Brown Cloud Research Articles

Seasonal variations in characteristics, sources and diurnal patterns of carbonaceous and water-soluble constituents in urban aerosols from the east coast of tropical India

Environmental context The export of various man-made pollutants from northern India has a large impact on aerosol formation processes, their transformations and regional environmental chemistry over tropical peninsular India. The quantitative source apportionment of organic aerosols performed in this study provides a better understanding of their sources and implications for climate and air-quality management policies in South Asia. Abstract This study highlights seasonal characteristics, sources, daytime (sea-breeze) and night-time (land-breeze) variations of carbonaceous and water-soluble ionic components in PM10 (<10 µm particulate matter) aerosols from the east coast (Chennai city) of tropical India. Elemental and organic carbon (EC and OC) were found to be higher in winter when air masses were delivered from the northern part of India covered by the Indo-Gangetic-Plains whereas lower concentrations were observed during summer and monsoon associated with marine air masses. Sea salts (Na+ and Cl–), dust (Ca2+ and Mg2+) and nitrates (NO3–) were found to be highest in monsoon, suggesting these species may be co-transported over the sampling site with marine air masses. Using air mass back-trajectory analysis, linear relationships between chemical species and specific mass ratios, we demonstrate that east coast urban aerosols are strongly influenced by aged anthropogenic sources including biomass burning in winter and post monsoon while aged marine emissions mixed with local pollutants (dust and vehicular) are important in monsoon and summer. Further, the mesoscale phenomenon was reflected in measured chemical constituents during the study period. Positive-matrix-factorisation (PMF) analysis confirmed that OC aerosols are largely attributable to chemically aged anthropogenic (53 % in the day and 39 % in the night) and combustion-derived (17 % and 39 %) sources in winter and sea salts mixed with dust and vehicular emissions (61 % and 52 %) during monsoon. These important insights about the sources and formation processes of organic aerosols will help in understanding the formation of atmospheric brown clouds over south Asia.

A 150-year record of black carbon (soot and char) and polycyclic aromatic compounds deposition in Lake Phayao, north Thailand.

An improved understanding of the historical variation in the emissions and sources (biomass burning, BB vs. fossil fuel, FF combustion) of soot and char, the two components of black carbon (BC), and polycyclic aromatic compounds (PACs) may help in assessing the environmental effects of the Atmospheric Brown Cloud (ABC) in SE Asia. We therefore determined historical variations of the fluxes of soot, char, and PACs (24 polycyclic aromatic hydrocarbons (PAHs), 12 oxygenated PAHs (OPAHs), and 4 azaarenes) in a dated sediment core (covering the past ∼150 years) of Phayao Lake in Thailand. The soot fluxes have been increasing in recent times, but at a far lower rate than previously estimated based on BC emission inventories. This may be associated with a decreasing BB contribution as indicated by the decreasing char fluxes from old to young sediments. The fluxes of high- and low-molecular-weight (HMW and LMW) PAHs, OPAHs, and azaarenes all sharply increased after ∼1980, while the ΣLMW-/ΣHMW-PAHs ratios decreased, further supporting the reduction in BB contribution at the expense of increasing FF combustion emissions. We also suggest that the separate record of char and soot, which has up to now not been done in aerosol studies, is useful to assess the environmental effects of ABC because of the different light-absorbing properties of these two BC components. Our results suggest that besides the establishment of improved FF combustion technology, BB must be further reduced in the SE Asian region in order to weaken the ABC haze.

PRELIMINARY ESTIMATION ON AIR POLLUTION LOAD OVER BOGOR CITY TOWARDS DEVELOPMENT OF CLEAN AIR ACTION PLAN

Emission inventory (EI) data are crucial to provide source apportionment and relative strength of various air pollutant sources in a city. The process of EI compilation can be either bottom-up or top-down, which depends on data availability and other resources. For a city like Bogor, known as a buffer zone of the capital of the Republic of Indonesia, these EI data are now available only for greenhouse gases (GHGs) but not for the air pollutants. Therefore, a top-down EI was designed and implemented for the city in the base year of 2016. Note that the sources of activity data were compiled from the previously arranged GHGs EI database as well as some other data gathered from the local authority. We adopted the EI framework of the Atmospheric Brown Cloud Emission Inventory Manual spreadsheet for the compilation. We included SO2, CO, NO2, PM10, PM2.5, NMVOC, and PM components (black carbon and organic carbon). Point sources, area sources, as well as mobile sources, were considered in the emission estimation. The latter species were included as they are known as strong short-lived climate-forcing pollutants (SLCPs). On-road transport contributed significantly to SO2, NMVOC, and PM2.5, with a portion of 60-86% of the total emission. Industrial combustion sources dominated the shares to the total emissions of NOx (91%) and CO (92%). Based on this baseline information, we then proposed the source wise clean air action plan for the city in order to reduce the emission. A more accurate and up to date EI database should be done through a survey to get local representative activity data and to be compiled on a regular basis.

