Browsing by Author "Sachchidanand Singh"

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Aerosol optical properties and radiative effects over Manora Peak in the Himalayan foothills: Seasonal variability and role of transported aerosols
(Elsevier, 2015) A.K. Srivastava; K. Ram; Sachchidanand Singh; Sanjeev Kumar; S. Tiwari
The higher altitude regions of Himalayas and Tibetan Plateau are influenced by the dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. In this study, we present impacts of advection of polluted air masses of natural and anthropogenic emissions, on aerosol optical and radiative properties at Manora Peak (~2000m amsl) in central Himalaya over a period of more than two years (February 2006-May 2008). We used the most updated and comprehensive data of chemical and optical properties available in one of the most climatically sensitive region, the Himalaya, to estimate atmospheric radiative forcing and heating rate. Aerosol optical depth (AOD) was found to vary from 0.04 to 0.45 with significantly higher values in summer mainly due to an increase in mineral dust and biomass burning aerosols due to transport. In contrast, single scattering albedo (SSA) varied from 0.74 to 0.88 with relatively lower values during summer, suggesting an increase in absorbing BC and mineral dust aerosols. As a result, a large positive atmospheric radiative forcing (about 28±5 Wm-2) and high values of corresponding heating rate (0.80±0.14 Kday-1) has been found during summer. During the entire observation period, radiative forcing at the top of the atmosphere varied from -2 to +14 Wm-2 and from -3 to -50 Wm-2 at the surface whereas atmospheric forcing was in the range of 3 to 65 Wm-2 resulting in a heating rate of 0.1-1.8 Kday-1. © 2014 Elsevier B.V.
Black carbon and chemical characteristics of PM10 and PM 2.5 at an urban site of North India
(2009) Suresh Tiwari; Atul K. Srivastava; Deewan S. Bisht; Tarannum Bano; Sachchidanand Singh; Sudhamayee Behura; Manoj K. Srivastava; D.M. Chate; B. Padmanabhamurty
The concentrations of PM10, PM2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi (28.63° N, 77.18° E), India. The annual mean PM10 and PM2.5 concentrations (± standard deviation) were about 219 (± 84) and 97 (±56) μgm -3 respectively, about twice the prescribed Indian National Ambient Air Quality Standards values. The monthly average ratio of PM 2.5/PM10 varied between 0.18 (June) and 0.86 (February) with an annual mean of ∼0.48 (±0.2), suggesting the dominance of coarser in summer and fine size particles in winter. The difference between the concentrations of PM10 and PM2.5, is deemed as the contribution of the coarse fraction (PM10-2.5). The analyzed coarse fractions mainly composed of secondary inorganic aerosols species (16.0 μgm-3, 13.07%), mineral matter (12.32 μgm-3, 10.06%) and salt particles (4.92 μgm-3, 4.02%). PM2.5 are mainly made up of undetermined fractions (39.46 μgm-3, 40.9%), secondary inorganic aerosols (26.15 μgm-3, 27.1%), salt aerosols (22.48 μgm-3, 23.3%) and mineral matter (8.41 μgm-3, 8.7%). The black carbon aerosols concentrations measured at a nearby (∼300 m) location to aerosol sampling site, registered an annual mean of ∼14 (±12) μgm-3, which is significantly large compared to those observed at other locations in India. The source identifications are made for the ionic species in PM10 and PM2.5. The results are discussed by way of correlations and factor analyses. The significant correlations of Cl-, SO 4 2-, K+, Na+, Ca2+, NO 3 - and Mg 2+ with PM2.5 on one hand and Mg2+ with PM 10 on the other suggest the dominance of anthropogenic and soil origin aerosols in Delhi. © 2010 Springer Science+Business Media B.V.
