T. K. Mandal

Variability of Mixed-Layer Heights over the Indian Ocean and Central Arabian Sea during INDOEX, IFP-99

The upper air data collected from the balloon-borne GLASS Sondes launched from the Oceanic Research Vessel (ORV) Sagar Kanya during the Intensive Field Phase of the Indian Ocean experiment (INDOEX, IFP-99;SK-141 Cruise) are utilized forstudying the variability in the mixed-layer heights observed over the western tropical Indian Ocean and central Arabian Sea. During the entire cruise, typical daytime convective mixed-layer heights (roughly corresponding to 1400 LT) obtained from θV and q profiles, were observed to be in the range 200–900 m. Shallowmixed -layer heights are observed, in general, over the Inter-Tropical Convergence Zone (ITCZ). Over the central Arabian Sea, vertical profiles of θV and q demonstrate a double mixed-layer structure of the marine atmospheric boundary layer (MABL), which gradually disappears close to the Indian coastline.

Levels, Sources, and Toxic Potential of Polycyclic Aromatic Hydrocarbons in Urban Soil of Delhi, India

ABSTRACT This study was done to determine the concentration of PAHs in urban soil of Delhi (India). Surface top soil (up to 10 cm depth) samples were collected from four different sampling sites including industrial, roadside, residential, and agricultural areas of Delhi and 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) were evaluated. Total PAH concentrations at industrial, roadside, residential, and agricultural sites were 11.46 ± 8.39, 6.96 ± 4.82, 2.12 ± 1.12, and 1.55 ± 1.07 mg/kg (dry weight), respectively, with 3–7 times greater concentrations in industrial and roadside soils than that in residential and agricultural soils. The PAH pattern was dominated by 4- and 5-ring PAHs (contributing >50% to the total PAHs) at industrial and roadside sites with greater concentration of fluoranthene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]anthracene, benzo[ghi]perylene, and pyrene, whereas, residential and agricultural sites showed a predominance of low molecular weight 2- and 3-ring PAHs (fluoranthene, acenaphthene, naphthalene, chrysene, and anthracene). Isomeric pair ratios suggested biomass combustion and fossil fuel emissions as the main sources of PAHs. The toxic equivalency factors (TEFs) showed that carcinogenic potency (benzo[a]pyrene-equivalent concentration (B[a]Peq) of PAH load in industrial and roadside soils was ∼10 and ∼6 times greater than the agricultural soil.

Emission Estimates of Particulate PAHs from Biomass Fuels Used in Delhi, India

ABSTRACT The emission factors for particulate-phase polycyclic aromatic hydrocarbons (PAHs) were evaluated for various biomass fuels (fuelwood, dung cakes, and agricultural residue) that are being commonly used in Delhi as a source of energy. Emission factors of total particulate PAHs varied from 35.9 ± 1.9 to 59.7 ± 4.4 mg/kg. Higher levels of total PAHs and particulate matter (PM) were found from dung cakes as compared to fuelwood and agricultural residue. The emission factors for PM from dung cake, fuelwood, and agricultural residue are 25 ± 8, 15 ± 3.2, and 12.1 ± 9.4 g/kg, respectively. The total PAH emissions showed an increase with high particulate matter emission rates and lower combustion efficiency. Fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and benzo[a]pyrene constituted the major fraction of PAH emissions from all biomass fuels. The annual budget estimates (total emissions per year) for PAHs and PM from biomass fuels used in Delhi are 30.5 ± 2.3 Mg (Megagrams) and 11.6 ± 4.4 Gg (Gigagrams), respectively. An attempt has also been made to evaluate the preliminary budget estimates of PAHs and PM emitted from the use of biomass fuels as a source of energy in India by using the emission factors obtained in the present study.

Emissions of Polycyclic Aromatic Hydrocarbons in the Atmosphere: An Indian Perspective

ABSTRACT Organic compounds form a major fraction of airborne particles in the atmosphere and hence it is important to measure and identify them, especially the proportion of Polycyclic (Polynuclear) Aromatic Hydrocarbons (PAHs). The control and abatement of PAHs contamination requires the knowledge of the nature, source, and extent of pollution and hence existing literature on Indian studies was reviewed to gather information on the sources and emission rates of PAHs. Based on the results of the present study along with the data available from literature for particular PAHs in the ambient atmosphere, the vehicular and residential sector was identified as a major source of PAHs emission in many major Indian cities including Ahmedabad, Agra, Delhi, Kanpur, Lucknow, Mumbai, and Nagpur. Emissions of total PAHs range from 23–190 ng/m3, 369–1067 ng/m3, 20.8–100.8 ng/m3, and 12.7–206.4 μg/m3 from gasoline, diesel, petroleum refinery, and biomass, respectively, although it is recognized that this will vary from location to location. Additionally, the regulation and control of PAHs emission, and air quality standards for PAHs were also examined. Based on the toxicity assessment, the study highlights the need to include not only benzo[a]pyrene but also other probable human carcinogenic PAHs while developing a new air quality index for India.

