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Abstract Background Exposure to indoor biomass fuel smoke is associated with increased morbidity and mortality. The aim of this study is to evaluate the association between exposure to indoor biomass burning and early pulmonary and cardiovascular damage. Methods The indoor levels of particulate matter (PM) [PM 10 , PM 2.5 ] and black carbon (BC) were monitored in 32 houses in a Himalayan village. Seventy-eight subjects were submitted to spirometry and cardiovascular evaluation [carotid to femoral pulse wave velocity (PWV) and echocardiography]. Results Peak indoor BC concentration up to 100 μg m−3 and PM 10 - PM 2.5 up to 1945–592 μg m−3 were measured. We found a non-reversible bronchial obstruction in 18% of subjects ≥40 yr; mean forced expiratory flow between 25% and 75% of the forced vital capacity (FEF 25–75) <80% in 54% of subjects, suggestive of early respiratory impairment, significantly and inversely related to age. Average BC was correlated with right ventricular-right atrium gradient (R = 0.449, p =.002), total peripheral resistances (TPR) (R = 0.313, p =.029) and PWV (R = 0.589, p <.0001) especially in subjects >30 yr. In multiple variable analysis, BC remained an independent predictor of PWV (β = 0.556, p =.001), and TPR (β = 0.366; p =.018). Conclusions Indoor pollution exposure is associated to early pulmonary and cardiovascular damages, more evident for longer duration and higher intensity exposure. Highlights • Indoor air pollution (IAP) is a cause of morbidity and mortality in the population of the poorest countries. • The effects of IAP on cardiovascular and pulmonary diseases 'is not well known. • Poor indoor air quality induces an impairment of airways function and cardiovascular damage. • Long term IAP exposure is associated to substantial burden of COPD and of cardiovascular dysfunction. • The use of clean cook stoves and fuels could dramatically reduce IAP and the associated adverse health effects. [ABSTRACT FROM AUTHOR]

Abstract Raising population, deteriorating environmental conditions and limiting natural resources to handle the key environmental health problems have critically affected human health and the environment. Policy makers and planners in Nepal are more concerned today than at any other time in the past about the deterioration of the environmental condition. Therefore, understanding the connection between pollution and human wellbeing is fundamental endeavors to control pollution exposures and secure human wellbeing. This ability is especially critical for countries like Nepal where the issues of environmental pollution have customarily taken a second place to request for economic development. In this study, spatial distribution and sources of 12 heavy metals (HMs) were investigated in surface soils (n = 24) and house dust (n = 24) from four major urban areas of Nepal in order to mark the pollution level. Additionally, a health risk was estimated to establish the link between HMs pollution and human health. Results showed that the median concentration of Ag, Cd, Co, Cr, Cu, Ni, Pb, Sb, Mn and Zn in soil and dust were 2–13 times greater than the background value. The As, Zn, Cu, Cd, and Pb showed a relatively higher spatial variability in soil and dust. Zn was the most abundant metal measured in dust and soil and accounted for 59% and 55% of ∑ 7 HMs, respectively. The HMs in soil and dust were poorly correlated with total organic carbon (TOC) and black carbon (BC), suggesting little or no influence on HMs contamination. Source analysis study indicated the distribution of Cr, Ni, Sb, Ag, Pb, Cu, and Zn in soil and dust are mainly affected by anthropogenic sources, particularly traffic emissions, industrial source, and domestic households materials, while Co, Fe, As, Mn and Cd were from natural sources. The estimated carcinogenic risk (CR) of HMs in soil and dust exceeded the acceptable level of human exposure, recommending significant CR to the local population. Graphical abstract Image 1 Highlights • Heavy metals concentration in dust was slightly higher than those in soil. • Zn was the most abundant metal measured both in dust and soil. • Majority of metals in both mediums were mainly affected by anthropogenic sources. • Co, Fe, As, Mn and Cd were mainly originated from natural sources. • The average cancer risk exceeded the acceptable level. [ABSTRACT FROM AUTHOR]

