Browsing by Author "S. Tiwari"

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Aerosol characteristics at a rural station in southern peninsular India during CAIPEEX-IGOC: physical and chemical properties
(Springer Verlag, 2015) D.S. Bisht; A.K. Srivastava; A.S. Pipal; M.K. Srivastava; A.K. Pandey; S. Tiwari; G. Pandithurai
To understand the boundary layer characteristics and pathways of aerosol–cloud interaction, an Integrated Ground Observational Campaign, concurrent with Cloud Aerosol Interaction and Precipitation Enhancement Experiment, was conducted by the Indian Institute of Tropical Meteorology, Pune, under Ministry of Earth Sciences at Mahabubnagar (a rural environment, which is ~100 km away from an urban city Hyderabad in Andhra Pradesh), during the period of July–November 2011. Collected samples of PM2.5 and PM10 were analyzed for water-soluble ionic species along with organic carbon (OC) and elemental carbon (EC). During study period, the average mass concentrations of PM2.5 and PM10 were about 50(±10) and 69(±14) μg m−3, respectively, which are significantly higher than the prescribed Indian National Ambient Air Quality Standards values. The chemical species such as sum of anions and cations from measured chemical constituents were contributed to be 31.27 and 38.49 % in PM2.5 and 6.35 and 5.65 % to the PM10, whereas carbonaceous species contributed ~17.3 and 20.47 % for OC and ~3.0 and 3.10 % for EC, respectively. The average ratio of PM2.5/PM10 during study period was ~0.73(±0.2), indicating that the dominance of fine size particles. Carbonaceous analysis results showed that the average concentration of OC was 14 and 8.7 μg m−3, while EC was 2.1 and 1.5 μg m−3 for PM10 and PM2.5, respectively. The ratios between OC and EC were estimated, which were 6.6 and 5.7 for PM10 and PM2.5, suggesting the presence of secondary organic aerosol. Total carbonaceous aerosol accounts 23 % of PM10 in which the contribution of OC is 20 % and EC is 3 %, while 20 % of PM2.5 mass in which the contribution of OC is 17 % and EC is 3 %. Out of the total aerosols mass, water-soluble constituents contributed an average of 45 % in PM10 and 38 % in PM2.5 including about 39 % anions and 6 % cations in PM10, while 31 % anions and 7 % cations in PM2.5 aerosol mass collectively at study site. © 2014, Springer-Verlag Berlin Heidelberg.
Aerosol chemical characterization and role of carbonaceous aerosol on radiative effect over Varanasi in central Indo-Gangetic Plain
(Elsevier Ltd, 2016) S. Tiwari; U.C. Dumka; D.G. Kaskaoutis; Kirpa Ram; A.S. Panicker; M.K. Srivastava; Shani Tiwari; S.D. Attri; V.K. Soni; A.K. Pandey
This study investigates the chemical composition of PM10 aerosols at Varanasi, in the central Indo-Gangetic Plain (IGP) during April to July 2011, with emphasis on examining the contribution of elemental carbon (EC) to the estimates of direct aerosol radiative effect (DARE). PM10 samples are analysed for carbonaceous aerosols (Organic Carbon, OC and EC) and water-soluble ionic species (WSIS: Cl-, SO42-, NO3-, PO42- NH4+, Na+, K+, Mg2+ and Ca2+) and several diagnostic ratios (OC/EC, K+/EC, etc) have been also used for studying the aerosol sources at Varanasi. PM10 mass concentration varies between 53 and 310 μgm-3 (mean of 168 ± 73 μgm-3), which is much higher than the National and International air quality standards. The OC mass concentration varies from 6 μg m-3 to 24 μg m-3 (mean of 12 ± 5 μg m-3; 7% of PM10 mass), whereas EC ranges between 1.0 and 14.3 μg m-3 (4.4 ± 3.9 μg m-3; ~3% of PM10 mass). The relative low OC/EC of 3.9 ± 2.0 and strong correlation (R2 = 0.82) between them suggest the dominance of primary carbonaceous aerosols. The contribution of WSIS to PM10 is found to be ~12%, out of which ~57% and 43% are anions and cations, respectively. The composite DARE estimates via SBDART model reveal significant radiative effect and atmospheric heating rates (0.9-2.3 Kday-1). Although the EC contributes only ~3% to the PM10 mass, its contribution to the surface and atmospheric forcing is significantly high (37-63% and 54-77%, respectively), thus playing a major role in climate implications over Varanasi. © 2015 Elsevier Ltd.
