Abundance and distribution of gaseous ammonia and particulate ammonium at Delhi, India

This study reports abundance and distribution of gaseous NH<sub>3</sub> and particulate NH<sub>4</sub><sup>+</sup> at Delhi. Gaseous NH<sub>3</sub> and particulate NH<sub>4</sub><sup>+</sup> concentrations were measured during pre-monsoon, monsoon and post-monsoon seasons of the years 2010 and 2011. Average concentrations of gaseous NH<sub>3</sub> during pre-monsoon, monsoon and post-monsoon seasons were recorded as 26.4, 33.2 and 32.5 μg m<sup>−3</sup>, respectively. Gaseous NH<sub>3</sub> concentrations were the highest during monsoon, thought to be due to decay and decomposition of plants and other biogenic material under wet conditions, leading to increased NH<sub>3</sub> emission. The results showed that particulate NH<sub>4</sub><sup>+</sup> was always lower than the gaseous NH<sub>3</sub> during all the seasons. The concentrations of particulate NH<sub>4</sub><sup>+</sup> were recorded as 11.6, 22.9 and 8.5 μg m<sup>−3</sup> during pre-monsoon, monsoon and post-monsoon seasons, respectively. The percent fraction of particulate NH<sub>4</sub><sup>+</sup> was noticed to be highest during the monsoon season, which is attributed to increased humidity levels favouring partitioning into the aerosol phase. On an average, 33.3% of total N-NH<sub>x</sub> was present as particulate NH<sub>4</sub><sup>+</sup>. Higher concentrations of NH<sub>3</sub> noticed during night time may be due to stable atmospheric conditions. The study highlighted that, as compared with rural sites, urban sites showed higher concentrations of gaseous NH<sub>3</sub> in India, which may be due to higher population density, human activities and poor sanitation arrangements

Chemical characteristics of PM<SUB>10</SUB> aerosols and airmass trajectories over Bay of Bengal and Arabian sea during ICARB

For the first time, chemical characterization of PM10 aerosols was attempted over the Bay of Bengal (BoB) and Arabian Sea (AS) during the ICARB campaign. Dominance of SO42-, NH4+ and NO3- was noticed over both the regions which indicated the presence of ammonium sulphate and ammonium nitrate as major water soluble particles playing a very important role in the radiation budget. It was observed that all the chemical constituents had higher concentrations over Bay of Bengal as compared to Arabian Sea. Higher concentrations were observed near the Indian coast showing influence of landmass indicating that gaseous pollutants like SO2, NH3 and NO x are transported over to the sea regions which consequently contribute to higher SO42-, NH4+ and NO3- aerosols respectively. The most polluted region over BoB was 13&#176;-19&#176;N and 70&#176;-90&#176;E while it was near 11&#176;N and 75&#176;E over AS. Although the concentrations were higher over Bay of Bengal for all the chemical constituents of PM10 aerosols, per cent non-sea salt (nss) fraction (with respect to Na) was higher over Arabian Sea. Very low Ca2+ concentration was observed at Arabian Sea which led to higher atmospheric acidity as compared to BoB. Nss SO42-alone contributed 48% of total water soluble fraction over BoB as well as AS. Ratios SO42- /NO3- over both the regions (7.8 and 9 over BoB and AS respectively) were very high as compared to reported values at land sites like Allahabad (0.63) and Kanpur (0.66) which may be due to very low NO.3 over sea regions as compared to land sites. Air trajectory analysis showed four classes: (i) airmass passing through Indian land, (ii) from oceanic region, (iii) northern Arabian Sea and Middle East and (iv) African continent. The highest nss SO42- was observed during airmasses coming from the Indian land side while lowest concentrations were observed when the air was coming from oceanic regions. Moderate concentrations of nss SO2- 4 were observed when air was seen moving from the Middle East and African continent. The pH of rainwater was observed to be in the range of 5.9-6.5 which is lower than the values reported over land sites. Similar feature was reported over the Indian Ocean during INDOEX indicating that marine atmosphere had more free acidity than land atmosphere

Chemical characteristics and source apportionment of aerosols over Indian Ocean during INDOEX-1999