Observation and analysis of spatiotemporal characteristics of surface ozone and carbon monoxide at multiple sites in the Kathmandu Valley, Nepal

Abstract. Residents of the Kathmandu Valley experience severe particulate and gaseous air pollution throughout most of the year, even during much of the rainy season. The knowledge base for understanding the air pollution in the Kathmandu Valley was previously very limited but is improving rapidly due to several field measurement studies conducted in the last few years. Thus far, most analyses of observations in the Kathmandu Valley have been limited to short periods of time at single locations. This study extends the past studies by examining the spatial and temporal characteristics of two important gaseous air pollutants (CO and O3) based on simultaneous observations over a longer period at five locations within the valley and on its rim, including a supersite (at Bode in the valley center, 1345 m above sea level) and four satellite sites: Paknajol (1380 m a.s.l.) in the Kathmandu city center; Bhimdhunga (1522 m a.s.l.), a mountain pass on the valley's western rim; Nagarkot (1901 m a.s.l.), another mountain pass on the eastern rim; and Naikhandi (1233 m a.s.l.), near the valley's only river outlet. CO and O3 mixing ratios were monitored from January to July 2013, along with other gases and aerosol particles by instruments deployed at the Bode supersite during the international air pollution measurement campaign SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley – endorsed by the Atmospheric Brown Clouds program of UNEP). The monitoring of O3 at Bode, Paknajol and Nagarkot as well as the CO monitoring at Bode were extended until March 2014 to investigate their variability over a complete annual cycle. Higher CO mixing ratios were found at Bode than at the outskirt sites (Bhimdhunga, Naikhandi and Nagarkot), and all sites except Nagarkot showed distinct diurnal cycles of CO mixing ratio, with morning peaks and daytime lows. Seasonally, CO was higher during premonsoon (March–May) season and winter (December–February) season than during monsoon season (June–September) and postmonsoon (October–November) season. This is primarily due to the emissions from brick industries, which are only operational during this period (January–April), as well as increased domestic heating during winter, and regional forest fires and agro-residue burning during the premonsoon season. It was lower during the monsoon due to rainfall, which reduces open burning activities within the valley and in the surrounding regions and thus reduces sources of CO. The meteorology of the valley also played a key role in determining the CO mixing ratios. The wind is calm and easterly in the shallow mixing layer, with a mixing layer height (MLH) of about 250 m, during the night and early morning. The MLH slowly increases after sunrise and decreases in the afternoon. As a result, the westerly wind becomes active and reduces the mixing ratio during the daytime. Furthermore, there was evidence of an increase in the O3 mixing ratios in the Kathmandu Valley as a result of emissions in the Indo-Gangetic Plain (IGP) region, particularly from biomass burning including agro-residue burning. A top-down estimate of the CO emission flux was made by using the CO mixing ratio and mixing layer height measured at Bode. The estimated annual CO flux at Bode was 4.9 µg m−2 s−1, which is 2–14 times higher than that in widely used emission inventory databases (EDGAR HTAP, REAS and INTEX-B). This difference in CO flux between Bode and other emission databases likely arises from large uncertainties in both the top-down and bottom-up approaches to estimating the emission flux. The O3 mixing ratio was found to be highest during the premonsoon season at all sites, while the timing of the seasonal minimum varied across the sites. The daily maximum 8 h average O3 exceeded the WHO recommended guideline of 50 ppb on more days at the hilltop station of Nagarkot (159 out of 357 days) than at the urban valley bottom sites of Paknajol (132 out of 354 days) and Bode (102 out of 353 days), presumably due to the influence of free-tropospheric air at the high-altitude site (as also indicated by Putero et al., 2015, for the Paknajol site in the Kathmandu Valley) as well as to titration of O3 by fresh NOx emissions near the urban sites. More than 78 % of the exceedance days were during the premonsoon period at all sites. The high O3 mixing ratio observed during the premonsoon period is of a concern for human health and ecosystems, including agroecosystems in the Kathmandu Valley and surrounding regions.

Variations in surface ozone and carbon monoxide in the Kathmandu Valley and surrounding broader regions during SusKat-ABC field campaign: role of local and regional sources

