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 heating fire. Fuel-based emission factors (EFs; with units of pollutant mass emitted per kilogram of fuel combusted) were determined for fine particulate matter (PM2.5), organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals, and organic species. For the forced-draft zigzag brick kiln, EFPM2.5 ranged from 12 to 19 g kg−1 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, EFPM2.5 ranged from 8 to 13 g kg−1, with major contributions from OC (63.2 %), sulfate (23.4 %), and ammonium (16 %). Our brick kiln EFPM2.5 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 EFPM2.5 of 7.4 ± 1.2 g kg−1, whereas damp conditions generated the highest EFPM2.5 of all combustion sources in this study, reaching up to 125 ± 23 g kg−1. Garbage burning emissions contained triphenylbenzene and relatively high concentrations of 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 EFPM2.5 than other biofuel sources and consistently emitted more PM2.5 and OC than burning hardwood and/or twigs; this trend was consistent across traditional mud stoves, chimney stoves, and three-stone cooking fires. The comparisons of different cooking stoves and cooking fires revealed the highest PM emissions from three-stone cooking fires (7.6–73 g kg−1), followed by traditional mud stoves (5.3–19.7 g kg−1), mud stoves with a chimney for exhaust (3.0–6.8 g kg−1), rocket stoves (1.5–7.2 g kg−1), induced-draft stoves (1.2–5.7 g kg−1), and the bhuse chulo stove (3.2 g kg−1), while biogas had no detectable PM emissions. Idling motorcycle emissions were evaluated before and after routine servicing at a local shop, which decreased EFPM2.5 from 8.8 ± 1.3 to 0.71 ± 0.45 g kg−1 when averaged across five motorcycles. Organic species analysis indicated that this reduction in PM2.5 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.
It is important to improve our understanding of exposure to particulate matter (PM) in residences because of associated health risks. The HOMEChem campaign was conducted to investigate indoor ...chemistry in a manufactured test house during prescribed everyday activities, such as cooking, cleaning, and opening doors and windows. This paper focuses on measured size distributions of PM (0.001-20 μm), along with estimated exposures and respiratory-tract deposition. Number concentrations were highest for sub-10 nm particles during cooking using a propane-fueled stovetop. During some cooking activities, calculated PM
mass concentrations (assuming a density of 1 g cm
) exceeded 250 μg m
, and exposure during the postcooking decay phase exceeded that of the cooking period itself. The modeled PM respiratory deposition for an adult residing in the test house kitchen for 12 h varied from 7 μg on a day with no indoor activities to 68 μg during a simulated day (including breakfast, lunch, and dinner preparation interspersed by cleaning activities) and rose to 149 μg during a simulated Thanksgiving day.
Different on-line submicron particle sizing techniques report different "equivalent diameters." For example, differential mobility analyzers (DMAs) report electrical mobility diameter (d
m
), while a ...number of recently developed instruments (such as the Aerodyne aerosol mass spectrometer, or AMS) measure vacuum aerodynamic diameter (d
va
). Particle density and physical morphology (shape) have important effects on diameter measurements. Here a framework is presented for combining the information content of different equivalent diameter measurements into a single coherent mathematical description of the particles. We first present a review of the mathematical formulations used in the literature and their relationships. We then show that combining d
m
and d
va
measurements for the same particle population allows the placing of constraints on particle density, dynamic shape factor (x), and fraction of internal void space. The amount of information that can be deduced from the combination of d
m
and d
m
measurements for various particle types is shown. With additional measurements and/or some assumptions, all relevant parameters can be determined. Specifically, particle mass can be determined from d
m
and d
va
measurements if the particle density is known and an assumption about x is made. Even if x and density are not known, particle mass can be estimated within about a factor of 2 from d
m
and d
va
measurements alone. The mass of a fractal particle can also be estimated under certain conditions. The meaning of various definitions of "effective density" used in the literature is placed in the context of the theory. This theoretical framework is applied to measurements of fractal (soot-like) particles by using experimental results from the literature as additional constraints.
