Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE): Emissions of particulate matter from wood and dung cooking fires, garbage and crop residue burning, brick kilns, and other sources

摘要

The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) characterized widespread and under-sampled combustion sources common to South Asia, including brick kilns, garbage burning, diesel and gasoline generators, diesel groundwater pumps, idling motorcycles, traditional and modern cooking stoves and fires, crop residue burning, and a heating fire. Fuel-based emission factors (EF; with units of pollutant mass emitted per kg of fuel combusted) were determined for fine particulate matter (PM), organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals, and organic species. For the forced draught zig-zag brick kiln, EF ranged 1–19 g kg with major contributions from OC (7 %), sulfate expected to be in the form of sulfuric acid (31.9 %), and other chemicals not measured (e.g., particle bound water). For the clamp kiln, EF ranged 8–13 g kg, with major contributions from OC (63.2 %), sulfate (20.8 %), and ammonium (14.2 %). Our brick kiln EF values may exceed those previously reported, partly because we sampled emissions at ambient temperature after emission from the stack or kiln allowing some particle-phase OC and sulfate to form from gaseous precursors. The combustion of mixed household garbage under dry conditions had an EF of 7.4 ± 1.2 g kg, whereas damp conditions generated the highest EF of all combustion sources in this study, reaching up to 125 ± 23 g kg. Garbage burning emissions contained relatively high concentrations of polycyclic aromatic compounds (PAHs), triphenylbenzene, and heavy metals (Cu, Pb, Sb), making these useful markers of this source. A variety of cooking stoves and fires fueled with dung, hardwood, twigs, and/or other biofuels were studied. The use of dung for cooking and heating produced higher EF than other biofuel sources and consistently emitted more PM and OC than burning hardwood and/or twigs; this trend was consistent across traditional mud stoves, chimney stoves, and 3-stone cooking fires. The comparisons of different cooking stoves and cooking fires revealed the highest PM emissions from 3-stone cooking fires (7.6–73 g kg), followed by traditional mud stoves (5.3–19.7 g kg), mud stoves with a chimney for exhaust (3.0–6.8 g kg), rocket stoves (1.5–7.2 g kg), induced-draught stoves (1.2–5.7 g kg), and the bhuse chulo stove (3.2 g kg), while biogas had no detectable PM emissions. Idling motorcycle emissions were evaluated before and after routine servicing at a local shop, which decreased EF from 8.8 ± 1.3 g kg to 0.71 ± 0.4 g kg when averaged across five motorcycles. Organic species analysis indicated that this reduction in PM was largely due to a decrease in emission of motor oil, probably from the crankcase. The EF and chemical emissions profiles developed in this study may be used for source apportionment and to update regional emission inventories.