Research Articles by Dr. PRASHANT RAJPUT
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The concentration of bioaerosols, thus measured, is widely represented in colony forming units (C... more The concentration of bioaerosols, thus measured, is widely represented in colony forming units (CFU/m3). Each specific agar mediums viz. Mannitol Salt (11.10 %; w/v), MacConkey (5.15 %; w/v) and Sabouroud Dextrose (6.50 %; w/v) were boiled for ~ 1 h with double distilled water in a sterilized pressure-cooker. The prepared stuffs were allowed to cool and then poured into petri dishes. The lids of petri dishes (3 required on each sampling day) were closed and allowed to cool down to normal temperature in a bio-safety cabinet equipped with ultraviolet (UV) lamp. The concentrations of each agar medium mentioned above and incubation at 35 °C temperature were considered to be optimal for the bioaerosols culture. In regional scenario, a large variability in weather conditions (on a seasonal basis) and associated anthropogenic emissions has been witnessed. Therefore, the number of viable bioaerosols colonies was expected to vary in orders of magnitude over a period of 1 year in this study. Thus, the only critical parameter that could affect significantly on our observations of colony counting is the time-period of incubation. Towards this, about 40% of the total collected bioaerosols samples were incubated for different time-periods (24, 48, 72, 96 and 120 h). Subsequently their colonies counting were performed. All other conditions including specific agar medium strength and incubation temperature were kept identical. The observations of colony counting for GPB, GNB and Fungi for different incubation periods are shown in Figures (S2a, b, c). The results shown in figure S2 suggest that 48 h of incubation is the optimum culture period for GPB and GNB, whereas 72 h is optimum period for Fungi culture. Thus, finally for these 50 samples we have considered the colony counting data pertaining to 48 h of incubation for GPB and GNB, whereas 72 h incubated counting data for Fungi was considered. For rest of the sampling, GPB and GNB colony counting was performed post to 48 h of incubation, whereas 72 h of incubation was strictly followed for Fungi colony counting.
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Previous studies worldwide have suggested the potential role of bioaerosols as ice-nuclei and clo... more Previous studies worldwide have suggested the potential role of bioaerosols as ice-nuclei and cloud-condensation nuclei. Furthermore, their participation in regulating the global carbon cycle urges systematic studies from different environmental conditions throughout the globe. Towards this through one-year study, conducted from June 2015‒May 2016, we report on atmospheric abundance and variability of viable bioaerosols, organic carbon (OC) and particles number and deduced mass concentrations from Indo-Gangetic Plain (IGP; at Kanpur). Among viable bioaerosols, the highest concentrations of Gram-positive bacteria (GPB), Gram-negative bacteria (GNB) and Fungi were recorded during December‒January (Avg.: 189 CFU/m3), November (244 CFU/m3) and September months (188 CFU/m3), respectively. Annual average concentration of GPB, GNB and Fungi are 105 ± 58, 144 ± 82 and 116 ± 51 CFU/m3. Particle number concentration (PNC) associated with fine-fraction aerosols (FFA) predominates throughout the year. However, mineral dust (coarser particle) remains a perennial constituent of atmospheric aerosols over the IGP. Temporal variability records and significant linear positive correlation (p < 0.05) of GPB and GNB with OC and biomass burning derived potassium (K+BB) indicates their association with massive emissions from paddy-residue burning (PRB) and bio-fuel burning. Influence of meteorological parameters on viable bioaerosols abundance has been rigorously investigated herein. Accordingly, ambient temperature seems to be more affecting the bacteria (anti-correlation), whereas wet-precipitation (1‒4 mm) relates to higher abundance of Fungi. High abundance of GNB from large-scale biomass burning emissions has implications to endotoxin exposure on human health. Thus, field-based data-set of bioaerosols, OC, PNC and deduced mass concentrations reported herein could serve to better constraint their role in human health and climate relevance.