Abstract. Air pollution resulting from rapid urbanization and associated human activities in the Kathmandu Valley of Nepal has been leading to serious public health concerns over the past 2 decades. These concerns led to a multinational field campaign SusKat-ABC (Sustainable atmosphere for the Kathmandu Valley – Atmospheric Brown Clouds) that measured different trace gases, aerosols and meteorological parameters in the Kathmandu Valley and surrounding regions during December 2012 to June 2013 to understand local- to regional-scale processes influencing air quality of the Kathmandu Valley. This study provides information about the regional distribution of ozone and some precursor gases using simultaneous in situ measurements from a SusKat-ABC supersite at Bode, Nepal, and two Indian sites: a high-altitude site, Nainital, located in the central Himalayan region and a low-altitude site, Pantnagar, located in the Indo-Gangetic Plain (IGP). The diurnal variations at Bode showed a daytime buildup in O3 while CO shows morning and evening peaks. Similar variations (with lower levels) were also observed at Pantnagar but not at Nainital. Several events of hourly ozone levels exceeding 80 ppbv were also observed at Bode. The CO levels showed a decrease from their peak level of about 2000 ppbv in January to about 680 ppbv in June at Bode. The hourly mean ozone and CO levels showed a strong negative correlation during winter (r2 = 0.82 in January and r2 = 0.71 in February), but this negative correlation gradually becomes weaker, with the lowest value in May (r2 = 0.12). The background O3 and CO mixing ratios at Bode were estimated to be about 14 and 325 ppbv, respectively. The rate of change of ozone at Bode showed a more rapid increase ( ∼ 17 ppbv h−1) during morning than the decrease in the evening (5–6 ppbv h−1), suggesting the prevalence of a semi-urban environ. The lower CO levels during spring suggest that regional transport also contributes appreciably to springtime ozone enhancement in the Kathmandu Valley on top of the local in situ ozone production. We show that regional pollution resulting from agricultural crop residue burning in northwestern IGP led to simultaneous increases in O3 and CO levels at Bode and Nainital during the first week of May 2013. A biomass-burning-induced increase in ozone and related gases was also confirmed by a global model and balloon-borne observations over Nainital. A comparison of surface ozone variations and composition of light non-methane hydrocarbons among different sites indicated the differences in emission sources of the Kathmandu Valley and the IGP. These results highlight that it is important to consider regional sources in air quality management of the Kathmandu Valley.

Transport of regional pollutants through a remote trans-Himalayan valley in Nepal

Abstract. Anthropogenic emissions from the combustion of fossil fuels and biomass in Asia have increased in recent years. High concentrations of reactive trace gases and light-absorbing and light-scattering particles from these sources form persistent haze layers, also known as atmospheric brown clouds, over the Indo–Gangetic plains (IGP) from December through early June. Models and satellite imagery suggest that strong wind systems within deep Himalayan valleys are major pathways by which pollutants from the IGP are transported to the higher Himalaya. However, observational evidence of the transport of polluted air masses through Himalayan valleys has been lacking to date. To evaluate this pathway, we measured black carbon (BC), ozone (O3), and associated meteorological conditions within the Kali Gandaki Valley (KGV), Nepal, from January 2013 to July 2015. BC and O3 varied over both diurnal and seasonal cycles. Relative to nighttime, mean BC and O3 concentrations within the valley were higher during daytime when the up-valley flow (average velocity of 17 m s−1) dominated. BC and O3 concentrations also varied seasonally with minima during the monsoon season (July to September). Concentrations of both species subsequently increased post-monsoon and peaked during March to May. Average concentrations for O3 during the seasonally representative months of April, August, and November were 41.7, 24.5, and 29.4 ppbv, respectively, while the corresponding BC concentrations were 1.17, 0.24, and 1.01 µg m−3, respectively. Up-valley fluxes of BC were significantly greater than down-valley fluxes during all seasons. In addition, frequent episodes of BC concentrations 2–3 times higher than average persisted from several days to a week during non-monsoon months. Our observations of increases in BC concentration and fluxes in the valley, particularly during pre-monsoon, provide evidence that trans-Himalayan valleys are important conduits for transport of pollutants from the IGP to the higher Himalaya.

Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas

Abstract. The SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley–Atmospheric Brown Clouds) international air pollution measurement campaign was carried out from December 2012 to June 2013 in the Kathmandu Valley and surrounding regions in Nepal. The Kathmandu Valley is a bowl-shaped basin with a severe air pollution problem. This paper reports measurements of two major greenhouse gases (GHGs), methane (CH4) and carbon dioxide (CO2), along with the pollutant CO, that began during the campaign and were extended for 1 year at the SusKat-ABC supersite in Bode, a semi-urban location in the Kathmandu Valley. Simultaneous measurements were also made during 2015 in Bode and a nearby rural site (Chanban) ∼ 25 km (aerial distance) to the southwest of Bode on the other side of a tall ridge. The ambient mixing ratios of methane (CH4), carbon dioxide (CO2), water vapor, and carbon monoxide (CO) were measured with a cavity ring-down spectrometer (G2401; Picarro, USA) along with meteorological parameters for 1 year (March 2013–March 2014). These measurements are the first of their kind in the central Himalayan foothills. At Bode, the annual average mixing ratios of CO2 and CH4 were 419.3 (±6.0) ppm and 2.192 (±0.066) ppm, respectively. These values are higher than the levels observed at background sites such as Mauna Loa, USA (CO2: 396.8 ± 2.0 ppm, CH4: 1.831 ± 0.110 ppm) and Waliguan, China (CO2: 397.7 ± 3.6 ppm, CH4: 1.879 ± 0.009 ppm) during the same period and at other urban and semi-urban sites in the region, such as Ahmedabad and Shadnagar (India). They varied slightly across the seasons at Bode, with seasonal average CH4 mixing ratios of 2.157 (±0.230) ppm in the pre-monsoon season, 2.199 (±0.241) ppm in the monsoon, 2.210 (±0.200) ppm in the post-monsoon, and 2.214 (±0.209) ppm in the winter season. The average CO2 mixing ratios were 426.2 (±25.5) ppm in the pre-monsoon, 413.5 (±24.2) ppm in the monsoon, 417.3 (±23.1) ppm in the post-monsoon, and 421.9 (±20.3) ppm in the winter season. The maximum seasonal mean mixing ratio of CH4 in winter was only 0.057 ppm or 2.6 % higher than the seasonal minimum during the pre-monsoon period, while CO2 was 12.8 ppm or 3.1 % higher during the pre-monsoon period (seasonal maximum) than during the monsoon (seasonal minimum). On the other hand, the CO mixing ratio at Bode was 191 % higher during the winter than during the monsoon season. The enhancement in CO2 mixing ratios during the pre-monsoon season is associated with additional CO2 emissions from forest fires and agro-residue burning in northern South Asia in addition to local emissions in the Kathmandu Valley. Published CO∕CO2 ratios of different emission sources in Nepal and India were compared with the observed CO∕CO2 ratios in this study. This comparison suggested that the major sources in the Kathmandu Valley were residential cooking and vehicle exhaust in all seasons except winter. In winter, brick kiln emissions were a major source. Simultaneous measurements in Bode and Chanban (15 July–3 October 2015) revealed that the mixing ratios of CO2, CH4, and CO were 3.8, 12, and 64 % higher in Bode than Chanban. The Kathmandu Valley thus has significant emissions from local sources, which can also be attributed to its bowl-shaped geography that is conducive to pollution build-up. At Bode, all three gas species (CO2, CH4, and CO) showed strong diurnal patterns in their mixing ratios with a pronounced morning peak (ca. 08:00), a dip in the afternoon, and a gradual increase again through the night until the next morning. CH4 and CO at Chanban, however, did not show any noticeable diurnal variations. These measurements provide the first insights into the diurnal and seasonal variation in key greenhouse gases and air pollutants and their local and regional sources, which is important information for atmospheric research in the region.

Pre-monsoon air quality over Lumbini, a world heritage site along the Himalayan foothills

Abstract. Lumbini, in southern Nepal, is a UNESCO world heritage site of universal value as the birthplace of Buddha. Poor air quality in Lumbini and surrounding regions is a great concern for public health as well as for preservation, protection and promotion of Buddhist heritage and culture. We present here results from measurements of ambient concentrations of key air pollutants (PM, BC, CO, O3) in Lumbini, first of its kind for Lumbini, conducted during an intensive measurement period of 3 months (April–June 2013) in the pre-monsoon season. The measurements were carried out as a part of the international air pollution measurement campaign; SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley – Atmospheric Brown Clouds). The main objective of this work is to understand and document the level of air pollution, diurnal characteristics and influence of open burning on air quality in Lumbini. The hourly average concentrations during the entire measurement campaign ranged as follows: BC was 0.3–30.0 µg m−3, PM1 was 3.6–197.6 µg m−3, PM2. 5 was 6.1–272.2 µg m−3, PM10 was 10.5–604.0 µg m−3, O3 was 1.0–118.1 ppbv and CO was 125.0–1430.0 ppbv. These levels are comparable to other very heavily polluted sites in South Asia. Higher fraction of coarse-mode PM was found as compared to other nearby sites in the Indo-Gangetic Plain region. The ΔBC ∕ ΔCO ratio obtained in Lumbini indicated considerable contributions of emissions from both residential and transportation sectors. The 24 h average PM2. 5 and PM10 concentrations exceeded the WHO guideline very frequently (94 and 85 % of the sampled period, respectively), which implies significant health risks for the residents and visitors in the region. These air pollutants exhibited clear diurnal cycles with high values in the morning and evening. During the study period, the worst air pollution episodes were mainly due to agro-residue burning and regional forest fires combined with meteorological conditions conducive of pollution transport to Lumbini. Fossil fuel combustion also contributed significantly, accounting for more than half of the ambient BC concentration according to aerosol spectral light absorption coefficients obtained in Lumbini. WRF-STEM, a regional chemical transport model, was used to simulate the meteorology and the concentrations of pollutants to understand the pollutant transport pathways. The model estimated values were ∼ 1. 5 to 5 times lower than the observed concentrations for CO and PM10, respectively. Model-simulated regionally tagged CO tracers showed that the majority of CO came from the upwind region of Ganges Valley. Model performance needs significant improvement in simulating aerosols in the region. Given the high air pollution level, there is a clear and urgent need for setting up a network of long-term air quality monitoring stations in the greater Lumbini region.

