Effects of wood moisture on emission factors for PM2.5, particle numbers and particulate-phase PAHs from Eucalyptus globulus combustion using a controlled combustion chamber for emissions

Abstract

Polycyclic aromatic hydrocarbons, PM_2.5 and micrometer-sized particles are mainly emitted by residential wood combustion, affecting air pollution in the cities of Chile. Eucalyptus globulus (EG) at 0% and 25% wood moisture was burning using a new controlled combustion chamber for emissions (3CE) to determine the emission factors of PM_2.5, micrometer-sized particle numbers (0.265μm to 34.00μm) and 16 EPA-PAHs plus retene adsorbed on PM_2.5 quartz filters. A method using accelerated solvent extraction, concentration, clean-up and GC-MS is proposed for determining emission factors for 16 EPA-PAHs for the concentration from biomass combustion. Chromatographic conditions and analytical steps were optimized in terms of linearity, selectivity, limits of detection and quantification, precision and accuracy. The recovery obtained from urban dust SRM 1649A (NIST reference material) analyses was between 63% (benzo[b]fluoranthene) and 102% (benzo[k]fluoranthene). In this investigation, it was shown that increasing the wood moisture in combustion tests decreased combustion efficiency (93% to 49%) and increased the emission factors of total PAHs (5215.47ngg^-1 to 7644.48ngg^-1), the gravimetric PM2.5 (2.01g kg^-1 to 22.90gkg^-1) and the total number of measured micrometer-sized particles (3.15×1012 particles kg^-1 to 1.33×1013 particles kg^-1) due to incomplete combustion. The PM_2.5 emission rates (ERs) were estimated using EG at 0% WM (2.39g^-1 to 3.15gh^-1) and 25% WM (27.32gh^-1 to 35.77gh^-1) for three regions of Chile. In almost all regions, the Chilean emission regulations were exceeded for PM_2.5 from wood combustion in the heater (stove with thermal power ≤8kW and emission limit of 2.5gh^-1). Finally, when using wet wood for residential combustion, the amount of PAHs on the PM_2.5 increased, presenting a potential hazard to population health. Therefore, improvements are necessary in the current regulation of PM emissions.

Keywords: Combustion chamber; Emission factors; Emission rates PM(2.5); Eucalyptus wood combustion; Polycyclic aromatic hydrocarbons; Wood humidity.