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A B S T R A C T Assessment of atmospheric metals produced from natural or anthropogenic sources i... more A B S T R A C T Assessment of atmospheric metals produced from natural or anthropogenic sources is a major concern of many researchers worldwide for their source characterization and hazardous health impacts. Currently, many high tier labs, equipped with chemical (microwave digestion system), optical (X-ray fluorescence spectroscopy) or nuclear techniques (instrumental neutron activation analysis) can lead to or produce accurate data of metals rapidly. Owing to low concentration of several metals, large heterogeneity and matrix effect in atmospheric aerosol samples, many a times the chemical digestion followed by quantification approach is widely preferred. However, in South and Southeast Asia, the major data set of atmospheric metals is relatively lacking, due to unavailability of rapid digestion technique in many labs. Towards this we report a new and facile analytical protocol for complete digestion of metals in atmospheric aerosols. Finalized protocol for metal digestion in ~ 12 h involves sample treatment with a mixture of HF+HNO 3 +H 2 O 2 +H 2 O in 1: 4: 1: 6 (v/v) at 150 ºC. This protocol has been successfully applied for complete digestion and quantification of several metals (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, V and Zn) in high-loading ambient PM 2.5 (particulate matter of aerodynamic diameter ≤2.5 µm; 95240 µg m-3).Mineral dust composition over IGP (Northern India) looks distinctly different than that over western India (reported previously). Several toxic metals (As, Cd, Cu,Pb, V and Zn) show enrichment factor more than 10, suggesting their significant inputs from anthropogenic sources.Thus, our analytical protocol could facilitate for accurate and rapid analysis of metals pertaining to environmental and toxicological research.
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According to the meteorological long-term variability pattern, year 2015 was influenced by El Niñ... more According to the meteorological long-term variability pattern, year 2015 was influenced by El Niño and PDO ...............
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According to the meteorological long-term variability pattern, year 2015 was influenced by El Niñ... more According to the meteorological long-term variability pattern, year 2015 was influenced by El Niño and PDO (Pacific Decadal Oscillation; causes weakening of Indian Summer Monsoon). These conditions facilitate the assessment of chemical characteristics of fine-mode ambient aerosols (PM2.5; n = 48) and individual rain waters (pH: 6.4‒7.6; n = 15) during the South-west monsoon (July‒September, 2015) in the central Indo-Gangetic Plain (IGP; Kanpur). Water-soluble ionic species (WSIS) have been measured to assess the undergoing processes (neutralization, formation and below-cloud scavenging) and estimate their dry and wet deposition fluxes. The ∑WSIS varies from 4‒32 μg/m3 in PM2.5, whereas it ranges from 32‒102 mg/L in rain waters. The NH4+ and SO42- are found to be predominant in PM2.5 (16‒120μg/m3), whereas HCO3- and Ca2+ are predominant in rain water samples. The difference in chemical composition of PM2.5 and rain water is largely attributed to additional contribution of coarse-mode mineral dust in rain water. The Ca2+ and Mg2+ in both aerosols and rain water samples are associated with HCO3-. The NO3- and SO42- are neutralized predominantly by NH4+ and ∑-/∑+ ratio is ≈ 1 in both aerosols and rain waters. Furthermore, co-variability of NO3- with nss-Ca2+ in PM2.5 indicates role of fine-mode mineral dust surface in the formation of ammonium nitrate. Various characteristic mass ratios (HCO3-/Ca2+ and SO42-/NH4+) in rain water look quite similar to those in aerosols (PM2.5). This suggests that below-cloud scavenging is predominant mechanism of aerosols wash-out. Dry deposition fluxes of Mg2+, NH4+ and SO42- are ~13% of their wet deposition fluxes, whereas for K+, Ca2+ and NO3- it is < 6%.
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We have conducted......
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We have conducted this study (November 09‒February 10) during daytime (average PM1: 113 µg m-3; n... more We have conducted this study (November 09‒February 10) during daytime (average PM1: 113 µg m-3; n = 51) and nighttime (average PM1: 159 µg m-3; n = 49) in the Indo-Gangetic Plain (IGP). Air-mass back trajectories suggest impact of local emission and long-range transport (predominantly from north-west direction). Mass fractions of SO42- and NO3- in PM1 are significantly (p < 0.05) different during daytime and nighttime, whereas NH4+/PM1 look similar during day and night. Relatively high concentration of SO42- during daytime is explained based on heterogeneous-phase reactivity due to positive response of Fe and Mn species (inferred from correlation and multi-linear regression analysis: MLRA). Likewise lower concentration of NO3- is explained based on negative response of Fe during heterogeneous phase formation. Role of wet-bulb temperature and solar flux has also been studied. From field-based measurements our study shows that heterogeneous formation of SO42- (involving Fe and Mn) and NO3- undergo via selective endothermic pathways. Proposed mechanism for sulfate and nitrate formation via heterogeneous phase reactivity is in good agreement with field-based measurements in this study (IGP). Impact of heterogeneous-phase reactivity via endothermic pathways relates to uptake of various reactive species during winters in IGP. This, in turn, has implications to fog-formation and tropospheric oxidative cleansing. Furthermore, uptake of various species would lead to alter size, morphology and optical properties of aerosols. This would have impact on regional scale radiative forcing estimates and future climate projections.