During INDOEX IFP-99, the samples of aerosols were collected onboard ORV Sagar Kanya over Indian Ocean along the cruise track, for chemical characterization and identification of dominating sources of aerosols. The concentrations of nss-SO4, nss-Ca, nss-Mg, NO3, K, NH4 and SO2 were observed to be significantly higher before ITCZ in northern hemisphere than across ITCZ in southern hemisphere. In this study, variation of concentrations of nss-SO4, nss-Ca and nss-K with respect to change in latitude, wind direction, wind speed and relative humidity have been highlighted. North of ITCZ, nss-SO4 varied from 2.20 to 18.31 μg/m3 and south of ITCZ from 0.50 to 2.79 μg/m3 while nss-Ca varied from 0.02 to 0.72 μg/m3 north of ITCZ and from 0.01 to 0.14 μg/m3 south of ITCZ. nss-K ranged 0.09-1.43 μg/m3 and 0.07-0.60 μg/m3 before ITCZ and across ITCZ respectively. nss-Ca and nss-SO4 were contributed mainly by NNW and ENE winds while nss-K was observed to be contributed mainly by SSW and ENE winds. Wind speed greater than 4.5 m/s negatively influenced the concentration of nss-Ca concentrations. Correlation coefficients of nss-SO4 with SO2 (r = 0.7) and RH (r = 0.5) suggested a significant contribution of nss-SO4 by aqueous phase oxidation of SO2. Using PCA, four major sources namely sea salt, biogenic combustion, secondary SO4 and crustal contribution were identified over Indian Ocean during INDOEX period

The study of atmospheric ice-nucleating particles via microfluidically generated droplets

Ice-nucleating particles (INPs) play a significant role in the climate and hydrological cycle by triggering ice formation in supercooled clouds, thereby causing precipitation and affecting cloud lifetimes and their radiative properties. However, despite their importance, INP often comprise only 1 in 10³–10⁶ ambient particles, making it difficult to ascertain and predict their type, source, and concentration. The typical techniques for quantifying INP concentrations tend to be highly labour-intensive, suffer from poor time resolution, or are limited in sensitivity to low concentrations. Here, we present the application of microfluidic devices to the study of atmospheric INPs via the simple and rapid production of monodisperse droplets and their subsequent freezing on a cold stage. This device offers the potential for the testing of INP concentrations in aqueous samples with high sensitivity and high counting statistics. Various INPs were tested for validation of the platform, including mineral dust and biological species, with results compared to literature values. We also describe a methodology for sampling atmospheric aerosol in a manner that minimises sampling biases and which is compatible with the microfluidic device. We present results for INP concentrations in air sampled during two field campaigns: (1) from a rural location in the UK and (2) during the UK’s annual Bonfire Night festival. These initial results will provide a route for deployment of the microfluidic platform for the study and quantification of INPs in upcoming field campaigns around the globe, while providing a benchmark for future lab-on-a-chip-based INP studies

Rural versus urban gaseous inorganic reactive nitrogen in the Indo-Gangetic plains (IGP) of India

The present study reports on the abundance of reactive nitrogen (NH _3 and NO _2 ) at two sites, i.e. Okhla (urban site) in Delhi and Mai (rural site), located in the nearby state: Uttar Pradesh. The measurements were carried out during the period from October, 2012 to September, 2013 on a monthly basis. The average concentrations of NH _3 at Okhla and Mai have been recorded as 40.4 ± 16.8 and 51.57 ± 22.8 μ g m ^−3 , respectively. The average concentrations of NO _2 have been recorded as 24.4 ± 13.5 and 18.8 ± 12.6 μ g m ^−3 at Okhla and Mai, respectively. Results show that the seasonal variation at Mai was more prominent where NH _3 concentrations varied at 72.0 μ g m ^−3 during the winter, 47.2 μ g m ^−3 during the summer and 30.7 μ g m ^−3 during the monsoon season, whereas at Okhla the average NH _3 concentrations were almost equal during different seasons, namely 44.2 μ g m ^−3 during the winter, 42.5 μ g m ^−3 during the summer and 38.9 μ g m ^−3 during the monsoon season. This is probably due to significant differences in crops and in the fertilizer amounts applied across the seasons in rural areas, while urban areas have almost constant sources throughout the year. Winter concentrations were highest at both sites, followed by summer and then the monsoon season. The average NO _2 concentrations were recorded as 39.6 μ g m ^−3 , 24.5 μ g m ^−3 and 10.4 μ g m ^−3 during the winter, summer and monsoon season at Okhla, whereas the average NO _2 concentrations were recorded as 27.5 μ g m ^−3 , 17.2 μ g m ^−3 and 4.1 μ g m ^−3 during the winter, summer and monsoon season, respectively. NO _2 emissions at Okhla may be attributed to various urban activities, such as vehicular traffic and industries, while NO _2 emissions at Mai may be attributed to biomass burning as a major source. However, NO _2 concentrations from vehicular traffic and nearby industries cannot be ignored at Mai