Abstract In Nepal, majority of households still burn solid fuels in inefficient cook stoves inside poorly ventilated kitchens, which results in very high levels of indoor pollutants, including black carbon (BC). Previous studies have not yet reported BC concentrations in typical kitchen configurations in rural Nepal. In this study, fine particulate matter (PM) and BC concentrations were monitored continuously inside two types of kitchens (separated from and attached to the main house) under actual cooking practices. Prior to monitoring of pollutants, a field survey was conducted to gain insight into the types of kitchens, cook stoves and fuels used. Indoor PM and BC concentrations were monitored using biomass fuels in traditional cook stoves (TC) and improved cook stoves (ICS). Clear diurnal variations of the pollutants were observed in both kitchens, with the highest concentrations during cooking times. BC and PM concentrations during cooking and non-cooking periods demonstrated clear reductions in the concentrations during non-cooking periods. It was observed that the concentrations rose steeply during the first half hour of cooking, then decreased slightly and finally leveled off to the non-cooking period concentrations. 24-hour average indoor PM concentrations in both kitchens frequently exceeded Nepal's indoor air quality standards and the WHO PM 2.5 guidelines, by a factor of ~8 to ~28. We found that the specific type of ICS used in this study, a commonly used ICS in Nepal and other developing countries might help in PM emission reductions but not necessarily BC emission reduction. [ABSTRACT FROM AUTHOR]

This paper describes the design, implementation and results of a uniform-price reverse auction and real payment system to incentivize the avoidance of open-field burning of rice straw by smallholder farmers in Nepal. The main objective of the study was to reveal the private costs to farmers of avoiding rice straw burning. The study used survey and auction data from a sample of 317 farmers from 18 villages in Southern Nepal. Using a sealed bid one-shot reverse auction a level of payment was determined at which farmers would find acceptable to not engage in residue burning. Based on the bid amount, 167 winner farmers were enrolled in a real payment programme. The results revealed that 86 % of the farmers complied with the programme to refrain from burning rice straw with an average payment of US$ 78.76/ha of paddy farm, which represents US$ 13.17/ton of $$\hbox {CO}_{\mathrm{2-eq}}$$ of emissions. To identify the policy variables, linear and log-linear regressions were fitted with the bid amount using socioeconomic variables. Land area, farmer education, practice of joint household decision making, wage rate for farm labour and straw yield increased the bid amount. The design and methods of field implementation of the reverse auction gave useful information for the advancement of conservation auctions and their replication in developing countries. [ABSTRACT FROM AUTHOR]

Abstract: Black carbon (BC) aerosols were measured using an aethalometer (AE-31) at Pulchowk Campus, an urban location of Kathmandu valley, Nepal from May 2009 to April 2010. The amount of BC in the total mass of the suspended particulate matter (TSP) were estimated by comparing the average BC with mass of particulate matter simultaneously measured with frm Omni Ambient Air Sampler for the last two months (March–April, 2010). BC concentration shows significant temporal variation with monthly mean concentration varying between 14.9 μg m− 3 and 3.0 μg m− 3. The highest daily mean concentration was recorded as high as 39.9 μg m− 3. The highest concentration of BC occurred during winter and pre-monsoon seasons. The lowest concentration of BC was found during monsoon and post-monsoon seasons. A distinct diurnal variation of BC with two high peaks occurred; one in around 09:00 morning and another late evening around 20:00 local time. Minimum BC concentration was also observed in the afternoon. The annual average of BC for observation period was 8.6 ± 4.4 μg m− 3. The seasonal, monthly and diurnal variation of BC were found to be significantly influenced by the local traffic movements, the domestic and industrial fuel consuming activities, wind speed, wind direction and rain. The amount of BC in the total mass of particulate matters during the observed period varied between 11.6 and 56.2 percent. This variation is attributed to the high amount of re-suspension of dust particles in the atmosphere of the valley. [Copyright &y& Elsevier]

This study was conducted to investigate the organic carbon (C) content and its chemical fractions in soils under forest, grassland, and agricultural uses in the Mardi Watershed of Nepal. Surface soil samples from 0 to 15 cm were collected. Classical extracting procedure with alkali and acid solution was used to separate humic acid (HA), fulvic acid (FA), and humin fractions. Hydrogen peroxide was used to separate black carbon (BC) from humin. The results showed that higher amounts of total soil organic carbon (SOC), as well as of different SOC fractions, i.e., FA, HA, humin and BC, existed in the forest soils compared to those from grassland and agricultural areas. The carbon proportion of FA, HA, and humin fractions accounted for 25, 29, and 37% of the total SOC in forest soils. The corresponding values were 34, 27, and 36% in grassland, and 28, 18, and 54% in agricultural land. The grassland soil showed a higher FA fraction, while the agricultural soil contained lower HA fraction and higher humin fraction as compared to the forest soil. Forest soil showed higher HA/FA ratio and lower (HA + FA)/SOC ratio, indicating high degree of humification and large humification rate in this soil. Black carbon contents occupied 3.4, 3.4, and 11.5% of SOC under forest, grass, and agricultural lands, respectively. [ABSTRACT FROM AUTHOR]