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It has been widely realized that assessing the temporal variability records of PM 1 is of utmost ... more It has been widely realized that assessing the temporal variability records of PM 1 is of utmost importance owing to its impact on heterogeneous formation of secondary aerosols, cloud condensation nuclei (CCN) activation efficiency and health hazards. However, in general there is a scarcity of PM 1 chemical composition data (both offline and online) in the Northern India.
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In today's scenario of increasing anthropogenic emissions, arising due to development in urban an... more In today's scenario of increasing anthropogenic emissions, arising due to development in urban and rural areas, it has been widely realized to assess the atmospheric impact of various sources. In this context, we investigated the source contribution of ambient fine-mode aerosols (PM1; n = 51) during wintertime (mid of November 2009 to February 2010) over Kanpur site in the Indo-Gangetic Plain (IGP). PM1 mass concentration centers at 113 µg m-3. The high loading of fine-mode aerosols is attributable to source strength and shallower planetary boundary layer. In PM1 a total of 20 chemical constituents have been measured that include trace metals (Pb, Cd, Se, V, Cr), major elements (Fe, Mg, Ca, Na and K) and water-soluble inorganic species (NH4 + , NO3-, Cl-and SO4 2-). A recent version of positive matrix factorization (PMF 5.0) was utilized to quantify the contribution of fine-mode aerosols from various sources. This study reveals that nearly 80% of the fine-mode aerosols over Kanpur region are contributed by fossil-fuel sources that include point and mobile sources (vehicular and industrial emissions). However, the contribution from biomass burning emission is about 20%. One of the most interesting features of our study relates to the observation that secondary sources (contributing 40% of PM1 loading) are predominantly formed from vehicular emission sources (fossil-fuel combustion). Thus, our study highlights the high concentration of PM1 loading and atmospheric fog prevalent during wintertime in the IGP can have severe impact over the human health.
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A B S T R A C T This study assesses temporal variability and source contributions of PM 1 (partic... more A B S T R A C T This study assesses temporal variability and source contributions of PM 1 (particles with aerodynamic diameter 5 1.0 mm) samples (n051; November 2009ÁFebruary 2010) from an urban location at Kanpur (26.308N; 80.138E; 142 m above mean sea-level) in the Indo-Gangetic Plain (IGP). A study period from November to February is preferred owing to massive loading of particulate matter in entire IGP. PM 1 varies from 18 to 348 (Avg9SD: 113972) mg m (3 in this study. A total of 11 trace metals, five major elements and four water-soluble inorganic species (WSIS) have been measured. Mass fraction of total metals (ametals 0 tra-trace ' major) centres at 18914 %, of which nearly 15 % is contributed by major elements. Furthermore, aWSIS contributes about 26 % to PM 1 mass concentration. Abundance pattern among assessed WSIS in this study follows the order: NH 4 ' :SO 4 2 (! NO 3 (! Cl (. The K-to-PM 1 mass fraction (Avg: 2 %) in conjunction with air-mass back trajectories (AMBT) indicates that the prevailing north-westerly winds transport biomass burning derived pollutants from upwind IGP. A recent version of positive matrix factorisation (PMF 5.0) has been utilised to quantify the contribution of fine-mode aerosols from various sources. The contribution from each source is highly variable and shows a strong dependence on AMBT. Events with predominant contribution from biomass burning emission (!70 %) indicate origin of air-masses from source region upwind in IGP. One of the most interesting features of our study relates to the observation that secondary aerosols (contributing as high as Â60 % to PM 1 loading) are predominantly derived from stationary combustion sources (NO 3 (/SO 4 2 (ratio: 0.3090.23). Thus, our study highlights a high concentration of PM 1 loading and atmospheric fog prevalent during wintertime can have a severe impact on atmospheric chemistry in the air-shed of IGP.
