The present study critically investigated the effect of meteorological parameters on the mass con... more The present study critically investigated the effect of meteorological parameters on the mass concentration of Ultrafine Particulate Matter (PM1) between October 2018 and September 2019 (n=102) in a semiarid region of Rajasthan, India. The concentration of PM1 ranged between 72-110.85 μg.m-3 with distinct seasonal variation. Higher PM1 concentrations are closely linked to decreased wind speeds and colder temperatures, according to the findings. The winter season showed the highest concentration followed by post monsoon and pre monsoon season. The cumulative effect of environmental variables such as temperature, relative humidity, and wind speed, as well as the height of the planetary boundary layer, was investigated using multiple regression analysis (HPBL). A significant negative correlation (p < 0.001) with HPBL and wind speed was observed in all three seasons. The temperature was found to have a significant (p<0.001) negative correlation during winters whereas in other seas...
Measurements of aerosol optical properties were carried out at an urban mega city Delhi, which is... more 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 p...
Atmospheric PM2.5 pollution, has shown potential impact on the human health in general, thus it r... more Atmospheric PM2.5 pollution, has shown potential impact on the human health in general, thus it requires to look into the chemical characteristics of PM2.5 masses for designing effective policies to reduce health risks amongst public under exposure. The study carried out, here, has presented the ambient PM2.5 concentrations, concentrations of chemical components and associated health risks over rural and urban environments in the area of mineral based coal-fired industrial areas of central India for a period of one year (2015–16). Overall 260 PM2.5 samples, collected from rural, urban and industrial sites, were analyzed for various elements Al, As, Ca, Hg, Cr, Co, Cu, Fe, Mn, K, Cd, Mo, Ni, Pb, Se, Sb, Na, Mg, K, V and Zn, ions such as Na+, Mg2+, K+, Ca2+, F–, Cl–, NH4+, NO3–, SO42– and carbonaceous matter. The annual average PM2.5 mass concentrations were found to be ~2 to ~6 folds higher than the annual National Ambient Air Quality standard (40 µg m–3). Further this study also eva...
Eight composite PM 10-2.5 source profiles were developed for resuspended dust and vehicle exhaust... more Eight composite PM 10-2.5 source profiles were developed for resuspended dust and vehicle exhaust emissions with 32 chemical species, including 21 elements (Al,
Simultaneous long-term measurements of near-surface air pollutants at an urban station, New Delhi... more Simultaneous long-term measurements of near-surface air pollutants at an urban station, New Delhi, were studied during 2005-2012 to understand their distribution on different temporal scales. The annual mean mass concentrations of nitrogen dioxide (NO 2), sulphur dioxide (SO 2), particulate matter less than 10 µm (PM 10) and suspended particulate matter (SPM) were found to be 62.0 ± 27.6, 12.5 ± 8.2, 253.7 ± 134 and 529.2 ± 213.1 µg/m 3 , respectively. The 24-hr mean mass concentrations of NO 2 , PM 10 and SPM were exceeded on ∼27%, 87% and 99% days that of total available measurement days to their respective National Ambient Air Quality Standard (NAAQS) level. However, it never exceeded for SO 2 , which could be attributed to reduction of sulphur in diesel, use of cleaner fuels such as compressed natural gas, LPG, etc. The mean mass concentrations of measured air pollutants were found to be the highest during the winter/post-monsoon seasons, which are of concern for both climate and human health. The annual mean mass concentrations of NO 2 , PM 10 and SPM showed an increasing trend while SO 2 appears to be decreasing since 2008. Air mass cluster analysis showed that north-northwest trajectories accounted for the highest mass concentrations of air pollutants (more prominent in the winter/post-monsoon season); however, the lowest were associated with the southeast trajectory cluster.
The frequency and intensity of fog episodes during the winter season has been increasing during t... more The frequency and intensity of fog episodes during the winter season has been increasing during the past decade over the megacity of Delhi due to the high pollution load. The role of atmospheric aerosols is very important in the life cycle of fog in the urban areas. This paper presents the results on the variation in aerosol optical properties (scattering and absorption coefficients) and the black carbon (BC) mass concentration during the foggy period in winter (December 2015 to February 2016) at the Indira Gandhi International (IGI) Airport, New Delhi. The interaction between scattering and absorbing aerosols, and fog before, during and after the foggy period has been studied as a typical case. The BC mass concentration, along with the aerosol scattering and absorption coefficients, increased before and during the initial phase of the dense foggy period. However, there was a steep decrease in them after the sustained period of dense fog, which suggests possible scavenging by fog droplets. Also, it was observed that the decrease in ambient temperature and depression temperature (DT) and the increase in relative humidity (RH) played a major role in sustaining the dense fog despite the reduction in aerosol load. The single-scattering albedo (SSA) decreased during the dense fog due to a higher reduction of the scattering aerosols than the absorbing ones. Both the scattering and the absorption coefficients showed a significant correlation with cloud condensation nuclei (CCN).
