Browsing by Author "Maheswar Rupakheti"

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Light absorption properties of elemental carbon (EC) and water-soluble brown carbon (WS–BrC) in the Kathmandu Valley, Nepal: A 5-year study
(Elsevier Ltd, 2020) Pengfei Chen; Shichang Kang; Lekhendra Tripathee; Kirpa Ram; Maheswar Rupakheti; Arnico K. Panday; Qianggong Zhang; Junming Guo; Xiaoxiang Wang; Tao Pu; Chaoliu Li
This study presents a comprehensive analysis of organic carbon (OC), elemental carbon (EC), and particularly the light absorption characteristics of EC and water-soluble brown carbon (WS–BrC) in total suspended particles in the Kathmandu Valley from April 2013 to January 2018. The mean OC, EC, and water-soluble organic carbon (WSOC) concentrations were 34.8 ± 27.1, 9.9 ± 5.8, and 17.4 ± 12.5 μg m−3, respectively. A clear seasonal variation was observed for all carbonaceous components with higher concentrations occurring during colder months and lower concentrations in the monsoon season. The relatively low OC/EC ratio (3.6 ± 2.0) indicates fossil fuel combustion as the primary source of carbonaceous components. The optical attenuation (ATN) at 632 nm was significantly connected with EC loading (ECS) below 15 μg cm−2 but ceased as ECS increased, reflecting the increased influence of the shadowing effect. The derived average mass absorption cross-section of EC (MACEC) (7.0 ± 4.2 m2 g−1) is comparable to that of freshly emitted EC particles, further attesting that EC was mainly produced from local sources with minimal atmospheric aging processes. Relatively intensive coating with organic aerosols and/or salts (e.g., sulfate, nitrate) was probably the reason for the slightly higher MACEC during the monsoon season, whereas increased biomass burning was a major factor leading to lower MACEC in other seasons. The average MACWS-BrC at 365 nm was 1.4 ± 0.3 m2 g−1 with minimal seasonal variations. In contrast to MACEC, biomass burning was the main reason for a higher MACWS-BrC in the non-monsoon season. The relative light absorption contribution of WS-BrC to EC was 9.9% over the 300–700 nm wavelength range, with a slightly higher ratio (13.6%) in the pre-monsoon season. Therefore, both EC and WS-BrC should be considered in the study of optical properties and radiative forcing of carbonaceous aerosols in this region. © 2020 Elsevier Ltd
Nitrogenous and carbonaceous aerosols in PM2.5 and TSP during pre-monsoon: Characteristics and sources in the highly polluted mountain valley
(Chinese Academy of Sciences, 2022) Hemraj Bhattarai; Lekhendra Tripathee; Shichang Kang; Pengfei Chen; Chhatra Mani Sharma; Kirpa Ram; Junming Guo; Maheswar Rupakheti
This study reports for the first time a comprehensive analysis of nitrogenous and carbonaceous aerosols in simultaneously collected PM2.5 and TSP during pre-monsoon (March–May 2018) from a highly polluted urban Kathmandu Valley (KV) of the Himalayan foothills. The mean mass concentration of PM2.5 (129.8 µg/m3) was only ~25% of TSP mass (558.7 µg/ m3) indicating the dominance of coarser mode aerosols. However, the mean concentration as well as fractional contributions of water-soluble total nitrogen (WSTN) and carbonaceous species reveal their predominance in find-mode aerosols. The mean mass concentration of WSTN was 17.43±4.70 µg/m3 (14%) in PM2.5 and 24.64±8.07 µg/m3 (5%) in TSP. Moreover, the fractional contribution of total carbonaceous aerosols (TCA) is much higher in PM2.5 (~34%) than that in TSP (~20%). The relatively low OC/EC ratio in PM2.5 (3.03 ± 1.47) and TSP (4.64 ± 1.73) suggests fossil fuel combustion as the major sources of carbonaceous aerosols with contributions from secondary organic aerosols. Five-day air mass back trajectories simulated with the HYSPLIT model, together with MODIS fire counts indicate the influence of local emissions as well as transported pollutants from the Indo-Gangetic Plain region to the south of the Himalayan foothills. Principal component analysis (PCA) also suggests a mixed contribution from other local anthropogenic, biomass burning, and crustal sources. Our results highlight that it is necessary to control local emissions as well as regional transport while designing mitigation measures to reduce the KV's air pollution. © 2021
Upscaling residential solar rooftop in Uttar Pradesh: review of policy, practices and stakeholders perspective, identification of challenges and solutions
(Elsevier Ltd, 2025) Ashish Tiwari; R. K. Mall; Maheswar Rupakheti
This research paper examines the barriers and solutions related to the adoption of residential rooftop solar (R-RTS) in Uttar Pradesh. Despite government policy interventions, R-RTS uptake remains limited compared to the state's energy consumption-based potential. The study systematically analyses key adoption issues, stakeholder perspectives, policy landscape and identifies critical issues such as policy gaps, implementation challenges, and stakeholder collaboration deficits through policy review, stakeholder analysis, and adoption drivers. Methodologically, the study employs a mixed qualitative approach, including document analysis, stakeholder consultations, and field insights. The study proposes following actionable solutions: i) Policy interventions for subsidies beyond 3 kW. ii) Relaxation on system capacity limits. iii) Enhanced compensation for excess electricity injected into the grid. iv) Strategies to improve vendor participation. v) Addressing DISCOM inefficiencies regarding net meter availability and verification delays. vi) Speedier subsidy transfers. vii) Targeted awareness campaigns.The research highlights the importance of post-installation service ecosystems, advocating for skilled manpower development and product standardization to improve local service access. The intended policy outcome is to create a more enabling environment for residential R-RTS adoption, supporting climate goals and decentralized renewable energy expansion. This paper provides a structured roadmap for policymakers, vendors, consumers, and implementors to scale rooftop solar adoption in Uttar Pradesh. © 2025 Elsevier B.V.