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Atmospheric PM 2.5 (particulate matter with aerodynamic diameter of # 2.5 mm), collected from a s... more Atmospheric PM 2.5 (particulate matter with aerodynamic diameter of # 2.5 mm), collected from a source region [Patiala: 30.2 N; 76.3 E; 250 m above mean sea level] of emissions from post-harvest agricultural-waste (paddy-residue) burning in the Indo-Gangetic Plain (IGP), North India, has been studied for its chemical composition and impact on regional atmospheric radiative forcing. On average, organic aerosol mass accounts for 63% of PM 2.5 , whereas the contribution of elemental carbon (EC) is $3.5%. Sulphate, nitrate and ammonium contribute up to $85% of the total water-soluble inorganic species (WSIS), which constitutes $23% of PM 2.5. The potassium-to-organic carbon ratio from paddy-residue burning emissions (K BB + /OC: 0.05 AE 0.01) is quite similar to that reported from Amazonian and Savanna forest-fires; whereas non-sea-salt-sulphate-to-OC ratio (nss-SO 4 2À /OC: 0.21) and nss-SO 4 2À / EC ratio of 2.6 are significantly higher (by factor of 5 to 8). The mass absorption efficiency of EC (3.8 AE 1.3 m 2 g À1) shows significant decrease with a parallel increase in the concentrations of organic aerosols and scattering species (sulphate and nitrate). A cross plot of OC/EC and nss-SO 4 2À /EC ratios show distinct differences for post-harvest burning emissions from paddy-residue as compared to those from fossil-fuel combustion sources in southeast Asia. Environmental impact Emissions from open agricultural-waste burning in the Indo-Gangetic Plain are a dominant source of atmospheric organic aerosols and black carbon in northern India, and are largely responsible for the formation of haze and fog during winter (December–February). Therefore, scattering species (organic aerosols and sulphate) could have a dominant impact on regional atmospheric chemistry and radiative forcing. A systematic decrease in the mass absorption efficiency of elemental carbon (EC) with an increase in the abundance of scattering species (as documented in this study) suggests internal mixing of absorbing EC, which is consistent with single scattering albedo at 500 nm derived from satellite (NASA-GES DISC) measurements. These results have implications in the over estimation of atmospheric radiative forcing due to black carbon over northern India.
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We compare the mass concentrations of black carbon (BC) and elemental carbon (EC) from different ... more We compare the mass concentrations of black carbon (BC) and elemental carbon (EC) from different emissions in the Indo-Gangetic Plain (IGP), using optical (Aethalometer; 880 nm) and thermooptical technique (EC-OC analyzer; 678 nm), respectively. The fractional contribution of BC mass concentration measured at two different channels (370 and 880 nm), OC/EC ratio, and non-sea-salt K + /EC ratios have been systematically monitored for representing the source characteristics of BC and EC in this study. The mass concentrations of BC varied from 8.5 to 19.6, 2.4 to 18.2, and 2.2 to 9.4 í µí¼g m −3 during October-November (paddy-residue burning emission), December–March (emission from bio-and fossil-fuel combustion) and April-May (wheat-residue burning emission), respectively. In contrast, the mass concentrations of EC varied from 3.8 to 17.5, 2.3 to 8.9, and 2.0 to 8.8 í µí¼g m −3 during these emissions, respectively. The BC/EC ratios conspicuously greater than 1.0 have been observed during paddy-residue burning emissions associated with high mass concentrations of EC, OC, and OC/EC ratio. TheÅngström exponent (í µí»¼) derived from Aethalometer data is approximately 1.5 for the postharvest agricultural-waste burning emissions, hitherto unknown for the IGP. The mass absorption efficiency (MAE) of BC and EC centers at ∼1–4 m 2 g −1 and 2-3 m 2 g −1 during the entire study period in the IGP.
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This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights
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A B S T R A C T Characteristics and emission budget of carbonaceous species from two distinct pos... more A B S T R A C T Characteristics and emission budget of carbonaceous species from two distinct post-harvest agricultural-waste (paddy-and wheat-residue) burning emissions have been studied from a source region (Patiala: 30.28N, 76.38E; 250 m amsl) in the Indo-Gangetic Plain (IGP), Northern India. The PM 2.5 mass concentration varies from 60 to 390 mg m (3 during paddy-residue burning (OctoberÁNovember) with dominant contribution from organic carbon (OC:33%), whereas contribution from elemental carbon (EC) centres at Â4%. Water-soluble organic carbon (WSOC) accounts for about 50% of OC. In contrast, mass concentration of PM 2.5 during the period of wheat-residue burning (AprilÁMay) is significantly lower, varies from 18 to 123 mg m (3 and mass fractions of EC and OC are 7 and 26%, respectively. The diagnostic ratios of OC/EC (1192), WSOC/OC (0.5290.02), nss-K ' /OC (0.0690.00) and SPAHs/EC (4.390.7 mg/g) from paddy-residue burning emissions are significantly different than those from wheat-residue burning (OC/EC: 3.090.4; WSOC/OC: 0.6090.03; nss-K ' /OC: 0.1490.01 and SPAHs/EC: 1.390.2 mg/g). The emission budget of OC, EC and SPAHs from post-harvest agricultural-waste burning in the IGP are estimated to be 505968 Gg/y, 5992 Gg/y and 182932 Mg/y, respectively. From a global perspective, crop-residue burning in Northern India contributes nearly 20% of both OC and EC to the total emission budget from the agricultural-waste burning.