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.
Aerosol optical properties and their relationship with meteorological parameters during wintertime in Delhi, India
(Elsevier Ltd, 2015) S. Tiwari; G. Pandithurai; S.D. Attri; A.K. Srivastava; V.K. Soni; D.S. Bisht; V. Anil Kumar; Manoj K. Srivastava
In situ and columnar measurements of aerosol optical properties (AOPs) [Aerosol optical depth (AOD), Angstrom Exponent (AE), Aerosol scattering (σscat) and absorption (σabs) coefficients and single scattering albedo (SSA)] along with soot particles (Black carbon: BC) and fine particles (PM2.5: d ≤2.5) were continuously measured at an urban site in Delhi, India during winter period (December 2011 to March 2012). Average values of AOD, σscat, σabs, and SSA at 500nm; and AE for the observation period were found to be 0.95±0.32, 1027.36±797.1Mm-1, 85.95±73.2Mm-1 and 0.93±0.03; and 0.94±0.19, respectively. Higher values of σscat and σabs were occurred in the month of December (1857 and 148Mm-1) while relatively lower values of σscat (585Mm-1) and σabs (44Mm-1) were occurred in March and February respectively. SSA, however, was higher during January (0.94) and lower in March (0.89). The mass concentration of PM2.5 and BC were 195.34±157.99 and 10.11±8.83μgm-3 respectively during study period. Bimodal distributions were observed in σscat and σabs coefficients during 0800 and 0900h LT (traffic rush hours) and at 2200 and 2300h LT (low boundary layer conditions) with lower values during daytime between 1500 and 1700h LT, respectively. The σscat peak in morning may be attributed to large emissions of aerosol in the traffic rush hours and production of secondary aerosols with increasing solar radiation and temperature. During study period, the σscat (mean) coefficient was 13% lower during daytime as compared to nighttime. An interesting feature was seen in monthly analysis of σscat in between day and nighttime which was 18% and 22% higher in December and January in nighttime however ~4% lower during February and March; it is due to effect of local meteorology. The impact of meteorological parameters such as wind speed (WS), wind direction (WD), visibility (VIS) and mixed layer depths (MLDs) on AOPs along with fine and soot particles were studied. A clear negative significant correlation between atmospheric visibility with σscat (-0.64); σabs (-0.57) and PM2.5 (-0.56) were observed. During foggy days (VIS ≤1000m), the AOPs, fine and soot particles were substantially (~1.8 times) higher as compared to clean days, however, it was ~2.3 times higher during dense foggy days (VIS ≤500m). Similarly higher (~2 times) AOPs and aerosol concentrations were also seen below 200m MLDs. In addition to this, ~4 times higher AOPs and aerosol mass concentrations were observed when WS was below 1m/s. In view of the above results and regression analysis, we can say that the meteorological parameters play a crucial role in enhancement of aerosols at ground level during winter period over Delhi. © 2014 Elsevier B.V.