Light‐absorbing impurities enhance glacier albedo reduction in the southeastern Tibetan plateau

AbstractLight‐absorbing impurities (LAIs) in snow of the southeastern Tibetan Plateau (TP) and their climatic impacts are of interest not only because this region borders areas affected by the South Asian atmospheric brown clouds but also because the seasonal snow and glacier melt from this region form important headwaters of large rivers. In this study, we collected surface snow and snowpit samples from four glaciers in the southeastern TP in June 2015 to investigate the comprehensive observational data set of LAIs. Results showed that the LAI concentrations were much higher in the aged snow and granular ice than in the fresh snow and snowpits due to postdepositional processes. Impurity concentrations fluctuated across snowpits, with maximum LAI concentrations frequently occurring toward the bottom of snowpits. Based on the SNow ICe Aerosol Radiative model, the albedo simulation indicated that black carbon and dust account for approximately 20% of the albedo reduction relative to clean snow. The radiative forcing caused by black carbon and dust deposition on the glaciers were between 1.0–141 W m−2 and 1.5–120 W m−2, respectively. Black carbon (BC) played a larger role in albedo reduction and radiative forcing than dust in the study area, enhancing approximately 15% of glacier melt. Analysis based on the Fire INventory from NCAR indicated that nonbiomass‐burning sources of BC played an important role in the total BC deposition, especially during the monsoon season. This study suggests that eliminating anthropogenic BC could mitigate glacier melt in the future of the southeastern TP.

Benefits of improved municipal solid waste management on greenhouse gas reduction in Luangprabang, Laos

ABSTRACTClimate change is a consequence of greenhouse gas emissions. Greenhouse gas (GHG) emissions from the waste sector contribute to 3% of total anthropogenic emissions. In this study, applicable solutions for municipal solid waste (MSW) management in Luangprabang (LPB) and Laos were examined. Material flow analysis of MSW was performed to estimate the amount of MSW generated in 2015. Approximately 29,419 tonnes of MSW is estimated for 2015. Unmanaged landfilling was the main disposal method, while MSW open burning was also practiced to some extent. The International Panel on Climate Change 2006 model and the Atmospheric Brown Clouds Emission Inventory Manual were used to estimate GHG emissions from existing MSW management, and total emissions are 33,889 tonnes/year carbon dioxide-equivalents (CO2-eq). Three scenarios were developed in order to reduce GHG emissions and environmental problems. Improvement of the MSW management by expanding MSW collection services, introducing composting and recycling, and avoiding open burning, can be considered as solutions to overcome the problems for LPB. The lowest GHG emissions are achieved in the scenario where composting and recycling are proposed, with the total GHG emissions reduction by 18,264 tonnes/year CO2-eq.

Effect of reduced PAR on growth and photosynthetic efficiency of soybean genotypes

Soybean is an important crop, and physiologically, it is photosensitive in nature and therefore, is likely to be highly affected by the atmospheric brown clouds (ABCs) which reduce PAR (Photosynthetically Active Radiation) availability, and moisture stress conditions those may prevail as a consequence of climate change scenario. Therefore, the impact of reduced natural PAR was evaluated on its determinate (DT; cv. JS-93-05), semi-determinate (SDT; cv. JS-335) and indeterminate (IDT; cv. Kalitur) genotypes. For simulating the reduced PAR condition, three different shapes of structures, viz., rectangular-cuboid, octagonal-dome and hemispherical-dome with shade-net covering were initially tested to check the uniformity of PAR availability inside the structure and the last one was found better. The light saturation point (LSP) was found to be 800, 1200 and 1000 PAR μmol m-2s-1 in case of DT, SDT and IDT genotypes,respectively. Under reduced PAR and restricted irrigation condition, the photosynthetic rate was 20.8, 21.9 and 28.9 μmol m-2s-1 in case of DT, SDT and IDT cultivars, respectively, while their seed yields were 151.3, 238.7 and 264.2 kg ha-1 indicating better source-sink relations of the IDT cultivar. Therefore, it is projected that IDT cultivars are likely to be popular under futuristic scenarios of low PAR availability and water scarcities.

A new species of Polyplocia Lestage from Malaysia with comments on the genus (Ephemeroptera, Euthyplociidae, Euthyplociinae).

