Airborne particulate in Varanasi over middle Indo-Gangetic Plain: variation in particulate types and meteorological influences

• Published in: Environmental monitoring and assessment Vol. 189; no. 4; p. 157
• Main Authors: Murari, Vishnu, Kumar, Manish, Mhawish, Alaa, Barman, S. C., Banerjee, Tirthankar
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01-04-2017; Springer Nature B.V
• Subjects: Aerosols; Air Pollutants - analysis; Air quality; Air quality standards; Airborne particulates; Atmospheric boundary layer; Atmospheric Protection/Air Quality Control/Air Pollution; Boundary layers; Diurnal variations; Earth and Environmental Science; Ecology; Ecotoxicology; Emissions; Environment; Environmental Management; Environmental Monitoring; Ground stations; Humidity; India; Meteorology; Monitoring/Environmental Analysis; Monsoons; Outdoor air quality; Particle Size; Particulate matter; Particulate Matter - analysis; Relative humidity; Research methodology; Rivers; Seasons; Summer; Sustainable development; Urban areas; Visibility; Wind; Wind speed; Winter; Particulate; Visibility; Indo-Gangetic Plain; Humidity; Boundary layer
• ISSN: 0167-6369; 1573-2959
• DOI: 10.1007/s10661-017-5859-9

The variation in particulate mass and particulate types (PM
2.5
and PM
10
) with respect to local/regional meteorology was analyzed from January to December 2014 (
n
 = 104) for an urban location over the middle Indo-Gangetic Plain (IGP). Both coarser (mean ± SD; PM
10
161.3 ± 110.4 μg m
−3
,
n
 = 104) and finer particulates (PM
2.5
81.78 ± 66.4 μg m
−3
) revealed enormous mass loading with distinct seasonal effects (range: PM
10
12–535 μg m
−3
; PM
2.5
8–362 μg m
−3
). Further, 56% (for PM
2.5
) to 81% (for PM
10
) of monitoring events revealed non-attainment national air quality standard especially during winter months. Particulate types (in terms of PM
2.5
/PM
10
0.49 ± 0.19) also exhibited temporal variations with high PM
2.5
loading particularly during winter (0.62) compared to summer months (0.38). Local meteorology has clear distinguishing trends in terms of dry summer (March to June), wet winter (December to February), and monsoon (July to September). Among all the meteorological variables (average temperature, rainfall, relative humidity (RH), wind speed (WS)), temperature was found to be inversely related with particulate loading (r
PM10
−0.79; r
PM2.5
−0.87) while RH only resulted a significant association with PM
2.5
during summer (r
PM10
0.07; r
PM2.5
0.55) and with PM
10
during winter (r
PM10
0.53; r
PM2.5
0.24). Temperature, atmospheric boundary layer (ABL), and RH were cumulatively recognized as the dominant factors regulating particulate concentration as days with high particulate loading (PM
2.5
>150 μg m
−3
; PM
10
>260 μg m
−3
) appeared to have lower ABL (mean 660 m), minimum temperature (<22.6 °C), and high RH (∼79%). The diurnal variations of particulate ratio were mostly insignificant except minor increases during night having a high wintertime ratio (0.58 ± 0.07) over monsoon (0.34 ± 0.05) and summer (0.30 ± 0.07). Across the region, atmospheric visibility appeared to be inversely associated with particulate (r
PM2.5
−0.84; r
PM10
−0.79) for all humid conditions, while at RH ≥80%, RH appeared as the most dominant factor in regulating visibility compared to particulate loading. The Lagrangian particle dispersion model was further used to identify possible regions contributing particulate loading through regional/transboundary movement.