Aerosol optical properties over delhi and manora peak during a rare dust event in early april 2005
(Taylor and Francis Ltd., 2011) S.K. Srivastava; M.K. Srivastava; A. Saha; S. Tiwari; S. Singh; U.C. Dumka; B.P. Singh; N.P. Singh
Dust storm events are annual phenomena observed over the Indo-Gangetic plain (IGP) during the pre-monsoon period (May-June). These dust storms affect the air quality, weather conditions and radiation budget of the region. In this paper we characterize the aerosol optical parameters associated with a rare dust storm event that hit the IGP during early April 2005. This event was considered rare as it occurred much earlier than the general occurrence of dust storms in India (May-June), and in the year 2005, the warmest year in the span of the previous hundred years. In this study we considered the optical aerosol parameters for two places in the IGP: Delhi (28.5° N, 77.2° E, 325 m asl) and the high altitude station, Manora Peak (29.4° N, 79.5° E, 1958 m asl). Of the two selected stations, Delhi represents a highly populated and polluted location whereas Manora Peak represents a cleaner location in the central Himalayan region. During this dust storm event, the aerosol optical depth (AOD) was observed to increase considerably. The increment was 2.6-4.6 times over Delhi and 1.6-3.2 times over Manora Peak at wavelengths 380 and 1020 nm, respectively, with respect to the background values, whereas the Ångström exponent (α) for both the stations remained close to zero during the event. The effect shows a considerable increase in direct dust radiative forcing in terms of a reduction in the broadband global irradiance for Delhi as well as for Manora Peak stations. The direct aerosol radiative forcing thus obtained was about 34% in the 400-1100 nm wavelength band at Manora Peak. © 2011 Taylor & Francis.
Anemia a common aliment in women and its prevalence in ruler population: A random survey report
(Publishers, 2016) M. Dwivedi; S. Prakash; P.K. Singh; A. Kumar; R.K. Dubey; S. Tiwari
This study was conducted to assess the prevalence of anemia in women (15-60 years) in rural area of Varanasi district of Uttar Pradesh, India. Villages were randomly selected for this survey and 113 women were included. Mean Hemoglobin level in g/dL 9.5 respectively. A high prevalence of anaemia (68.04%) was observed in women of mixed vegetarian. Majority of the women were moderately anaemic (59.56%) and were under BMI18.5. Occurrence of anaemia in women was found to be inversely proportional to the literacy status. Statistically significant association (P <0.05) were found amongst anaemic antenatal women with their literacy status and BMI however statistically significant association was not found in various dietary factors.
Assessment of air quality during 19th Common Wealth Games at Delhi, India
(Kluwer Academic Publishers, 2013) D.S. Bisht; S. Tiwari; A.K. Srivastava; Manoj K. Srivastava
The 19th Common Wealth Games was organized at Delhi, India, during October 3 to 14, 2010, where more than 8,000 athletes from 71 Commonwealth Nations have participated. In order to give them better environment information for proper preparedness, mass concentrations of particulate matters below 10 microns (PM10) and 2. 5 microns (PM2. 5), black carbon (BC) particles and gaseous pollutants such as carbon monoxide (CO) and nitrogen oxide (NO) were monitored and displayed online for ten different locations around Delhi, including inside and outside the stadiums. This extensive information system for air quality has been set up for the period from September 24 to October 21, 2010, and data have been archived at 5-min interval for further research. During the study period, average concentration of PM10 and PM2. 5 was observed to be 229. 7 ± 85. 5 and 112. 1 ± 56. 0 μg m-3, respectively, which is far in excess of the corresponding annual averages, stipulated by the national ambient air quality standards. Significant large and positive correlation (r = 0. 93) between PM10 and PM2. 5 implies that variations in PM10 mass are governed by the variations in PM2. 5 mass. The mass concentrations of PM2. 5 inside the stadium were found to be ~18 % lower than those outside; however, no large variations were observed in PM10. Mean concentrations of BC, CO and NO for the observation period were 10. 9 μg m-3 (Min, 02 μg m-3; Max, 31 μg m-3), 1. 83 ± 0. 89 ppm (Min, 0. 48 ppm; Max, 4. 55 ppm) and 37. 82 ppb (Min, 2. 4 ppb; Max, 206. 05 ppb), respectively. BC showed positive correlation (r = 0. 73) with CO suggests unified source for both of them, mainly from combustion emissions. All the measured parameters, however, show a significant diurnal variation with enhanced peaks in the morning and late night hours and lower values during daytime. © 2012 Springer Science+Business Media B.V.
