Black carbon aerosols in the ambient air of Gangotri Glacier valley of north-western Himalaya in India

Abstract

The warming effect of equivalent Black Carbon (EBC) aerosols due to their light absorbing nature is a serious environmental concern, particularly, in the eco-sensitive and glaciated Himalayan region. Moreover, baseline data on BC is rarely available from most of the glaciated Himalayan region. For the first time, measurements on ambient EBC mass concentration were made at a high altitude site Chirbasa (3600 m, amsl), near Gangotri Glacier in the Indian Himalaya, during the year 2016. The change in the EBC concentration over the year was recorded from 0.01 μg m−3 to 4.62 μg m−3 with a diurnal variability of 0.10 μg m−3 to 1.8 μg m−3. The monthly mean concentration of EBC was found to be minimum (0.089 ± 0.052 μg m−3) in August and maximum (0.840 ± 0.743 μg m−3) in the month of May. The observed seasonal mean concentrations of EBC are less than 0.566 μg m−3 whereas the annual mean is 0.395 ± 0.408 μgm−3 indicating a pristine glacial and absence of locality EBC sources. Further, investigation on the occasional high values extricated that the seasonal cycle of EBC was significantly influenced by the emissions resulting from agriculture burning (in western part of the country), forest fires (along the Himalayan slopes) in summer, and to some extent the contribution from long range transport of pollutants in winter, depending the prevailing meteorological condition.