Aryabhatta Research Institute of Observational Sciences

Air pollution, once considered a problem of urban and industrial centers, is now increasingly impacting remote and ecologically fragile regions like the Indian Himalayas, threatening both environmental stability and public health. This study presents a comprehensive assessment of PM₁₀-bound elements across the Indian Himalayan Region, covering western (Mohal-Kullu), central (Almora and Nainital), and eastern (Darjeeling) Himalayas. Extensive sampling from January 2019 to December 2020 revealed a complex mixture of natural and anthropogenic emissions. Morphological characterization using field emission-scanning electron microscopy identified diverse particle types-spherical, irregular, and flocculent-indicating sources such as crustal dust, combustion, and vehicular emissions. Elemental analysis via WD-XRF quantified 23 major and trace elements (e.g., Al, Fe, Ca, Cr, Zn, Cu) consistently across all sites. Source apportionment using dispersion-normalized positive matrix factorization identified 9  major pollution sources, including road dust, industrial activities, biomass burning, and vehicular emissions. Conditional bivariate probability function and concentration weighted trajectory analyses further highlighted dominant local sources and significant regional and transboundary pollution transport. A multi-pathway health risk assessment revealed that toxic elements like Cr(VI), Mn, and As pose both carcinogenic and non-carcinogenic risks, particularly to children. Seasonal variations in PM₁₀ levels reflected region-specific emission characteristics. This study is the first of its kind to integrate source apportionment and health risk assessment across the entire IHR, providing critical insights necessary for targeted mitigation and sustainable environmental management in this under-studied but highly sensitive region.

The current work illustrates the phys. activation of raw charcoal to produce activated carbon (AC) at low temperatures (300 and 500°C).Prepared ACs are tested for Methylene blue (MB) adsorption experiments at various adsorption conditions (e.g., pH, temperature) and discussed efficiency, kinetics, isotherm models, and adsorption mechanism to determine the optimal adsorption conditions for the removal of MB dye.The results show that the prepared ACs (AC1, AC2 at 300 and 500°C) efficiently absorb MB and obtain removal efficiency of ∼100 and 83‰ in 1 h, resp.When the pseudo-first-order and pseudo-second-order adsorption kinematic models are used to test the adsorption data, the result fits the pseudo-first-order model better.The Freundlich and Langmuir adsorption isotherms are employed to model the isotherm data to get the maximum adsorption capacity (MAC).The MAC for AC1 and AC2 is found to be 39.14 and 40.98 mg/g, resp.Addnl., MB adsorption has been analyzed using the Temkin and Dubinin-Radushkevich isotherm models, along with the inter-particle diffusion model.The Dubinin-Radushkevich model suggests that MB adsorption is a phys. absorption process.The Temkin model showed that the Temkin constant (B) values are pos. indicating that the adsorption is exothermic.The inter-particle diffusion model revealed that AC2 displays greater adsorption kinetics consistency due to its larger pore diameterThe results reveal that the Langmuir model captured the data better, demonstrating that monolayer adsorption dominated the absorption process.Addnl., prepared ACs are examined for reuse, and exhibit three cycles of recyclability.As a result, ACs made from oak wood charcoal are an easy affordable way to get rid of MB dye.

This study simulates the BC concentrations in India using the WRF-Chem model with four emissions inventories: Expt-I (Constrained emissions), Expt-II (SMOG-India), Expt-III (EDGAR-HTAP V3), and Expt-IV (Mix), emphasizing on two domains, the whole Indian region (D01) and the Indo-Gangetic Plains (IGP) (D02).The simulated BC over D01 was 2-3 times higher using Expt-I compared to Expt-II and Expt-III, despite the similar spatial-seasonal variations.BC simulations from Expt-I show good agreement with observed data, particularly at megacities like Delhi and Kolkata with high anthropogenic emissions.However, Expt-III underestimates BC concentrations at certain stations, suggesting the need for improvement in emission-inventory strength and proper distribution of emissions.The diurnal BC pattern from Expt-I matches well with measured BC, with higher concentrations during late evening and night hours in the IGP and large cities.High-altitude stations present a BC peak during late afternoon hours due to the transport of pollutants from the IGP within a deeper mixing layer.BC simulations show better agreement during the daytime than nighttime, indicating the effect of nighttime emission strength that needs better representation, while the model underestimations maximize in winter, associated with the highest BC concentrationsSource apportionment anal. revealed the highest contribution from the domestic sector to total BC emissions (58%) during winter, underscoring the reliance on biofuel combustion for household cooking and heating.The energy and industrial sector contributed significantly to the annual BC levels over the IGP, ranging from 22% in winter to 28% in monsoon.The increased contribution from the open burning sector during post-monsoon indicates the effect of crop residue burning in NW IGP.By quantifying BC concentration and identifying its dominant sources utilizing the robust emission inventory, this work provides actionable insights for policymakers and a scientific basis for strategies to mitigate BC pollution and its associated environmental and health impacts.