10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Gaseous and Speciated Particulate Emissions from the Open Burning of Wastes from Tree Pruning
CÉLIA ALVES, Ana Vicente, Estela Vicente, Margarita Evtyugina, María Fernández-Amado, Purificación López-Mahía, University of Aveiro
Abstract Number: 409 Working Group: Carbonaceous Aerosol
Abstract Open-air burning of wastes from tree pruning is a common practice in many regions worldwide. However, this practice degrades air quality and contributes to the greenhouse effect. Aiming at characterizing the gaseous emissions, the smoke from the open burning of vine, olive, willow and acacia branches was sampled into Tedlar bags. In parallel, a high volume sampler was used to collect PM10 on quartz filters. The gaseous compounds in Tedlar bags were assessed using a Fourier transform infrared gas analyzer. PM10 filters were subjected to the following determinations: ion chromatography, organic and elemental carbon (OC and EC) by a thermo-optical technique, and organic speciation by gas chromatography-mass spectrometry after multisolvent extraction. Emission factors were calculated by stoichiometric considerations using the carbon mass balance method and were as follows (g/kg biofuel, dry basis): 1564-1663 CO2, 40.6-87.7 CO, 2.06-5.82 CH4, 0.91-3.73 ethane, < 0.99 ethylene, < 1.80 formaldehyde, 2.70-7.44 OC, 0.32-1.18 EC, and 8.76-20.1 PM10. The modified combustion efficiency (MCE) was always higher than 0.95, suggesting predominance of flaming combustions. MCE was strongly correlated with CO2 and anticorrelated with CO. From the PM10 emitted, water soluble ions represented from 5.3 % (vines) to 12.7 % (acacia). Potassium was the dominant ionic species, accounting for a PM10 content from 1.4 to 4.7 % wt. While in smoke from vines and olive combustion the NaCl mass fractions were lower than 0.9 %, higher weight percentages were obtained for willow (3.6) and acacia (6.7). On average, OC accounted for PM10 mass fractions of 33.4, 19.3, 32.3 and 36.5 % for willow, acacia, vines and olive, respectively, whist EC represented 5.04, 2.34, 3.53 and 7.32 %, by the same order. Mean levoglucosan (L) mass fractions of 18.1, 13.2, 17.1 and 12.4 mg/g PM10 were obtained in samples from the combustion of vines, olive, willow and acacia, respectively. The ratios between this anhydrosugar and its stereoisomers, mannosan (M) and galactosan (G), were within the wide range of values reported for other sources, such as residential biomass burning of hardwood and softwood, forest fire smoke or grass combustion [1]. In the present study, the mean ratios varied from 4.2 and 8.8 for L/M and between 2.3 and 3.7 for L/(M+G). PAH emissions from the combustion of vines and olive branches were one order of magnitude higher than those from acacia and willow. PAHs with 3 or 4-rings were dominant. Among these, the most representative in terms of mass concentrations (µg/g PM10) were: acenaphthylene (27.7-90.9), fluorene (92.7-133), phenanthrene (3.96-281), fluoranthene (17.8-510), pyrene (22.7-511), and chrysene (16.5-545). Benzo[a]pyrene is often used as a surrogate for all carcinogenic PAHs. Its mean mass fractions ranged from 6.51 (willow) to 91.3 (vines) µg/g PM10. Retene, commonly pointed out as a molecular tracer of softwood combustion, was always present (8.23-18.9 µg/g PM10), regardless of the pruning residue. The detection of this polyaromatic in particles from multiple sources raises doubts about its suitability as a tracer for the combustion of conifers [2]. The new databases of the present study can potentially contribute to more accurate source apportionment results when applying receptor models, as well as to improve emission inventories.
Acknowledgments: M.F.A. is grateful to REGATA Network for the grant for her research stay at University of Aveiro. Thanks are given to FCT for funding CESAM (UID/AMB/50017) and scholarships SFRH/BPD/88988/2012, FRH/BD/117993/2016 and SFRH/BPD/123176/2016.