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Atmospheric concentrations of elemental, organic and water–soluble organic carbon (EC, OC and WSO... more Atmospheric concentrations of elemental, organic and water–soluble organic carbon (EC, OC and WSOC) and polycyclic aromatic hydrocarbons (PAHs) have been studied in PM 2.5 (particulate matter of aerodynamic diameter ≤2.5 μm) from a site (Barapani: 25.7 °N; 91.9 °E; 1 064 m amsl) in the foot–hills of NE–Himalaya (NE–H). Under favorable wind–regimes, during the wintertime (January–March), study region is influenced by the long–range transport of aerosols from the Indo–Gangetic Plain (IGP). For rest of the year, ambient atmosphere over the NE–H is relatively clean due to frequent precipitation events associated with the SW– and NE–monsoon. The concentration of PM 2.5 over NE–H, during the wintertime, varied from 39–348 μg m –3 , with average contribution of OC and EC as 36±8% (AVG±SD) and 6±3%, respectively. For the OC/EC ratio as high as 10–15 (relatively high compared to fossil–fuel source) associated with WSOC/OC ratio exceeding 0.5 in NE–H, it can be inferred that dominant source of carbonaceous aerosols is attributable to biomass burning emissions and/or contributions from secondary organic aerosols (SOA). The OC/PM 2.5 ratio from NE–H is somewhat higher compared to upwind regions in the IGP (Range: 0.16–0.24). The abundance of ΣPAHs show large variability, ranging from 4–46 ng m –3 , and the ratio of sum of 4– to 6–ring PAHs (Σ (4– to 6–) PAHs) to EC is 2.4 mg g –1 ; similar to that in the upwind IGP and is about a factor of two higher than that from the fossil–fuel combustion sources. The cross–plot of PAH isomers [FLA/(FLA+PYR) vs. ANTH/(ANTH+PHEN), BaA/(BaA+CHRY+TRIPH), BaP/(BaP+B[b,j,k]FLA) and IcdP/(IcdP+BghiP)] reaffirms the dominant impact of biomass burning emissions. These results have implications to large temporal variability in aerosol radiative forcing and environmental change over the NE–Himalaya.
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This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright a b s t r a c t Atmospheric concentrations of particulate polycyclic aromatic hydrocarbons (PAHs) and their isomer ratios have been studied for two distinct biomass burning emissions (post-harvest burning of paddy-residue in OcteNov and wheat-residue burning during AprileMay) in the Indo-Gangetic Plain (IGP). The mass concentrations of PM 2.5 (Av: 246 mg m À3), OC (92 mg m À3), EC (7 mg m À3) and SPAHs (40 ng m À3) are significantly higher from the paddy-residue burning. In contrast, for wheat-residue burning emissions, concentrations of PM 2.5 (53 mg m À3), OC (15 mg m À3), EC (4 mg m À3) and SPAHs (7 ng m À3) are about 4e5 times lower. The large temporal variability in the concentrations of particulate species and OC/EC ratio (range: 1.9e25.7) is attributed to differences in the two biomass burning emissions and their relative source strength. The mass fraction of EC (Av: 3.1%), associated with the poor combustion efficiency of moist paddy-residue, is significantly lower than that from the wheat-residue burning (EC/PM 2.5 ¼ 7.6%) during dry weather conditions. Furthermore, OC mass fractions from paddy-and wheat-residue burning emissions are 37% and 28% respectively; whereas SPAHs/EC ratios are significantly different, 5.7 and 1.6 mg g À1 , from the two emission sources. The particulate concentrations of 5-and 6-ring isomers (normalized to EC) from paddy-residue burning are about 3e5 times higher than those from the wheat-residue burning emissions. The cross plots of PAHs show distinct differences in isomer ratios from agricultural-waste burning emissions vis-à-vis fossil-fuel combustion.
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Research Articles by Dr. PRASHANT RAJPUT