Atmospheric aerosols play a crucial role in climate change, especially in the Himalayas and Tibetan Plateau. Here, we present the seasonal and diurnal characteristics of aerosol vertical profiles measured using a Mie lidar, along with surface black carbon (BC) measurements, at Mt. Qomolangma (QOMS), in the central Himalayas, in 2018–2019. Lidar-retrieved profiles of aerosols showed a distinct seasonal pattern of aerosol loading (aerosol extinction coefficient, AEC), with a maximum in the pre-monsoon (19.8 ± 22.7 Mm−1 of AEC) and minimum in the summer monsoon (7.0 ± 11.2 Mm−1 of AEC) seasons. The diurnal variation characteristics of AEC and BC were quite different in the non-monsoon seasons with enriched aerosols being maintained from 00:00 to 10:00 in the pre-monsoon season. The major aerosol types at QOMS were identified as background, pollution, and dust aerosols, especially during the pre-monsoon season. The occurrence of pollution events influenced the vertical distribution, seasonal/diurnal patterns, and types of aerosols. Source contribution of BC based on the weather research and forecasting chemical model showed that approximately 64.2% ± 17.0% of BC at the QOMS originated from India and Nepal in South Asia during the non-monsoon seasons, whereas approximately 47.7% was from local emission sources in monsoon season. In particular, the high abundance of BC at the QOMS in the pre-monsoon season was attributed to biomass burning, whereas anthropogenic emissions were the likely sources during the other seasons. The maximum aerosol concentration appeared in the near-surface layer (approximately 4.3 km ASL), and high concentrations of transported aerosols were mainly found at 4.98, 4.58, 4.74, and 4.88 km ASL in the pre-monsoon, monsoon, post-monsoon, and winter seasons, respectively. The investigation of the vertical profiles of aerosols at the QOMS can help verify the representation of aerosols in the air quality model and satellite products and regulate the anthropogenic disturbance over the Tibetan Plateau. [Display omitted] • The vertical aerosol loading has a distinct seasonal pattern in the Himalayas. • Major aerosol types were identified as background, pollution and dust aerosol. • Emissions from India and Nepal were the main sources of BC in non-monsoon seasons. [ABSTRACT FROM AUTHOR]

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. During a field campaign, fresh snow samples were collected from the surface of the Yala Glacier in May 2017, which were analysed for BC and water-insoluble organic carbon mass concentration in order to estimate the scavenging ratio and surface albedo reduction. The maximum BC mass concentration in the ambient atmosphere (0.73 μg m−3) was recorded in the pre-monsoon season. The BC and water-insoluble organic carbon analysed from the snow samples were in the range of 96–542 ng g−1 and 152–827 ng g−1, respectively. The source apportionment study using the absorption Ångström exponent from in situ observations indicated approximately 44% contribution of BC from biomass-burning sources and the remainder from fossil-fuel sources during the entire study period. The source contribution study, using model data sets, indicated ∼14% contribution of BC from open-burning and ∼77% from anthropogenic sources during the study period. Our analysis of regional contributions of BC indicated that the highest contribution was from both Nepal and India combined, followed by China, while the rest was distributed among the nearby countries. The surface snow albedo reduction, estimated by an online model – Snow, Ice, and Aerosol Radiation – was in the range of 0.8–3.8% during the pre-monsoon season. The glacier mass balance analysis suggested that BC contributed to approximately 39% of the total mass loss in the pre-monsoon season. Image 1 • Open-burning sources contributed ∼14% of annual atmospheric BC over central Himalayas. • Biomass sources contributed 44% of annual atmospheric BC over central Himalayas. • India and Nepal together contributed 69% of atmospheric BC over central Himalayas. • BC deposition contributed to ∼39% of the total melting in the pre-monsoon season. [ABSTRACT FROM AUTHOR]

