Abstract:
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This study uses spatiotemporal patterns in ambient
concentrations to infer the contribution of regional versus
local sources. We collected 12 months of monitoring data for
outdoor fine particulate matter (PM2.5) in rural southern India.
Rural India includes more than one-tenth of the global
population and annually accounts for around half a million air
pollution deaths, yet little is known about the relative
contribution of local sources to outdoor air pollution. We
measured 1-min averaged outdoor PM2.5 concentrations during June
2015-May 2016 in three villages, which varied in population
size, socioeconomic status, and type and usage of domestic fuel.
The daily geometric-mean PM2.5 concentration was approximately
30mugm(-3) (geometric standard deviation: approximately 1.5).
Concentrations exceeded the Indian National Ambient Air Quality
standards (60mugm(-3)) during 2-5% of observation days. Average
concentrations were approximately 25mugm(-3) higher during
winter than during monsoon and approximately 8mugm(-3) higher
during morning hours than the diurnal average. A moving average
subtraction method based on 1-min average PM2.5 concentrations
indicated that local contributions (e.g., nearby biomass
combustion, brick kilns) were greater in the most populated
village, and that overall the majority of ambient PM2.5 in our
study was regional, implying that local air pollution control
strategies alone may have limited influence on local ambient
concentrations. We compared the relatively new moving average
subtraction method against a more established approach. Both
methods broadly agree on the relative contribution of local
sources across the three sites. The moving average subtraction
method has broad applicability across locations. |