Polyplocia nebulosa sp. nov. is described based on male and female imagos from Malaysia, Sabah State. Nymphs provisionally assigned to this species are also described. This species can be readily separated from P. vitalisi by the color pattern of the wings, with light brown longitudinal veins, narrow dark brown clouds on cross veins and margins of wings tinged with brown. The male genitalia are distinct from those of other species of Polyplocia: penes are broad, T-shaped, with large lateral projecting lobes, which are apically rounded, and with a small dorsolateral spine on each lobe; the styliger plate is short and not projected posteriorly. Eggs of the genus are described for the first time using scanning electron microscopy. Eggs are 265-267 µm in length, 170-186 µm in width, barrel-shaped, without polar caps or other attachment structures, with one visible micropyle and with chorion forming an irregular mesh with raised ridges (mesh between 3.8-8 µm). A key to male adults of Polyplocia is provided and additional records of Polyplocia from Thailand are given.

Overview of VOC emissions and chemistry from PTR-TOF-MS measurements during the SusKat-ABC campaign: high acetaldehyde, isoprene and isocyanic acid in wintertime air of the Kathmandu Valley

Abstract. The Kathmandu Valley in Nepal suffers from severe wintertime air pollution. Volatile organic compounds (VOCs) are key constituents of air pollution, though their specific role in the valley is poorly understood due to insufficient data. During the SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley–Atmospheric Brown Clouds) field campaign conducted in Nepal in the winter of 2012–2013, a comprehensive study was carried out to characterise the chemical composition of ambient Kathmandu air, including the determination of speciated VOCs, by deploying a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) – the first such deployment in South Asia. In the study, 71 ion peaks (for which measured ambient concentrations exceeded the 2σ detection limit) were detected in the PTR-TOF-MS mass scan data, highlighting the chemical complexity of ambient air in the valley. Of the 71 species, 37 were found to have campaign average concentrations greater than 200 ppt and were identified based on their spectral characteristics, ambient diel profiles and correlation with specific emission tracers as a result of the high mass resolution (m ∕ Δm > 4200) and temporal resolution (1 min) of the PTR-TOF-MS. The concentration ranking in the average VOC mixing ratios during our wintertime deployment was acetaldehyde (8.8 ppb) > methanol (7.4 ppb) > acetone + propanal (4.2 ppb) > benzene (2.7 ppb) > toluene (1.5 ppb) > isoprene (1.1 ppb) > acetonitrile (1.1 ppb) > C8-aromatics ( ∼ 1 ppb) > furan ( ∼ 0.5 ppb) > C9-aromatics (0.4 ppb). Distinct diel profiles were observed for the nominal isobaric compounds isoprene (m ∕ z = 69.070) and furan (m ∕ z = 69.033). Comparison with wintertime measurements from several locations elsewhere in the world showed mixing ratios of acetaldehyde ( ∼ 9 ppb), acetonitrile ( ∼ 1 ppb) and isoprene ( ∼ 1 ppb) to be among the highest reported to date. Two "new" ambient compounds, namely formamide (m ∕ z = 46.029) and acetamide (m ∕ z = 60.051), which can photochemically produce isocyanic acid in the atmosphere, are reported in this study along with nitromethane (a tracer for diesel exhaust), which has only recently been detected in ambient studies. Two distinct periods were selected during the campaign for detailed analysis: the first was associated with high wintertime emissions of biogenic isoprene and the second with elevated levels of ambient acetonitrile, benzene and isocyanic acid from biomass burning activities. Emissions from biomass burning and biomass co-fired brick kilns were found to be the dominant sources for compounds such as propyne, propene, benzene and propanenitrile, which correlated strongly with acetonitrile (r2 > 0.7), a chemical tracer for biomass burning. The calculated total VOC OH reactivity was dominated by acetaldehyde (24.0 %), isoprene (20.2 %) and propene (18.7 %), while oxygenated VOCs and isoprene collectively contributed to more than 68 % of the total ozone production potential. Based on known secondary organic aerosol (SOA) yields and measured ambient concentrations in the Kathmandu Valley, the relative SOA production potential of VOCs were benzene > naphthalene > toluene > xylenes > monoterpenes > trimethylbenzenes > styrene > isoprene. The first ambient measurements from any site in South Asia of compounds with significant health effects such as isocyanic acid, formamide, acetamide, naphthalene and nitromethane have been reported in this study. Our results suggest that mitigation of intense wintertime biomass burning activities, in particular point sources such biomass co-fired brick kilns, would be important to reduce the emission and formation of toxic VOCs (such as benzene and isocyanic acid) in the Kathmandu Valley.

