Submicron Aerosol Composition and Source Contribution across the Kathmandu Valley, Nepal, in Winter.

The Kathmandu valley experiences an average wintertime PM concentration of ∼100 μg m and daily peaks over 200 μg m. We present ambient nonrefractory PM chemical composition, and concentration measured by a mini aerosol mass spectrometer (mAMS) sequentially at Dhulikhel (on the valley exterior), then urban Ratnapark, and finally suburban Lalitpur in winter 2018. At all sites, organic aerosol (OA) was the largest contributor to combined PM (C-PM) (49%) and black carbon (BC) was the second largest contributor (21%).

Variability of ambient black carbon concentration in the Central Himalaya and its assessment over the Hindu Kush Himalayan region.

During 2015-2018, eight black carbon (BC) monitoring sites were established in Nepal and Bhutan to fill a significant data gap regarding BC measurement in Central Himalaya. This manuscript analyzes and presents data from these eight stations and one additional station on the Tibetan plateau (TP). Complex topography, varied emission sources, and atmospheric transport pathways significantly impacted the BC concentrations across these stations, with annual mean concentrations varying from 36 ng m to 45,737 ng m.

Emission factors and emission inventory of diesel vehicles in Nepal.

A comprehensive emission inventory of the transport sector through fuel-based emission factors (EFs) was developed for the first time in Nepal. This study estimates air pollutants emission from diesel vehicles between the years 1989 and 2018 based on national statistical data, average vehicle kilometers travelled, fuel mileage, and measurement-based EFs for each vehicle category during idle and moving conditions. The consumption of diesel by vehicle category was also estimated and total consumption was compared with national sales data.

Black carbon concentration in the central Himalayas: Impact on glacier melt and potential source contribution.

This study discusses year-long (October 2016-September 2017) observations of atmospheric black carbon (BC) mass concentration, its source and sector contributions using a chemical transport model at a high-altitude (28°12'49.21″N, 85°36'33.77″E, 4900 masl) site located near the Yala Glacier in the central Himalayas, Nepal.

A model-ready emission inventory for crop residue open burning in the context of Nepal.

Open burning of crop residue is an important source of air pollution which is poorly characterized in South Asia. Currently, the gridded inventory reported by Global Fire Emissions Database for biomass burning including open burning of crop residue are of coarse resolution (0.25° × 0.

Proinflammatory Effects in Human Lung Tissue of Respirable Smoke Extracts from Indoor Cooking in Nepal.

Exposure to biomass smoke is believed to increase the risk of developing chronic obstructive pulmonary disease. However, little is known about the mechanisms underlying responses to biomass smoke in human lungs. This study had two objectives: first, to quantify "real-life" exposures to particulate matter <2 μm in diameter (PM) and carbon monoxide (CO) measured during cooking on stoves in rural areas of Nepal in different geographical settings; and second, to assess the effect of biomass smoke extracts on inflammatory responses in human lung tissue.

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

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 PM (particulate matter of less than 2.

Ambient endotoxin in PM and association with inflammatory activity, air pollutants, and meteorology, in Chitwan, Nepal.

Background: Endotoxin associated with ambient PM (particulate matter) has been linked to adverse respiratory symptoms, but there have been few studies of ambient endotoxin and its association with co-pollutants and inflammation.

Objectives: Our aim was to measure endotoxin associated with ambient PM (particulate matter with aerodynamic diameter<10μm) in summer 2016 at four locations in Chitwan, Nepal, and investigate its association with meteorology, co-pollutants, and inflammatory activity.

Methods: PM concentrations were recorded and filter paper samples were collected using E-samplers; PM PM, black carbon (BC), methane (CH), and carbon monoxide (CO) were also measured.

Black carbon solar absorption suppresses turbulence in the atmospheric boundary layer.

The introduction of cloud condensation nuclei and radiative heating by sunlight-absorbing aerosols can modify the thickness and coverage of low clouds, yielding significant radiative forcing of climate. The magnitude and sign of changes in cloud coverage and depth in response to changing aerosols are impacted by turbulent dynamics of the cloudy atmosphere, but integrated measurements of aerosol solar absorption and turbulent fluxes have not been reported thus far. Here we report such integrated measurements made from unmanned aerial vehicles (UAVs) during the CARDEX (Cloud Aerosol Radiative Forcing and Dynamics Experiment) investigation conducted over the northern Indian Ocean.

Solar absorption by elemental and brown carbon determined from spectral observations.

Black carbon (BC) is functionally defined as the absorbing component of atmospheric total carbonaceous aerosols (TC) and is typically dominated by soot-like elemental carbon (EC). However, organic carbon (OC) has also been shown to absorb strongly at visible to UV wavelengths and the absorbing organics are referred to as brown carbon (BrC), which is typically not represented in climate models. We propose an observationally based analytical method for rigorously partitioning measured absorption aerosol optical depths (AAOD) and single scattering albedo (SSA) among EC and BrC, using multiwavelength measurements of total (EC, OC, and dust) absorption.

Real-time assessment of black carbon pollution in Indian households due to traditional and improved biomass cookstoves.

Use of improved (biomass) cookstoves (ICs) has been widely proposed as a Black Carbon (BC) mitigation measure with significant climate and health benefits. ICs encompass a range of technologies, including natural draft (ND) stoves, which feature structural modifications to enhance air flow, and forced draft (FD) stoves, which additionally employ an external fan to force air into the combustion chamber. We present here, under Project Surya, the first real-time in situ Black Carbon (BC) concentration measurements from five commercial ICs and a traditional (mud) cookstove for comparison.