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

Abstract

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, O 3 ) 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 , PM 1 was 3.6-197.6 µg m −3 , PM 2.5 was 6.1-272.2 µg m −3 , PM 10 was 10.5-604.0 µg m −3 , O 3 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 coarsemode PM was found as compared to other nearby sites in the Indo-Gangetic Plain region. The BC / CO ratio obtained in Lumbini indicated considerable contributions of emissions from both residential and transportation sectors. The 24 h average PM 2.5 and PM 10 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 PM 10 , 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 Published by Copernicus Publications on behalf of the European Geosciences Union.

Study of Aerosol Optical Properties Over Two Sites in the Foothills of the Central Himalayas

“…However, recently, both of the sites have gained popularity as one of the polluted regions in south Asia. More on these sites have already been explained elsewhere (Rupakheti et al, 2017;Rupakheti et al, 2018;Tripathee et al, 2017). Figure 1.…”

“…However, over both sites, aerosol types were identified as those from anthropogenic activities, biomass burning and mixed (undetermined) in high frequency. During the pre-monsoon and post-monsoon seasons, IGP also experiences extensive forest fire and agro-residue burning (Habib et al, 2006;Ram and Sarin, 2011;Rupakheti et al, 2017) which impacts the distant locations even across the Himalayas in the Tibetan Plateau too (Cong et al, 2015).…”

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

“…Recent studies have indicated the likelihood of regional longrange transport contributing to air pollution in different parts of Nepal (Marinoni et al, 2013;Tripathee et al, 2014;Dhungel et al, 2018;Rupakheti et al, 2017;Lüthi et al, 2015;Wan et al, 2017, including the Kathmandu Valley, especially during the premonsoon period (Panday and Prinn, 2009;Putero et al, 2015;Bhardwaj et al, 2018). During the premonsoon season, frequent agro-residue burning and forest fires are reported in the IGP region, including southern Nepal and the Himalayan foothills in India and Nepal (Ram and Sarin, 2010;Vadrevu et al, 2012), as well as in the Kathmandu Valley.…”

Molecular characterization of organic aerosols in the Kathmandu Valley, Nepal: insights into primary and secondary sources

“…Until recently the emissions, types, levels, atmospheric transport and transformation, impacts, and mitigation of various atmospheric pollutants were not well characterized in the vast mountain areas and the foothill region in South Asia. In this context, the international project of "A Sustainable Atmosphere for the Kathmandu Valley (SusKat)" was launched, aiming to comprehensively understand the causes of the severe air pollution in the region, and identifying appropriate solutions to reduce its impacts (Rupakheti et al, 2019). This paper presents analyses of samples collected as part of the SusKat field campaign.…”