Identification of aerosol types over Indo-Gangetic Basin: implications to optical properties and associated radiative forcing
(Springer Verlag, 2015) S. Tiwari; A.K. Srivastava; A.K. Singh; Sachchidanand Singh
The aerosols in the Indo-Gangetic Basin (IGB) are a mixture of sulfate, dust, black carbon, and other soluble and insoluble components. It is a challenge not only to identify these various aerosol types, but also to assess the optical and radiative implications of these components. In the present study, appropriate thresholds for fine-mode fraction and single-scattering albedo have been used to first identify the aerosol types over IGB. Four major aerosol types may be identified as polluted dust (PD), polluted continental (PC), black carbon-enriched (BCE), and organic carbon-enriched (OCE). Further, the implications of these different types of aerosols on optical properties and radiative forcing have been studied. The aerosol products derived from CIMEL sun/sky radiometer measurements, deployed under Aerosol Robotic Network program of NASA, USA were used from four different sites Karachi, Lahore, Jaipur, and Kanpur, spread over Pakistan and Northern India. PD is the most dominant aerosol type at Karachi and Jaipur, contributing more than 50 % of all the aerosol types. OCE, on the other hand, contributes only about 12–15 % at all the stations except at Kanpur where its contribution is ∼38 %. The spectral dependence of AOD was relatively low for PD aerosol type, with the lowest AE values (<0.5); whereas, large spectral dependence in AOD was observed for the remaining aerosol types, with the highest AE values (>1.0). SSA was found to be the highest for OCE (>0.9) and the lowest for BCE (<0.9) type aerosols, with drastically different spectral variability. The direct aerosol radiative forcing at the surface and in the atmosphere was found to be the maximum at Lahore among all the four stations in the IGB. © 2015, Springer-Verlag Berlin Heidelberg.
Identification of Potential Recharge Zones in Drought Prone Area of Bundelkhand Region, India, Using SCS-CN and MIF Technique Under GIS-frame work
(Springer Science and Business Media B.V., 2021) Prashant Pandey; S.K. Tiwari; H.K. Pandey; Abhishek Kumar Chaurasia; Sachchidanand Singh
Jaspura watershed a part of Yamuna basin is situated in drought prone area lying in the Banda district of Bundelkhand region, Uttar Pradesh, India. The drastic decline of groundwater level and consistently drying up of the phreatic aquifer has led to the acute shortage of groundwater in the study area. The situation is further aggravated due to base flow in the areas adjoining the major order streams. To mitigate such problem in study area, MIF technique, combined with RS and GIS, has been effectively used to delineate the potential recharge zone using seven thematic layers, viz., LULC, soil, slope, drainage density (Dd), geomorphology, depth to water level map of post-monsoon, and groundwater fluctuation map. Relative rates and weight of each influencing factor have been calculated on the basis of major and minor effect of these thematic layers. Based on their influence on groundwater recharge capacity using seven thematic layers under potential zone, five classes under artificial recharge have been identified, viz., very high (96.4 km2), high (157.4 km2), moderate (146.1 km2), low (72.9 km2), and very low (34.2km2). The runoff in 15 micro-watersheds has been estimated using SCS-CN approach. Integration of runoff and potential recharge zone has yielded the suitable sites and type of groundwater recharge structure. On the basis of its percolation tank (PT), check dam (CD) and sub-surface dam (SD) have been identified as feasible and suitable groundwater recharge structure. © 2021, The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd.
Impacts of black carbon on environment and health
(Elsevier, 2021) Shani Tiwari; Bing Chen; Sachchidanand Singh; A.K. Singh; Atul K. Srivastava
During the last few decades, black carbon (BC) has attracted significant attention among scientific communities due to its observable hostile effects on air quality, agriculture, forests, human health, the economy, and environment. BC is a light-absorbing particle in the atmosphere that is emitted mainly from fossil fuels, biomass burning, and vehicular emissions. Although ample studies on BC aerosol characteristics have been carried out worldwide, significant uncertainties remain due to the different emission sources and their interactions with complex atmospheric processes. Thus, an in-depth understanding of BC and its potential impacts is greatly needed. This chapter presents a brief overview of the characteristics, sources, and transport mechanisms of BC and its impacts on the environment as well as human health. In addition, the chapter also highlights instructions to the public, policymakers, and local environmental bodies to control BC emissions. © 2021 Elsevier Inc. All rights reserved.