In contrast to more frequently investigated priority pollutants, such as polycyclic aromatic hydrocarbons (PAHs), only little is known about the fate and distribution of nitrated- and oxygenated-PAHs (NPAHs and OPAHs) in urban soils, particularly in Indian sub-continent. Moreover, experimental data on air-soil exchange and soil-air partitioning are also lacking, which is critical in assessing the partitioning, fugacity coefficient, and secondary emission of PAH-derivatives. Hence, this article provides an insight into the fate, sources, air-soil exchange, and soil-air partitioning of PAH-derivatives on a molecular basis. Prospective health risk due to their exposure has also been discussed. The result showed that PAH-derivatives had significantly polluted all four Nepalese cities. Ʃ 15 NPAHs and Ʃ 2 OPAHs in soil were 4 and 20 times lower than their parent-PAHs, and ranged 396–2530 ng/g (median 458 ng/g) and 91.9–199 ng/g (median 94.9 ng/g), respectively. Ʃ 15 NPAHs was higher than a few global studies, while Ʃ 2 OPAHs was lower than some of the less urbanized/remote areas worldwide. The 6-Nitobenzo[ a ]pyrene (6-NBaP) was most abundant in soil, and accounted for 10–12% of Ʃ 15 NPAHs, while Benzanthrone (BZONE) exceeded among OPAHs, and represented 71–76% of Ʃ 2 OPAHs, respectively. Source identification study indicated that direct emissions from domestic/residential cooking and heating and secondary formations are the essential sources of derivative chemicals in soil. Fugacity fraction ratio (f ratio) indicated volatilization from the soil. The soil-air partitioning study showed sorption by soil organic matter/black carbon has little role in soil-air partitioning of PAH-derivatives in Nepal's urban soil. The toxicity equivalency quotients (TEQs) of NPAHs (314 ± 102 ng/g) was estimated slightly higher than their parent-PAHs (294 ± 121 ng/g) suggesting a relatively higher risk of soil toxicity in Nepal. • All four Nepalese cities are polluted with PAH-derivative chemicals. • Ʃ 15 NPAH in soil was higher than few global studies. • 6-NBaP was the most abundant NPAHs, while BZONE prevailed among OPAH. • Fugacity fraction ratio indicated the volatilization of NPAH/OPAH out of the soil. • Soil-air partitioning indicated soil organic matter doesn't affect NPAH/OPAH. [ABSTRACT FROM AUTHOR]

We estimated the individual contributions of black carbon (BC) and brown carbon (BrC) to the aerosol absorption coefficient (σ ap) and absorption aerosol optical depth (AAOD) in the highly polluted Kathmandu Valley, Nepal, by applying the absorption Ångström exponent (AÅE) method to multi-wavelength aethalometer and AERONET sun/sky radiometer measurements. The elevated σ ap levels observed during the winter and pre-monsoon periods were primarily due to increased usage of diesel generators and low-grade fuel/coal. The AAOD BC and AAOD BrC values were substantially higher during the pre-monsoon period, almost two-fold higher than winter levels, due to seasonally increased biomass-burning activities from agricultural residue burning and forest fires. The overall contribution of BC to σ ap was approximately 80%–95%, whereas BrC accounted for 5%–20% at 520 nm. However, the BrC contribution to σ ap at 370 nm was substantially higher during the winter, ranging from 29.3% to 34.0%. The portioning of AERONET measurements indicates that BC contributed 80% (69%) while BrC contributed 20% (31%) to AAOD of carbonaceous aerosols at 520 nm (370 nm). Although the observation principles and techniques are completely independent, the BC and BrC absorption for simultaneous daytime data points shows a strong correlation between surface aethalometer-based and column AERONET-based estimates. The contributions of BC and BrC to absorption in Kathmandu Valley are similar to those observed under open biomass and garbage-burning conditions; however, the BrC absorption at both 370 and 520 nm is approximately 2- to 3-fold higher than those observed for urban areas in East Asia. • Estimate the contributions of BC and BrC to σ ap and AAOD in the Kathmandu Valley. • The overall contribution of BC to σ ap was 80%-95%, whereas BrC accounted for 5%-20% at 520 nm. • However, the BrC contribution at 370 nm was much higher, ranging from 29.3% to 34.0%, with a peak in winter. • Compared to the surface, AAOD BC and AAOD BrC were nearly two-fold higher during the pre-monsoon period than winter values. • The BC and BrC absorption showed a strong correlation between surface aethalometer-based and column AERONET-based estimates. [ABSTRACT FROM AUTHOR]

