Black carbon pollutants in pristine Himalayan ecosystem: a pilot study along Gangotri Glacier Valley.

Abstract

The present study provides the first multi-year (2015-2020) random observation of black carbon (BC) aerosols from pristine localities along the Gangotri Glacier Valley in the north-western Indian Himalaya. Due to the harsh climatic conditions and inaccessible terrain, hardly any BC observation is available from glaciated Himalaya. To investigate the background concentration of BC in the high Himalaya, random measurements are conducted at five locations at variable microclimates with different anthropogenic influences along a 24-km-long Gangotri Glacier Valley trek, viz. Gangotri (~ 3200m amsl), Chirbasa (~ 3600m amsl), Bhojbasa (~ 3800m amsl), Gaumukh (~ 4000m amsl), and Tapovan (~ 4400m amsl). A relatively high concentration of BC (up to 2.23 ± 0.57μgm-3) was recorded at Gangotri which is a famous Indian pilgrimage centre which remains highly crowded during the peak tourist season, i.e. May-June and Oct-Nov every year. Surprisingly, we also recorded high BC (up to 1.27 ± 0.57μgm-3) at Tapovan, which is a high altitude meadow surrounded by high ice-snow peaks, viz. Bhagirathi Peak (6856m amsl), Shivling (6543m amsl), and Meru Parvat (6660m amsl). The HYSPLIT cluster trajectory and CALIPSO data images suggest that besides local anthropogenic activities, polluted air mass-produced due to burning of forest and agriculture biomass and fossil fuels, etc. transported from Indo Gangetic Basin might be playing a potential role in ambient BC concentration in the study area. The present preliminary investigations of BC in the Gangotri Glacier Valley open new vision and possibilities for further extensive ground-based observation of aerosol air pollutants in Himalayan glacier valley systems.