Atmospheric Aerosol Elements over the Inland Tibetan Plateau: Concentration, Seasonality, and Transport

Between November 2005 and November 2007, weekly total suspended particle samples were collected at the Nam Co station in the inland Tibetan Plateau (TP). Through inductively coupled plasma mass spectrometry, twenty-nine elements were analyzed and their sources and fluxes were investigated. Mean elemental concentrations were lower than those at the edge of the TP. Some elements, such as Cr, Ni, Cd, and Pb, exhibited high enrichment factors (Cr: 22; Ni: 17; Cd: 23; and Pb: 9), indicating possible anthropogenic influence in this remote region, particularly during the pre-monsoon and monsoon seasons. In addition, an empirical orthogonal function analysis revealed the dominance of crustal-origin elements, rather than anthropogenic elements, in the aerosol. Furthermore, backward air mass trajectories demonstrated that the Nam Co region was mainly influenced by air masses from Central and South Asia. Accordingly, because of dust storms from Central Asia and within the TP, crustal element concentrations, such as of Al, were higher during winter and pre-monsoon seasons than during the monsoon season. By contrast, anthropogenic elements, such as Cr and Cd, were relatively higher during the pre-monsoon and monsoon seasons because of pollutants transported from South Asia, where atmospheric brown clouds are concentrated and biomass combustion is prevalent. Dry deposition of aerosols dominated in the Nam Co region, particularly during the non-monsoon period, which is useful to interpret the elemental records in the TP ice cores and lake sediments.

Greenhouse gas emissions from municipal solid waste management in Vientiane, Lao PDR.

Municipal solid waste (MSW) is one of the major environmental problems throughout the world including in Lao PDR. In Vientiane, due to the lack of a collection service, open burning and illegal dumping are commonly practised. This study aims to estimate the greenhouse gas (GHG) emission from the current situation of MSW management (MSWM) in Vientiane and proposes an alternative solution to reduce the GHG emission and environmental impacts. The 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories (IPCC 2006 model) are used for the estimation of GHG emission from landfill and composting. For the estimation of GHG emission from open burning, the Atmospheric Brown Clouds Emission Inventory Manual (ABC EIM) is used. In Vientiane, a total of 232, 505 tonnes year(-1) of MSW was generated in 2011. Waste generation in Vientiane is 0.69 kg per capita per day, and about 31% of the total MSW generated was directly sent to landfill (71,162 tonnes year(-1)). The total potential GHG emission from the baseline scenario in 2011 was 110,182 tonnes year(-1) CO2-eq, which is 0.15 tonne year(-1) CO2-eq per capita. From the three MSWM scenarios proposed, scenario S3, which includes recycling, composting and landfilling, seems to be an effective solution for dealing with MSW in Vientiane with less air pollution, and is environmentally friendly. The total GHG emission in scenario S3 is reduced to 91,920 tonnes year(-1) CO2-eq (47% reduction), compared with the S1 scenario where all uncollected waste is diverted to landfill.

Spatial and temporal variation of rainfall trends of Sri Lanka

This study was based on daily rainfall data of 48 stations distributed over the entire island covering a 30-year period from 1981 to 2010. Data analysis was done to identify the spatial pattern of rainfall trends. The methods employed in data analysis are linear regression and interpolation by Universal Kriging and Radial Basis function. The slope of linear regression curves of 48 stations was used in interpolation. The regression coefficients show spatially and seasonally variable positive and negative trends of annual and seasonal rainfall. About half of the mean annual pentad series show negative trends, while the rest shows positive trends. By contrast, the rainfall trends of the Southwest Monsoon (SWM) season are predominantly negative throughout the country. The first phase of the Northeast Monsoon (NEM1) displays downward trends everywhere, with the exception of the Southeastern coastal area. The strongest negative trends were found in the Northeast and in the Central Highlands. The second phase (NEM2) is mostly positive, except in the Northeast. The Inter-Monsoon (IM) periods have predominantly upward trends almost everywhere, but still the trends in some parts of the Highlands and Northeast are negative. The long-term data at Watawala Nuwara Eliya and Sandringham show a consistent decline in the rainfall over the last 100 years, particularly during the SWM. There seems to be a faster decline in the rainfall in the last 3 decades. These trends are consistent with the observations in India. It is generally accepted that there has been changes in the circulation pattern. Weakening of the SWM circulation parameters caused by global warming appears to be the main causes of recent changes. Effect of the Asian Brown Cloud may also play a role in these changes.

Atmospheric brown clouds reach the Tibetan Plateau by crossing the Himalayas

Abstract. The Himalayas and the Tibetan Plateau region (HTP), despite being a remote and sparsely populated area, is regularly exposed to polluted air masses with significant amounts of aerosols including black carbon. These dark, light-absorbing particles are known to exert a great melting potential on mountain cryospheric reservoirs through albedo reduction and radiative forcing. This study combines ground-based and satellite remote sensing data to identify a severe aerosol pollution episode observed simultaneously in central Tibet and on the southern side of the Himalayas during 13–19 March 2009 (pre-monsoon). Trajectory calculations based on the high-resolution numerical weather prediction model COSMO are used to locate the source regions and study the mechanisms of pollution transport in the complex topography of the HTP. We detail how polluted air masses from an atmospheric brown cloud (ABC) over South Asia reach the Tibetan Plateau within a few days. Lifting and advection of polluted air masses over the great mountain range is enabled by a combination of synoptic-scale and local meteorological processes. During the days prior to the event, winds over the Indo-Gangetic Plain (IGP) are generally weak at lower levels, allowing for accumulation of pollutants and thus the formation of ABCs. The subsequent passing of synoptic-scale troughs leads to southwesterly flow in the middle troposphere over northern and central India, carrying the polluted air masses across the Himalayas. As the IGP is known to be a hotspot of ABCs, the cross-Himalayan transport of polluted air masses may have serious implications for the cryosphere in the HTP and impact climate on regional to global scales. Since the current study focuses on one particularly strong pollution episode, quantifying the frequency and magnitude of similar events in a climatological study is required to assess the total impact.