Household air pollution from solid fuel cooking causes millions of deaths each year and contributes to climate change. These emissions can be reduced if households transition to cleaner cooking fuels such as LPG or biogas, yet emission measurements during actual use are limited. Six LPG and 57 biogas cooking event emissions were measured during typical cooking practices in Nepal. Emission factors are reported for elemental carbon (EC), organic carbon (OC), particulate matter (PM 2.5 ), and carbon monoxide (CO) and compared to measurements from wood stoves in the same households. Biogas cooking emission factors were 7.4 ± 10.9 mg MJ − 1 for PM 2.5 and 0.2 ± 0.3 mg MJ − 1 for EC on a fuel energy basis, and were not significantly different from LPG stoves (9.5 ± 6.8 mg MJ − 1 for PM 2.5 and 0.3 ± 0.3 mg MJ − 1 for EC, p > 0.05). Wood stoves emitted 50 times more PM 2.5 than biogas on a fuel energy basis and 230 times more EC. EC emissions were about 3% of total particle emissions from biogas and LPG stoves. Most PM 2.5 emissions from gas stoves were attributed to food frying and stove ignition (90%), not the gas fuel (10%), implying that there is a limit to emission reductions that can be achieved with improved fuels. [ABSTRACT FROM AUTHOR]

Chitwan National Park in south-central Nepal is one of the few remaining protected forest ecosystems in South Asia with rich flora and fauna. However, in recent years, southern Nepal including the region of the National park area have experienced deteriorating air quality, which has raised concerns about its impact on ecosystem and public health. The region experiences forest fires during pre-monsoon season and thus, provide an ideal opportunity not only to study its impact on air quality but also to provide source specific diagnostic ratios. In this study, we report measurements of black carbon (BC), trace gases as well as particulate matter (PM 10 , PM 2.5 and PM 1) from Chitwan Air Quality Monitoring Station (CAQMS) during pre-monsoon season (February–May 2016). Average concentrations of BC, PM 10 , PM 2.5 , PM 1 were found to be 10.9 ± 6.9 μg m−3, 156.4 ± 68.2 μg m−3, 95.9 ± 49.0 μg m−3, 80.1 ± 45.5 μg m−3 which are much higher than the prescribed 24 h limits of World Health Organization (25 μg m−3 for PM 10 and 10 μg m−3 for PM 2.5). Furthermore, average concentrations of trace gases, CO, CO 2 and CH 4 were 713.4 ± 476.6 ppbv, 446.0 ± 15.3 ppm and 2.182 ± 0.117 ppm respectively which are also higher than those in the surrounding regions. We identified two pollution events (Event #1 from 16 to 28 March 2016 and Event #2 from 6 to 17 April 2016) and found that surface concentrations of all measured species increased by a factor of 2–3 during these events. The BC/CO ratio of 16.3 ± 2.0, 11.1 ± 3.7 and 9.9 ± 4.2 ng m−3 ppbv−1 was observed during Event#1, Event#2 and during non-event period. Based on MODIS active fire counts and Ängstrȯm absorption exponent (AAE values of 1.8 and 1.9 during Event #1 and #2 respectively), we found that biomass burning (BB) activities were an important source during these events. This is further substantiated by relatively higher contribution of BB to observed BC concentration during both the events (73% and 75% during Event#1 and #2 respectively). Furthermore, a Langrangian modeling framework was used to quantify the contribution of local and regional fires to BC concentration. The contribution of local fires to modelled BC at CAQMS during Event #1 and #2 is estimated to be ~70% and ~78%, respectively. The satellite retrievals of AOD, NO 2 and CO also exhibit a significant increase in columnar concentration during these pollution events. The CALIOP retrieved vertical profile of extinction coefficient further confirmed that these pollutants are not only confined near the surface but are lifted up to 2 km altitude, which can subsequently be transported to high-altitude pristine sites and can impose serious implications on the cryosphere. • Real time measurements of PM, BC and CO at Chitwan, Nepal during pre-monsoon season when forest fires are common. • Forest fires resulted into 2 to 3-fold increase in PM, BC and CO concentration on certain days in month of March and April. • Diagnostic BC/CO ratios during forest fire events are reported. • WRF HYSPLIT model is used to estimate relative contribution of local and regional fires to BC concentration during the events. • Local fires are major contributor of modelled BC concentration at CAQMS during the events. [ABSTRACT FROM AUTHOR]