The study of precipitation chemistry in the winter season over the northern part of India is vita... more The study of precipitation chemistry in the winter season over the northern part of India is vital as the atmosphere is highly loaded with atmospheric aerosols due to emissions and meteorological conditions. Precipitation samples were collected in Delhi and analyzed for major cations (Na + , NH 4 + , K + , Ca 2+ , and Mg 2+) and anions (F-, Cl-, NO 3-, SO 4 2and HCO 3-) along with pH and conductivity. The volume weighted mean pH of rainwater (RW) was 5.76 ± 0.61, with ~ 42% samples being acidic (mean pH = 5.20 of acidic rain). Specific conductivity was ~16 % (84.93 µS/cm) lower specific conductivity for the acid RW samples as compared to the non-acidic RW samples (101.20 µS/cm). The sum of ionic constituents was 1273.41 ± 749.91 µeq/l, with anion's sum contribution being 17 % lower than the sum of cations. Neutralization factors of major cations were in the order of Ca 2+ (0.83) > NH 4 + (0.36) > Mg 2+ (0.11) over Delhi. Second higher (cation) contribution of NH 4 + in RW over Delhi may be attributed to the ever increasing vehicular density and the initiation of catalytic converters in public transport. Different source apportionment methods, including principal component analysis (PCA), enrichment factor (EF), and backtrajectory (72 h) analysis were used for estimating the sources of RW. Trajectory analysis indicated three different air masses over Delhi of easterly, westerly and southerly/southeasterly wind regime. The PCA analysis shows three major factors for measured ions and was assigned to mixed source influenced by crustal, anthropogenic and marine origins, whereas, NH 4 + and HCO 3 to the local biomass burning and soil dust respectively.
The Science of the total environment, Jan 15, 2018
To develop coarse particle (PM, 2.5 to 10μm) chemical source profiles, real-world source sampling... more To develop coarse particle (PM, 2.5 to 10μm) chemical source profiles, real-world source sampling from four domestic cooking and seven industrial processing facilities were carried out in "Raipur-Bhilai" of Central India. Collected samples were analysed for 32 chemical species including 21 elements (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, S, Sb, Se, V, and Zn) by atomic absorption spectrophotometry (AAS), 8 water-soluble ions (Na, K, Mg, Ca, Cl, F, NO, and SO) by ion chromatography, ammonium (NH) by spectrophotometry, and carbonaceous fractions (OC and EC) by thermal/optical transmittance. The carbonaceous fractions were most abundant fraction in household fuel and municipal solid waste combustion emissions while elemental species were more abundant in industrial emissions. Most of the elemental species were enriched in PM (<2.5μm) size fraction as compared to the PM fraction. Abundant Ca (13-28%) was found in steel-rolling mill (SRM) and cement p...
The objectives of the Winter Fog Experiment (WIFEX) over the Indo-Gangetic Plains of India are to... more The objectives of the Winter Fog Experiment (WIFEX) over the Indo-Gangetic Plains of India are to develop better now-casting and forecasting of winter fog on various time-and spatial scales. Maximum fog occurrence over northwest India is about 48 days (visibility <1000 m) per year, and it occurs mostly during the December-February time-period. The physical and chemical characteristics of fog, meteorological factors responsible for its genesis, sustenance, intensity and dissipation are poorly understood. Improved understanding on the above aspects is required to develop reliable forecasting models and observational techniques for accurate prediction of the fog events. Extensive sets of comprehensive ground-based instrumentation were deployed at the Indira Gandhi International Airport, New Delhi. Major in situ sensors were deployed to measure surface micrometeorological conditions, radiation balance, turbulence, thermodynamical structure of the surface layer, fog droplet and aerosol microphysics, aerosol optical properties, and aerosol and fog water chemistry to describe the complete environmental conditions under which fog develops. In addition, Weather Forecasting Model coupled with chemistry is planned for fog prediction at a spatial resolution of 2 km. The present study provides an introductory overview of the winter fog field campaign with its unique instrumentation.
h i g h l i g h t s 76% higher loading of chemical constituents over Delhi than Pune. Higher seco... more h i g h l i g h t s 76% higher loading of chemical constituents over Delhi than Pune. Higher secondary aerosols in RW over Delhi from NW direction. ~4 and 26% acidic samples were observed in Pune and Delhi. Lower concentrations of ions from the Arabian Sea.
