Characteristics of equivalent black carbon aerosols over Doon Valley in NW Indian Himalaya during COVID-19 lockdown 2020.

Recently, black carbon (BC) has been identified as a potential transmitter for COVID-19 besides being responsible for climate change and serious health hazards. To mitigate the dreaded consequences of COVID-19 pandemic, the Government of India declared a nationwide lockdown on March 24, 2020. Accordingly, observations on equivalent black carbon (EBC) aerosols using AE 51 Aethalometer were performed during different lockdowns in Doon Valley. During April, May, June, and July, the monthly average EBC mass concentration recorded 2.12 ± 1.14 µg m-3, 2.58 ± 1.46 µg m-3, 2.74 ± 1.49 µg m-3, and 2.12 ± 1.32 µg m-3, respectively. A comparison of diurnal variation patterns with earlier studies indicates a significant reduction in EBC mass concentration levels. Bipolar NWR analysis for April and May depicts that relatively high EBC concentration was experienced with prominent south-easterly winds. The EBC concentration level during daytime was high compared to nighttime hours. Preliminary visualization of scanning electron micrographs indicates the variable morphology of aerosols. The bulk particle EDX spectral analysis indicates C, O, Na, F, Al, Si, K, Ca, and Ti elements with a dominance of C and O. Windblown dust seems to be the major contributor to the ambient aerosols. Furthermore, MODIS recorded the fire anomaly (attributed to the wheat stubble burning) starting from mid of April to early-June along the Indo-Gangetic Basin. Heavy loading of polluted aerosols was visible in CALIPSO data imageries. HYSPLIT cluster trajectories indicate that the study region is strongly influenced by the air mass transporting from the Gangetic Plain, Iran, Pakistan, Afghanistan, and Gulf region.

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

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 (~ 3200 m amsl), Chirbasa (~ 3600 m amsl), Bhojbasa (~ 3800 m amsl), Gaumukh (~ 4000 m amsl), and Tapovan (~ 4400 m amsl). A relatively high concentration of BC (up to 2.23 ± 0.57 µg m-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 ± 0.57 µg m-3) at Tapovan, which is a high altitude meadow surrounded by high ice-snow peaks, viz. Bhagirathi Peak (6856 m amsl), Shivling (6543 m amsl), and Meru Parvat (6660 m 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.

Potential seismic precursors and surficial dynamics of a deadly Himalayan disaster: an early warning approach.

On 7 February 2021, Chamoli district (Uttarakhand, India) was devastated by a deadly rock-ice avalanche that led to a large causality of more than 200 people and a huge economic loss. We found noteworthy sequence of precursory signals of main failure/detachment preceded by a dynamic nucleation phase. The rock-ice avalanche appears to have been initiated by seismic precursors which were continuously active for 2:30 h prior to main detachment. The seismic amplitude, frequency characteristics and signal-to-noise ratio variation of detected tremors indicate static to dynamic changes in nucleation phase located at the source of detached wedge. The characteristics of seismic data distinguished debris flow and hitting obstacles from other seismic sources and allowed the estimations of debris flow speed. We analyzed and verified the seismic signals with field evidences to estimate the associated impacts and velocity of dynamic flow. The proximal high-quality seismic data allowed us to reconstruct the complete chronological sequence and evaluate impacts since the initiation of nucleation phase to its advancement. Furthermore, we suggest that real-time seismic monitoring with existing network and future deployment of integrated dense network can be used for forecasting of flow events and hazard mitigation in the downstream.