Classification of Aerosols in an Urban Environment on the Basis of Optical Measurements

Abstract

The present study investigates various types of aerosol in the Lahore city of Pakistan using Aerosol Robotic Network (AERONET) data over a six year period from 2007 to 2012. Aerosol optical depths (AODs) observed was in the range 0.2-1.12. An analysis of seasonal variations in AOD has indicated that the highest AOD values occurred in summer and the lowest in winter. The urban aerosols of the study area were classified on the basis of optical parameters such as AOD, Extinction Angstrom Exponent (EAE), Absorption Angstrom Exponent (AAE), Single Scattering Albedo (SSA), Asymmetry Parameter (ASY) and Refractive Index (RI). The AAE values were in the range from 0.25 to 3.2. Real Refractive Index (RRI) and Imaginary part of the Refractive Index (IRI) values were in the range from 1.5 to 1.6 and 0 to 0.005 respectively. The major contributions to the atmospheric aerosols over Lahore were from urban industrial emissions, fossil fuel burning and road/soil dust. Higher RRI values reflected larger re-suspended road dust particles and long-range transported particles, while lower values reflected increased anthropogenic absorbing carbonaceous aerosols over the area. The AERONET retrieved SSA (0.80-0.89) and ASY (0.70-0.83) values suggested a predominance of urban industrial, vehicular and dust aerosols over Lahore. The Derivative of Angstrom Exponent (DAE) was derived at a wavelength of 500 nm and was found to indicate a predominance of fine aerosols across all seasons, particularly during summer and autumn seasons. Back-trajectory analyses using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model revealed that the major air masses over Lahore originated from India, Iran and Afghanistan.

Investigation of A Potted Plant (Hedera helix) with Photo-Regulation to Remove Volatile Formaldehyde for Improving Indoor Air Quality

“…However, increased industrial development and urban activities have brought about worsened outdoor air quality (Alam et al, 2016). Air pollution in China and India has received a lot of scientific attention, even affecting the lives of people in neighboring countries in Asia (Venkatachalam, 2017).…”

Seasonal assessment and classification of aerosols transported to Lahore using AERONET and MODIS deep blue retrievals

“…Alam et al . () has performed 5‐day air‐back trajectory analysis during summer and winter over Lahore which also reveals that air masses originate mostly from Thar Desert of the sub‐continent, Dasht in Iran, and from Afghanistan.…”

“…Of both the altitudes, a noticeable contribution from air masses originating from Saudi Arabia was observed at 4000 m and from India at 2000 m, whereas, from Afghanistan and Iran, a reasonable contribution was present at both heights. Alam et al (2016) has performed 5-day air-back trajectory analysis during summer and winter over Lahore which also reveals that air masses originate mostly from Thar Desert of the sub-continent, Dasht in Iran, and from Afghanistan.…”

“…This makes Lahore particularly a sensitive receptor site in terms of long-range transport of different types of aerosols coming from remote locations carried along seasonal air masses. Previous studies indicate that arriving dust aerosols mainly originate from arid/semi-arid locations as remote as deserts of the sub-continent, Afghanistan, Iran, Saudi Arabia and Sahara (Kaskaoutis et al, 2009;Guleria et al, 2011aGuleria et al, , 2011bGuleria et al, , 2012aAlam et al, 2012Alam et al, , 2016Ali et al, 2014), polluted particles from large urban and industrial centres of India (Biswas et al, 2008) while biomass burning particles transported primarily from agricultural crop residue burning activities especially from the northwestern Indian parts (Vadrevu et al, 2011). These biomass burning activities are also found to contribute in building up an aerosol layer over neighbouring areas of Pakistan Sharma et al, 2010;Vadrevu et al, 2011;.…”

Analysis of Radiative Properties and Direct Radiative Forcing Estimates of Dominant Aerosol Clusters over an Urban-Desert Region in West Africa

“…As shown in several studies, for example, Bibi et al (2016) and Alam et al (2016), atmospheric aerosols could be clustered using the inter-relationships between different pairs of their microphysical and optical properties. Using similar techniques, prominent aerosol classes were identified at the study site in Fawole et al (2016b) as: Biomass burning (BB), Desert dust (DD), Urban (UB) and Gas flaring (GF) aerosols.…”