BATAL: The balloon measurement campaigns of the Asian tropopause aerosol layer
(American Meteorological Society, 2018) J.-P. Vernier; T.D. Fairlie; T. Deshler; M. Venkat Ratnam; H. Gadhavi; B.S. Kumar; M. Natarajan; A.K. Pandit; S.T. Akhil Raj; A. Hemanth Kumar; A. Jayaraman; A.K. Singh; N. Rastogi; P.R. Sinha; S. Kumar; S. Tiwari; T. Wegner; N. Baker; D. Vignelles; G. Stenchikov; I. Shevchenko; J. Smith; K. Bedka; A. Kesarkar; V. Singh; J. Bhate; V. Ravikiran; M. Durga Rao; S. Ravindrababu; A. Patel; H. Vernier; F.G. Wienhold; H. Liu; T.N. Knepp; L. Thomason; J. Crawford; L. Ziemba; J. Moore; S. Crumeyrolle; M. Williamson; G. Berthet; F. Jégou; J.-B. Renard
A series of NASA-ISRO-sponsored balloon campaigns in India and Saudi Arabia, called the Asian tropopause aerosol layer (ATAL) was conducted between 2014 and 2017 to study the nature, formation, and transport of polluted aerosols in the upper troposphere and lower stratosphere during the Asian summer monsoon (ASM). The ATAL was confirmed through solar occultation observations by Stratospheric Aerosol and Gas Experiment (SAGE) II after improving the cloud-aerosol separation approach using the ratio between aerosol extinction coefficients retrieved at two wavelengths. Analysis of long-term satellite measurements of upper troposphere and lower stratosphere (UTLS) aerosols suggested that ATAL's aerosol optical depth had increased by 2-3 times since the late 1990s, pointing out its possible connection with Asian pollution growth.
Characterization of carbonaceous aerosols over Delhi in Ganga basin: Seasonal variability and possible sources
(Springer Verlag, 2014) A.K. Srivastava; D.S. Bisht; K. Ram; S. Tiwari; Manoj K. Srivastava
The mass concentration of carbonaceous species, organic carbon (OC), and elemental carbon (EC) using a semicontinuous thermo-optical EC-OC analyzer, and black carbon (BC) using an Aethalometer were measured simultaneously at an urban mega city Delhi in Ganga basin from January 2011 to May 2012. The concentrations of OC, EC, and BC exhibit seasonal variability, and their concentrations were ~2 times higher during winter (OC 38.1 ± 17.9 μg m-3, EC 15.8 ± 7.3 μg m-3, and BC 10.1 ± 5.3 μg m-3) compared to those in summer (OC 14.1 ± 4.3 μg m-3, EC 7.5 ± 1.5 μg m-3, and BC 4.9 ± 1.5 μg m-3). A significant correlation between OC and EC (R = 0.95, n = 232) indicate their common emission sources with relatively lower OC/EC ratio (range 1.0-3.6, mean 2.2 ± 0.5) suggests fossil fuel emission as a major source of carbonaceous aerosols over the station. On average, mass concentration of EC was found to be ~38 % higher than BC during the study period. The measured absorption coefficient (babs) was significantly correlated with EC, suggesting EC as a major absorbing species in ambient aerosols at Delhi. Furthermore, the estimated mass absorption efficiency (σabs) values are similar during winter (5.0 ± 1.5 m2 g-1) and summer (4.8 ± 2.8 m2 g-1). Significantly high aerosol loading of carbonaceous species emphasize an urgent need to focus on air quality management and proper impact assessment on health perspective in these regions. © 2014 Springer-Verlag Berlin Heidelberg.
