Inter and Intra-Annual Variability in Aerosol Characteristics over Northwestern Indo-Gangetic Plain

Atinderpal Singh,Deepti Sharma,Neeraj Rastogi,Darshan Singh

doi:10.4209/aaqr.2014.04.0080

Atinderpal Singh, Deepti Sharma + Show 2 more

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https://doi.org/10.4209/aaqr.2014.04.0080

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Abstract

This study reports the temporal characteristics of aerosols mass concentration (PM10, PM2.5, PM1), size distribution and optical depth from December 2011 to November 2013 over Patiala (30.33°N, 76.4°E, 249 a.s.l.), a site located in Indo-Gangetic Plain (IGP) in northwestern India, a region with the highest population density in the world. PM10, PM2.5, and PM1 varied from 71 to 221, 27 to 92, and 17 to 75 µg/m3, respectively, with the highest concentration of PM10 during summer of 2012, and PM2.5 and PM1 during autumn of 2013. These mass concentrations were significantly higher than National Ambient Air Quality (NAAQ) standards (PM10 = 60 and PM2.5 = 40 µg/m3), suggesting poor quality of air over IGP. Both natural and anthropogenic sources were found to be responsible for poor air quality of IGP with more contribution from the latter source as inferred from Ångström exponent (α380–870) and fine mode fraction (FMF: PM2.5/PM10) of aerosols, which have shown large temporal variability. The particle size distribution is skewed towards particles with size less than 1.00 µm and very few particles are having the size greater than 6.25 µm. Aerosol optical depth at 500 nm (AOD500) ranged from 0.36 to 0.64 and shows the highest value during summer of 2012 (0.64 ± 0.09) and autumn of 2013 (0.64 ± 0.25) and minimum (0.36 ± 0.05) in spring of 2013, further reflecting the different effects of aerosols on climate during different seasons. The relation between AOD500 and PM mass has also been investigated, which has exhibited significant seasonality and AOD500 is more sensitive towards the concentration of PM1 rather than PM2.5 and PM10. These results give insight to the relative contribution of natural as well as anthropogenic aerosol sources to their total atmospheric abundances and their possible effect on ambient air quality and Earth’s radiation balance.

Highlights

Aerosols are important constituent of the atmosphere due to their impact on air quality, human health, precipitation pattern and radiation budget (Poschal, 2005)
This study reports the temporal characteristics of aerosols mass concentration (PM10, PM2.5, PM1), size distribution and optical depth from December 2011 to November 2013 over Patiala (30.33°N, 76.40°E, 249 a.s.l.), a site located in IndoGangetic Plain (IGP) in northwestern India, a region with the highest population density in the world
PM1 can be considered as secondary aerosols if the contribution of black carbon (BC) and primary organic carbon (POC) is excluded; PM2.5 can be both primary and aged secondary whereas PM2.5–10 are mainly primary particles from natural sources

Summary

Introduction

Aerosols are important constituent of the atmosphere due to their impact on air quality, human health, precipitation pattern and radiation budget (Poschal, 2005). Aerosols are emitted naturally (e.g., dust, sea-salt, biogenic emissions) as well as anthropogenically (industrial emissions, vehicular emissions, biomass and fossil fuel burning). These are produced and modified by chemical reactions in the atmosphere and constantly cycled among the Earth's oceans, atmosphere and biosphere. The atmospheric aerosols have drawn greater significance recently because of their potential to perturb the radiation balance of Earth at regional and global scales (Charlson et al, 1992). The direct aerosol effect consists of direct interaction of radiation with atmospheric

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