S. K. Sharma

Characteristics of ambient ammonia over Delhi, India

In the present paper, we have characterized the ambient ammonia over Delhi along with other trace gases (NH3, NO, NO2, SO2 and CO) and particulates (PM2.5 and PM10) measured during December 2011 to June 2012. The average mixing ratios of ambient NH3, NO, NO2, SO2 and CO were recorded as 21.2xa0±xa05.4, 19.5xa0±xa04.9, 17.4xa0±xa01.4, 1.7xa0±xa00.5xa0ppb and 1.6xa0±xa00.7xa0ppm, respectively, during winter, whereas the average mixing ratios of ambient NH3, NO, NO2, SO2 and CO were recorded as 20.8xa0±xa04.7, 21.7xa0±xa06.3, 16.8xa0±xa03.1, 2.2xa0±xa00.8xa0ppb and 1.8xa0±xa00.9xa0ppm, respectively, during summer. In the present case, non-significant seasonal and diurnal variations of NH3, NO, NO2, SO2 and CO were observed during both the seasons. The average monthly NH3/NH4+ ratios varied from 0.28 to 2.56 with an average value of 1.46 in winter. The higher NH3/NH4+ ratio (3.5) observed in summer indicates the abundance of NH3 in the atmosphere during summer. The higher fraction of particulate NH4+ observed in winter than summer attributes to the conversion of gaseous NH3 into NH4+. The results emphasized that the traffic could be one of the significant sources of ambient NH3 at the urban site of Delhi as illustrated by positive correlations of NH3 with traffic-related pollutants (NO, NO2 and CO). Surface wind analysis and wind directions also support the roadside traffic and agricultural activities at the nearby area indicating possible major sources of ambient NH3 at the study site.

Source Apportionment of PM2.5 in Delhi, India Using PMF Model

Chemical characterization of PM2.5 [organic carbon, elemental carbon, water soluble inorganic ionic components, and major and trace elements] was carried out for a source apportionment study of PM2.5 at an urban site of Delhi, India from January, 2013, to December, 2014. The annual average mass concentration of PM2.5 was 122xa0±xa094.1xa0µgxa0m−3. Strong seasonal variation was observed in PM2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon. A receptor model, positive matrix factorization (PMF) was applied for source apportionment of PM2.5 mass concentration. The PMF model resolved the major sources of PM2.5 as secondary aerosols (21.3xa0%), followed by soil dust (20.5xa0%), vehicle emissions (19.7xa0%), biomass burning (14.3xa0%), fossil fuel combustion (13.7xa0%), industrial emissions (6.2xa0%) and sea salt (4.3xa0%).

Slowing down of MeV heavy ions with Z=6–29 in PEN (C7H5O2)

The stopping power for heavy ions with Z ¼ 6–29 in PEN (C7H5O2)foil has been measured in reflection geometry using the elastic recoil detection technique in the energy range � 0.2–3.0 MeV/u. These measurements have been carried out utilizing the 140 MeV Ag 13þ primary beam from the Pelletron accelerator facility at Nuclear Science Centre (NSC), New Delhi, India. All these stopping power measurements are new. The calculated stopping power values based on Lindhard, Scharff and Schiott (LSS)theory, Northcliffe and Schilling, Ziegler et al. (SRIM-2000.38 code)and extended Hubert et al. formulations have been compared with the experimental values. LSS theory agrees with the experimental data in the ion velocity range � 0:7v0Z 2=3

Variation of Stable Carbon and Nitrogen Isotopic Composition of PM10 at Urban Sites of Indo Gangetic Plain (IGP) of India.

This paper presents the variation of elemental concentrations of total carbon (TC), total nitrogen (TN) and isotopic ratios of δ13C and δ15N along with δ13OC and OC of PM10 mass over Delhi, Varanasi and Kolkata of the Indo Gangetic Plain (IGP), India. For Delhi, the average concentrations of TC and TN of PM10 were 53.0xa0±xa033.6 and 14.9xa0±xa010.8xa0µgxa0m−3, whereas δ13C and δ15N of PM10 were −25.5xa0±xa00.5 and 9.6xa0±xa02.8xa0‰, respectively. For Varanasi, the average values of δ13C and δ15N of PM10 were −25.4xa0±xa00.8 and 6.8xa0±xa02.4xa0‰, respectively. For Kolkata, TC and TN values for PM10 ranged from 9.1–98.2 to 1.4–25.9xa0µgxa0m−3, respectively with average values of 32.6xa0±xa024.9 and 9.3xa0±xa08.2xa0µgxa0m−3, respectively. The average concentrations of δ13C and δ15N were −26.0xa0±xa00.4 and 7.4xa0±xa02.7xa0‰, respectively over Kolkata with ranges of −26.6 to −24.9xa0‰ and 2.8xa0±xa011.5xa0‰, respectively. The isotopic analysis revealed that biomass burning, vehicular emission and secondary inorganic aerosols were likely sources of PM10 mass over IGP, India.