Although ammonia (NH3) is usually found at outdoor concentrations of 1–5 ppb, indoor ammonia concentrations can be much higher. Indoor ammonia is strongly emitted from cleaning products, tobacco ...smoke, building materials, and humans. Because of ammonia’s high reactivity, solubility in water, and tendency to sorb to a variety of surfaces, it is difficult to measure, and thus a comprehensive evaluation of indoor ammonia concentrations remains an understudied topic. During HOMEChem, which was a comprehensive indoor chemistry study occurring in a test house during June 2018, the real-time concentration of ammonia indoors was measured using cavity ring-down spectroscopy. A mean unoccupied background concentration of 32 ppb was observed, with further enhancements of ammonia occurring during cooking, cleaning, and occupancy activities, reaching maximum concentrations during these activities of 130, 1592, and 99 ppb, respectively. Furthermore, ammonia concentrations were strongly influenced by indoor temperatures and heating, ventilation, and air conditioning (HVAC) operation. In the absence of activity-based sources, the HVAC operation was the main modulator of ammonia concentration indoors.
The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary ...organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.
The Nepal Ambient Monitoring and Source Testing Experiment (NAMaSTE) campaign took place in and around the Kathmandu Valley and in the Indo-Gangetic Plain (IGP) of southern Nepal during April 2015. ...The source characterization phase targeted numerous important but undersampled (and often inefficient) combustion sources that are widespread in the developing world such as cooking with a variety of stoves and solid fuels, brick kilns, open burning of municipal solid waste (a.k.a. trash or garbage burning), crop residue burning, generators, irrigation pumps, and motorcycles. NAMaSTE produced the first, or rare, measurements of aerosol optical properties, aerosol mass, and detailed trace gas chemistry for the emissions from many of the sources. This paper reports the trace gas and aerosol measurements obtained by Fourier transform infrared (FTIR) spectroscopy, whole-air sampling (WAS), and photoacoustic extinctiometers (PAX; 405 and 870 nm) based on field work with a moveable lab sampling authentic sources. The primary aerosol optical properties reported include emission factors (EFs) for scattering and absorption coefficients (EF Bscat, EF Babs, in m2 kg−1 fuel burned), single scattering albedos (SSAs), and absorption Ångström exponents (AAEs). From these data we estimate black and brown carbon (BC, BrC) emission factors (g kg−1 fuel burned). The trace gas measurements provide EFs (g kg−1) for CO2, CO, CH4, selected non-methane hydrocarbons up to C10, a large suite of oxygenated organic compounds, NH3, HCN, NOx, SO2, HCl, HF, etc. (up to ∼ 80 gases in all). The emissions varied significantly by source, and light absorption by both BrC and BC was important for many sources. The AAE for dung-fuel cooking fires (4.63 ± 0.68) was significantly higher than for wood-fuel cooking fires (3.01 ± 0.10). Dung-fuel cooking fires also emitted high levels of NH3 (3.00 ± 1.33 g kg−1), organic acids (7.66 ± 6.90 g kg−1), and HCN (2.01 ± 1.25 g kg−1), where the latter could contribute to satellite observations of high levels of HCN in the lower stratosphere above the Asian monsoon. HCN was also emitted in significant quantities by several non-biomass burning sources. BTEX compounds (benzene, toluene, ethylbenzene, xylenes) were major emissions from both dung- (∼ 4.5 g kg−1) and wood-fuel (∼ 1.5 g kg−1) cooking fires, and a simple method to estimate indoor exposure to the many measured important air toxics is described. Biogas emerged as the cleanest cooking technology of approximately a dozen stove–fuel combinations measured. Crop residue burning produced relatively high emissions of oxygenated organic compounds (∼ 12 g kg−1) and SO2 (2.54 ± 1.09 g kg−1). Two brick kilns co-firing different amounts of biomass with coal as the primary fuel produced contrasting results. A zigzag kiln burning mostly coal at high efficiency produced larger amounts of BC, HF, HCl, and NOx, with the halogenated emissions likely coming from the clay. The clamp kiln (with relatively more biomass fuel) produced much greater quantities of most individual organic gases, about twice as much BrC, and significantly more known and likely organic aerosol precursors. Both kilns were significant SO2 sources with their emission factors averaging 12.8 ± 0.2 g kg−1. Mixed-garbage burning produced significantly more BC (3.3 ± 3.88 g kg−1) and BTEX (∼ 4.5 g kg−1) emissions than in previous measurements. For all fossil fuel sources, diesel burned more efficiently than gasoline but produced larger NOx and aerosol emission factors. Among the least efficient sources sampled were gasoline-fueled motorcycles during start-up and idling for which the CO EF was on the order of ∼ 700 g kg−1 – or about 10 times that of a typical biomass fire. Minor motorcycle servicing led to minimal if any reduction in gaseous pollutants but reduced particulate emissions, as detailed in a companion paper (Jayarathne et al., 2016). A small gasoline-powered generator and an “insect repellent fire” were also among the sources with the highest emission factors for pollutants. These measurements begin to address the critical data gap for these important, undersampled sources, but due to their diversity and abundance, more work is needed.