Chemical characterization of rainwater at a high-altitude site “Nainital” in the central Himalayas, India
(Springer Verlag, 2017) Deewan Singh Bisht; A.K. Srivastava; H. Joshi; K. Ram; N. Singh; M. Naja; M.K. Srivastava; S. Tiwari
The present study investigates the chemical composition of rainwater (RW) from a high-altitude site “Nainital” (1958 m above msl) in the central Himalaya region, to understand the influence of local, regional, and long-range transport of pollutants. A total of 55 (2 in pre-monsoon and 53 in monsoon) RW samples were collected during the study period (June–September 2012) and were analyzed for major anions and cations using an ion chromatograph. The pH of precipitation events ranged from 4.95 to 6.50 (average 5.6 ± 0.3) was observed during the monsoon period (near to the acidic), whereas during the pre-monsoon, the pH was 6.25 ± 0.49 (alkaline) over the study region; it is due the mixture of anthropogenic as well as the natural chemical constituents. The average ionic concentration (sum of measured chemical constituents) was ∼3 times higher during the pre-monsoon (986 ± 101 μeq/1) compared to that in the monsoon season (373 ± 37 μeq/1). This is mainly due to the presence of more natural aerosols in the pre-monsoon season which is also reflected in the pH of rainwater (average 6.25 ± 0.50) as well as ionic concentration. The chemical composition suggests that Ca2+ was the major contributor (34%) among cations, followed by Na+ (10%), K+ (8%), and Mg2+ (9%), whereas Cl−, NO3 −, and SO4 2− contributed ∼13, 11, and 9%, respectively, among anions. The average ratio of acidic species (SO4 2−/NO3 −) is 1.56, suggesting 61 and 39% contribution of SO4 2− and NO3 −, respectively, which is very close to the estimated contribution of H2SO4 (60–70%) and HNO3 (30–40%) in the precipitation samples. Neutralization factors for Ca2+, Mg2+, and NH4 + in RW at Nainital are 4.94, 1.21, and 0.37, respectively, indicating their crucial role in neutralization of acidic species. The non-sea-salt (NSS) contribution to total Ca2+, K+, and Mg2+ is estimated to be ∼98, 97, and 74%, respectively, suggesting the dominance of crustal sources for cations. In contrast, the NSS contribution to the total Cl− and SO4 2− is 16 and 69% indicating their anthropogenic origin, respectively. Principle component analysis also suggests that the first factor (i.e., natural sources, mainly dust, and sea-salts) accounts for ∼33% variance, whereas the second factor (i.e., fossil fuel and biomass burning) accounts for ∼18% variance of the measured ionic composition. The remaining contributions are attributed to the mixed emission sources and transport of pollutants from Indo-Gangetic Plain (IGP) and western parts of India. The results of the present study reveal a significant contribution of crustal and anthropogenic sources in the RW and neutralization processes in the central Himalaya. © 2016, Springer-Verlag Berlin Heidelberg.
Detecting aerobic bacterial diversity in patients with diabetic foot wounds using ERIC-PCR: A preliminary communication
(2009) Surya K. Singh; K. Gupta; S. Tiwari; Shailesh K. Shahi; S. Kumar; A. Kumar; Sanjeev K. Gupta
The polymicrobial nature of diabetic foot infection is a reflection of the immune compromised state of the host.The methods of microbial identification based on colony morphology and biochemical characteristics have limitations as they may not differentiate the diverse microorganisms that infect foot wounds. The aim of the present study was to find out the bacterial diversity in diabetic foot infections at genetic level by finger printing, that is, ERIC-PCR (enterobacterial repetitive intergenic consensus -polymerase chain reaction). Nine patients with infected diabetic foot ulcers were recruited to the study. Pus and tissue samples were collected from the wound site. Aerobic bacteria were isolated employing standard microbiological culture methods and their genetic variability was analyzed using the ERIC-PCR. Sensitivity test for these isolates against commonly used antibiotics were performed using disc diffusion method. The standard microbiological culture technique yielded 38 morphotypes of bacteria and their genetic diversity was confirmed by ERIC-PCR assay. Analysis of the similarity index using NTSYSpc 2.1 software revealed 34 types of banding pattern among these isolates. Based on the similarity index these isolates were divided into 7 groups. As many as 8 types of aerobic bacterial isolates were detected from a single patient using the above technique compared with 2 on routine culture analysis. Genetically diverse isolates showed differential sensitivity pattern against commonly used antibiotics in the assay. The observed diversity at genetic level is attributed to variable sensitivity pattern of these isolates against the class of antibiotics. A molecular technique such as ERIC-PCR is a more sensitive detection method than conventional techniques, the potential of which needs to be fully understood.