Relationships of surface ozone with its precursors, particulate matter and meteorology over Delhi

The paper presents the temporal variations of surface ozone (O3) and its precursors (oxides of nitrogen (NOX), carbon monoxide (CO), methane (CH4) and non-methane hydrocarbons (NMHCs)) along with particulate matter (PM10 and PM2.5) and their relationship with meteorology during January 2012 to December 2014 at an urban site of Delhi, India. The mean mixing ratio of surface O3, NOX, CO, CH4 and NMHCs were 29.5xa0±xa07.3xa0ppb, 34.7xa0±xa011.2xa0ppb, 1.82xa0±xa00.52xa0ppm, 3.07xa0±xa00.37xa0ppm and 0.53xa0±xa00.17xa0ppm, respectively. This study also comprises an analysis of the relation between UV irradiance and surface O3. A relationship between the total oxidant concentrations (OX) and NOX has been used to identify the regional background O3 values and the local levels of primary pollution. An attempt has been made to identify the existence of NOX or NMHC sensitive regime by charting out relationships between O3, NOX and NMHCs. The respective high pollution periods of surface O3 and PM differ on a seasonal timescale. Linear regression analysis has been used to quantify the negative influence of the chemical constituents of PM (elemental carbon, NO3−, SO42−) on O3 values. Statistical validation using bivariate correlation analysis, multiple linear regression (MLR) analysis and principal component analysis (PCA) strongly describes the intricate relationships among the aforesaid variables and meteorology. Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) analysis indicated upper Indo-Gangetic Plain (IGP) as a significant source region of O3 precursor gases contributing for O3 values at the study site.

Seasonal characteristics of water-soluble inorganic ions and carbonaceous aerosols in total suspended particulate matter at a rural semi-arid site, Kadapa (India)

To better understand the sources as well as characterization of regional aerosols at a rural semi-arid region Kadapa (India), size-resolved composition of atmospheric particulate matter (PM) mass concentrations was sampled and analysed. This was carried out by using the Anderson low-pressure impactor for a period of 2xa0years during March 2013–February 2015. Also, the variations of organic carbon (OC), elemental carbon (EC) and water-soluble inorganic ion components (WSICs) present in total suspended particulate matter (TSPM) were studied over the measurement site. From the statistical analysis, the PM mass concentration showed a higher abundance of coarse mode particles than the fine mode during pre-monsoon season. In contrast, fine mode particles in the PM concentration showed dominance over coarse mode particle contribution during the winter. During the post-monsoon season, the percentage contributions of coarse and fine fractions were equal, whereas during the monsoon, coarse mode fraction was approximately 26xa0% higher than the fine mode. This distinct feature in the case of fine mode particles during the studied period is mainly attributed to large-scale anthropogenic activities and regional prevailing meteorological conditions. Further, the potential sources of PM have been identified qualitatively by using the ratios of certain ions. A high sulphate (SO4) concentration at the measurement site was observed during the studied period which is caused by the nearby/surrounding mining activity. Carbon fractions (OC and EC) were also analysed from the TSPM, and the results indicated (OC/EC ratio of ~4.2) the formation of a secondary organic aerosol. At last, the cluster backward trajectory analyses were also performed at Kadapa for different seasons to reveal the origin of sources from long-range transport during the study period.

Seasonal variations and source profile of n-alkanes in particulate matter (PM10) at a heavy traffic site, Delhi

Delhi is one of the most polluted cities in the world. The generation of aerosols in the lower atmosphere of the city is mainly due to a large amount of natural dust advection and sizable anthropogenic activities. The compositions of organic compounds in aerosols are highly variable in this region and need to be investigated thoroughly. Twenty-four-hour sampling to assess concentrations of n-alkanes (ng/m3) in PM10 was carried out during January 2015 to June 2015 at Indira Gandhi Delhi Technical University for Women (IGDTUW) Campus, Delhi, India. The total average concentration of n-alkanes, 243.7xa0±xa05.5xa0ng/m3, along with the diagnostic tools has been calculated. The values of CPI1, CPI2, and CPI3 for the whole range of n-alkanes series, petrogenic n-alkanes, and biogenic n-alkanes were 1.00, 1.02, and 1.04, respectively, and Cmax were at C25 and C27. Diagnostic indices and curves indicated that the dominant inputs of n-alkanes are from petrogenic emissions, with lower contribution from biogenic emissions. Significant seasonal variations were observed in average concentrations of n-alkanes, which is comparatively higher in winter (187.4xa0±xa04.3xa0ng/m3) than during the summer season (56.3xa0±xa01.1xa0ng/m3).