Black carbon (BC) particles play a unique and important role in Earth's climate system. BC was me... more Black carbon (BC) particles play a unique and important role in Earth's climate system. BC was measured (in situ) in central part of Indo-Gangetic Plains (IGP) at Varanasi, which is highly populated and polluted regiondue to its topography and extensive emission sources. The annual mean BC mass concentration was 8.92 ± 7.0 µg m-3 with 34% samples exceeding the average value. Seasonally, BC was highest during the post-monsoon and winter periods (~18 µg m-3) and lower in the pre-monsoon / monsoon seasons (~ 6 µg m-3). The highest frequency (~ 46%) observed for BC mass was in the interval from 5 to 10 µg m-3. However, during the postmonsoon, the most common values (~23%) were between 20 to 25 μg m−3. The night concentrations of BC were approximately twice the daytime values because of the lower nighttime boundary layer heights. The Ångström exponent was significantly positively correlated (0.55) with ground-level BC concentrations indicating the impact of BC on the columnar aerosol properties. The estimated mean Absorption Ångström Exponent was 1.02 ± 0.08 indicating the major source of BC was from fossil fuel combustion. Significant negative correlations between BC mass and meteorological parameters indicate a pronounced effect of atmospheric dynamics on the BC mass in this region. The highest mean BC mass concentration as a function of wind speed (18.1 ± 6.9 µg m-3) was under calm wind conditions (38% of the time).
This paper describes results from a detailed source profile characterization study conducted in R... more This paper describes results from a detailed source profile characterization study conducted in Raipur, India to prepare source profiles for traffic and dust-related sources. A companion paper has been published with results for a range of other combustion sources. PM 2.5 samples were analyzed for mass, elements (Al, As,
A study has been performed to develop PM 2.5 (particles with aerodynamic diameters ≤ 2.5) chemica... more A study has been performed to develop PM 2.5 (particles with aerodynamic diameters ≤ 2.5) chemically speciated source profiles of different industrial and domestic burning practices in India. A total of fifty-five PM 2.5 samples have been collected in emissions resulting from (1) industrial furnaces, (2) household fuels, (3) municipal solid waste burning, and (4) welding workshop burning practices, and categorized for eleven subtypes of sources. The collected samples were subjected to chemical analysis for twenty-one elemental (Al, As
Aerosols particles are dominant particles in study of climate change. Its characteristic, composi... more Aerosols particles are dominant particles in study of climate change. Its characteristic, composition, distribution and boundary layer dynamics are poorly known. Aerosols optical depth (AOD) is an important parameter for study of aerosols. At Varanasi, a station located in the heart of Indo-Gangetic basin (IGB), we are using Micro Pulsed LIDAR, MicroTOPS sunphotometer and Portable laser Aerosol spectrometer for measuring aerosol physical parameters during winter of 2010-2011. The results of the variability of aerosol physical properties over the IGB and concentration of dust particles in different locations at Varanasi are presented and discussed.
Atmospheric aerosol consists of both natural and anthropogenic origin. Studies have shown that co... more Atmospheric aerosol consists of both natural and anthropogenic origin. Studies have shown that continuous exposure to these particles is associated with a high percentage of death from respiratory and cardiovascular disease. In the present study, we have first time used both SEM-EDX analysis as well as chemical analysis to understand the differences in morphology and elemental composition of aerosols sample from a suburban clean and green area of Banaras Hindu University campus and some much polluted urban areas of the Varanasi city situated in the eastern Indo-Gangetic plain. The analysis was done by using scanning electron microscope (SEM) coupled with energy dispersive X-ray microanalyzer (EDX) and ionchromatography (IC). Analyses show that C, Ca, Na, S, Si, Al have dominated the samples. The concentration for urban areas of city were more than the pollution of suburban area and followed the trend as Na + > SO 4 2-> Ca 2+ > Cl -> Mg 2+ > NO 3 -> K + > HCO 3 + > F -, where as for suburban area showed the trend as Na + > SO 4 2-> NO 3 -> Ca 2+ > Cl -> Mg 2+ > K + > HCO 3 + > F -. This shows that more polluted urban areas were dominated by soil-dust generated due to heavy traffic movement and construction/industries. To establish differences among sites more measurements are necessary in different meteorological conditions.