Diurnal and seasonal variations of black carbon and PM2.5 over New Delhi, India: Influence of meteorology
(2013) S. Tiwari; A.K. Srivastava; D.S. Bisht; P. Parmita; Manoj K. Srivastava; S.D. Attri
Black carbon (BC), which is one of the highly absorbing capacities of solar radiation, reduces albedo of atmospheric aerosol. BC along with fine particulate matters (PM2.5), which play crucial role in climate and health, was monitored online for an entire year of 2011 at an urban megacity of Delhi, situated in the northern part of India. Daily mass concentration of BC varies from 0.9 to 25.5μgm-3, with an annual mean of 6.7±5.7μgm-3 displayed clear monsoon minima and winter maxima; however, PM2.5 concentration was ranging from 54.3 to 338.7μgm-3, with an annual mean of 122.3±90.7μgm-3. BC typically peaked between 0800 and 1000 LST and again between 2100 and 2300 LST, corresponding to the morning and evening traffic combined with the ambient meteorological effect. During summer and monsoon, the BC concentrations were found less than 5μgm-3; however, the highest concentrations occurred during winter in segments from <5 to >10μgm-3. In over all study, the BC mass concentration was accounted for ~6% of the total PM2.5 mass, with a range from 1.0% to 14.3%. The relationship between meteorological parameters and BC mass concentrations was studied and a clear inverse relationship (r=-0.53) between BC and wind speed was observed. Relation between visibility and BC mass concentrations was also significantly negative (-0.81), having relatively higher correlation during post-monsoon (-0.85) and winter (-0.78) periods and lower during summer (-0.45) and monsoon (-0.54) periods. The mixed layer depths (MLDs) were found to be shallower during post monsoon (379m) and winter (335m) as compared during summer (1023m) and monsoon (603m). The study indicated that during post-monsoon season, the impact of biomass burning is higher as compared to combustion of fossil fuels. Results are well associated with the rapid growth of anthropogenic emissions and ambient meteorological conditions over the station. © 2013 Elsevier B.V.
Effects of elevated ozone on photosynthesis and stomatal conductance of two soybean varieties: A case study to assess impacts of one component of predicted global climate change
(2009) E. Singh; S. Tiwari; M. Agrawal
Global climatic change scenarios predict a significant increase in future tropospheric ozone (O3) concentrations. The present investigation was done to assess the effects of elevated O3 (70 and 100ppb) on electron transport, carbon fixation, stomatal conductance and pigment concentrations in two tropical soybean (Glycine max L.) varieties, PK 472 and Bragg. Plants were exposed to O3 for 4h·day-1 from 10:00 to 14:00 from germination to maturity. Photosynthesis of both varieties were adversely affected, but the reduction was higher in PK 472 than Bragg. A comparison of chlorophyll a fluorescence kinetics with carbon fixation suggested greater sensitivity of dark reactions than light reactions of photosynthesis to O3 stress. The O3-induced uncoupling between photosynthesis and stomatal conductance in PK 472 suggests the reduction in photosynthesis may be attributed to a factor other than reduced stomatal conductance. An increase in internal CO2 concentration in both O3-treated soybean varieties compared suggests that the reduction in photosynthesis was due to damage to the photosynthetic apparatus, leading to accumulation of internal CO2 and stomatal closure. The adverse impact of O3 stress increased at higher O3 concentrations in both soybean varieties leading to large reductions in photosynthesis. This study suggests that O3-induced reductions in photosynthesis in tropical and temperate varieties are similar. © 2009 German Botanical Society and The Royal Botanical Society of the Netherlands.