Five-year measurements of ambient ammonia and its relationships with other trace gases at an urban site of Delhi, India

In this study, we present the 5-year measurements of ambientxa0ammonia (NH3), oxides of nitrogen (NO and NO2) and carbon monoxide (CO) along with the meteorological parameters at an urban site of Delhi, India from January 2011 to December 2015. The average mixing ratios of ambient NH3, NO, NO2 and CO over the entire period of observations were recorded as 19.3xa0±xa04.4 (ppb), 20.1xa0±xa05.9 (ppb), 18.6xa0±xa04.6 (ppb) and 1.8xa0±xa00.5 (ppm), respectively. The mixing ratios of NH3, NO, NO2 and CO were recorded highest during winter season, followed by summer and monsoon season. In the present case, a substantial seasonal variation of NH3 was observed during all the seasons except NO, NO2 and CO. The results emphasized that the traffic could be one of the significant sources of ambient NH3 at the urban site of Delhi as illustrated by positive correlations of NH3 with traffic related pollutants (NOx and CO). Surface wind as well as back trajectory analysis also supports the road side traffic and agricultural activities at the nearby area indicating possible major sources of ambient NH3 at observational site. Trajectory analysis, potential source contribution function and concentration weighted trajectory analysis indicated the surrounding nearby areas (NCR, Haryana, Punjab, Rajasthan and Uttar Pradesh) as a significant source region of ambient NH3 at the observational site of Delhi.

Inter-annual Variation of Ambient Ammonia and Related Trace Gases in Delhi, India

In this study, ambient NH3, NO, NO2, CO and SO2 were measured continuously from February, 2008, to December, 2016. The annual average mixing ratios (mole/mole) of NH3, NO, NO2, CO and SO2 were 17.8u2009±u20093.4xa0ppb; 21.2u2009±u20092.3xa0ppb, 18.1u2009±u20093.2xa0ppb; 1.7u2009±u20090.3xa0ppm and 2.0u2009±u20090.3xa0ppb, respectively. All the trace gases (NH3, NO, NO2, CO and SO2) showed significant annual variation during the study. A significant increasing trend in mixing ratios of ambient NH3 and NO2 were observed at the observational site of Delhi, whereas, increasing trend were recorded in case of NO, CO and NO2 mixing ratios. The results emphasized that traffic could be one of the significant sources of ambient NH3 at the urban site of Delhi, as illustrated by positive correlations of NH3 with traffic related co-pollutants (NO and CO).

Carbonaceous and inorganic species in PM10 during wintertime over Giridih, Jharkhand (India)

Ambient concentrations of organic carbon (OC), elemental carbon (EC) and water soluble inorganic ionic components (WSIC) of PM10 were studied at Giridih, Jharkhand, a sub-urban site near the Indo Gangatic Plain (IGP) of India during two consecutive winter seasons (November 2011–February 2012 and November 2012–February 2013). The abundance of carbonaceous and water soluble inorganic species of PM10 was recorded at the study site of Giridih. During winter 2011–12, the average concentrations of PM10, OC, EC and WSIC were 180.2u2009±u200946.4; 37.2u2009±u20096.2; 15.2u2009±u20095.4 and 18.0u2009±u20095.1xa0μg m−3, respectively. Similar concentrations of PM10, OC, EC and WSIC were also recorded during winter 2012–13. In the present case, a positive linear trend is observed between OC and EC at sampling site of Giridih indicates the coal burning, as well as dispersed coal powder and vehicular emissions may be the source of carbonaceous aerosols. The principal components analysis (PCA) also identifies the contribution of coal burningu2009xa0+u2009soil dust, vehicular emissionsu2009+u2009biomass burning and seconday aerosol to PM10 mass concentration at the study site. Backward trajectoy and potential source contributing function (PSCF) analysis indicated that the aerosols being transported to Giridih from upwind IGP (Punjab, Haryana, Uttar Pradesh and Bihar) and surrounding region.