Multifaceted application of crop residue biochar as a tool for sustainable agriculture: An ecological perspective

Lignocellulosic crop residue biomass, in surplus, is of vital importance due to its multifaceted utilization potential on- and off-site to agricultural systems; therefore, its management is essential for sustainable agriculture. The malpractice of open crop residue burning leading to the brown cloud phenomenon and contributing significantly to atmospheric heterogeneity through enhanced gaseous and particulate emissions is of greater off-late concern. Available traditional crop residue management (CRM) technologies have not achieved wider adaptation; therefore, recently thermochemical conversion has been foreseen as an interesting tool for potential CRM under changing climate scenario. Biochar, a by-product of thermochemical processes, has been evaluated as a potential soil ameliorant and C sequestration agent. As soil ameliorant, it improves soil basic properties directly along with subdued release of greenhouse gases from agroecosystems, provides adsorption surface to agrochemicals and improves essential nutrient dynamics. Since the potential benefits of biochar in soil are governed by initial pyrolysis conditions and soil types; therefore, its wider utilization potential as suitable tool in sustainable agriculture and climate change mitigation needs to be critically analyzed before its specific recommendation to an agroecosystem. The present review provides a critical insight on current research on various aspects, particularly ecological, of crop residue biochar starting from the feedstock sources, pyrolysis conditions and changes after application. Additionally, a brief account is given on the agronomic relevance and major constraints of biochar amendment as an ecological engineering tool for sustainable agriculture. After reviewing various aspects of crop residue as feedstock, we recommend its use as a blend, rather than sole use, along with several other lignocellulosic materials under pyrolysis process as well as ameliorating agent.

Global warming, the atmospheric brown cloud, and the changing Indian summer monsoon

Much scientific discussion has focused on rising greenhouse gas emissions and changing rainfall patterns in an increasingly warmer world. In fact, preventing the worst impacts of climate change on future human well-being will mean dealing with heightened flood and drought risks. The authors explain why the complex science of the shifting rainfall patterns and intensities caused by global warming is made even more complex by increasingly extreme air pollution. The article describes how scientists now think that the so-called “atmospheric brown cloud” over India affects the summer monsoon more than global warming does. In India, agriculture, industrial productivity, and life in general depend on monsoonal downpours that bring huge amounts of water to the subcontinent, feeding rivers and aquifers and cooling the land between June and September. As bad as it sounds, the scenario in which air pollution plays a major role in climate is actually good news for developing nations such as India. Pollution control is a regional and local problem that developing nations need to address in any case because of the huge human health costs related to it. The authors also warn that once pollution is brought under control, the full extent of global warming caused by developed nations’ greenhouse gas emissions from decades ago will become more prevalent and its impacts on the Indian monsoon will be unmasked.

Atmospheric Aerosol Elements over the Inland Tibetan Plateau: Concentration, Seasonality, and Transport

Between November 2005 and November 2007, weekly total suspended particle samples were collected at the Nam Co station in the inland Tibetan Plateau (TP). Through inductively coupled plasma mass spectrometry, twenty-nine elements were analyzed and their sources and fluxes were investigated. Mean elemental concentrations were lower than those at the edge of the TP. Some elements, such as Cr, Ni, Cd, and Pb, exhibited high enrichment factors (Cr: 22; Ni: 17; Cd: 23; and Pb: 9), indicating possible anthropogenic influence in this remote region, particularly during the pre-monsoon and monsoon seasons. In addition, an empirical orthogonal function analysis revealed the dominance of crustal-origin elements, rather than anthropogenic elements, in the aerosol. Furthermore, backward air mass trajectories demonstrated that the Nam Co region was mainly influenced by air masses from Central and South Asia. Accordingly, because of dust storms from Central Asia and within the TP, crustal element concentrations, such as of Al, were higher during winter and pre-monsoon seasons than during the monsoon season. By contrast, anthropogenic elements, such as Cr and Cd, were relatively higher during the pre-monsoon and monsoon seasons because of pollutants transported from South Asia, where atmospheric brown clouds are concentrated and biomass combustion is prevalent. Dry deposition of aerosols dominated in the Nam Co region, particularly during the non-monsoon period, which is useful to interpret the elemental records in the TP ice cores and lake sediments.