Pre-monsoon air quality over Lumbini, a world heritage site along the Himalayan foothills
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...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/11041/2017/acp-17-11041-2017.pdf |
| Summary: | 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<sub>3</sub>) 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<sup>−3</sup>, PM<sub>1</sub> was
3.6–197.6 µg m<sup>−3</sup>, PM<sub>2. 5</sub> was
6.1–272.2 µg m<sup>−3</sup>, PM<sub>10</sub> was
10.5–604.0 µg m<sup>−3</sup>, O<sub>3</sub> 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 PM<sub>2. 5</sub> and
PM<sub>10</sub> 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<sub>10</sub>, 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. |
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| ISSN: | 1680-7316 1680-7324 |