We report elevated levels of gaseous inorganic chlorinated and nitrogenated compounds in indoor air while cleaning with a commercial bleach solution during the House Observations of Microbial and ...Environmental Chemistry field campaign in summer 2018. Hypochlorous acid (HOCl), chlorine (Cl2), and nitryl chloride (ClNO2) reached part-per-billion by volume levels indoors during bleach cleaningseveral orders of magnitude higher than typically measured in the outdoor atmosphere. Kinetic modeling revealed that multiphase chemistry plays a central role in controlling indoor chlorine and reactive nitrogen chemistry during these periods. Cl2 production occurred via heterogeneous reactions of HOCl on indoor surfaces. ClNO2 and chloramine (NH2Cl, NHCl2, NCl3) production occurred in the applied bleach via aqueous reactions involving nitrite (NO2 –) and ammonia (NH3), respectively. Aqueous-phase and surface chemistry resulted in elevated levels of gas-phase nitrogen dioxide (NO2). We predict hydroxyl (OH) and chlorine (Cl) radical production during these periods (106 and 107 molecules cm–3 s–1, respectively) driven by HOCl and Cl2 photolysis. Ventilation and photolysis accounted for <50% and <0.1% total loss of bleach-related compounds from indoor air, respectively; we conclude that uptake to indoor surfaces is an important additional loss process. Indoor HOCl and nitrogen trichloride (NCl3) mixing ratios during bleach cleaning reported herein are likely detrimental to human health.
Nitrogen oxides (NO X ) and methane impact air quality through the promotion of ozone formation, and methane is also a strong greenhouse gas. Despite the importance of these pollutants, emissions in ...urban areas are poorly quantified. We present measurements of NO X , CH4, CO, and CO2 made at Drexel University in Philadelphia along with NO X and CO observations at two roadside monitors. Because CO2 concentrations in the winter result almost entirely from combustion with negligible influence from photosynthesis and respiration, we are able to infer fleet-averaged fuel-based emission factors (EFs) for NO X and CO, similar in some ways to how EFs are determined from tunnel studies. Comparison of the inferred NO X and CO fuel-based EF to the National Emissions Inventory (NEI) suggests errors in NEI emissions of either NO X , CO, or both. From the measurements of CH4 and CO2, which are not emitted by the same sources, we infer the ratio of CH4 emissions (from leaks in the natural gas infrastructure) to CO2 emissions (from fossil fuel combustion) in Philadelphia. Comparison of the CH4/CO2 emission ratios to emission inventories from the Environmental Protection Agency suggests underestimates in CH4 emissions by almost a factor of 4. These results demonstrate the need for the addition of long-term observations of CH4 and CO2 to existing monitoring networks in urban areas to better constrain emissions and complement existing measurements of NO X and CO.
The Kathmandu Valley in Nepal is a bowl-shaped urban basin that experiences severe air pollution that poses health risks to its 3.5 million inhabitants.
