Assessment of carbonaceous fractions in ambient aerosols at high altitude and lowland urban locations of Kumaon Province, Indian Himalaya

Amit Kumar,Sapna Chourasiya,Sachchidanand Singh,Narendra Singh,Krishan Kumar,Niraj Kumar

doi:10.1007/s42452-020-04010-4

Abstract

The present study investigates the characteristics of carbonaceous species like organic carbon (OC) and elemental carbon (EC) in ambient total suspended particulates (TSP) at Bhimtal (high altitude urban, 1413 m asl) and Pantnagar (lowland urban, 224 m asl) sites of Kumaon province in Uttarakhand, Indian Himalayan region during winter and summer 2017–2018. Ambient TSP samples were taken on quartz filters with high volume sampler followed by OC and EC quantification using IMPROVE_thermal optical reflectance protocol. Results showed that distinct seasonal differences in carbonaceous species levels were observed at both sites, while day- and night-time concentrations did not show notable variations. Further, total carbonaceous aerosols (TCA) at Pantnagar were approximately 3.0 and 1.3 times higher than Bhimtal for winter and summer, respectively, where estimated TCA accounted for ~ 30% to total TSP at both sites. Among quantified eight carbon fractions, OC2 and OC3 at Bhimtal while EC1 and EC2 at Pantnagar were the most abundant components. The char-EC and soot-EC concentrations showed a similar seasonal pattern where char contributed significantly as 89–90% to total EC at both sites. The observed OC/EC ratios suggested the formation of secondary organic carbon and char-EC/soot-EC ratios implied biomass burning as major sources for carbonaceous aerosols. Pearson correlation analysis indicated that char-EC showed significant higher correlations with OC and EC than soot-EC which infers different formation mechanisms of char and soot. Most of the carbonaceous parameters exhibited contrasting positive and negative correlations with the boundary layer height, temperature, and solar radiation at Bhimtal and Pantnagar, respectively.

Highlights

In the last few decades, numerous studies have been reported concerning carbonaceous species of ambient aerosols and their impact on local/global climate, atmospheric chemistry, air quality, biodiversity and human health [1,2,3,4,5,6]
It can be seen that the levels of total suspended particulates (TSP) and organic carbon (OC)/elemental carbon (EC) concentrations at Pantnagar site were higher than Bhimtal site
The seasonal analysis suggested that TSP and OC/EC concentrations were higher during summer in contrast to winter at Bhimtal while contrasting results at Pantnagar with higher and lower concentrations of these parameters during winter and summer, respectively

Summary

Introduction

In the last few decades, numerous studies have been reported concerning carbonaceous species of ambient aerosols and their impact on local/global climate, atmospheric chemistry, air quality, biodiversity and human health [1,2,3,4,5,6]. Carbonaceous aerosols are ubiquitous in nature mainly consisted of organic carbon (OC) and elemental carbon (EC) which have significant portions in atmospheric aerosols [7, 8]. OC comprises a diversity of organic compounds, and their atmospheric sources could be both primary and secondary in origin. Primary OC may release from fossil fuel combustion/biomass burning as fine particulates and mechanical processes of the

Methods

Results

Conclusion