Source apportionment of particulates by receptor models over Bay of Bengal during ICARB campaign

Source apportionment study of aerosols over Bay of Bengal (BOB) were investigated during Integrated Campaign on Aerosol Radiation Budget (ICARB) in the pre–monsoon (March–April 2006) and winter (December–January 2008–09) seasons. Positive matrix factorization (PMF) was applied to identify sources of ambient particulate matter using daily chemical composition data collected in the pre–monsoon (total suspended particles, TSP) and winter season (particles with a diameter < 10 µm, PM10). Sea salt (SS), secondary aerosol (SA), Si–dust, fossil fuel combustion (FFC), biomass burning (BB) sources have been identified in both seasons, however their relative contributions were different. The combined contribution of Si–dust, secondary aerosol and fossil fuel combustion, constitute 67% of particulate matter in pre–monsoon, whereas, secondary aerosols and biomass burning were the major contributors (63.2%) to particulate matter in winter. The identified sources effectively predict the measured particulate concentration in the pre–monsoon (r 2 =0.74) and winter season (r 2 =0.82). Another receptor model, principal component analysis (PCA) was done to increase the plausibility of the results obtained by PMF. PCA resulted in the identification of the sources that were comparable to the PMF outputs. PCA of TSP in the pre–monsoon season resulted in the extraction of three components (crustal dust + secondary aerosol, biomass burning, fossil fuel combustion + industrial emissions) that explained the 83% of the variance in the data. Similarly, in winter season, PCA resulted in the extraction of four components (biomass burning + secondary aerosol, industrial emission, crustal dust, sea salt) that explained the 86% of the variance of the data.

Characterization of Gaseous and Particulate Polycyclic Aromatic Hydrocarbons in Ambient Air of Delhi, India

Three seasonal sampling campaigns were undertaken at an urban site of Delhi for collection of PAHs in particulate and gas phase. Sampling was done by using modified Respirable Dust (PM ≤10μm) sampler attached with polyurethane foam (PUF) plugs and compared with conventional Respirable Dust (PM ≤10 μm) sampler. Total 16 EPA PAH (gaseous + particulate) were determined by Gas Chromatograph-Mass Spectrophotometer (GC-MS). The 3-ring PAH constitutes approximately 90% of the gaseous PAHs with phenanthrene, fluoranthene, acenapthylene, and acenaphthene being the most abundant gaseous PAHs. PAHs with 4- to 6- rings accounted for 92%, 87% and 78% in samples collected during winter, summer and monsoon season respectively. Gaseous PAHs, particulate PAHs and total PAHs were higher during winter as compared to summer and monsoon seasons. The contribution of particulate PAHs were 1.4, 2.1, and 2.5 times higher in winter, summer and monsoon, respectively than of gaseous PAHs. Indeno[123-cd]pyrene, benzo[ghi]perylene, dibenzo[ah]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene and chrysene were found to be the most abundant PAH compounds in the particulate PAHs during all the seasons. The result from application of diagnostic ratio suggests that the higher particulate PAHs emissions were predominantly associated with vehicular emissions along with emissions from biomass burning during winter season.

Stable carbon and nitrogen isotopic composition of PM10 over Indo-Gangetic Plains (IGP), adjoining regions and Indo-Himalayan Range (IHR) during a winter 2014 campaign

AbstractFor source identification, a field campaign involving simultaneous sampling of particulate matter (PM10) was conducted at eight sampling sites in the Indian mainland during winter 2014. The sampling sites include Delhi (upper IGP), Lucknow (middle IGP), and Kolkata (lower IGP) in the Indo-Gangetic Plains (IGP); Mohal-Kullu and Darjeeling in the Indo-Himalayan Range (IHR). In addition, Ajmer, located upwind of the IGP in NW-India and Giridih and Bhubaneswar, in the downwind to the IGP has also been chosen. To characterize the sources of the ambient PM10, stable isotope ratios of carbon (δ13CTC) and nitrogen (δ15NTN) for the total carbon (TC) and total nitrogen (TN) fractions have been considered. Ancillary chemical parameters, such as organic carbon (OC), elemental carbon (EC), and water-soluble ionic components (WSIC) mass concentrations are also presented in this paper. There was very small variation in the daily average δ13CTC ratios (− 24.8 to − 25.9‰) among the sites. Comparison with end-member stable C isotopic signatures of major typical sources suggests that the PM10 at the sites was mainly from fossil fuel and biofuel and biomass combustion. Daily average δ15NTN ratios were not observed to vary much between sites either (8.3 to 11.0‰), and the low δ15NTN levels also indicate substantial contributions from biofuel and biomass burning of primarily C3 andC4 plant matter. Graphical abstractScatter plot of the average (± 1 standard deviation (SD)) δ13CTC (‰) compared to δ15NTN (‰) at the sampling sites.