Real-time wet scavenging of major chemical constituents of aerosols and role of rain intensity in Indian region

Real-time simultaneous studies on chemical characteristics of rainwater and PM10 aerosols were carried out to understand the scavenging of major chemical components in Indian region. The concentrations of Ca2+, NH4+, SO42− and NO3− were observed to be lower in the aerosol samples collected during rain as compared to before and after rain events. The most significant reduction was noticed for Ca2+ (74%) during rain which showed highest scavenging ratio (SR) and indicated that below-cloud scavenging is an effective removal process for Ca2+ in Indian region. Among non-sea salt components, Ca2+ had highest SR at Hyderabad indicating typical characteristics of crustal influence as abundance of calcium carbonate in soil dust has been reported in India. However, the levels of these major chemical components gradually got build-up in due course of time. After rain events, the levels of SO42− aerosols were noticed to be substantially higher (more than double) within 24 h. In general, scavenging ratios for all components (except Ca2+, NH4+ and K+) were higher over BOB as compared to Hyderabad. The maximum fall in aerosol levels (BR minus AR) was observed during continuous and low intensity rain events that did not allow building up of aerosol concentrations

Concentrations and behaviour of surface O₃, NO and NO₂ at Delhi

82-84Ambient concentrations of O3, NO and NO2 at Delhi were studied at National Physical Laboratory, New Delhi. Analysis of the data revealed the highest concentrations of O3 during winter which may be due to lowering of inversion layer. During monsoon, O3 concentrations were minimum which may be due to the wash out effect by unpolluted mosoonal air masses. During day, O3 concentrations were maximum in afternoon when the concentrations of NO were minimum and those of NO2 were also low. The concentrations of O3 were observed to be higher at 30 m than at 13 m above the ground

Application of capillary electrophoresis for the analysis of nicotine content in Gutkha samples

33-35Recently, the chewing of Gutkha is increased in every age group of Indian society. It is severely affecting the youth. The nicotine content of tobacco of Gutkha is harmful for the body. This paper presents the nicotine content in six famous brands of Gutkha which were analysed by Capillary Electrophoresis (CE). CE is a relatively new technique of analysis. In this study, it was observed that CE is very much suitable technique for the determination of nicotine in Gutkha samples. It is simple and economical technique

Separation and determination of 3,4-dimethoxybenzaldehyde and related compounds by high performance capillary electrophoresis

662-6653,4-Dimethoxybenzaldehyde and five related compounds have been separated and determined by high performance capillary electrophoresis using micellar electrokinetic chromatography method. Good separation for all the compounds is achieved using 10 mM di-sodium tetraborate, 100 mM sodium dodecyl sulphate and 10% acetonitrile. The detection has been carried out at 214 nm using UV-vis detector. The proposed method has been further applied for the quality control of two commercial samples

Separation and determination of 3,4-dimethoxybenzaldehyde and related compounds by high performance capillary electrophoresis

3,4-Dimethoxybenzaldehyde and five related compounds have been separated and determined by high performance capillary electrophoresis using micellar electrokinetic chromatography method. Good separation for all the compounds is achieved using 10 mM di-sodium tetnborate, 100 mM sodium dodecyl sulphate and 10% acetonitrile