Evaluation of ambient air pollution impact on carrot plants at a sub urban site using open top chambers
(2006) S. Tiwari; M. Agrawal; F.M. Marshall
The present experiment was done to evaluate the impact of ambient air pollution on carrot (Dacus carota var. Pusa Kesar) plants using open top chambers (OTCs) ventilated with ambient (NFCs) or charcoal filtered air (FCs) at a suburban site of Varanasi, India. Various morphological, physiological and biochemical characteristics of the plants were studied at different growth stages. Air monitoring data clearly showed high concentrations of SO2, NO2 and O3 in the ambient air of study site. SO2 and NO2 concentrations were higher during early growth stages of carrot, whereas O3 concentration was highest during later growth stages. Filtration of air has caused significant reductions in all the three pollutant concentrations in FCs as compared to NFCs. Plants growing in FCs showed significantly higher photosynthetic rate, stomatal conductance, water use efficiency and variable fluorescence as compared to plants growing in NFCs. Protein content also showed a similar pattern, however, lipid peroxidation, ascorbic acid content and peroxidase activity were higher in plants growing in NFCs as compared to FCs. Shoot length, number of leaves per plant, leaf area and root and shoot weight increased significantly upon filtration of ambient air. Total nitrogen decreased significantly in root, but increased significantly in shoot of plants grown in NFCs. Total P, Mg, Ca and K contents decreased significantly in plants grown in NFCs as compared to FCs. The individual pollutant concentrations were below threshold for plant injury, but the combined effect of all the three seems to act synergistically in causing greater adverse impact on dry weight and physiology of carrot plants. The study clearly indicates that air pollutants are high enough in the ambient air to cause significant unfavorable impact on carrot plants. The work further supports the usefulness of OTCs for assessing air pollution damage under field conditions in developing countries. © Springer Science & Business Media, Inc. 2005.
Heterogeneity in pre-monsoon aerosol characteristics over the Indo-Gangetic Basin
(2013) S. Tiwari; A.K. Srivastava; A.K. Singh
Heterogeneity in aerosol characteristics was studied at five different locations over the Indo-Gangetic Basin (IGB) region during the pre-monsoon period (April-June 2011) using concurrent measurements from sun/sky radiometer, which is hypothesized to affect the Indian monsoon circulation and also the global climate system. Based on the measured aerosol products, distribution of aerosols and the associated optical properties were examined over the entire region. The pre-monsoon mean aerosol optical depth (AOD) was found to be maximum at Lahore (0.78) and Kanpur (0.68); however, a minimum AOD (~0.6) was observed at Karachi, Jaipur and Gandhi College, with relatively high variability at Karachi and low at Gandhi College. On the other hand, a significant gradient in Angstrom exponent (AE) from Karachi (0.30) in the west to Gandhi College (0.98) in the east IGB region suggests relative dominance of coarse particles over the western part and fine particles at the eastern part of the IGB. Results are confirmed with the aerosol size distribution and the air mass back-trajectory analysis at all the stations. The corresponding pre-monsoon mean single scattering albedo (SSA) shows relatively higher value at Karachi (0.94), suggests relative dominance of scattering type particles. On the other hand, lower SSA, ranging from 0.85 to 0.92, was observed at the other stations, with the lowest value at Gandhi College (0.85), which suggests absorbing aerosol distributions over the region. © 2013 Elsevier Ltd.
High aerosol loading over mega city Delhi in the western Indo-Gangetic plain: Optical characteristics
(India Meteorological Department, 2016) S.D. Attri; V.K. Soni; S. Tiwari; A.K. Srivastava; Shani Tiwari; Kanika Taneja
Measurements of aerosol optical properties were carried out at an urban mega city Delhi, which is situated in the western Indo-Gangetic Plain (IGP) region in north India using an automatic sun/sky radiometer during 2006-2008. The present study revealed high aerosol loading over the station, which could be due to its topography surrounded by different natural and anthropogenic emission sources, and may have major implications towards health, air quality and climate system. Results show a large variability in AOD during the study period, with nearly equal values during winter (0.67 ± 0.06) and summer (0.71 ± 0.11). The Ångström exponent (AE) values were found to be relatively higher during winter (1.19 ± 0.07, suggests dominance of fine-mode aerosols) and lower during summer (0.74±0.06, suggests dominance of coarse-mode aerosols). A slight decrease in single scattering albedo (SSA) was observed during the study period, with a mean value of ~0.9. SSA was found to be about 0.93 during post-monsoon and 0.96 during the winter period whereas during summer and monsoon, SSA was about 0.95. The estimated monthly absorption Ångström exponent (AAE) values over the station varied from 0.11 to 1.87, which were found to be less than 1.0 by ~55% time (mostly during winter and monsoon), and greater than 1.0 by ~45% time (mostly during summer and post-monsoon). © 2016, India Meteorological Department. All rights reserved.
