveness of several types of manufacturer-designed, precyclonic impactor inserts intended to improve removal of particles >2.5µm. Ninety-one mothers and children each wore two collocated monitors for 24–48 hours: one with the original cyclone-only inlet and the other with an updated impactor insert plus cyclone. These paired deployments addressed two questions: (1) whether precyclonic inserts eliminated large-particle breakthrough and (2) does the large particle composition inform the cause of the breakthrough or allow for a correction factor for the biased filters. Close visual  inspections of the filters and inlets were performed in Ghana, leading to subsequent insert improvements and use of silicone grease. Monitors with precyclonic impactors collected one-half to one-third of the gravimetric mass measured on collocated cyclone-only monitors. Differences in elemental concentrations measured by energy dispersive XRF on collocated filters were used to estimate large breakthrough particle composition, while filters from units with later impactor inserts characterized PM2.5 composition. K&Cl and Si&Fe were strongly correlated and served as tracers for biomass combustion and crustal material, respectively. Assuming each pair of collocated monitors sampled the same PM2.5, elemental concentrations from the insert filter were subtracted from those of the collocated cyclone-only monitor to estimate large particle composition. Biomass tracer elements exhibited similar elemental ratios in large and fine particles but had lower concentrations in breakthrough particles, whereas crustal elements showed similar ratios and concentrations, indicating large breakthrough particles were dominated by crustal material and had a smaller biomass contribution than that measured in the PM2.5 fraction. Consequently, XRF analyses indicate there is nothing special about the large breakthrough particles nor suggest a correction method. Importantly, precyclonic impactors appear to largely eliminate large-particle breakthrough thereby preserving gravimetric PM2.5 measurements. Additional testing is ongoing.

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