Background: There is an urgent need for an improved understanding of the sources, distributions a... more Background: There is an urgent need for an improved understanding of the sources, distributions and properties of atmospheric aerosol in order to control the atmospheric pollution over northeastern Himalayas where rising anthropogenic interferences from rapid urbanization and development is becoming an increasing concern. Methodology/Principal Findings: An extensive aerosol sampling program was conducted in Darjeeling (altitude ,2200 meter above sea level (masl), latitude 27u019N and longitude 88u159E), a high altitude station in northeastern Himalayas, during January-December 2005. Samples were collected using a respirable dust sampler and a fine dust sampler simultaneously. Ion chromatograph was used to analyze the water soluble ionic species of aerosol. The average concentrations of fine and coarse mode aerosol were found to be 29.5620.8 mg m 23 and 19.6611.1 mg m 23 respectively. Fine mode aerosol dominated during dry seasons and coarse mode aerosol dominated during monsoon. Nitrate existed as NH 4 NO 3 in fine mode aerosol during winter and as NaNO 3 in coarse mode aerosol during monsoon. Gas phase photochemical oxidation of SO 2 during premonsoon and aqueous phase oxidation during winter and postmonsoon were the major pathways for the formation of SO 4 22 in the atmosphere. Long range transport of dust aerosol from arid regions of western India was observed during premonsoon. The acidity of fine mode aerosol was higher in dry seasons compared to monsoon whereas the coarse mode acidity was higher in monsoon compared to dry seasons. Biomass burning, vehicular emissions and dust particles were the major types of aerosol from local and continental regions whereas sea salt particles were the major types of aerosol from marine source regions. Conclusions/Significance: The year-long data presented in this paper provide substantial improvements to the heretofore poor knowledge regarding aerosol chemistry over northeastern Himalayas, and should be useful to policy makers in making control strategies.
A discrimination of aerosol types over the Indo-Gangetic Basin (IGB) region during pre-monsoon pe... more A discrimination of aerosol types over the Indo-Gangetic Basin (IGB) region during pre-monsoon period was made using multi-year ground based sun/sky radiometer measured aerosol products associated with the size of aerosols and radiation absorptivity. High dust enriched aerosols (i.e. polluted dust, PD) were found to contribute more over the central IGB station at Kanpur (KNP, 62%) as compared to the eastern IGB station at Gandhi College (GC, 31%) whereas vice-versa was observed for polluted continental (PC) aerosols, which contain high anthropogenic and less dust aerosols. Contributions of carbonaceous particles having high absorbing (mostly black carbon, MBC) and low absorbing (mostly organic carbon, MOC) aerosols were found to be 11% and 10%, respectively at GC, which was~46% and 62% higher than the observed contributions at KNP; however, very less contribution of non-absorbing (NA) aerosols was observed only at GC (2%). Variability in aerosol types together with single scattering albedo (SSA) at both the stations were also studied during the forenoon (FN) and afternoon (AN) hour, which suggests their strong association with emission sources. Results were well substantiated with the air mass backtrajectories and the fire products. Spectral information of SSA for each aerosol type discriminates the dominance of natural dust (SSA increases with increasing wavelength) with anthropogenic aerosols (SSA decreases with increasing wavelength) at both the locations. The estimated absorption Ångström exponent (AAE) values suggest relative dominance of absorbing type aerosols over the central part of IGB (due to dominant dust absorption) as compared to the eastern part during pre-monsoon period.
Rainwater samples were collected at three different locati o ns during two consecutive summer mo ... more Rainwater samples were collected at three different locati o ns during two consecutive summer mo nsoo ns of 1990 and 1991 at De lhi. These locations were Okhla, Red Fort and Rajinder Nagar whi ch represent industrial, commercial and residenti al locations, respectively. The major anio ns (Cl, S0 4 , and N0 3) and catio ns (Na, K, Ca, Mg and NH 4) along with p H of the above sa mpl es were determined. The bicarbonate (HC0 3) concentrati ons were also calcul ated. Hi gh levels of Ca and S0 4 were observed. Together, Ca and S0 4 made up more than 50% of the total ion mass, whi le Ca alo ne contri buted over 55% of the total cations mass. The pH value of rainwater was found to be alkaline in nature with an average of 6. 13 and the values varied from 5.0 I to 7.12. The relative impo rtance of natural and anthropogenic sources was estimated by chemical balancin g. In some cases, acidity was found due to the presence of sulphuri c and nitric ac id. Hi gh concentration of soil-oriented elements especially Ca has been found to pl ay an impo rtant role in ne utralizing the ac idity of rainwater and maintaining hi g h alkaline pH. Most of the S0 4 in rainwater was in the fo rm of CaS0 4. The results of the present study sugges ted th at the atmospheri c composition in the city has been stro ngly influenced by natural sou rces (sea and soil) rather than anthropogenic sources.
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Papers by Suresh Tiwari