Air quality trends of the Kathmandu Valley: A satellite, observation and modeling perspective

Mahapatra, Parth Sarathi; Praveen, P. S.; Adhikary, Bhupesh; Shrestha, Kundan Lal; Dawadi, Durga Prasad; Paudel, Shankar Prasad; Panday, Arnico K.

doi:10.1016/j.atmosenv.2018.12.043

Cited by 42 publications

(36 citation statements)

References 44 publications

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“…High daily average concentrations of PM 2.5 (up to 160 µg m −3 ) (Shakya et al, 2017a) and PM 10 (up to 579 µg m −3 ) have been documented in the Kathmandu Valley (Giri et al, 2006). A satellite-derived aerosol optical depth study indicates substantial increases in particulate loading in the Kathmandu Valley and nearby background sites over the past 15 years (Mahapatra et al, 2019). Measured components of regional PM have included black carbon (BC; 17 %), sulfate (17 %), and ammonium (11 %) in PM 2.5 (Shakya et al, 2017a) and organic carbon (OC; 23 %) and nitrate (2.5 %) in PM 10 (Kim et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Ambient air quality in the Kathmandu Valley, Nepal, during the pre-monsoon: concentrations and sources of particulate matter and trace gases

et al. 2020

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Abstract. 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.

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Section: Introductionmentioning

confidence: 99%

Ambient air quality in the Kathmandu Valley, Nepal, during the pre-monsoon: concentrations and sources of particulate matter and trace gases

et al. 2020

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“…The sampling location of southern Nepal is situated next to the Indo-Gangetic Plain (IGP), which is known to have a high population density, pollution sources and thick haze [80]. Several studies reported IGP air pollution and its widespread nature through observation, model and satellite based studies [81][82][83][84]. Hence, IGP pollution can be one of the major contributors to background pollution at the sampling site.…”

Section: Health Risk Assessment Using Air Q+mentioning

confidence: 99%

Cookstove Smoke Impact on Ambient Air Quality and Probable Consequences for Human Health in Rural Locations of Southern Nepal

Adhikari

Mahapatra

Pokheral

et al. 2020

IJERPH

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Residential emission from traditional biomass cookstoves is a major source of indoor and outdoor air pollution in developing countries. However, exact quantification of the contribution of biomass cookstove emissions to outdoor air is still lacking. In order to address this gap, we designed a field study to estimate the emission factors of PM2.5 (particulate matter of less than 2.5 µ diameter) and BC (black carbon) indoors, from cookstove smoke using biomass fuel and with smoke escaping outdoors from the roof of the house. The field study was conducted in four randomly selected households in two rural locations of southern Nepal during April 2017. In addition, real-time measurement of ambient PM2.5 was performed for 20 days during the campaign in those two rural sites and one background location to quantify the contribution of cooking-related emissions to the ambient PM2.5. Emission factor estimates indicate that 66% of PM2.5 and 80% of BC emissions from biomass cookstoves directly escape into ambient air. During the cooking period, ambient PM2.5 concentrations in the rural sites were observed to be 37% higher than in the nearby background location. Based on the World Health Organization (WHO)’s AirQ+ model simulation, this 37% rise in ambient PM2.5 during cooking hours can lead to approximately 82 cases of annual premature deaths among the rural population of Chitwan district.

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“…A recent study conducted by Mahapatra et al (2019) indicates an increasing trend of aerosol loading within the Kathmandu Valley by approximately 50-60% in between 2000-2015. This high pollution load could be attributed to rapid population and vehicular growth along with the increase in the energy demands of the valley.…”

Section: Introductionmentioning

confidence: 99%

“…Extensive research has been conducted in the urban areas of LMIC in recent decades (Edgerton et al, 1999;Molina and Molina, 2004;Petkova et al, 2013;Wang et al, 2013;Sahu and Kota, 2017), but the pace of air quality improvement remains slow in many of those cities (Colbeck et al, 2010;Maji et al, 2015;Njoku et al, 2016). Among those cities, the Kathmandu Valley is one such highly polluted area in the † Now at North Carolina State University, Raleigh, NC, USA South Asian region (Parajuly, 2016;Mahapatra et al, 2019). Earlier, air quality studies were limited in scope, especially because of the absence of appropriate instruments for measurements in the valley.…”

Section: Introductionmentioning

confidence: 99%

“…These emission inventories were prepared using decades-old EFs from different countries (Shrestha and Malla, 1996;Shrestha et al, 2013;Ghimire and Shrestha, 2014;Bajracharya and Bhattarai, 2016). This created a huge uncertainty (in terms of overestimation or underestimation) in the emission inventory of the Kathmandu Valley (Sarkar et al, 2017;Mahapatra et al, 2019). A realistic and updated emission inventory of the vehicle fleet in the valley has yet to be developed and there is a strong need to develop it by incorporating local estimates to reflect the real scenario of the area (Mues et al, 2018;Mahapatra et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Traffic Condition and Emission Factor from Diesel Vehicles within the Kathmandu Valley

Mool

Bhave

Khanal

et al. 2019

Aerosol Air Qual. Res.

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Past research on air quality within the Kathmandu Valley indicates that diesel vehicles make a substantial contribution to the ambient pollution. Hence, it's important to identify cost-effective measures for reducing their emissions. As a first step, roadside observations of diesel vehicles were recorded between February and April 2017 at six locations: two on the ring road (RR), two inside the RR, and two on major arterial highways outside the RR. Out of all diesel vehicles observed (n = 12,039), 35% were emitting a visible plume of black smoke and hereafter are referred to as "superemitters". Of the 4,248 superemitters, 45% were buses of varying sizes, 34% were large trucks, and 19% were small pickups. Superemitters made up the largest fraction of diesel vehicle traffic on the RR (43%-46%) but were also abundant inside the RR (27%-29%), where human population and pollutant exposure is greatest. Upon developing a comprehensive understanding of the superemitting vehicle types and ownership, maintenance patterns and servicing costs were studied through a survey of vehicle owners, vehicle drivers, and local maintenance centers. The costs of general servicing ranged between USD 16 for tractors and USD 203 for construction vehicles depending on the size of the vehicle. Lastly, the effect of general servicing on emissions while idling was explored for a small sample of superemitters (n = 4). PM 2.5 emissions reduced from 10.90 g L-1 to 3.76 g L-1 and BC emissions reduced from 0.847 g L-1 to 0.596 g L-1 after servicing. Taken together, results from this roadside surveillance study and exploratory emission-measurement campaign provide preliminary evidence that a policy of mandatory, routine maintenance of a targeted subset of the diesel fleet can systematically reduce emissions and improve air quality in the Kathmandu Valley and other cities around the world that are facing similar problems.

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Air quality trends of the Kathmandu Valley: A satellite, observation and modeling perspective

Cited by 42 publications

References 44 publications

Ambient air quality in the Kathmandu Valley, Nepal, during the pre-monsoon: concentrations and sources of particulate matter and trace gases

Ambient air quality in the Kathmandu Valley, Nepal, during the pre-monsoon: concentrations and sources of particulate matter and trace gases

Cookstove Smoke Impact on Ambient Air Quality and Probable Consequences for Human Health in Rural Locations of Southern Nepal

Traffic Condition and Emission Factor from Diesel Vehicles within the Kathmandu Valley

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