Browsing by Author "Deewan S. Bisht"

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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.
Intra-urban variability of particulate matter (PM2.5 and PM10) and its relationship with optical properties of aerosols over Delhi, India
(Elsevier Ltd, 2015) Suresh Tiwari; Philip K. Hopke; Atar S. Pipal; Atul K. Srivastava; Deewan S. Bisht; Shani Tiwari; Abhay K. Singh; Vijay K. Soni; Shiv D. Attri
Highly time-resolved measurements of particulate matter (PM: PM2.5 and PM10) were made at three different sites across Delhi (CCRI: a highly traffic site, IMD: a less traffic site and IITM: an urban background site) from 1st December, 2011 to 30th June, 2013. Also, coarse mode (PM10-2.5) mass was estimated as the difference between PM10 and PM2.5. In addition, columnar aerosol optical properties such as aerosol optical depth (AOD) and Angstrom exponent (AE) were studied concurrently over IMD. The mean mass concentrations of PM2.5, PM10-2.5 and PM10 were 118.3±81.7, 113.6±70.4 and 232.1±131.1μgm-3, respectively. Among the three sites, relatively higher mass concentrations of PM2.5 (~35% and 3%) were observed at CRRI compared to IMD and IITM.PM10 and PM10-2.5 were higher at these sites by ~31% and 19%; and 27% and 40%, respectively, compared to CRRI. Coefficients of divergence (COD) and correlation coefficients (r) were calculated between site pairs to assess the spatial and temporal heterogeneity of PM and moderate spatial divergence was found over the three sites. Traffic emission particles (PM2.5) exhibited high spatial heterogeneity as well. The mass concentrations of PM2.5 and PM10 were found to be higher during the night compared to the day. The mean PM2.5/PM10 ratio was ~51%, indicating generally equal amounts of coarse and fine mode PM in the Delhi urban atmosphere. AOD and PM2.5 were positively correlated and a negative correlation was observed between AE and PM10-2.5. PM2.5 particles were significantly correlated with AOD during post-monsoon and winter. Because of the lower vehicular emissions on weekends compared to weekdays, PM at CRRI, IMD, and IITM were separated by day of week and large heterogeneities were found. During weekdays, the mass concentrations of PM10 were ~4, 2, and 12% higher than on weekends. However, for PM2.5, weekend values were 5, 7, and 9% higher for CRRI, IMD and IITM, respectively. © 2015 Elsevier B.V.
Nature and sources of ionic species in precipitation across the indo-gangetic plains, India
(AAGR Aerosol and Air Quality Research, 2016) Suresh Tiwari; Philip K. Hopke; Devraj Thimmaiah; Umesh C. Dumka; Atui K. Srivastava; Deewan S. Bisht; Pasumarti S.P. Rao; Dilip M. Chate; Manoj K. Srivastava; Sachchida N. Tripathi
The spatial distribution of rainwater chemistry over the densely-populated and highly polluted Indo-Gangetic Plains (IGP) was investigated using samples (total = 687) collected during three consecutive summer monsoon seasons from 2009 to 2011. The concentrations of secondary ionic species (SO42– and NO3–) were measured along with the other major ions (F–, Cl–, Na+, K+, Ca2+, Mg2+ and NH4+) and pH and specific conductivity. The weighted mean pH (± std) and conductivity of rainwater were 5.73 (± 0.17) and 31.6 (± 31.0) µS cm–1, respectively. Approximately 16% of rainwater samples were acidic (pH < 5.61) with a mean pH = 5.38 of acid rain and rest of them were more alkaline (pH > 5.61) (mean pH = 6.34 for the more basic samples). Specific conductivity was ~39% lower (20.6 µS cm–1) for the acidic rain compared to the more basic (33.6 µS cm–1) samples. The mean sum of all of the measured ions is 351.6 ± 130.1 µeq L–1 with the highest contributions being Ca2+ (30%) and SO42– (15%). Mean [SO42–] (52 µeq L–1) and [NO3–] (29 µeq L–1) were approximately five and ten times higher, respectively, compared to background hemispheric values. Secondary ions had the highest deposition fluxes (SO42–, 25.2 kg ha–1 y–1 and NO3–: 18.3 kg ha–1 y–1). The mean ratio of H+/(NO3– + SO42–) was 0.02 indicating ~98% of the acidity was neutralized. Ca2+, (57%), Mg2 (25%), NH4+ (15%) and K+ (4%) were important neutralizing species. Positive Matrix Factorization (PMF) was applied to the deposition fluxes. Five factors were identified and identified as ammonia neutralized, sea salt, soil, biomass burning, and calcium neutralized. © Taiwan Association for Aerosol Research.