High concentration of acidic species in rainwater at Varanasi in the Indo-Gangetic Plains, India
(Kluwer Academic Publishers, 2015) D.S. Bisht; S. Tiwari; A.K. Srivastava; J.V. Singh; B.P. Singh; M.K. Srivastava
The Indo-Gangetic Plains (IGP), straddling the northeastern parts of India near the foothills of the Himalayas, are one of the most densely populated and polluted regions on the globe, with consequent large anthropogenic emissions. In particular, the use of traditional biofuels in the rural areas along the plains leads to strong emissions of various pollutants. Due to this importance, a comprehensive study on the chemical characteristics of rainwater was carried out during southwest summer monsoon season of 2009 at two different locations over Varanasi, India, located in the middle of IGP region in the eastern part of Uttar Pradesh. The rainwater samples were analyzed for major chemical constituents along with pH and its electric conductivity. The pH values ranged from 5.18 to 7.08 with a mean of 5.82 ± 0.45 suggest the alkaline nature of rainwater over Varanasi. During the study period, ~14 % rainwater samples were found to be acidic when the winds blew from south–southeast direction. The weighted mean pH and electric conductivity were found higher (5.92 ± 0.45) and (24.59 µS/cm) at Maldahiya site than Banaras Hindu University (5.89 ± 0.46) and (17.16 µS/cm) due to dominance of soil-derived particles. The equivalent concentration of ionic species is of the order: Ca2+ > SO4 2− > NO3 − > Cl− > Mg2+ > Na+ > HCO3 − > NH4 + > K+ > F− > H+. The weighted mean concentration of dominant ions in rainwater over Varanasi was Ca2+ (67.1 ± 56 µeq/l), SO4 2− (37 ± 23 µeq/l) and NO3 − (27.1 ± 28 µeq/l). Significant correlation (r = 0.81; P < 0.001) between the sum of major cations (NH4 + + Ca2+ + Mg2+) and the sum of acidic species (SO4 2− + NO3 −) corroborates that these alkaline species may act as a neutralizing agent for the acidity of rainwater. The source contribution of SO4 2− in rainwater was estimated and was ~95 % by man-made activities, which is mainly derived from burning of fossil/biofuels over this region. The source of nitrate (11 %) emissions was mainly from automobiles and biomass burning. Statistical analysis such as principle component analysis was performed to find out possible sources of measured ions. First factor accounted for ~54 % variance suggested that most of the ions were from natural sources especially soil dust and sea; however, factor 2 accounted only for ~12 % variance suggests their sources from burning of fossil fuel and biomass. The third factor also indicates the mixed sources into the atmosphere. © 2014, Springer Science+Business Media Dordrecht.
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.
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.
Implications of different aerosol species to direct radiative forcing and atmospheric heating rate
(Elsevier Ltd, 2020) A.K. Srivastava; Bharat Ji Mehrotra; Abhishek Singh; V. Singh; D.S. Bisht; S. Tiwari; Manoj K. Srivastava
The optical and radiative characteristics of water-soluble and carbonaceous aerosol species in the PM2.5 samples were examined for a representative megacity over the Indo-Gangetic Basin (IGB). Aerosol optical and radiative transfer models were used to extract sulphate (SO4), nitrate (NO3), organic carbon (OC) and elemental carbon (EC) from the observations done in 2012. Initial results suggest that the mass concentration of OC dominated over other species, but impacts on optical characteristics were mostly due to the SO4 aerosols. Further, EC shows relatively large impact on radiative forcing. The aerosol optical depth (AOD) at 500 nm for SO4, NO3, EC and OC was found to be contributing ~36%, 20%, 27% and 9%, respectively in the total AOD value (0.61 ± 0.18) during the entire study period. The single scattering albedo (SSA) for SO4 and NO3 was high and suggested their scattering nature; however, being the highly absorbing species, EC was found to show the lowest values of SSA during the study period. SSA for OC was, however, ~0.70, which was found to show the second highest warming species in the atmosphere with contribution of ~10%, after EC, which caused the highest warming (~70%), to the total atmospheric forcing. © 2020 Elsevier Ltd