As part of the Nepal Ambient Monitoring and ...Source Testing Experiment
(NAMaSTE), ambient air quality in the Kathmandu Valley was investigated from
11 to 24 April 2015, during the pre-monsoon season. Ambient concentrations
of fine and coarse particulate matter (PM2.5 and PM10,
respectively), online PM1, inorganic trace gases (NH3, HNO3,
SO2, and HCl), and carbon-containing gases (CO2, CO, CH4, and
93 non-methane volatile organic compounds; NMVOCs) were quantified at a
semi-urban location near the center of the valley. Concentrations and ratios
of NMVOC indicated origins primarily from poorly maintained vehicle
emissions, biomass burning, and solvent/gasoline evaporation. During those
2 weeks, daily average PM2.5 concentrations ranged from 30 to 207 µg m−3, which exceeded the World Health Organization 24 h
guideline by factors of 1.2 to 8.3. On average, the non-water mass of
PM2.5 was composed of organic matter (48 %), elemental carbon
(13 %), sulfate (16 %), nitrate (4 %), ammonium (9 %), chloride
(2 %), calcium (1 %), magnesium (0.05 %), and potassium (1 %). Large
diurnal variability in temperature and relative humidity drove corresponding
variability in aerosol liquid water content, the gas–aerosol phase
partitioning of NH3, HNO3, and HCl, and aerosol solution pH. The
observed levels of gas-phase halogens suggest that multiphase
halogen-radical chemistry involving both Cl and Br impacted regional air
quality. To gain insight into the origins of organic carbon (OC), molecular
markers for primary and secondary sources were quantified. Levoglucosan
(averaging 1230±1154 ng m−3), 1,3,5-triphenylbenzene (0.8±0.6 ng m−3), cholesterol (2.9±6.6 ng m−3), stigmastanol (1.0
±0.8 ng m−3), and cis-pinonic acid (4.5±1.9 ng m−3)
indicate contributions from biomass burning, garbage burning, food cooking,
cow dung burning, and monoterpene secondary organic aerosol, respectively.
Drawing on source profiles developed in NAMaSTE, chemical mass balance (CMB)
source apportionment modeling was used to estimate contributions to OC from
major primary sources including garbage burning (18±5 %), biomass
burning (17±10 %) inclusive of open burning and biomass-fueled
cooking stoves, and internal-combustion (gasoline and diesel) engines (18±9 %). Model sensitivity tests with newly developed source profiles
indicated contributions from biomass burning within a factor of 2 of
previous estimates but greater contributions from garbage burning
(up to three times), indicating large potential impacts of garbage burning
on regional air quality and the need for further evaluation of this source.
Contributions of secondary organic carbon (SOC) to PM2.5 OC included
those originating from anthropogenic precursors such as naphthalene (10±4 %) and methylnaphthalene (0.3±0.1 %) and biogenic
precursors for monoterpenes (0.13±0.07 %) and sesquiterpenes (5±2 %). An average of 25 % of the PM2.5 OC was unapportioned,
indicating the presence of additional sources (e.g., evaporative and/or
industrial emissions such as brick kilns, food cooking, and other types of
SOC) and/or underestimation of the contributions from the identified source
types. The source apportionment results indicate that anthropogenic
combustion sources (including biomass burning, garbage burning, and
fossil fuel combustion) were the greatest contributors to PM2.5 and, as
such, should be considered primary targets for controlling ambient PM
pollution.
We present a new elemental analysis (EA) technique for organic species (CHNO) that allows fast on-line analysis (10 s) and reduces the required sample size to ∼1 ng, ∼6 orders of magnitude less than ...standard techniques. The composition of the analyzed samples is approximated by the average elemental composition of the ions from high-resolution electron ionization (EI) mass spectra. EA of organic species can be performed on organic/inorganic mixtures. Elemental ratios for the total organic mass, such as oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C), in addition to the organic mass to organic carbon ratio (OM/OC), can be determined. As deviations between the molecular and the ionic composition can appear due to chemical influences on the ion fragmentation processes, the method was evaluated and calibrated using spectra from 20 compounds from the NIST database and from 35 laboratory standards sampled with the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The analysis of AMS (NIST) spectra indicates that quantification of O/C is possible with an error (average absolute value of the relative error) of 30% (17%) for individual species. Precision is much better than accuracy at ±5% in the absence of air for AMS data. AMS OM/OC has an average error of 5%. Additional calibration is recommended for types of species very different from those analyzed here. EA was applied to organic mixtures and ambient aerosols (sampled at 20 s from aircraft). The technique is also applicable to other EI-HRMS measurements such as direct injection MS.
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