Goetz, J. Douglas; Giordano, Michael R.; Stockwell, Chelsea E.; Christian, Ted J.; Maharjan, Rashmi; Adhikari, Sagar; Bhave, Prakash V.; Praveen, Puppala S.; Panday, Arnico K.; Jayarathne, Thilina; Stone, Elizabeth A.; Yokelson, Robert J.; DeCarlo, Peter F.

Combustion of biomass, garbage, and fossil fuels in South Asia has led to poor air quality in the region and has uncertain climate forcing impacts. Online measurements of submicron aerosol (PMinline-formula1) emissions were conducted as part of the Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) to investigate and report emission factors (EFs) and vacuum aerodynamic diameter (inline-formuladva) size distributions from prevalent but poorly characterized combustion sources. The online aerosol instrumentation included a “mini” aerosol mass spectrometer (mAMS) and a dual-spot eight-channel aethalometer (AE33). The mAMS measured non-refractory PMinline-formula1 mass, composition, and size. The AE33-measured black carbon (BC) mass and estimated light absorption at 370 nm due to organic aerosol or brown carbon. Complementary gas-phase measurements of carbon dioxide (inline-formulaCO2), carbon monoxide (CO), and methane (inline-formulaCH4) were collected using a Picarro Inc. cavity ring-down spectrometer (CRDS) to calculate fuel-based EFs using the carbon mass balance approach. The investigated emission sources include open garbage burning, diesel-powered irrigation pumps, idling motorcycles, traditional cookstoves fueled with dung and wood, agricultural residue fires, and coal-fired brick-making kilns, all of which were tested in the field. Open-garbage-burning emissions, which included mixed refuse and segregated plastics, were found to have some of the largest PMinline-formula1 EFs (3.77–19.8 g kginline-formula−1) and the highest variability of the investigated emission sources. Non-refractory organic aerosol (OA) size distributions measured by the mAMS from garbage-burning emissions were observed to have lognormal mode inline-formuladva values ranging from 145 to 380 nm. Particle-phase hydrogen chloride (HCl) was observed from open garbage burning and was attributed to the burning of chlorinated plastics. Emissions from two diesel-powered irrigation pumps with different operational ages were tested during NAMaSTE. Organic aerosol and BC were the primary components of the emissions and the OA size distributions were centered at inline-formula∼80 nm inline-formuladva. The older pump was observed to have significantly larger EFinline-formulaOA than the newer pump (5.18 g kginline-formula−1 compared to 0.45 g kginline-formula−1) and similar EFinline-formulaBC. Emissions from two distinct types of coal-fired brick-making kilns were investigated. The less advanced, intermittently fired clamp kiln was observed topage14654 have relatively large EFs of inorganic aerosol, including sulfate (0.48 g kginline-formula−1) and ammonium (0.17 g kginline-formula−1), compared to the other investigated emission sources. The clamp kiln was also observed to have the largest absorption Ångström exponent (AAE inline-formula= 4) and organic carbon (OC) to BC ratio (inline-formulaOCinline-formula:inline-formulaBCinline-formula= 52). The continuously fired zigzag kiln was observed to have the largest fraction of sulfate emissions with an EFinline-formula M24inlinescrollmathml chem normal SO normal 4 17pt10ptsvg-formulamathimg86d8fa05472e6e58fef92652b1861de5 acp-18-14653-2018-ie00001.svg17pt10ptacp-18-14653-2018-ie00001.png of 0.96 g kginline-formula−1. Non-refractory aerosol size distributions for the brick kilns were centered at inline-formula∼400 nm inline-formuladva. The biomass burning samples were all observed to have significant fractions of OA and non-refractory chloride; based on the size distribution results, the chloride was mostly externally mixed from the OA. The dung-fueled traditional cookstoves were observed to emit ammonium, suggesting that the chloride emissions were partially neutralized. In addition to reporting EFs and size distributions, aerosol optical properties and mass ratios of OC to BC were investigated to make comparisons with other NAMaSTE results (i.e., online photoacoustic extinctiometer (PAX) and off-line filter based) and the existing literature. This work provides critical field measurements of aerosol emissions from important yet under-characterized combustion sources common to South Asia and the developing world.



Goetz, J. Douglas / Giordano, Michael R. / Stockwell, Chelsea E. / et al: Speciated online PM1 from South Asian combustion sources – Part 1: Fuel-based emission factors and size distributions. 2018. Copernicus Publications.


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