Browsing by Author "D.M. Chate"

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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.
Impacts of the high loadings of primary and secondary aerosols on light extinction at Delhi during wintertime
(Elsevier Ltd, 2014) S. Tiwari; A.K. Srivastava; D.M. Chate; P.D. Safai; D.S. Bisht; M.K. Srivastava; G. Beig
High emissions of anthropogenic aerosols over Indo-Gangetic Plain (IGP) inspired continuous measurements of fine particles (PM2.5), carbonaceous aerosols (BC, OC and EC), oxides of nitrogen (NOx) and estimation of light extinction (bext) and absorption (babs) coefficients over Delhi during high pollution season in winter from December 2011 to March 2012. During study period, the mass concentrations of PM2.5, BC and NOx were 186.5±149.7μgm-3, 9.6±8.5μgm-3 and 23.8±16.1ppb, respectively. The mass concentrations of OC and EC were studied by two different techniques (i) off-line (gravimetric method) and (ii) semi-continuous (optical method) and their mean mass concentrations were 51.1±15.2, 10.4±5.5μgm-3 and 33.8±27.7, 8.2±6.2μgm-3, respectively during the study period. The ratios of mass concentration of OC to EC in both cases were in between 4 and 5. The source contribution of carbonaceous aerosols in PM2.5 estimated over 24hrs, during day- and night-time where motor vehicles accounted for ~69%, 90% and 61% whereas coal combustion accounted for ~31%, 10% and 39%, respectively. The estimated mean values of bext and babs over the station were 700.0±268.6 and 71.7±54.6Mm-1, respectively. In day and night analysis, bext is ~37% higher during night-time (863.4Mm-1) than in day-time (544.5Mm-1). Regression analysis between bext and visibility showed significant negative correlation (r=-0.85). The largest contribution in the light extinction coefficients was found to be due to organic carbon (~46%), followed by elemental carbon (~24%), coarse mode particles (~18%), ammonium sulfate (~8%) and ammonium nitrate (~4%). The individual analysis of light extinction due to chemical species and coarse mode particles indicates that scattering type aerosols dominated by ~76% over the absorbing type. The aforementioned results suggest that the policy-induced control measures at local administration level are needed to mitigate the excess emissions of carbonaceous aerosols over IGP region which ranks highest in India and elsewhere in worldwide. © 2014.
Rainwater chemistry in the North Western Himalayan Region, India
(Elsevier Ltd, 2012) S. Tiwari; D.M. Chate; D.S. Bisht; M.K. Srivastava; B. Padmanabhamurty
Precipitation chemistry studies were conducted at Kothi (32.31°N, 77.20°E), a rural Indian location, in the North Western Himalayas during June to October of 2006 and 2007. The volume weighted mean pH values ranged from 5.16 to 6.36 with a mean of 5.68±0.26 indicating mostly alkaline precipitation events. However, 18% samples were found acidic due to dominance of acidic components. The alkaline to acidic ions ratio (1.05) confirms that acidic components are neutralized by alkali radicals in rainwater. Of the total ionic composition 159μeq/l, in rainwater samples, dominant were Ca2+ (19%) followed by Na+ (14%). Among the anions, Cl- (17%) was slightly higher than SO42- (16%) and NO3- (11%). The ratio (NO3-+Cl-)/SO42-) 1.05 indicates acidity in rainwater by the cumulative effects of HNO3, H2SO4 and HCl. The ratios NH4+/NO3- as 0.76 and NH4+/SO42- as 0.50 show the pre-dominance of atmospheric NH4NO3 and (NH4)2SO4. Significant correlation between Na+ and Cl- (r=0.97; p<0.0001) and between SO42- and NO3- (r=0.60; p<0.0001) indicates their origin from similar sources. Neutralization factor calculations show that Ca2+ plays a major role in the neutralizing processes. Enrichment factors indicate that Ca2+, SO42- K+ and Mg2+ were originated from non-marine sources. The principle component analysis indicates the influence of transportation of air-born primary and secondary particles on the chemical composition of rainwater. © 2011 Elsevier B.V.
Relationship between aerosol and lightning over Indo-Gangetic Plain (IGP), India
(Springer Verlag, 2018) D.M. Lal; Sachin D. Ghude; M. Mahakur; R.T. Waghmare; S. Tiwari; Manoj K. Srivastava; G.S. Meena; D.M. Chate
The relationship between aerosol and lightning over the Indo-Gangetic Plain (IGP), India has been evaluated by utilising aerosol optical depth (AOD), cloud droplet effective radius and cloud fraction from Moderate Resolution Imaging Spectroradiometer. Lightning flashes have been observed by the lightning Imaging sensor on the board of Tropical Rainfall and Measuring Mission and humidity from modern-era retrospective-analysis for research and applications for the period of 2001–2012. In this study, the role of aerosol in lightning generation over the north-west sector of IGP has been revealed. It is found that lightning activity increases (decreases) with increasing aerosols during normal (deficient) monsoon rainfall years. However, lightning increases with increasing aerosol during deficient rainfall years when the average value of AOD is less than 0.88. We have found that during deficient rainfall years the moisture content of the atmosphere and cloud fraction is smaller than that during the years with normal or excess monsoon rainfall over the north-west IGP. Over the north-east Bay of Bengal and its adjoining region the variations of moisture and cloud fraction between the deficient and normal rainfall years are minimal. We have found that the occurrence of the lightning over this region is primarily due to its topography and localised circulation. The warm-dry air approaching from north-west converges with moist air emanating from the Bay of Bengal causing instability that creates an environment for deep convective cloud and lightning. The relationship between lightning and aerosol is stronger over the north-west sector of IGP than the north-east, whereas it is moderate over the central IGP. We conclude that aerosol is playing a major role in lightning activity over the north-west sector of IGP, but, local meteorological conditions such as convergences of dry and moist air is the principal cause of lightning over the north-east sector of IGP. In addition, atmospheric humidity also plays an important role in regulating the effect of aerosol on the microphysical properties of clouds over IGP region. © 2017, Springer-Verlag GmbH Germany.
Statistical evaluation of PM10 and distribution of PM1, PM2.5, and PM10 in ambient air due to extreme fireworks episodes (Deepawali festivals) in megacity Delhi
(Kluwer Academic Publishers, 2012) S. Tiwari; D.M. Chate; M.K. Srivastava; P.D. Safai; A.K. Srivastava; D.S. Bisht; B. Padmanabhamurty
Temporal variation of PM10 using 2-year data (January, 2007-December, 2008) of Delhi is presented. PM10 varied from 42 to 200 μg m-3 over January to December, with an average 114. 1 ± 81. 1 μg m-3. They are comparable with the data collected by Central Pollution Control Board (National Agency which monitors data over the entire country in India) and are lower than National Ambient Air Quality (NAAQ) standard during monsoon, close to NAAQ during summer but higher in winter. Among CO, NO2, SO2, rainfall, temperature, and wind speed, PM10 shows good correlation with CO. Also, PM10, PM2. 5, and PM1 levels on Deepawali days when fireworks were displayed are presented. In these festive days, PM10, PM2. 5, and PM1 levels were 723, 588, and 536 μg m-3 in 2007 and 501, 389, and 346 μg m-3 in 2008. PM10, PM2. 5, and PM1 levels in 2008 were 1. 5 times lower than those in 2007 probably due to higher mixing height (446 m), temperature (23. 8°C), and winds (0. 36 ms-1). © 2011 Springer Science+Business Media B.V.