Gaseous and speciated particulate emissions from the open burning of wastes from tree pruning

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 particle (PM10) and gaseous emissions, the smoke from the open burning of vine, olive, willow and acacia branches was sampled and then analyzed by multiple techniques. Emission factors of gaseous compounds were as follows (g kg−1 biofuel, dry basis): 1564–1663 CO2, 40.6–87.7 CO, 2.06–5.82 CH4, 0.91–3.73 ethane, <0.99 ethylene, and <1.80 formaldehyde. PM10, organic carbon (OC) and elemental carbon (EC) emissions were in the ranges 8.76–20.1, 2.70–7.44, and 0.32–1.18 g kg−1 biofuel, dry basis, respectively. From the PM10 emitted, water soluble ions represented from 5.3% (vines) to 13.6% (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%, while EC represented 5.04, 2.34, 3.53 and 7.32% for willow, acacia, vines and olive combustion, respectively. Emissions of polycyclic aromatic hydrocarbons (PAHs) from the combustion of vines and olive branches were one order of magnitude higher than those from acacia and willow. Mean levoglucosan mass fractions of 18.1, 13.2, 17.1 and 12.4 mg g−1 PM10 were obtained in samples from the combustion of vines, olive, willow and acacia, respectively. Smoke particles also encompassed several other polar constituents, such as various types of acids, phenolic compounds, sterols, and polyols, whose contribution to the PM10 mass varied with the biofuel burned.